With the announcement of the Digital Negative Specification, Adobe is attempting to standardize how digital cameras understand image data. Will this new imaging initiative take off with camera makers? And what does it mean for you?
(creativepro.com)
By Ben Long, creativepro.com senior editor
Tuesday, October 12, 2004
View More In:
Graphics
Systems & Hardware
Related Features:
Framed and Exposed: Making Sense of Camera Sensors
Related How-Tos:
Out of Gamut: Calibrating Camera Raw in Photoshop CS
Related Reviews:
The Raw Truth: Work with Raw Digital Camera Files in Photoshop
Related News:
Adobe Adds Support for New Digital Negative Specification in Updated Camera Raw Plug-in For Photoshop CS
Adobe Unifies Raw Photo Formats with Introduction of Digital Negative Specification
Foveon Announces X3F Raw File Support for Adobe Photoshop CS
Adobe Expands Photoshop CS Camera Raw File Support
Adobe Extends Camera Raw File Support in Photoshop CS
Adobe Delivers Easy Access and Control of Raw Digital Camera Files With New Photoshop Plug-in
Related Books:
Adobe Photoshop CS for Photographers
Be the first to tell us what you think.
Respond to this article
For photographers who demand maximum control and superior image quality, one of the great appeals of digital is the ability to shoot in "raw" format. Unfortunately, because "raw" is an undefined format, rather than an accepted standard, you have to have software tailored to your particular camera to access a raw file. Adobe hopes to change all that with the release of its new Digital Negative Specification.
The Raw and the Cooked
As explained in my earlier column about camera sensors, a digital camera has to do a tremendous amount of processing and calculation to turn the data collected by its image sensor into a full-color image. Raw format allows you to save all of that original, unprocessed, uncompressed data directly to your camera's media card. Through the use of special software, you can use your computer to perform all of that gnarly image processing and calculation later and with much greater control.
With raw format, you can alter your image's white balance, exposure, sharpening, noise reduction and more after shooting, as well as perform all of your usual edits in a more flexible, accurate 16-bit color space.
The downside to shooting raw is time and workflow. To even look at a raw file, you must process it through a special raw format reader. Vendors are diligent about including their own special raw software with each camera that provides raw support, but it's astonishing to see how universally bad this software is, in terms of performance, interface, and integration with existing image-editing workflows.
Fortunately, several third-party vendors have stepped in to create more usable raw solutions. However, because camera vendors usually don't publish the details of their raw specs, software developers are often forced to reverse engineer the raw format of every camera they want to support. This is the main reason that you don't see raw support in more applications.
Raw-image workflow saw its biggest boost when Adobe released its Camera Raw plug-in for Photoshop 7 (Camera Raw is now built-in to Photoshop CS). With the ability to handle raw files directly in Photoshop, raw workflow was suddenly much simpler. In addition, Adobe's raw plug-in yielded very good results (raw image data is so raw, that there can be a tremendous amount of variation in the way different pieces of software choose to interpret it).
However, the problem of varying, unpublished raw formats remains, which means that when you buy the latest camera, you may not be able to open its raw files in any software, Photoshop included.
To address this issue, Adobe has developed and published an open standard that aims to make today's raw confusion a thing of the past.
Setting the Standard
Obviously, a lot of this confusion would pass if camera makers would simply agree on a single standard for raw format files. With the release of the Digital Negative Specification, Adobe has stepped forward and offered a standard that could, if adopted, tremendously ease the development of raw-compatible software.
Based on the TIFF-EP file format, the new DNG format is controlled and maintained by Adobe (just like TIFF) but is free to be used by any developer who wants to support it. In other words, only Adobe can make changes to the format, but anyone else is free to use it.
In addition to all of the normal TIFF tags, the new specification can hold all of the raw-related information that a program needs to correctly interpret a raw file. The new spec also provides tags for all of the usual EXIF information (camera settings, etc.) as well as support for all of the same XMP metadata supported by the Adobe Creative Suite applications.
Most proprietary raw formats also include what Adobe refers to as "special sauce" information that is necessary to correctly interpret certain raw data. To facilitate this data, the DNG specification allows for camera vendors to create special "private" metadata that only they can use.
With the announcement of the spec, Adobe also released a free upgrade to the existing Camera Raw plug-in, which provides support for a slew of new cameras. In addition, they released a DNG Converter application that can convert raw files from any of the currently supported raw formats into the new DNG specification.
Who Cares? I Care!
On paper this all sounds great, but the actual benefit to end users is dependent on who ends up adopting and supporting the new format.
Right now, the only compelling reason to convert your raw images to DNG is paranoia. If you're afraid that the multi-national corporate giant that manufactured your camera might one day go out of business, leaving you with no software to read your library of extant raw files, then switching to this new open standard is probably a reasonable thing to do. Even if Adobe ever goes under, the fact that the standard is freely published means someone will probably continue to provide software that's compatible with it.
Adobe is currently recommending that you save all of your original raw files, even if you convert to DNG. Because there is still undocumented private metadata in your original files, you'll want to have them around for maximum compatibility.
In testing the Digital Negative Converter with raw files from a Canon EOS 20D, it took my 1-GHz G4 PowerBook about 5 seconds per image to convert from Canon's CR2 format to the new DNG format. The resulting files were a little smaller -- down anywhere from 500 k to 1 GB. In other words, if you want to switch to DNG now, you'll have to devote some time to processing your images, and you're gonna need twice the storage that you're using now.
The real advantage to the end user will come from vendor support of the format. Because cracking a camera raw format is time consuming, few applications provide direct support for it. In theory, Adobe's published standard should make it much easier for any software developer to add raw support -- and not have to update it every time a camera is released -- meaning that your imaging workflow could one day be much more flexible.
The ideal future, of course, would be a camera that writes directly to DNG format. Obviously, this is what Adobe wants, not because they necessarily stand to make money from the adoption of their standard, but because they don't want to have to keep supporting new raw formats.
Whether vendors will go for this remains to be seen. At the time of this writing, none of the camera vendors we talked to were ready to make a statement about their DNG opinions.
What Now?
In theory, there are tremendous advantages to camera vendors: They don't have to develop, test, and maintain their own raw format; they get instant compatibility with Photoshop and any other app that supports DNG format; Adobe's support for "private" metadata means they don't have to give up on any of their own proprietary designs.
In the end, Adobe could choose to play hardball. If the new spec gains some momentum in the form of adoption by a majority of camera vendors, Adobe could simply stop providing support for proprietary raw formats, meaning that any camera that doesn't support DNG is locked out of the Photoshop raw workflow. For the serious photographer, this might be reason enough to choose a different camera.
Until more vendors -- software and hardware -- support it, DNG will remain just a promise of improved workflow. As a photographer, you probably don't need to concern yourself with the format yet, but it's worth keeping an eye on its development.
http://www.creativepro.com/story/feature/22023.html
Thursday, May 17, 2007
Framed and Exposed: Buying a Digital Camera, Part 6
This is it: The final installment of Ben Long's guide to selecting a digital camera model. We're down to the pivotal issue of image quality. Here's how to evaluate cameras for color, noise, and other image essentials.
Over the last five installments of this column, you have been presented with a barrage of questions and options related to choosing a digital camera. If you've been following along, you've asked yourself what type of shooting you do, what features you think you want, what you need in terms of size and weight. After answering all of these questions, you should have narrowed down the field of possible candidates to just a handful of cameras. You're now at the very last stage: the final choice.
The good news is that making the final choice may not be too hard, because, in the end, one single question should outweigh all others when selecting a camera: How good are the images it produces? The bad news is that, if you're already favoring a particular camera for its features and design, you may have to nix it and go with a secondary camera that yields better image quality.
Image quality is, of course, a very subjective topic -- one person's hideous noise might be another's beautiful texture. Nevertheless, with a little bit of attention, you can identify problems up front that might vex you later.
In this final "Choosing a camera" installment, we're going to quickly take a look at the most common image-quality issues that you should consider when choosing a camera. In addition to aiding your camera choice, learning to identify these problems now can help in your image-editing efforts later.
Print or Monitor?
Before you can begin comparing image quality, you've gotta have some images to evaluate. A camera LCD is not good enough to evaluate image quality, because color and contrast are rarely accurate on a camera LCD. Camera screens are not intended for accurate output, and they're designed to be visible in very bright sunlight, which means that vendors often have to increase brightness and contrast to improve image quality.
So, if you want to evaluate image quality from a particular camera, you need to get some images out of the camera and back to your computer at home. The easiest way to do this is to buy a memory card that you can take to the camera store. You can then fill it up with images that you can look at back at home. If you're considering cameras that use different formats, then you might need to invest in several cards, but media is cheap right now and you don't need high-capacity cards for these kinds of tests.
Laptop owners have the option of taking their computer to the store and loading images in directly from the camera.
Finally, there are a number of camera review sites that regularly post full-resolution output from their review camera units. These are perfectly suited to evaluation, and usually cover a much greater range of lighting and shooting conditions than you could ever find in a typical camera store.
Obviously, your first evaluations will be performed on your computer monitor, and there's much that you can learn from these assessments. However, when viewing images onscreen, it's also possible to get hung up on issues that may not be a problem in your final output. Simply put: When you can zoom in to look at the individual pixels of an 8-megapixel image, you're likely to find some troublesome artifacts. Whether these artifacts will be visible in an 8-x-10-inch glossy is another question.
So, when evaluating an image, lend a little thought to what your final output will be. If you mostly shoot for the Web, or on-screen viewing, then consider the typical size that you use, and do a round of evaluations at that size.
If you predominantly take images for print, then you'll need a round of evaluation using your typical printing technology, media, and print sizes. Many troubles and artifacts that are visible onscreen may vanish when resized and output using a particular printing technology.
Noise Levels
Though there are a lot of things that can go wrong with an image, the issue you're most likely to notice first when comparing cameras is noise. Noise is roughly analogous to grain in a piece of film and, like grain, it's not necessarily a bad thing, as it can add texture and atmosphere to an image.
However, sometimes digital-camera noise has a more intrusive character than film grain, manifesting as speckly colored patterns rather than an underlying texture. What's more, there will be times when you don't want to have any noise in your images. Because noise can easily be added using an image-editing program, it's better to get a camera with very low noise, so that you'll have the choice of producing clean or noisy images.
The good news is that, these days, most cameras have their noise issues under control. What's more, on a higher-res camera, noise is typically much finer, meaning it will often vanish if you downsize the image.
Noise is almost always more prominent in the shadow parts of an image, and this is the first place to go looking when evaluating an image.
There are two types of noise: chrominance noise and luminance noise. Luminance noise is the preferable of the two, as it looks more like film grain. Where luminance noise is simply a variation in the brightness of the pixels in the image, chrominance noise is a variation in the color -- sometimes an extreme variation. If you see brightly colored blue, red, or even purple pixels, then your camera is exhibiting chrominance noise (see Figure 1).
Again, noise is not a problem that has to be completely avoided, but it's good to know the noise characteristics of a particular camera.
Noise gets worse as you increase the camera's ISO settings, so you'll want to do noise tests across the camera's ISO range. Because ISO is a valuable exposure parameter, you'll want to carefully consider noise levels at higher ISOs. If possible, you might also want to try evaluating some long-exposure images, as noise also increases with exposure time.
Color Troubles
Color reproduction is probably the most subjective of all image quality considerations. What you think of as beautiful, saturated color, someone else might perceive to be garish, velvet-Elvis-painting color. Neither is wrong, of course, so in the end you need to base your consideration on the color you like. As with noise, though, it's still a good idea to know if a particular camera has certain color tendencies. Some color issues to be aware of include:
* Color casts. Some cameras have a tendency to produce images with a particular cast -- an overall color tone that makes the image appear as if it were shot through a colored filter of some kind. Sometimes, the cast will only affect a particular part of the image -- perhaps shadows are too blue, for example.
* Bad white balance. Just as you must select a film that's appropriate for the light you're shooting in, your camera must calibrate its idea of color according to the current light. This process, called white balancing, can sometimes go awry, resulting in images with out-of-whack color. A bad white balance is similar to a color cast, except that white balance problems usually affect the entire color range, not just the shadows or highlights. White balance prowess is something you want to be very conscious of, as removing a bad white balance can be difficult, if not impossible. Most cameras offer a choice of automatic and manual white balances. Because you'll most often use automatic white balance, you'll want to closely evaluate images shot in auto white balance mode.
* Chromatic aberration. All cameras, including film cameras are subject to this weird type of artifact that's sometimes referred to as "purple fringing" (see Figure 2). Sometimes, chromatic aberration is caused by poor lens optics; at other times it's the result of pixels on the camera's image sensor essentially overflowing with light and corrupting neighboring pixels. Chromatic aberrations usually only occur when shooting high-contrast subjects in bright light -- you'll often see it appear along the edges of leaves against a bright sky -- and even then usually only at extreme focal lengths. Chromatic aberration that's readily apparent on-screen is often invisible in print, and it's usually not too difficult to remove, if need be.
* Inaccurate color. This one's a tricky one, because a camera can sometimes yield colors that are dead wrong, but that still look great -- maybe even better than the original. What's more, they might do this consistently. Some cameras, for example, pump up the saturation in an image to produce a "glossy" result. This process can boost the colors into the realm of "wrong" yet yield a more pleasing image. If you're a stickler for accuracy, then you're going to want to evaluate color with this in mind. If you simply want consistently attractive images that require little editing, then accuracy may not be as important.
In the Details
The amount of sharpness and detail in an image is the result of several camera factors: How much resolution your camera has, how good your lens is, and how good your camera's built-in sharpening routines are.
The tricky thing about assessing detail is that you may not know that there's detail missing. In other words, you may think the image looks fine simply because you're not aware of what's there.
The figure below shows the same scene shot with the same camera - a Canon EOS 10D - but using two different lenses (see figure 3). Though neither image looks bad, there's a marked difference in detail.
The easiest way to assess detail when comparing cameras is to examine identical images side-by-side. For this kind of testing, you'll want to go to your camera store and shoot the same scene with all of your candidate cameras. Even if all you can manage is a shot of the cash register, this should still be enough to give you an idea of the differences in detail and sharpness between the different models.
Because in-camera sharpening can greatly affect the quality of an image -- sometimes for the better, sometimes for the worse -- you'll want to take some images with varying degrees of sharpening applied.
Although you may think that more sharpness is inherently better, it is possible to oversharpen an image. To evaluate a camera's sharpening mechanism, look for bright and dark halos around high-contrast areas in an image.
Bad Exposure
You'll use your camera's automatic metering for almost all of your images, so you'll want to get a sense of how well it exposes in difficult lighting situations. Again, sample pictures downloadable from camera review Web sites should ease this problem. Pay particular attention to how well the camera meters in low light, in complex mixed lighting situations (lots of bright and dark in the scene), when shooting with flash, as well as overall consistency of metering.
Most cameras these days have very good light meters, and a skilled photographer can compensate for most difficult metering situations.
Some cameras exhibit lens distortions when shooting at the extreme wide or telephoto ends of their focal ranges. Though these problems are rarely deal-breakers, and can be corrected in post-production, it's worth keeping an eye out for them when evaluating image quality.
Finally, since JPEG compression can seriously degrade the quality of an image, look for JPEG artifacts -- regular, square blocky patterns throughout an image -- when shooting at the camera's highest quality level.
Conclusion
As discussed in the first installment of "Framed and Exposed," most modern digital cameras yield very good images. There are differences, and some might be more to your taste than others, but the good news is that your image evaluations should not be too trying, because you're probably going to see nice results from most cameras.
When considering the image quality issues discussed here, remember to factor in price. Yes, you may not be seeing images that are as good as what your friend gets from his $1,500 digital SLR, but if you're only aiming to spend $500, then you should expect to take a hit in image quality. For this reason, when comparing image quality, be sure to compare comparable cameras. Don't get hung up on how your candidate cameras compare to models that you can't afford.
http://www.creativepro.com/story/feature/21955.html
Over the last five installments of this column, you have been presented with a barrage of questions and options related to choosing a digital camera. If you've been following along, you've asked yourself what type of shooting you do, what features you think you want, what you need in terms of size and weight. After answering all of these questions, you should have narrowed down the field of possible candidates to just a handful of cameras. You're now at the very last stage: the final choice.
The good news is that making the final choice may not be too hard, because, in the end, one single question should outweigh all others when selecting a camera: How good are the images it produces? The bad news is that, if you're already favoring a particular camera for its features and design, you may have to nix it and go with a secondary camera that yields better image quality.
Image quality is, of course, a very subjective topic -- one person's hideous noise might be another's beautiful texture. Nevertheless, with a little bit of attention, you can identify problems up front that might vex you later.
In this final "Choosing a camera" installment, we're going to quickly take a look at the most common image-quality issues that you should consider when choosing a camera. In addition to aiding your camera choice, learning to identify these problems now can help in your image-editing efforts later.
Print or Monitor?
Before you can begin comparing image quality, you've gotta have some images to evaluate. A camera LCD is not good enough to evaluate image quality, because color and contrast are rarely accurate on a camera LCD. Camera screens are not intended for accurate output, and they're designed to be visible in very bright sunlight, which means that vendors often have to increase brightness and contrast to improve image quality.
So, if you want to evaluate image quality from a particular camera, you need to get some images out of the camera and back to your computer at home. The easiest way to do this is to buy a memory card that you can take to the camera store. You can then fill it up with images that you can look at back at home. If you're considering cameras that use different formats, then you might need to invest in several cards, but media is cheap right now and you don't need high-capacity cards for these kinds of tests.
Laptop owners have the option of taking their computer to the store and loading images in directly from the camera.
Finally, there are a number of camera review sites that regularly post full-resolution output from their review camera units. These are perfectly suited to evaluation, and usually cover a much greater range of lighting and shooting conditions than you could ever find in a typical camera store.
Obviously, your first evaluations will be performed on your computer monitor, and there's much that you can learn from these assessments. However, when viewing images onscreen, it's also possible to get hung up on issues that may not be a problem in your final output. Simply put: When you can zoom in to look at the individual pixels of an 8-megapixel image, you're likely to find some troublesome artifacts. Whether these artifacts will be visible in an 8-x-10-inch glossy is another question.
So, when evaluating an image, lend a little thought to what your final output will be. If you mostly shoot for the Web, or on-screen viewing, then consider the typical size that you use, and do a round of evaluations at that size.
If you predominantly take images for print, then you'll need a round of evaluation using your typical printing technology, media, and print sizes. Many troubles and artifacts that are visible onscreen may vanish when resized and output using a particular printing technology.
Noise Levels
Though there are a lot of things that can go wrong with an image, the issue you're most likely to notice first when comparing cameras is noise. Noise is roughly analogous to grain in a piece of film and, like grain, it's not necessarily a bad thing, as it can add texture and atmosphere to an image.
However, sometimes digital-camera noise has a more intrusive character than film grain, manifesting as speckly colored patterns rather than an underlying texture. What's more, there will be times when you don't want to have any noise in your images. Because noise can easily be added using an image-editing program, it's better to get a camera with very low noise, so that you'll have the choice of producing clean or noisy images.
The good news is that, these days, most cameras have their noise issues under control. What's more, on a higher-res camera, noise is typically much finer, meaning it will often vanish if you downsize the image.
Noise is almost always more prominent in the shadow parts of an image, and this is the first place to go looking when evaluating an image.
There are two types of noise: chrominance noise and luminance noise. Luminance noise is the preferable of the two, as it looks more like film grain. Where luminance noise is simply a variation in the brightness of the pixels in the image, chrominance noise is a variation in the color -- sometimes an extreme variation. If you see brightly colored blue, red, or even purple pixels, then your camera is exhibiting chrominance noise (see Figure 1).
Again, noise is not a problem that has to be completely avoided, but it's good to know the noise characteristics of a particular camera.
Noise gets worse as you increase the camera's ISO settings, so you'll want to do noise tests across the camera's ISO range. Because ISO is a valuable exposure parameter, you'll want to carefully consider noise levels at higher ISOs. If possible, you might also want to try evaluating some long-exposure images, as noise also increases with exposure time.
Color Troubles
Color reproduction is probably the most subjective of all image quality considerations. What you think of as beautiful, saturated color, someone else might perceive to be garish, velvet-Elvis-painting color. Neither is wrong, of course, so in the end you need to base your consideration on the color you like. As with noise, though, it's still a good idea to know if a particular camera has certain color tendencies. Some color issues to be aware of include:
* Color casts. Some cameras have a tendency to produce images with a particular cast -- an overall color tone that makes the image appear as if it were shot through a colored filter of some kind. Sometimes, the cast will only affect a particular part of the image -- perhaps shadows are too blue, for example.
* Bad white balance. Just as you must select a film that's appropriate for the light you're shooting in, your camera must calibrate its idea of color according to the current light. This process, called white balancing, can sometimes go awry, resulting in images with out-of-whack color. A bad white balance is similar to a color cast, except that white balance problems usually affect the entire color range, not just the shadows or highlights. White balance prowess is something you want to be very conscious of, as removing a bad white balance can be difficult, if not impossible. Most cameras offer a choice of automatic and manual white balances. Because you'll most often use automatic white balance, you'll want to closely evaluate images shot in auto white balance mode.
* Chromatic aberration. All cameras, including film cameras are subject to this weird type of artifact that's sometimes referred to as "purple fringing" (see Figure 2). Sometimes, chromatic aberration is caused by poor lens optics; at other times it's the result of pixels on the camera's image sensor essentially overflowing with light and corrupting neighboring pixels. Chromatic aberrations usually only occur when shooting high-contrast subjects in bright light -- you'll often see it appear along the edges of leaves against a bright sky -- and even then usually only at extreme focal lengths. Chromatic aberration that's readily apparent on-screen is often invisible in print, and it's usually not too difficult to remove, if need be.
* Inaccurate color. This one's a tricky one, because a camera can sometimes yield colors that are dead wrong, but that still look great -- maybe even better than the original. What's more, they might do this consistently. Some cameras, for example, pump up the saturation in an image to produce a "glossy" result. This process can boost the colors into the realm of "wrong" yet yield a more pleasing image. If you're a stickler for accuracy, then you're going to want to evaluate color with this in mind. If you simply want consistently attractive images that require little editing, then accuracy may not be as important.
In the Details
The amount of sharpness and detail in an image is the result of several camera factors: How much resolution your camera has, how good your lens is, and how good your camera's built-in sharpening routines are.
The tricky thing about assessing detail is that you may not know that there's detail missing. In other words, you may think the image looks fine simply because you're not aware of what's there.
The figure below shows the same scene shot with the same camera - a Canon EOS 10D - but using two different lenses (see figure 3). Though neither image looks bad, there's a marked difference in detail.
The easiest way to assess detail when comparing cameras is to examine identical images side-by-side. For this kind of testing, you'll want to go to your camera store and shoot the same scene with all of your candidate cameras. Even if all you can manage is a shot of the cash register, this should still be enough to give you an idea of the differences in detail and sharpness between the different models.
Because in-camera sharpening can greatly affect the quality of an image -- sometimes for the better, sometimes for the worse -- you'll want to take some images with varying degrees of sharpening applied.
Although you may think that more sharpness is inherently better, it is possible to oversharpen an image. To evaluate a camera's sharpening mechanism, look for bright and dark halos around high-contrast areas in an image.
Bad Exposure
You'll use your camera's automatic metering for almost all of your images, so you'll want to get a sense of how well it exposes in difficult lighting situations. Again, sample pictures downloadable from camera review Web sites should ease this problem. Pay particular attention to how well the camera meters in low light, in complex mixed lighting situations (lots of bright and dark in the scene), when shooting with flash, as well as overall consistency of metering.
Most cameras these days have very good light meters, and a skilled photographer can compensate for most difficult metering situations.
Some cameras exhibit lens distortions when shooting at the extreme wide or telephoto ends of their focal ranges. Though these problems are rarely deal-breakers, and can be corrected in post-production, it's worth keeping an eye out for them when evaluating image quality.
Finally, since JPEG compression can seriously degrade the quality of an image, look for JPEG artifacts -- regular, square blocky patterns throughout an image -- when shooting at the camera's highest quality level.
Conclusion
As discussed in the first installment of "Framed and Exposed," most modern digital cameras yield very good images. There are differences, and some might be more to your taste than others, but the good news is that your image evaluations should not be too trying, because you're probably going to see nice results from most cameras.
When considering the image quality issues discussed here, remember to factor in price. Yes, you may not be seeing images that are as good as what your friend gets from his $1,500 digital SLR, but if you're only aiming to spend $500, then you should expect to take a hit in image quality. For this reason, when comparing image quality, be sure to compare comparable cameras. Don't get hung up on how your candidate cameras compare to models that you can't afford.
http://www.creativepro.com/story/feature/21955.html
Framed and Exposed: Buying a Digital Camera, Part 4
The essential features to consider when buying a digital camera have been covered in previous columns. Now it's time for bells and whistles. Options like adjustable ISOs, in-camera histograms, and panoramic exposures can make your digital photography experience more fulfilling.
(creativepro.com)
By Ben Long, creativepro.com senior editor
Tuesday, August 31, 2004
View More In:
Systems & Hardware
Related Features:
Framed and Exposed: Making Sense of Camera Sensors
Related How-Tos:
Framed and Exposed: Buying a Digital Camera, Part 3
Framed and Exposed: Buying a Digital Camera, Part 2
Framed and Exposed: Buying a Digital Camera, Part 1
Related News:
Casio Announces World's Smallest Optical Zoom Digital Camera
Canon's Next "G"eneration PowerShot G6 Digital Camera Merges Advanced DSLR Functionality with Compact Portability
Nikon Announces Rebates of Up to $200 on Selected Award-Winning Coolpix Digital Cameras
Kodak Raises the Bar with its New EasyShare DX7590 Digital Camera
Fujifilm Unveils Versatile New Digital Camera Line
Be the first to tell us what you think.
Respond to this article
"Buying a Digital Camera, Part FOUR?!" Okay, so this may not exactly be your handy pocket guide to buying a digital camera, but the fact is that there are a lot of decisions involved in choosing a camera. This stems partly from the fact that, unlike with a film camera, you have to consider the quality of the images that a digital camera produces (with a film camera, a lot of that concern comes later, with film choice). But digital-camera choice is also complicated by the fact that digital cameras afford a much greater diversity of features and designs than do their film counterparts. So far, we've covered the primary issues of camera size, image-sensor characteristics, lens quality, exposure control, and the other factors that directly affect final image quality and camera usability.
Over the next two columns, we're gonna take a look at the extra, utilitarian features that you'll want to consider when making your choice. After that, we'll have one final column on assessing image quality, which will mark your final camera-buying decisions. (Yes, for those of you keeping tabs, that's a total of SIX columns about buying a digital camera. You'll have to trust me on this.)
If you've been shooting with a manual, or semi-automatic film camera, then a lot of the features we're going to look at here might seem like silly luxuries. But in almost every case, once you've spent a little time with them (gotten a little exposure, so to speak), you'll begin to realize that these features really do make you a more productive photographer.
ISO and Histogram
We've already discussed the need to evaluate a camera's exposure controls, so you should have given some thought to how much manual override you think you need for the type of shooting you do. You should also have considered your candidate camera's specific controls, with an eye toward evaluating priority modes, manual modes, and access to shutter speed and aperture settings. Digital cameras, though, offer an extra exposure control that film cameras don't have.
When the raw information is read off of a digital image sensor, it's passed through an amplifier before heading on to be analyzed and processed. Data can be amplified to varying degrees and, obviously, if you amplify the signal more, you won't need as much light to make a legible image. To gauge and measure the image sensor's sensitivity to light, digital camera manufacturers have adopted the same ISO scale that film manufacturers use. (If you're new to photography, higher ISO numbers mean more light sensitivity, which means you can shoot with a shorter exposure. This affords different creative options, as well as the ability to shoot in lower light.)
Most cameras these days default to a sensitivity that's somewhere between 80 and 120 ISO. What's more, most cameras also offer adjustable ISOs. That is, they can use more amplification to make their image sensors more sensitive. This means that many cameras these days offer a choice of ISOs, usually 100, 200, and 400.
With a film camera, when you pick a particular film speed, you're stuck with it for the entire roll. When shooting digitally, you can change the ISO for every frame, making it a third exposure parameter, in addition to shutter speed and aperture.
There is a price to pay for this flexibility, of course. As with any signal, when you amplify the data coming off of an image sensor, you also amplify any resident noise. This noise can be caused by the electronics in the camera or even just the stray cosmic ray. As such, higher ISOs produce noisier images than lower ISOs. Oftentimes, this noise looks just like the grain in a piece of film. However, some cameras produce noise that isn't so attractive.
Evaluating the ISO features of a camera is pretty simple. First, make sure it has adjustable ISOs (this is such a handy feature that there's really no reason not to consider it a must-have item) and take note of the range. For example, some cameras can go slower than 100, offering a super noise-free ISO 50, while others can go much higher than 400, pushing their ISOs up to 3200. As with other features, make sure the ISO control is easy to get to while shooting. Just as you want quick access to shutter speed and aperture settings, ISO control should be a fingertip feature.
Most importantly, though, you'll want to judge the quality of the camera's faster ISO's. We'll be discussing image detail at length in our next installment, and will cover the specifics of evaluating high ISO quality.
A histogram is a bar graph of the distribution of tones in an image. As you'll learn in future columns, a histogram is an indispensable tool both for shooting and editing. When shooting, a histogram makes it possible to see if you've over- or under-exposed an image -- something you usually can't tell from an LCD screen -- and makes it possible to gauge whether you're capturing the maximum dynamic range
Many cameras these days offer a histogram feature that allows you to view a histogram of any image you've shot. If you plan on doing any shooting more complex than simple snapshots, then a histogram feature is a must-have. If you've opted for a camera with any type of manual control, it's stilly not to look for a camera with a histogram.
When evaluating histogram features, look for a clear, easy-to-read histogram that highlights over- or under-exposed areas.
Some cameras now offer a Live Histogram feature that displays a histogram on the camera's LCD in real-time. A Live Histogram lets you immediately see the effects of exposure adjustments while you're shooting. Though it doesn't provide any extra functionality, it does save you the trouble of having to shoot and then review to evaluate an image's histogram.
Exposure Locks and Panorama Controls
Every time you press the shutter button on an automatic camera, the camera's light meter analyzes the scene and calculates an appropriate exposure. While this is a great convenience and a tremendous time-saver, there will be times you won't want the camera to meter off of the scene that it's looking at.
For example, when shooting a multi-shot panorama -- a series of images that will later be digitally stitched together to create a single, large image -- you usually don't want the camera to re-meter for each shot, as this will create an uneven exposure across your final composite.
With an exposure-lock feature, you can lock the camera at its last metering, allowing you to re-frame and shoot additional images. In addition to facilitating panoramic shooting, an exposure lock effectively allows you to separate the camera's auto-focus mechanism from its auto-metering, meaning you can meter and focus on different areas.
Some cameras include special panoramic shooting features that, in addition to locking exposure, provide guidelines on the camera's LCD that help ensure your images overlap properly in preparation for a good panoramic-stitching operation later.
If you plan on shooting panoramas, these are important features to have. An exposure lock is handy for more everyday shooting features as well, but if your camera offers multiple focus spots and several metering modes, an exposure lock won't be as critical.
Today, many cameras offer a choice of color spaces. Though most cameras default to sRGB, many offer the option of the Adobe RGB color space as well. If you've got an existing color-management workflow built around a particular color space, having a choice of spaces on your camera will make things easier.
To further refine your color controls, you might want to look for a camera that offers white-balance fine-tuning. (We discussed white-balance controls in part two of this feature.) A fine-tuning option lets you tweak the camera's pre-set white-balance options to achieve more realistic color.
Finally, if image and color quality are your ultimate concern, you'll want to get a camera that provides support for Raw files. When shooting in Raw mode, the camera stores the raw, unprocessed data that comes off of the camera's image sensor. Raw files offer the greatest image quality and image processing flexibility, and we'll be discussing them in more detail in future columns.
Once you've selected amongst these features, you're ready to take a more thorough look at the camera's design, performance, viewfinder, and some extra, possibly sillier features. We'll be taking a closer look at all of those options in our next installment.
http://www.creativepro.com/story/feature/21837.html
(creativepro.com)
By Ben Long, creativepro.com senior editor
Tuesday, August 31, 2004
View More In:
Systems & Hardware
Related Features:
Framed and Exposed: Making Sense of Camera Sensors
Related How-Tos:
Framed and Exposed: Buying a Digital Camera, Part 3
Framed and Exposed: Buying a Digital Camera, Part 2
Framed and Exposed: Buying a Digital Camera, Part 1
Related News:
Casio Announces World's Smallest Optical Zoom Digital Camera
Canon's Next "G"eneration PowerShot G6 Digital Camera Merges Advanced DSLR Functionality with Compact Portability
Nikon Announces Rebates of Up to $200 on Selected Award-Winning Coolpix Digital Cameras
Kodak Raises the Bar with its New EasyShare DX7590 Digital Camera
Fujifilm Unveils Versatile New Digital Camera Line
Be the first to tell us what you think.
Respond to this article
"Buying a Digital Camera, Part FOUR?!" Okay, so this may not exactly be your handy pocket guide to buying a digital camera, but the fact is that there are a lot of decisions involved in choosing a camera. This stems partly from the fact that, unlike with a film camera, you have to consider the quality of the images that a digital camera produces (with a film camera, a lot of that concern comes later, with film choice). But digital-camera choice is also complicated by the fact that digital cameras afford a much greater diversity of features and designs than do their film counterparts. So far, we've covered the primary issues of camera size, image-sensor characteristics, lens quality, exposure control, and the other factors that directly affect final image quality and camera usability.
Over the next two columns, we're gonna take a look at the extra, utilitarian features that you'll want to consider when making your choice. After that, we'll have one final column on assessing image quality, which will mark your final camera-buying decisions. (Yes, for those of you keeping tabs, that's a total of SIX columns about buying a digital camera. You'll have to trust me on this.)
If you've been shooting with a manual, or semi-automatic film camera, then a lot of the features we're going to look at here might seem like silly luxuries. But in almost every case, once you've spent a little time with them (gotten a little exposure, so to speak), you'll begin to realize that these features really do make you a more productive photographer.
ISO and Histogram
We've already discussed the need to evaluate a camera's exposure controls, so you should have given some thought to how much manual override you think you need for the type of shooting you do. You should also have considered your candidate camera's specific controls, with an eye toward evaluating priority modes, manual modes, and access to shutter speed and aperture settings. Digital cameras, though, offer an extra exposure control that film cameras don't have.
When the raw information is read off of a digital image sensor, it's passed through an amplifier before heading on to be analyzed and processed. Data can be amplified to varying degrees and, obviously, if you amplify the signal more, you won't need as much light to make a legible image. To gauge and measure the image sensor's sensitivity to light, digital camera manufacturers have adopted the same ISO scale that film manufacturers use. (If you're new to photography, higher ISO numbers mean more light sensitivity, which means you can shoot with a shorter exposure. This affords different creative options, as well as the ability to shoot in lower light.)
Most cameras these days default to a sensitivity that's somewhere between 80 and 120 ISO. What's more, most cameras also offer adjustable ISOs. That is, they can use more amplification to make their image sensors more sensitive. This means that many cameras these days offer a choice of ISOs, usually 100, 200, and 400.
With a film camera, when you pick a particular film speed, you're stuck with it for the entire roll. When shooting digitally, you can change the ISO for every frame, making it a third exposure parameter, in addition to shutter speed and aperture.
There is a price to pay for this flexibility, of course. As with any signal, when you amplify the data coming off of an image sensor, you also amplify any resident noise. This noise can be caused by the electronics in the camera or even just the stray cosmic ray. As such, higher ISOs produce noisier images than lower ISOs. Oftentimes, this noise looks just like the grain in a piece of film. However, some cameras produce noise that isn't so attractive.
Evaluating the ISO features of a camera is pretty simple. First, make sure it has adjustable ISOs (this is such a handy feature that there's really no reason not to consider it a must-have item) and take note of the range. For example, some cameras can go slower than 100, offering a super noise-free ISO 50, while others can go much higher than 400, pushing their ISOs up to 3200. As with other features, make sure the ISO control is easy to get to while shooting. Just as you want quick access to shutter speed and aperture settings, ISO control should be a fingertip feature.
Most importantly, though, you'll want to judge the quality of the camera's faster ISO's. We'll be discussing image detail at length in our next installment, and will cover the specifics of evaluating high ISO quality.
A histogram is a bar graph of the distribution of tones in an image. As you'll learn in future columns, a histogram is an indispensable tool both for shooting and editing. When shooting, a histogram makes it possible to see if you've over- or under-exposed an image -- something you usually can't tell from an LCD screen -- and makes it possible to gauge whether you're capturing the maximum dynamic range
Many cameras these days offer a histogram feature that allows you to view a histogram of any image you've shot. If you plan on doing any shooting more complex than simple snapshots, then a histogram feature is a must-have. If you've opted for a camera with any type of manual control, it's stilly not to look for a camera with a histogram.
When evaluating histogram features, look for a clear, easy-to-read histogram that highlights over- or under-exposed areas.
Some cameras now offer a Live Histogram feature that displays a histogram on the camera's LCD in real-time. A Live Histogram lets you immediately see the effects of exposure adjustments while you're shooting. Though it doesn't provide any extra functionality, it does save you the trouble of having to shoot and then review to evaluate an image's histogram.
Exposure Locks and Panorama Controls
Every time you press the shutter button on an automatic camera, the camera's light meter analyzes the scene and calculates an appropriate exposure. While this is a great convenience and a tremendous time-saver, there will be times you won't want the camera to meter off of the scene that it's looking at.
For example, when shooting a multi-shot panorama -- a series of images that will later be digitally stitched together to create a single, large image -- you usually don't want the camera to re-meter for each shot, as this will create an uneven exposure across your final composite.
With an exposure-lock feature, you can lock the camera at its last metering, allowing you to re-frame and shoot additional images. In addition to facilitating panoramic shooting, an exposure lock effectively allows you to separate the camera's auto-focus mechanism from its auto-metering, meaning you can meter and focus on different areas.
Some cameras include special panoramic shooting features that, in addition to locking exposure, provide guidelines on the camera's LCD that help ensure your images overlap properly in preparation for a good panoramic-stitching operation later.
If you plan on shooting panoramas, these are important features to have. An exposure lock is handy for more everyday shooting features as well, but if your camera offers multiple focus spots and several metering modes, an exposure lock won't be as critical.
Today, many cameras offer a choice of color spaces. Though most cameras default to sRGB, many offer the option of the Adobe RGB color space as well. If you've got an existing color-management workflow built around a particular color space, having a choice of spaces on your camera will make things easier.
To further refine your color controls, you might want to look for a camera that offers white-balance fine-tuning. (We discussed white-balance controls in part two of this feature.) A fine-tuning option lets you tweak the camera's pre-set white-balance options to achieve more realistic color.
Finally, if image and color quality are your ultimate concern, you'll want to get a camera that provides support for Raw files. When shooting in Raw mode, the camera stores the raw, unprocessed data that comes off of the camera's image sensor. Raw files offer the greatest image quality and image processing flexibility, and we'll be discussing them in more detail in future columns.
Once you've selected amongst these features, you're ready to take a more thorough look at the camera's design, performance, viewfinder, and some extra, possibly sillier features. We'll be taking a closer look at all of those options in our next installment.
http://www.creativepro.com/story/feature/21837.html
Subscribe to:
Posts (Atom)