Price while obvious and not really a feature, it is worth mentioning for two reasons. First, it differentiates the cameras in this segment. Second, it is a significant investment.
With respect to the first point, many of the features listed here are available on many or all SLRs to some degree. However, realize that a $5,000 camera and a $1,000 camera cannot be compared head to head. The main reason is not the sensor. It is a range of details that come into play. Amongst those is build quality, convenience features, and performance/speed.
On the second point, since the price is high, it is not common for people to change dSLR cameras yearly. Your decision is one you will work with for some time. Spending a little time reading this can help.
Sensor Megapixels: This is the single most commonly quoted spec in a digital camera is the megapixel (MP) count. Unfortunately, because of the gross numbers involved (millions) much more is made of it than there should be. Surely you've heard it, "this camera has 2 million more pixels than that camera." If it were dollars we were talking about, fine, but in a digital image, it's just dots. In reality, when printed, the image from a 6MP camera is almost indistinguishable from that of an 8MP camera. The latter is only 10 to 12% larger on each side when printed. If you crop the image, for example to 8x10 or 5x7, you lose that. If you print on 8x10 or smaller, it makes no difference at all. It suffices to say that, in a given price range, today, the sensors from all dSLRs are about on par with one another.
Sensor Type: Sensors are available in two types today. CCD & CMOS. They are basically two different ways to make a photo sensitive digital device. Neither is clearly superior to the other. Each claims advantages over the other. The fact remains that both are widely used in today's digital market and both can meet the needs and demands of any digital photographer.
Sensor Size: Here we refer to the physical dimensions of the sensor and how it compares to the 35mm frame size. All dSLRs with the exception of two (as of 12/2005) use sensors that are smaller than a 35mm frame. Most of these have crop factors of 1.5x or 1.6x and some have a crop factor of 2x. Now that this has been mentioned, we should clear up a common misconception. The crop factor is sometimes referred to as a "lens multiplier" or a "focal length conversion". Regardless of the name, the smaller sensor does not change or add to the focal length of a lens. That is a physical characteristic of the lens. What is actually happening is that the sensor, since it is smaller than a 35mm frame, is cropping or ignoring the image edges that the lens produces. This makes it "seem" like a longer lens. Realize, however, that while this may be neat for the long lenses it is a problem for the wide angle lens. For more details on this, feel free to search the forums as it is beyond the scope of the article. So again here, all cameras in the sub $3,000 price range (as of 12/2005) have a crop factor and they are about equal.
ISO Sensitivity Range: The sensitivity of a digital sensor has been equated to the sensitivity ratings of film. This is actually quite good as it is a preset standard and it is something many are familiar with already. The International Organization for Standardization or as it is more commonly known, ISO, sets all sorts of international standards. The acronym "ISO" is derived from the Greek "Isos" or "equal". It is not an acronym for the name. As you can imagine, each country, based on language, would have a different acronym. So in the interest of "standardization" we get ISO as the worldwide acronym. ISO sets standards for photography in the film sensitivity area. The range of sensitivity that the camera can handle gives you an idea of the ability of the sensor to work in differing light. Most cameras have a good range. They start at ISO 100 or 200 and range up to ISO 1600 or higher. In general the lower the ISO rating the less noise (equivalent of film grain) you get in the image. The reality is that today's bodies have noise almost non-existent at or below ISO 400. All dSLRs start below ISO 400. The other side is the maximum. Again the higher the maximum the better, but in reality, most photographers rarely use ISO 1600 because the digital noise is obvious. However, to be fair, ISO 1600 film is also quite grainy. So, in short, most dSLRs have ample ISO range for the vast majority of photographers.
Image stabilization: While only one dSLR has image stabilization (IS) functionality built into the camera itself (as of 12/2005), it is worth mentioning. All other manufacturers put the IS capability into specific lenses. Image stabilization is a system that helps eliminate the problems associated with camera shake. This basically allows you to take pictures at slower shutter speeds and still get sharp results. This is helps a great deal with ambient light photography when not using a flash. Each manufacturer has its trademark name for IS, but the end result is similar, sharper pictures.
White Balance: All light has some color tonality to it and is categorized using a Kelvin (K) temperature scale. For example, sunlight has a different color tone than does florescent bulbs. Your eyes can adjust for the variations in the color of the light sources around you so that white is neutral, ie no color cast. Your camera cannot do this. That is where White Balance (WB) comes in. By setting the WB according to the light source, you can eliminate any color cast in your images. Most digital cameras today give you certain presets. Tungsten (common light bulb), florescent, sunlight and shade are common ones. Some cameras allow you to set a WB preset using a white subject or reference. Other cameras have the ability to set the K temperature to any K temperature value. Either one of these options gives you ultimate control and allows you to get accurate color in almost any light. To sum it up, common WB settings (sunlight, cloudy, shade, incandescent, etc) is good. Preset white balance using a reference, is better. Ability to select specific K WB temperatures is even better.
Minimum and Maximum Shutter Speeds: This refers to the fastest (shortest time) and slowest (longest time) shutter speeds the camera (or more precisely the shutter mechanism) can attain. These speeds are actually fractions of a second. So when you see 500 on the display it is referring to 1/500s. When looking at the maximum, the faster the shutter speed the better. The faster the shutter, the more likely you are to freeze any motion. However, in practice, one will rarely need anything near the maximum most dSLRs have today which is 1/4000s. In fact, you will find that in most cases you will usually be below 1/1000 or 1/2000 s. When looking at the minimum you will see full second amounts. In most cases it will be 30s followed by the term "bulb". The bulb setting is one that allows the photographer to shoot with exposures of any length. So long as the shutter release is held down, the camera will leave the shutter open. This is something that is used, most commonly, for night photography.
Built-in Flash: Most photographers, regardless of ability, are familiar with the idea behind the flash. A built in flash is very convenient. What many may not be aware of is how to differentiate one from another. The Guide Number (GN) for electronic flash defines its strength. This number allows you to calculate the maximum distance, for a given ISO sensitivity, that a flash can expose correctly. This GN is divided by the f-stop to get the distance. For example, if the GN is 80ft at ISO 100 then, at f/4, then the maximum distance you can be from the subject to properly illuminate it is 20ft. If you shot at f/10 it would be 8ft. If you take a great deal of photos that will require flash, and you do not plan on or like carrying a dedicated flash unit, then a built in flash is key. The higher the GN for the flash the better. However, be careful because not all GNs are equal. If the ISO quoted is not the same between two specifications then you need to apply some conversion. When the ISO sensitivity doubles, the GN changes by a factor of, approximately, 1.4. When the ISO is cut in half, the guide number changes by a factor of, approximately 0.7. For example, a GN of 100ft at ISO 100 is equal to a GN of 140ft at ISO 200 or a GN of 196ft at ISO 400.
External flash & Flash Sync: All dSLRs today have a hot shoe for mounting external or dedicated flash units. This typically sits above the lens on top of the viewfinder. These dedicated flash units vary in power and capability, but that is independent of the camera body. What is important is the maximum flash sync speed. Without getting into a huge amount of detail, this is the maximum shutter speed the camera can use that will permit synchronization with the flash unit. If you go above that speed, you run the risk of have one section of the frame darker than the others. With this, the higher the sync speed, the better. A good speed now is 1/180s and better would be 1/250s. Be aware, however, that some manufacturers say that there is no maximum, in other words it will sync at all speeds. This is usually only true when using their proprietary, current, flash technology. However, you should still consider the flash sync speed posted in the specs. One benefit to higher speeds is the better flexibility when using the flash as a fill light. This is done to lessen harsh shadows, for example. The faster the sync speed, the more useful the flash can be in fill situations when used outdoors. Another benefit is when shooting using other flash systems like studio flash units. The higher the shutter speed limit, the better you ability to lessen motion blur. This is particularly helpful when photographing children.
Depth of Field Preview: This is a feature most dSLRs have today. Few people use it. It is useful for letting you preview how the photo will look using the lens settings in place when you shoot the photo. When you press a button, the lens aperture is set to what it will be to take the photo. It will change the Depth of Field (DoF) you see in the viewfinder. Well some may ask doesn't the camera let you see this anyway? Isn't that the whole point of an SLR? Well yes and no. Yes the camera uses the actual photo lens to display the image in the viewfinder but it does it at the maximum aperture of the lens. That is done to keep the viewfinder as bright as possible which will aid in focusing and composition. The camera will shoot at the aperture that you or the camera determines to be necessary. The DoF button simply lets you check that the DoF is good by setting the lens' aperture to what it will be when you take the photo. With this, be certain the DoF preview is someplace that is comfortable for you to use. It is a really useful tool, when used.
Exposure modes: There are four common exposure modes most dSLRs have. They are Aperture priority, Shutter priority, Automatic and Manual modes. In the first three the camera's meter determines the proper exposure. How it is applied varies. In Aperture Priority mode, the photographer set the aperture they desire. The camera then sets the shutter speed to get the right exposure. In Shutter Priority mode, the photographer sets the shutter speed and the camera, in turn sets the aperture. In Automatic (Program) mode, the camera sets both shutter and aperture. The last mode, Manual, the photographer determines both shutter and aperture. In addition to these basic modes, there are certain options that some cameras have. They are quite helpful, particularly to beginning photographers. These typically include a Portraiture, Landscape, Sports and Macro mode. Some go into others like Night and/or indoor modes. What these do is basically "bias" the camera settings to get certain results. For example, Sports mode will keep the shutter speed as high as possible to freeze action. The Landscape mode will keep the aperture small (large number) to get more of the image in sharp focus. Eventually, if you have the inclination, you will likely bypass these, however, for casual quick shots where you do not want to set up a great deal these preset modes help a great deal.
Storage types: Compact Flash (CF) or Secure Digital (SD) are the two memory cards commonly in use today. For the most part, there is little difference in performance. The big difference right now seems to be capacity. The CF cards come in capacities as high as 8GB while SD cards max out at about 1GB. While this is a huge difference, most casual photographers will rarely use 1GB cards at this time. To give you an idea a 1GB card will fit over 350 8MP JPG images. This number of shots will likely more than enough for most. On the other hand, SD cards are smaller. The size difference is not really a big deal to most because most already feel CF cards are small enough.
Viewfinder Specs: These specs seem confusing and meaningless but should be looked at. Magnification, Eyepoint and Coverage are the three numbers you tend to see. Coverage is the percentage of the image that will be captured by the sensor visible in the viewfinder. In most dSLRs this is less than 100%. Again, most people ask "wasn't that the point of an SLR?" Yes but a 100% viewfinder is expensive to make. Hence they are usually found only in the top of the line cameras. The higher the coverage the easier it is to compose precisely. Magnification is how large the image in the viewfinder is when compared to the naked eye. This varies with the lens on the camera, however, most specs are based on using a 50mm lens. This is usually a number smaller than one. A 1x magnification would mean that the image in the viewfinder was just like looking at it with the naked eye. Again, here the higher the better, however, larger magnifications typically mean smaller coverage. The last is eyepoint. This is most critical for photographers with glasses. This refers to how far you can hold the camera from your eye and still see the whole images a data in the viewfinder. Here again, the larger the better. In general, the order of importance should be Coverage then Magnification and, lastly, Eyepoint. The only exception to this is with glasses. With those, Eyepoint becomes more important.
Viewfinder Information: This is the information displayed to the photographer when looking through the viewfinder. It is an important option to have and something that is easy for you to see and understand. Minimally you should see the following for the photo you are composing. Exposure Mode indicator, Focus Indicator, Shutter Speed, Aperture, Shot count or countdown, some sort of exposure meter, ISO sensitivity and a Flash Ready indicator. How the different manufacturers displays this will vary but they all include this. Some include some additional information. Ultimately how this is displayed is a matter of taste but make certain it is easy for you to understand or see.
LCD Size: Much is made about the size of the LCD on digital cameras. Don't get me wrong, having a good sized LCD is nice, but it is for reasons most don't consider. The biggest myth, "a bigger screen gives you better previews". I can't tell you how misleading this is. Even a 2.5" LCD is worthless as a display device to determine more than the most basic composition and the most obvious focus problems. The displays are simply not precise enough. The display on a dSLR is used to quickly review images for composition and basic lighting issues. For example, did you get everything in the shot? Are the shadows too strong? Was the subject completely blurred because of motion? etc. Another common use is to review the Histogram. This is simply a graph showing how the brightness of image is distributed. The last use is to set menu options or to perform common tasks like formatting cards etc. With all of these a larger display makes life easier.
USB and/or Firewire (IEEE 1394) ports: These are ports used to connect your camera to a computer or other device. The most common today is the USB port. The main issue to consider here is speed. USB has various standards and today's USB 2.0 is the faster option. If your computer has a USB 2.0 port, then this is something you can look for. Having said that, today, more and more users tend to have dedicated memory card readers on their computers. This makes the likelihood of connecting your camera to the computer smaller and thus USB connections on the cameras less necessary.
Metering Options: This refers to the most common metering methods. These are spot, center weighted and complete frame metering. Spot metering is the most precise of the options. In essence it determines exposure based on a spot you decide. This is usually less than 3% of the frame. Center weighted is the next most precise. It determines exposure by paying more attention to the center of the frame vs. the rest of the composition. The idea being your subject is there. The most general method is complete frame. This method takes the entire frame into account and determines exposure based on a set parameters. The last option has different names given to it by manufacturers but, ultimately, it is simply full frame metering.
Battery Type: This, today has come down to two options. They use Nickel Metal Hydride (NiMH) or Lithium Ion batteries. Currently most use the lithium cells. The big advantage is battery power and size. Lithium Ion batteries can be smaller and can accommodate high capacities. The downside to them is price. Lithium Ion batteries are more expensive which sometimes can be pricey if you plan on having second or third batteries.
Build: The build refers to how the body feels. Rigidity and balance are important. Better builds will take more every day use than lower quality builds. While weight is important for some users, realize this may come at the cost of sturdiness.
Dimensions & Weight: This is something that can come into play but has more to do with personal taste. For example, lighter bodies are great to carry but will feel awkward when you put a longer, heavier lens on the camera. Another example is dimensions. A larger camera body might be more comfortable for people with larger hands while a physically smaller package might be easier to handle for smaller hands. It is something to consider, however, the point is smaller and lighter is not always better.
AF System: This varies with each manufacturer. Many times you hear people refer to focus speed and this or that manufacturer having the fastest AF speed. Any AF system is good in the hands of a person that knows how to use his/her system. What differences may be important are focus sensor positions, number of sensors and AF options.
Image Formats: Three types of image formats have become mainstream in digital photography. Two of those are industry/computer standards. JPG (pronounced jay-peg) and TIFF are those two. The last is an image format that is proprietary to each manufacturer and those are RAW files. The two most common today in dSLRs are JPG and RAW. JPG files are compressed photographic files that are ready to go right out of the camera. They are "processed", so to say, by the camera. RAW files need to be translated first into something the PC can manipulate and then it is ready for output. In short, you process the RAW files. I feel most photographers are just fine working with JPG files. However many want the creative latitude offered by RAW files. Unfortunately this discussion is beyond the scope of this article. For the purposes of a camera choice, all dSLRs offer JPG and RAW files, so this will not be a decision point.
Ergonomics: This is a difficult on to cover but I mention it simply to bring it to your attention when purchasing a camera. With ergonomics I am referring to how easy the camera is to operate for you from a physical standpoint. For example, are the button sizes comfortable? Are the icons clear? Are the dials easy to access? Are the shooting parameters (aperture, shutter, ISO, etc.) easy to change? Are the buttons used to navigate menus comfortable? Is the grip comfortable? Is the shutter release in the right position? Unfortunately, in today's day and age, internet purchasing hampers the ability to "put your hands" on the camera so to say. So many times you have to rely on others. Ultimately, ask if that is your only option, however, if you can get your hands on a camera. Ultimately, this is something that you will be using for some time. The more comfortable it is, the more likely you are to use the camera.
Convenience Features: This is another commonly overlooked set of issues. With these I mean functionality that aids in the day-to-day use of the camera. For example, the histogram display which is a graphical representation of exposure. While all cameras have them they are displayed in different ways. Some are smaller than others, some are superimposed, etc. Some of the features that help in the day-to-day are: Automatic rotation of images that are shot vertically with the camera. The ability to zoom into the image on the LCD display is sometimes helpful to check focus. Custom setup storage to store common options help you by storing settings for differing conditions. LCD display of shooting data such as exposure settings helps you see what changes you can apply to get your desired effects. Highlight warning display tells you about potentially blown out highlights of the image.
Optional Accessories: I had to separate this out this way because options abound and it would be impractical to cover every single one. There are a multitude of accessories out there for cameras. For the case of this discussion, I will not consider a lens an accessory. What I will include are things like, battery expansion & vertical grip units, AC Adapters for the camera, remote control units and viewfinder accessories. Of course there are many others. These all provide advantages and more usability, however, some are quite pricey. Do some research, see if these options exist. Are they something you might use? For example, and battery expansion pack option allows for adding a second battery to the camera so as to extend battery life. In some cases they add a vertical shutter release. If you go to places where a second battery would help and you have limited access to power, this may be critical. You may want a vertical shutter release. In short, look into these options as well when making your decision.
About the Author:
Luis Valladares, operates a professional portrait studio out of the Miami Florida area. A member of the National Association of Professional photographers, Luis enjoys sharing his photographic knowledge with others.
