This page will help you understand some of the jargon and technical definitions useful for digital SLR cameras . . . don’t worry . . . all the explanations are written in plain English and it’s not difficult to grasp . . .
Megapixels.
More megapixels means two things in practice . . . 1) you can print your photos larger (retaining the same clarity), and 2) you can crop to a smaller part of your photo without losing so much clarity.
But the downside is that the more megapixels, the larger the files size (assuming the same file format). This means that you will need larger memory, they will take longer to download, longer to send elsewhere etc. unless you reduce the megapixels using image-processing software. And of course the more megapixels, the more expensive the camera.
So, if all you want to do is to show photos to other people online, and/or print them out at 6 by 4 inches (standard photo print size) then you don’t actually need more than 2.0 Megapixels (unless you want to crop the photos).
So make sure you are aware of how this factor effects YOU, rather than just assuming that more is better.
ISO
Technically, the more ISO, the faster the sensor will absorb light. Which means in practice that the more the ISO, the easier it is to take photos in low light without a flash or tripod. The disadvantage is that increased ISO also adds more noise to the photo. Most digital cameras (including Canons and Nikons) have ways to reduce the noise, plus you can decrease the noise in more precise ways when you image-process your photos with software (such as Photoshop).
The term ISO applied in the same way to film cameras, so anyone familiar with the difference between using a film with an ISO of 100, and a film with an ISO of 400, can apply the same concepts to digital cameras, just by changing the settings.
So, again, think carefully how this applies to you personally, once you’ve defined what type(s) of photography you will be doing most (see later sections for much more on that).
Dust Control
Any time you change lenses on a digital SLR camera, dust can enter the camera and get on the sensor, and will then create small dark spots on all your photos. But, most new digital cameras have some form of dust-control system, which attempts to clean the dust automatically.
Additionally, it is possible to get the dust cleaned off by a qualified expert, or learn to clean it yourself (which of course has some risk), and also one can almost always correct the problem at the image processing stage (using Photoshop etc.).
So it you are going to be changing lenses a lot in dusty environments, then dust control is an important issue for you, otherwise it’s useful but not so important.
Image Stabilization
This feature is now offered in almost all Digital SLR Cameras, but different manufacturers do it differently and call it by different names . . .
Canon calls it “image stabilisation” (IS) and it works in the lens (only if you buy an IS lens).
Nikon calls it “vibration reduction” (VR) and it works in any VR lens.
Olympus, Pentax, Samsung and Sony call it “Sensor-Shift Stabilization”, “Shake Reduction”, “Shake Reduction”, and “Super Steady-Shot” respectively, and for all those manufacturers, it works in the camera (not the lens).
These systems attempt to reduce the motion of the camera, which is significant when you’re without a tripod in low-light or with a telephoto lens, or your hands shake. But none of the systems can help if the subject itself is moving.
If the system is in the lens, you can see the results through the viewfinder, but if it’s in the camera-body, you can’t. But on the other hand, if the system is in the camera-body, it works with any lens, where-as if it is in the lens itself, then it only works with certain lenses, which are more expensive.
Live View
This feature means that what you see on the LCD screen on the back of the camera, is “live”, ie. it is the same as what you see through the viewfinder. Which is useful if you’d rather look at the screen than look through the viewfinder, but has the disadvantage of slowing down the process of taking a photo, and requiring a separate button for auto-focus.
So, if you take photos mostly of still subjects, and would rather look at the screen than through the viewfinder, then Live-View is useful, but if you mostly take action photos (where the subject is moving), or if you don’t mind always looking through the viewfinder, then it’s not going to be of use to you.
Dynamic Range
Digital SLR cameras don’t yet have a dynamic range as wide as the human eye, which means that they can’t simultaneously capture the details in both very bright and very dark areas of the same photo, so either the highlights all appear pure white (with no detail) or the dark areas all appear pure black. However, there are now various systems which help to some degree with this problem.
Different manufacturers have different names for their dynamic-range-enhancement systems . . . Canon calls it “highlight tone priority”, and Nikon calls it “active D-lighting”.
This problem is more relevant where one is taking photos outside in bright sunlight, where there will be a wide dynamic range . . . so if you’re typically taking photos inside, then you don’t need dynamic-range-enhancement so much.
Also, a quick tip for compensating for the problem yourself . . . if highlights are overexposed, the data of the details is totally lost, and can’t be recovered, however, it the shadows are underexposed, even though they appear black, the data is still there and can be recovered (by careful use of processing with Photoshop).
Crop Factor
For most mid-priced Digital SLR cameras, the digital sensor is smaller than 35mm film. This means that if you use the same lens on a film SLR and a digital SLR, the photo will be cropped (you will lose the edges) on the digital SLR.
The crop factor can also be called “focal length multiplier”, “lens focal length conversion factor” or it could be described as one lens framing like a different lens.
For portrait, wildlife or macro photography, crop factor doesn’t really matter, but for landscape photography, it might be worth spending the extra money (about twice as much) for a Digital SLR which is “full-frame” which means its sensor is 35mm in size.
Autofocus
Autofocus systems on Digital SLR Cameras come with a variety of different numbers of focus points (from 1 to 11 or more), and are either one-shot or continuous.
The continuous system is much better for moving objects (such as action, animal or children photography) because it will continually try to keep the subject in focus, where-as one-shot will only focus once for each time you push the button half-way down.
Some autofocus systems light up the point which is being used to focus, which can be very helpful.
For landscape photography (or other mainly still subjects), one-point systems will be fine, or you can focus manually.
Continuous Drive
This feature lets you take several photos per second by holding down the shutter release button. Most Digital SLR’s now offer this feature, but the number of photos (sometimes called “frame”) per second varys.
The name of this feature is carried over from film cameras, where a “continuous drive” is actually a motor which move the film past the shutter instead of you having to do it manually.
Another factor is the “buffer” which stores photos temporarily while you use the continuous drive, instead of slowing down to process each one. This too can vary, and determines the number of photo’s you can take on the continuous drive setting, before the camera has to slow down.
So, if you are going to take a lot of action shots, then the continuous drive function can be very valuable, and it is worth spending extra money for more frames per second and a larger buffer. But if most of your subjects don’t move fast, then it is not something you need to be too concerned about.
File Formats: RAW and JPG
This is one of the most often dicussed topics in the digital SLR camera world. Sadly, there is a lot of mis-information out there, even from professional-looking websites. For example, I’ve seen it said tha JPGs only have 256 colors, or that they can’t be edited, or that their compression works by making similar colors the same, all of which are totally incorrect.
The good news is that most SLR digital cameras can store photos in either format, so this is one thing you don’t need to choose when buying a D-SLR . . . you just need to understand what it means when you use it!
JPG is a lossy compression format, which means that it approximates the images in your photos’ which makes the file-size smaller, but you lose details. Different JPG compressors have differing quality, so they are not all going to produce the same results.
RAW is a lossless compression format, so you keep all the original detail of your photo, but the file is a lot bigger, which means you need more memory for the same number of photos, but this format preserves all the original detail, which gives you more options and quality when editing.
You can shoot your photos using the RAW format, then import them into image-processing software (such as Photoshop), process them as much as you want, and then choose to compress them to JPG’s, with choice of different qualities. So in that sense, you can have the best of both worlds, the only thing you need more of is memory in your camera, if you are going to take a lot of shots between the times you download them to your computer.
If you some of your photos might be over or under-exposed when you shoot them, then using the RAW format will give you more chance to correct this at the editing stage.
Aspect Ratio
The sensor on any digital camera is rectangular, but of course, some rectangles are long and thin where as others are closer to a square.
The standard size of a photo print is 6 by 4 inches. So if you want to print most of your photos directly without doing any image-processing then buying a digital camera with an aspect-ratio of 3:2 makes most sense.
If you are going to do some image-processing on most of your photos, then if you plan to take a slightly wider shot than you would otherwise, aspect ratio is not going to be important, as you can crop the photos yourself to the aspect ratio you want to print at.