The following comments and observations are derived from my experience with the original Canon Digital Rebel SLR, and the Canon Rebel XSi. And considerable research that I have done. Some of the comments and observations are from my experience with the Canon cameras, but much of the information pertains to digital SLR's in general. The information presented here is as of mid-2008, and will hopefully change as dSLR design evolves.
dSLR design
In case you are unfamiliar with SLR camera design, versus point &
shoot camera design, you should know that there are some very different concepts
and mechanisms involved with SLR cameras, some of which handicap a SLR
camera's ability to perform as well as a P&S camera in some respects.
Unlike P&S cameras, SLR cameras incorporate a pair of mirrors which allow you to look directly through the main camera lens when you look through the view finder. This is good for more than one reason, but it also presents a technological challenge that doesn't exist with P&S cameras because the sensor(s) used to determine exposure, white balance, and auto-focus, sit behind the main SLR mirror. The main SLR mirror is raised to capture the image when the shutter is opened, but since the sensor(s) used for those three functions remains behind the main SLR mirror the rest of the time; this limits the ability of a SLR to perform those three functions, compared to P&S cameras which do not have the SLR mirror blocking the sensor(s) used for these functions.
How does this effect picture taking capabilities?
Since the sensor(s) used for exposure, white balance, and auto-focus, sit
behind the main SLR mirror, the sensor(s) are not able to operate as freely as
they can on their P&S counterparts. This has the following effects:
Exposure: This is the least significant problem, and the easiest to correct. If you end up with one of the dSLR's that over or under exposes significantly (usually under exposes), you can correct this by dialing in a little exposure compensation, BUT - you often cannot do this while shooting in automatic mode, and if you are getting into a dSLR with the idea that you want to shoot in auto mode until you learn to control the camera yourself, your photos will not not be exposed correctly (usually dark/under exposed), when you shoot in automatic mode.
White Balance: This is a more obnoxious problem that's not as easy to correct as exposure, and almost ALL dSLR's suffer from some level of white balance inadequacy. In case you are unfamiliar with white balance, and without going into a detailed description of it, just realize that it can cause a overall color shift in pictures, and if it's not correct it will make your pictures look bad, to very bad. dSLR's have improved in this area significantly, but they still often have problems with mixed lighting, like incandescent and fluorescent light in the same room. Or any kind of artificial light mixed with some sunlight.White balance can be most effectively and easily corrected by shooting in "RAW" mode and correcting the white balance when you convert the RAW images to JPEG's, or optionally TIFF's. But once again, if you are getting into a dSLR with the idea that you want to shoot in auto mode until you learn to control the camera yourself, you're screwed if your camera is significantly white balance challenged.
Auto-focus - The biggest problem. With the SLR mirror blocking the auto-focus sensor, most dSLR's utilize a totally different auto-focus algorithm than that which is used on P&S cameras. P&S's use contrast auto-focus, and dSLR's use phase detection auto-focus. Auto-focus is generally more reliable on P&S cameras..... This is the biggest problem because of the following;
| Using manual focus to compensate for poor auto-focus is a joke. Manual focus is very often impractical, and many many times it's totally impossible. Imagine trying to focus manually while photographing your child or pet.... |
| Unlike poor exposure or poor white balance, there's not much you can do to correct a shot that's OOF (Out Of Focus). The only way to help OOF shots is to use "sharpening", which only helps so much. A shot that is too far OOF is trash. |
| Since dSLR's have inherently much less Depth of Field than P&S cameras, a shot that is only slightly OOF can easily be unusable because nothing of interest in the shot is in focus. And it's not easy to obtain a reasonably wide depth of field with a dSLR. |
Issues with the Canon Rebel series
Original "Digital Rebel": Poor, to extremely poor, white balance. Mine was extremely poor, and often even shooting RAW would not allow the pitiful white balance to be corrected.
Rebel XT: Widely known for poor auto focus.
Rebel XTi: Widely known for under exposure problems.
Rebel XSi: Wide reports of auto focus problems (sound familiar?)
Do you notice the pattern with the Rebel series? All of the issues are due to the "big three" dSLR handicaps.....
The internet if FULL of rude, arrogant, self righteous, know-it-all, professional-photographer-wannabe's with "little guy syndrome", who will tell you that if you have ANY problem with your dSLR, it's because you are an idiot and you don't know how to use the camera. Pour a shaker of salt on them, and realize that while dSLR's have a learning curve, they are also technologically challenged compared to their P&S counterparts, and those technological limits could very well be causing part of, if not the majority of, your problems. People now-a-days are used to utilizing relatively complicated devices, and SLR cameras are not rocket science, so difficulties that you might experience are not necessarily your fault.....
If you have used a 35mm SLR in the past, digital SLR's are a different story, because when you shot film, the photo lab "post processed" your images for you when they developed the film and made your prints. Images from dSLR's quite frequently need post processing, especially if your a newbie, and you're left to do that post processing yourself with a dSLR, with something like Photoshop or the like.
Do your homework before you purchase. If you are more concerned with "artsy fartsy" looking shots, a dSLR will do that better than a P&S. But if you're primarily interested in "capturing the moment" with sharp, well exposed photos, without undergoing a dual learning curve to learn to use a SLR, and how to overcome the weaknesses of a dSLR, get a good P&S camera.