Originally posted by godwine I am sure there were plenty of debate on this, but which one is better in what way?
I was told that:
Pentax: Sharpest image
Nikon: Balance in speed and image quality
Canon: Fastest
Is this true? What do you think?
What you were told was nonsense.
First of all, an SLR is a "system" consisting of camera bodies, lenses, and accessories like flashes, extension tubes, etc. Within each system made by each manufacturer there are a variety of parts. Some are inexpensive and intended for the "consumer" market. Some are expensive and intended for the professional market. And some are in-between and intended for advanced amateur hobbyists. Within each category, performance may vary between poor performing duds to top performers. But, for the most part, performance is pretty good for the consumer parts and outstanding for the expensive "pro-grade" parts. Any generalization as to how each brand performs is pretty much impossible.
Second, what system is "best" depends on job for which the tool is intended to be used. Let's say you want to take family snapshots, vacation pictures, and occasional portraits of the kids. You intend to get a entry level 6-10 MPixel body, the wide angle to short telephoto kit lens, and use the on-camera flash. You may add a consumer grade mid to long telephoto zoom lens. In this case, I would say that the offerings from Canon, Nikon, Pentax (and Olympus) would all serve you equally well. Any differences in image quality and operation would be minor at best. Yes, there are some differences in features and performance, but overall the major brands are very similar in performance in this very competitive market segment. Your skills in picture taking and post-processing will make much more of a difference than the the brand of equipment.
Third, if you have other specific interests in photography that will require specialized equipment, then there may be some significant differences in brands. If I needed long, fast lenses for sports-action photography, then I would want to go with Canon for their superior selection of long lenses, high frame rates (in the professional bodies) and fast auto-focus performance. For serious macro photography, I might go with Nikon for their excellent macro lenses and their unique close-up flash system. Pentax makes some outstanding lenses, including some of the best ultra-wides for DSLRs (the DA 14mm and the DA 12-24mm) and the Limited prime lenses. There are also some very fine lenses available for the Olympus 4/3 system, such as the only telephoto zoom with a constant f2 maximum aperture. So for certain applications, there are definite differences between the manufacturers.