Originally Posted by
GrumpyDiver
Design is all about managing tradeoffs (by the way I am an engineer), and while I understand what you are trying to say, but cannot agree with a number of your assumptions and statements. The smaller format lenses are NOT sharper than the professional model full-frame lenses. They are in fact generally not as nearly as good; check out the lens test results at the DxO Optics website. They are however good enough. Sharpness is not the only measure of a lens; distortion, drop-off, aberrations, etc. all come into play as well; and the full-frame pro lenses beat the crop frame lenses on this front too. Over and above that, I also look the build quality of a lens; well it wear out quickly or will it last for a very long time. By the way, I am not saying that the lens makers could not make high quality crop frame lenses, it’s just that there is no reason for them to as there is no market for them.
I do agree that crop frame and 4/3 formats are legitimate engineering designs; what else could they be. That being said, smaller sensors = lower cost and that is the primary reason for their popularity. By the way I do own full-frame, crop frame and micro 4/3 equipment as well as high end film cameras. The cost of producing larger sensors has come down as manufacturing technology has advanced. The reason that smaller sensors were used in the past in pro cameras and continue to be used in consumer cameras was cost. Canon, Nikon and Sony all produce full-frame sensor cameras and lenses. Their doing so has nothing to do with PR issues; larger sensors allow you to produce larger, cleaner prints. This exactly the same reason as to why medium (and large) format cameras exist. In my view, this is far more important than the MP of the sensor.
Over and above this, a full-frame camera offers a few other advantages; larger viewfinder, about 1 stop better DoF (shallower), ultra-wide angle lens performance and as a rule tend to be more robustly built. They are of course larger, heavier and cost more, as a downside.
These are obviously not important to you, and so your choice in camera makes sense for you. It is not necessarily the right choice for everybody. The vast majority of people taking pictures use camera phones. Hasselblad and Phase 1 have a dedicated market niche as well, and I know a few folks out there that shoot large format film view cameras, and in their view (and I believe they are correct) that they are still the best specialty camera for architectural and product shots.
With your D7100, you really should be shooting pro Nikon glass to get the best out of the fantastic sensor that your camera has. If it were a full-frame, you would be shooting with a 58MP sensor, and the amateur glass is not getting the maximum benefit out of that sensor.