Okay, first off, posed studio portraits are not necessarily, or even usually, head and shoulders. If they were, then yeah, an SLR would be better. They are usually full length, head to knees or even groups. For those, a normal lens is the lens of choice. Rangefinder lenses are simply easier to make than SLR lenses and even a mid-priced rangefinder lens tends to be superb, compared to an SLR lens. Coincident rangefinders and split image rangefinders are far easier to focus accurately at 10 - 20 foot ranges, particularly compared to SLRs with autofocus. If you want to try this out, go on eBay, pick up a cheap Argus C3 or a Yashica Electro 35 GS (both are often under $20), clean it (those two are easy), and give it a shot. You'll see.
I really don't care about the camera. In my opinion, photography plays the most important role. Apart from that fact, there is a load of Image - Editing programs, that help you to make a photo better. Anyway, really helpful post, as I learned so much things about cameras! Thank you!
Absolutely, but, even if some camers cannot do the whole job, the use of some helpful programs is allowed. But you're totally right. The most important is the fact that the camera is able to do most of the job. This is the point of top - quality cameras.
Well, that's true, but only to a point. Two cases in point (large format view camera versus small format DSLR camera): 1. Let's say you have a custom built $15,000 8x10 large format Ebony view camera (one of the very highest quality view cameras out there), but the fastest you can shoot with it is about a photo every two minutes. If you need something with tracking autofocus that can shoot rapidly moving subjects at 8 frames per second, that isn't going to be able to do it -- not by a long shot. It's hopeless, no matter what programs you have. 2. Now let's say that you have the very best small format DSLR that money can buy and you have struck the photography lottery and are offered the chance to shoot for what will be a series of 6x9 foot framed photos of moving racecars, shot in excruciating detail, that will be displayed in a museum. Sorry, but your camera will not be up to the job, because no small format lens or sensor ever made has adequate resolution to make sharp and detailed 6x9 foot prints. The cars are moving, so you can't zoom way in, shoot a couple of dozen photos and stitch them; you only get one shot. Not even a $10,000 Hasselblad medium format DSLR can do that. Once again, it's hopeless.
Programs are not helpful if your camera can't capture enough for them to work with.