Bernie Gunther said:
OK, so assuming you've got good lenses, the difference between consumer and pro DSLRs seems to be mainly a matter of print size and build quality, rather than image quality per se?
So the right question, concentrating only on image quality, would presumably be more like 'how large a 300dpi print can you make from 35mm film vs any given DSLR?'
I know how to calculate that for any given DSLR, but what's the max print size for 35mm film, say Velvia?
Well Bernie, I'm sure there are equations out there that would allow you to make that comparison, although I don't have them.
Let's go back to a good quality 35mm film slide. And let's take a standard printing process. I wouldn't want to print that slide any bigger than say A4, although you could print it up to A3 and even beyond. I would expect the quality and sharpness of the image to fall off significantly between those sizes! It depends on where your perceptions of quality kick in, what you need the print for, the medium that it'll be printed on, not to mention the type of image, etc.
Imagine a 35mm slide, actually sitting on a piece of A4 paper. The paper represents how much you need to expand the image on the slide. Now tell me how good/sharp the focus on your slide is!
I could take that 35mm slide and print with a different process and still get acceptable print quality at much greater sizes that A3. And that would be on a different medium than say, standard magazine paper stock. Glosss, semi-gloss or matt stock? Coated, laminated or art paper? Brillaint white or something else?
Now let's take say an 8MP digital image. (And similar parameters to above, apply here as well.) Personally I would probably put the same restrictions on printing size as with the 35mm slide, although you could print much bigger than A3, and given an image of sufficient quality, (in terms of lack of noise and overall sharpness) you could interpolate that image by say 50% (making it effectively 12MP) and print even bigger. But if you were going to those sizes you'd probably use a different printing process... to maximise quality.
No, I don't think it's as simple as comparing 35mm film material with however many megapixels a DSLR offers you. Personally I'd always get as many pixels as I could afford and try to get a full 35mm sensor, to avoid the 1:6 lens crop ratio attached to the smaller sensors. (And of course, there are other buying criteria to take into account as well.)
If it helps at all, amongst other things, I'm shooting 16MP images with a DSLR, that are being printed on plastic and stretched across buildings.... and they look great from 150 feet away! From 2 feet away they look like shit!
Question: What do you want to do with your camera? If it's commercial, then 35mm film was never that much in favour anyway... other than photojournalism and sports reportage. If it's prints you want to make, frame and sell, then you can get exceptional quality from digital, with (I would suggest) less hassle and cost, than with 35mm film... albeit without the darkroom and hand printing magic!
If it's simply for the fun of photography, you probably don't need a pro DSLR. But the difference between the semi-pro and pro stuff is blurring more and more. No bad thing either!
Sorry I couldn't answer your question. Maybe someone else can, but it's one of those "How long's a piece of string... " jobbies I think.
Note on interpolation: Some image stock libraries won't accept submitted images that have
NOT been interpolated up to 48MB from an approximate 17MB/6MP image!
You see, according to your posts above this one, you guys are way ahead of me....
