I disagree that the D700 will give much better image quality. The D700 will be better at high ISO, but at lower ISO settings and the lenses attached being equal I don't think the D700 will be running away with the IQ.
OThe ONLY advantage D7100/5200/3200 have is ability to shoot something really far away and crop the image to gain perceived magnification. But that requires having the best of the best lens in front, otherwise might as well not take the shot!
Full frame have a magical feel to them, especially on film or those low MP full frames. There's more than just high ISO performance.
What would give better image quality??
For a crop format DSLR to match full-frame, the lens must deliver 1.5x more resolution at the same level of contrast. This is a very big ask, and is only achieved when comparing a cooking grade full-frame lens with the very best lenses designed specifically for the smaller format.
But shoot RAW and process a smaller format image for best effect including boosting the contrast if required and no matter what the theory unless it's a high ISO shot the chance of you telling a FF shot from a smaller format shot are probably no better than chance.
I tried comparing shots taken with a FF and APS-C with the same lens and later tried FF, APS-C and MFT with the same or very similar lenses and the differences at low to middle ISO settings are very small.
But when push comes to shove, if you do as close a comparison test as reasonably possible - same lens, same aperture, same framing, same subject, same light, same processing etc (say Canon 5D2 vs 7D - similar pixel counts, same generation; or Nikon D700 vs D300, again very similar) then the larger full-frame format always wins. As of course it must.
Edit: they key point is really that what makes the difference is the physical sensor area that allows the lens the perform better, rather than the pixel count that everyone obsesses over.
Yes, but how big do you have to print or how close do you have to view or pixel peep to tell the images apart?
Yes, but how big do you have to print or how close do you have to view or pixel peep to tell the images apart?
I used to print but these days much less so and some people hardly ever do. Even many who do print may never print an image large enough to make what can be minor differences visible. Of course once you start to crop and print differences can quickly appear so like higher ISO's that's a special case.
I think that if people can get over the feeling that they need to be able to print perfect images the size of a barn and instead think about what equipment they need to be able to produce images that'll stand up to (even close) viewing at the image size they are actually going to produce there'd be a lot less kit lust. I've long since accepted that my images are not going to be displayed ten foot wide on a gallery wall and therefore my 5D and even my G1 (if I keep the ISO down) are perfectly adequate for prints up to A3 and on screen images up to 100% crop and few if any people will ever be able to tell 5D images from G1 images any better than chance.
The ONLY advantage D7100/5200/3200 have is ability to shoot something really far away and crop the image to gain perceived magnification. But that requires having the best of the best lens in front, otherwise might as well not take the shot!
All things being equal (if that's possible) the physically larger sensor will always give best image quality. Pixels hardly comes into it, within reason. It's simply because the lens doesn't have to deliver such high resolution for the same size final image output, and the underlying fact of optical physics is that when resolution goes up, so contrast goes down. And it's contrast that contributes most to perceived sharpness. This is basic lens MTF theory.
For a crop format DSLR to match full-frame, the lens must deliver 1.5x more resolution at the same level of contrast. This is a very big ask, and is only achieved when comparing a cooking grade full-frame lens with the very best lenses designed specifically for the smaller format.
Larger sensors also collect more light, so high ISO performance is better.
Well I thought my budget was £500 (D7000) but now thinking should I just go for the D7100 as the 24mp and 60fps seems to be more up to date.
But from a business and practical point of view, seems silly not to spend the extra 250 on up to date gear?
I'd say the D600 at a minimum of £1100 second hand body only is way too much... haha my original budget was £500
This is what I was trying to say, badly explained, my apologies if it caused internet rage.
There is no point chasing the megapixel count, there however is big gain in getting the best lens you can afford.

The differences are there, but you really need to be a pixel peeper to see them.
But there is more to IQ than pixel peeping. It is more about how the overal image looks/is rendered rather than anything scientific liek a particular sharpness score.
That's surprising as the difference is usually noticeable if not particularly a big difference.
Maybe I've got dodgy eyes?
I agree that in certain circumstances the differences are most notable. For instance, full frame sensors own landscape photography. The images seem to 'pop' a bit more. In terms of detail, however, modern crop sensor cameras match up very well. As far as I'm aware the Nikon D7100 is the best crop sensor camera on the market currently and I'm sure its IQ is much on par with the older full frame cameras.
But there is more to IQ than pixel peeping. It is more about how the overal image looks/is rendered rather than anything scientific liek a particular sharpness score.

This is where the whole 'it depends on what the photographer needs' thing comes in...
...but there's no doubt the 5D2 utterly blows the 7D out of the water in image quality. I don't mean it's just a little bit better, I mean it's massively better. That isn't to say the 7D is terrible quality; it's a very capable camera but there's still a very clear difference between that and the full frame (and similar pixel count) 5D2.
When looking at my 5D, 20D and G1 shots I can initially see quite a difference and all things being more or less equal the 5D usually wins but after processing involving no real heroic measures, just a boost to contrast, saturation and vibrancy the gap closes to the point that even I can't tell many images apart unless I remember taking the shot or look at the file name.
What I have noticed is that many people I show shots to are attracted to vibrant colours and shallow DoF and of course if those shots come from the G1 whilst the 5D shots are taken in light less likely to produce a punchy image or have lots of DoF then the G1 shot gets the praise and I think it's important to recognise what each of us and the viewer thinks of as image quality.
