[JJ_SO]

Your contrast classification makes me think: Is he talking about the difference between max black and max white (meaning the range between straight black and white) or is he talking about the tonality in between the max marks? From a bad lens (contrast wise) with a rank of 3 I still can get contrasty pictures by raising the whites and lowering the blacks - but I loose a lot of tones in between.

 

Like Klaus said, lots information can't be recovered.

 

But with lenses of only 5% difference in contrast you need to compare the pictures directly and the comparison will be worthless, because the less contrasty lens could resolve 10% better and soon the better details would outrun the theoretically better contrast. Or a better colour fidelity. I just want to point out that contrast is only one characteristic of a lens, there are so much more and no picture (except test shots of test boards) can be repeated - so what's the point? A good lens should deliver sufficient contrast - if the tonality is maxed out, all the better and all the more versatile it will be.

 

But in dave'd samples if was not so much the contrast of the problem (the labels aside) but the contrast of the whole scene - and if the sensor doesn't cope with contrast, no lens can improve that.