Uncoated lenses often reduce contrast.
Doremus Scudder
Uncoated lenses always reduce the contrast, but the degree of reduction is very dependant on the amount of internal flare which varies with the direction of the light etc.
While it's quite easy to match the overall contrast of images/prints taken with an uncoated lens to those from a single or multi coated lens by adjusting development times or paper contrast there is still a subtle difference in the micro-contrasts in the images.
I've just printed an image made with a Symmar S (multi-coated) and compared it to an image made at the same location under similar lighting conditions earlier in the year with an uncoated Tessar. At f22/f32 the Tessar is for all practical purposes almost as sharp as the Symmar at 10"x12", both using 5x4 film, but the Tessar image just lacks the fine tonal details in things like grass leaves, rocks etc.
(there was a url link here which no longer exists)
This image with the Tessar was made under fairly ideal lighting conditions and the drop in contrast due to the lack of coating isn't much at all, but other images suffer much worse with muddy highlight details.
Ian