Originally posted by Designosophy Loco, I have noticed the same thing (though I don't have the particular lens you are talking about), and I think that JonhBee & newarts have hit on something. I'm going to take a guess at causes as well.
It seems to me that shadows tend to have more noise than highlights. Of course, noise also is amplified whenever exposure is pushed in post-processing. Furthermore, it seems that better lenses have better distribution of light and shadow — when exposed properly, resulting photos need less adjustment in post-processing. So, if a lens produces more accurate/pleasing distribution of lights and shadows, and noise occurs in shadows and areas of the image that are exposure-pushed, then you may see more noise when using a lens of lower quality, even at the same aperture and ISO.
All true I think.
It would be helpful if people would post examples of the lens effect on perceived noise/image quality.
The underlying problem is that a lens does not create noise nor does it affect noise in the light that passes through it.
So the effect of a lens on image quality from a noise standpoint must be related to some other aspect of the image created by the lens. A low contrast image with noise likey looks different than a high contrast version of the same image with the same amount of noise.
Other defects like chromatic abberation, while not noise, might be being lumped in with noise.
It is an interesting topic & what I've read so far about the effects of noise on human visual perception implies lens contrast in certain resolution ranges is important.
While one might expect that noise on an image with no contrast at all (a flat gray image) wouldn't be objectionable, it sounds like the reverse might be true; maybe we forgive noise if there is detail to see.