Effects of lens haze

What are the effects of moderate lens haze upon black and white photography?

Haven't got any Monochrome, but around 5 years ago I used a hazy Leica 35mm Summaron 3.5 on an A 12 Leica Mount with a Rocoh GXR. Indoor photos were fine, outdoor had a slight Haze / Fog. I can post a sample if you wish.

Leica "glow" effect on a transmogrified "Zorki"

Haze in general has the effect of reducing contrast due to light scattering. Slight haze on one surface will not necessarily affect the usability of a lens, but it might if it's on multiple surfaces of a more complex lens. You might not notice it much if it's just around the edges.

 

Sometimes, what appears to be haze (caused by oil or grease) can actually be the optical cement degrading in cemented lens groups.

Above is an example of an uncoated Leica Summar 5cm f:2.0 (1934) with milky haze on the elements on each side of the aperture.

Below is the same subject after cleaning:

not black and white, but the glow would be the same.

Convert the images to BW if that is important.

Edited August 19, 2021 by NHSN

Not monochrome, but there is a cloudy (balsam separation) lens here:

 

Guess the lens - a bit of fun.

Light haze loss of contrast. Heavy haze add distortion to the loss of contrast. IMHO in all cases of moderate haze, it is worth getting it cleaned unless you like unwanted "special effects".