Penumbra on prints - help, please

[Nicholas Sack]

I'd be grateful if anyone could solve my printing problem. Areas of deep black on the print spill over slightly to adjacent, lighter tones, forming a faint penumbra. Oddly, this phenomenon has recently arrived, without my changing method or materials. Nikon FE, Ilford Delta 100 film, Ilford Multigrade fibre paper, Durst enlarger. Any ideas as to cause and cure?

 

[tedr1]

This may be a symptom of diffusion taking place between the negative and the paper. Is the same enlarging lens in use? Is it in good condition?

 

[Svenedin]

You say the problem has only just started and you haven't changed anything. I am not sure what the cause is but perhaps try to print a known good negative that you know you got a good print from (from before the problem started). If there are problems it narrows thing down to something to do with the enlarger or printing process. If all is fine it's something to do with camera, film or developing.

Guessing, I am thinking something wrong with the enlarging lens.

 

[ic-racer]

Make sure you enlarging lens is clean. Stop down to F8.

 

[MattKing]

Any chance the lamp has shifted out of position?

 

[Nicholas Sack]

Many thanks to all for your thoughts and suggestions. I checked that the lens on the enlarger is clean, then took the advice of Svenedin, above, and printed a neg shot before the penumbra began appearing on the prints. I was surprised that this print looks fine.

If my logic is right, that rules out any problem with the enlarger. My film, processing and paper have remained unchanged. But around the time the penumbra first appeared, I switched cameras: from one Nikon FE to another. I wonder if this 'later' FE has a small light-leak or other fault that causes a slight flare or fogging - and hence the penumbra.

I can't immediately revert to the 'earlier' FE because its film advance mechanism needs repair. But when it is working again, I'll make a comparison.

 

[ic-racer]

Could just be out-of-focus camera negatives, that would cause dark to bleed into white. Usually flare in the camera causes white areas to bleed into dark.

 

[Nicholas Sack]

Members might like to know that I eventually traced the cause of the slight penumbra around dark areas of my prints. A fungus had invaded the enlarger lens, apparently a fairly common problem in humid conditions. This was visible as a very fine pattern of etched lines, seen when looking through the lens at wide aperture held up to the light. No wonder diffusion was occurring! I bought a new lens - and now my prints are as clean as a whistle. Many thanks to all who offered advice.