Why are my 4x5 enlarger prints sharp in the center but soft at the edges?
Asked 7/29/2017
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I'm printing 8x10 black-and-white enlargements from 4x5 negatives in a small darkroom. The negatives themselves look sharp edge to edge, including when scanned, but my darkroom prints are crisp in the center and go out of focus starting about 2–3 inches from the edges.
I'm using a 135mm Wollensack f/4.5 enlarging lens at about f/11 and a glassless negative carrier. What are the most likely causes of this edge softness, and what should I check on the enlarger?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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If this is a condenser enlarger, likely it has two large condensing lenses situated between the lamp and the negative. These are plano-convex lenses. Make sure the plano sides face the lens and the lamp i.e. the two convex sides face each other. Also check the location of the condensers. If it is adjustable to accommodate smaller negatives, it could be too near the negative. If adjustable, increase the space between condenser and negative. Also consider purchasing a better lens with a flatter field. When using a grain focuser, place it 1/3 out from the center. This will deliver a more uniform focus.
Addendum: The 135mm delivers too small a circle of good definition. For enlarging purposes a lens equal or greater than the diagonal measure is recommended. For the 4x5 negative the diagonal measure is 6.4 inches = 163mm. Suggested is a 150mm or longer for this task.
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
8y ago
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Generated from our catalog & community — verify before relying on it.
The most likely cause is the enlarging setup, especially the lens and negative flatness.
A 135mm Wollensack is likely an older 4-element Tessar-type design, and those can have weaker corner performance and less flat field than better 6-element enlarging lenses. That can show up exactly as sharp center / soft edges. A higher-quality enlarging lens with a flatter field may improve it.
Also check these:
- negative flatness: a glassless carrier can let 4x5 film bow, throwing edges out of focus. Test with a glass carrier.
- enlarger alignment: the negative stage, lens board, and easel should all be parallel.
- condenser setup: if it’s a condenser enlarger, make sure the condensers are oriented correctly and positioned for 4x5.
For focusing, don’t focus only in the center. Using a grain focuser about one-third of the way out from center can help achieve a more even compromise across the print.
So: first test film flatness and alignment, then consider the lens as the prime suspect if the problem remains.
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