Hi there. Can somebody tell me how the aperture of the enlarger matters in terms of contrast and sharpness of the print? How one can use it effectively besides to changing the print exposure time?

I am using agfa basic enlarger for Illford MGIV papers with the filters 0-4

Please help

Thanks.

-- Shreepad (middlegray@hotmail.com), June 10, 2000

Answers

Usually, with a glassless negative carrier, you will find the film has a curvature, away from the emulsion. Thus a wider depth of field, due to smaller aperture, will help assure sharpness across the whole negative. FYI, there are some who maintain that too small an aperture can lead to a type of distortion -- diffraction. I have not personally seen that problem, but you might want to keep that in mind.

--Sam

-- Sam (sselkind@home.com), June 10, 2000.

It counts.

At wide apertures, the corners of the image will be softer and of lower contrast; film curvature that results from not using a glass carrier will make it worse.

At the other end, at the smallest apertures, there will be a contrast and sharpness loss due to diffraction.

-- John Hicks (jbh@magicnet.net), June 10, 2000.

You should get a copy of Ctein's "Post Exposure". He goes into a lot about enlarger lenses and even gives test results on many of them.

Bottom line is that you normally need to stop down one stop, but you should stay around f4/f5.6 for best performance.

Also in color printing, it becomes important since there can be color crossover. This is where the different emulsion layers react differently to changing the exposure time. Very similar to reciprocity failure with film, but there are three emulsions on color paper (and film). So you make a lot of exposure changes using aperture rather than time.

-- Terry Carraway (TCarraway@compuserve.com), June 10, 2000.