Well there you go. I haven't found negative popping to be a problem with a diffusion type enlarger. Very little heat makes it to the negative stage. Condenser enlargers are a different story of course.
Originally Posted by Bob Carnie
Bob, I think we are actually in agreement. I admit that the depth of focus is extremely shallow (small) when compared to the depth of field. While I am not an optical engineer - I have always believed this to be a function short projection distances involved (not unlike the shallow depth of field experienced in macro work.)
Ron Wisner wrote of the flat field lens which I found to be informative and enlightening.
The point where we seem to disagree is whether the depth of focus is actually significant enough to resolve for a lack of flatness in the film plane. It has been my experience that it is (given my equipment and processes.) If that has not been your experience, I would certainly not try to invalidate that. I, too, switched to glass carriers because I have a broader range of exposure choices since I am easily bored with long exposures.
Good discussion. It is always valuable to learn of others' experiences.
Thank you for correcting me. I read his post as a 250mm lens.
Out of focus on one side..
It's an alignment issue no question. As to glass carriers, I have only had to resort to double glass with 6x9 cm or larger pano. format on 120 film,because of the thin film base. 6x7cm or smaller is fine with a single glass above the neg : lets face it ; thats the way the camera holds the film..
And that must be some 50mm lens if you are not getting vignetting of the image.
I really like the idea of a single glass above the negative, I tried this in the past with mixed results.
As others point out I use mainly condenser enlarger with a oversize 250w bulb which does push out a fair amount of heat. I find that I can close down 2 stops and print 16x20 fibres at 15 seconds.
With split printing and complicated burn patterns a shorter print time is really nice with the hotter bulb.
If I could make a single glass work well in my enlargers I would switch to that method in a heartbeat.
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