One thing I would like to summarize is that when enlarging, understanding depth of field is just as important as when taking pictures. Every enlarging system suffers from the following things to some extent:
1) Lack of parallelism
2) Lack of field flatness due to the lens
3) Curved or wavy negatives
4) concave, convex or wavy paper easels
The question of "how much to you need to stop down" to correct those things can be answered, to some extent, by the Peak magnifier. The main problem, is that things can look a little fuzzy under the Peak, and still be OK in a print viewed from a distance.
Therefore, determining the acceptable F-Number from the focusing equation takes into account a personal "acceptable circle of confusion" for viewing a print from a distance, and can take some of the guesswork out of interpreting the image under the Peak.
I have considered writing up an article on focusing the enlarger but,
a) Jeff Conrad came up with the math that substantiates that equation,
b) Jeff already has two good articles on focusing the view camera on the LF site,
c) the math in those articles is difficult to follow,
d) if you can follow the math for the view camera model, you don't need a separate article for the enlarger (its just a large format macro camera) and
e) if you can't follow the math in the view camera focusing articles, you probably won't be able to follow it in an enlarger focusing article
However, if there were interest I could try to come up with some kind of article like "The Basics of Optimum F-number Selection for Projection Printing Using Modular Transfer Function Criteria." Problem with that title is that no one will understand the title. If I called it "How to Focus the Enlarger" no one will read it
Last edited by ic-racer; 04-27-2009 at 12:51 PM. Click to view previous post history.