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Jeez Mike I thought I had the formula a few years ago! You are correct we are getting closer. Time to get some apertures made to find the 'sweet' spot and then a set that are a stop apart.
The field is very good from corner to corner. This image is slightly cropped to get rid of noisy corner bits due to too much vignetting. It is a big ask for a lens to produce an aberration free field with a diagonal FOV of 8.5 degrees!
These lenses were not designed for very long exposures with very faint objects. They lack the extra baffling needed for this task. I must put up an image of a spider web taken from thirty feet away with this lens at f/2.8. The depth of field is about 3mm! The lens is rectilinear across it's field within about 1%. Its MTF is second to none.
Thanks for your constructive criticisms Mike.
If you look very hard you can see a vestige of 'my wifes best friend'. You may have to squint.
Bert
Last edited by avandonk; 01-03-2009 at 10:08 PM.
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