Fall off mask

[Richard Littlewood]

Some time ago I saw a post that included a fall off mask made to correct an un-even distribution of light arriving on the baseboard from an Omega D3 enlarger with condenser head. This mask is like a centre filter and must slot in the head somehow. I'm interested in making one of these masks because with the D3 there is a certain light fall off at the corners as compared with my cold cathode head. Any suggestions as to how to make this mask and where it must sit would be welcome. When I finally have one made and working sweetly, I'll post instructions!

[David G. Gagnon]

Richard,

There was a post a few months ago that I saw that someone mentioned a mask (don't remember if it was for the D3 or another enlarger altogether), but I believe it was mentioned that one could be printed out on transparency paper from an inkjet printer. I have done this to get a color correction filter for an Aristo cold light head, so I know that can be done. If no one else responds, seems like you could make on in one of the drawing programs and print it out. Of course you'd have to experiment with geting the density right and where the printing needs to start at from the center of the circle. Good luck.

DG

[Robert C. McColloch]

One possibility is that your lens does not cover your negative size. However, even with lenses providing proper coverage, there is alway fall-off. This why you always
edge burn" (exceptions ocur) . My experience is that it is in the neighborhood of 15 to 20-percent of the base exposure.

[Henry Ambrose]

I made such a thing once by inkjet printing on over head transparency film. It improved the situation with the Elwood enlarger I used it in but did not completely fix it.

I scanned a sheet of paper exposed with a piece of evenly exposed camera film in the enlarger to get an image of the fall off. I reversed and resized the resulting print in Photoshop and printed it. After several tries I got pretty close.

[phil sweeney]

I have commented on this a few times. Here is the most recent response I could find.

http://largeformatphotography.info/lfforum/topic/501131.html

If you need details email me.

best