Cure for light fall off

RJS

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Jan 4, 2005

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246

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Southern Cal

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• May 31, 2009

• #26

Depending on the housing I would think white paint sprayed very evenly might be a good choice. You could even experiment with different shades of white if you don't like the contrast from the 'warm' tube. There would seem to be infinite possibilities!

 

nworth

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Aug 27, 2005

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Los Alamos,

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• Jun 2, 2009

• #27

It sounds like you have to work on your lamphouse a bit. Spacing it back another inch or so may help. Be sure to check the alignment. If you really need a center filter, you might try making one that fits above the negative in an unfocused area (like just below the lamp). You could probably print a circular gradient on inkjet transparency film that would work.

 

ic-racer

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Feb 25, 2007

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USA

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• Jun 5, 2009

• #28

Here is a picture showing my 8x10 Aristo mounting. My enlarger came with an adapter plate that was about 3/4 inch thick. I was able to position the diffuser closer to the negative by placing the diffuser UNDER the adapter plate. As seen in this 'After' picture.
John makes a good point on lamp size. In fact, mine is the 1414 model (14" across).

 

OP

OP

Erik L

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May 9, 2007

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831

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Grand Junction CO

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8x10 Format

• Jun 5, 2009

• #29

Thanks guys,
Ic-racer, I could move my diffuser directly on the glass carrier which would put it about 3/4 inch closer than it is now. Is that what you are suggesting?
thanks again guys for the help
erik

 

ic-racer

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• Jun 5, 2009

• #30

Erik L said:

Thanks guys,
Ic-racer, I could move my diffuser directly on the glass carrier which would put it about 3/4 inch closer than it is now. Is that what you are suggesting?
thanks again guys for the help
erik

Click to expand...

It should. I have actually been considering even moving the whole lamp closer (by making a thinner adapter).
Mine unit was custom built for wall projection (by the prior owner). So a thin metal adapter plate would not have held up to the sideways weight of the Aristo head.

A point on the negative in the middle gets light from all directions besides just straight above. A point on the edge of the negative only gets light from straight above and one direction. By having the diffuser extend beyond the edge of the negative, and moving the diffuser closer, the edge falloff can be minimized.

 

captainbedworthy

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May 16, 2010

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6

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35mm

• Mar 7, 2011

• #31

I'm posting this six years late to save someone a headache. Need to create an 8X10 filter to compensate accurately for light falloff? 1. Put a focusing neg into the carrier. 2. Project it 1:1 onto a borderless easel. 3. Set for white light and remove the neg. 4. Insert a sheet of 8X10 continuous tone ortho film with a nice clear base into the easel. 5. Measure the light at center with a hand held meter, calculate exposure for middle tones. 6. Develop it, it is now your filter. 7. Repeat as needed to adjust density.

 

Last edited by a moderator: Mar 7, 2011