Wratten #7 spectral properties?

Murray@uptowngallery

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• May 2, 2008

• #1

There are some graphic arts films that call for a Wratten #7 or equivalent safelight filter.

I don't think that has been made in a while...

It's apparently a dark green. Some people have suggested the old Brownie safelight.

Anyone have any idea what the spectral properties of a Wratten #7 were/are?

Thanks

 

keithwms

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• May 2, 2008

• #2

I'll measure it for you if you find it and it's worth knowing.

 

Jim Jones

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• May 2, 2008

• #3

The Kodak Safelight Filter No. 7 is fairly dark green with less than 1% peak transmittance at 520nm and less than .1% below 495nm or above 550nm. The only other similar Kodak safelight filter listed in the 1985 Kodak Filters for Scientific and Technical Use is the much darker No. 3.

 

fschifano

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• May 2, 2008

• #4

Here you go: http://www.kodak.com/global/en/professional/support/techPubs/ti0845/ti0845.pdf. There is no #7 filter but there is a #7B listed, and there is a chart showing the transmission characteristics. If you compare the spectral transmission characteristics of the #3 and #7B filters, you'll see that the #3 will be safe for materials requiring the #7B filter. The only problem is, of course, that you can't see a darned thing with the #3 filter. It will take a while before your eye become dark adapted enough to see anything except the light itself, and then it won't be much. The 7B filter emits a broader range and more light, but if you can't find one...

 

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Murray@uptowngallery

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• May 2, 2008

• #5

Thanks all.

I also went shopping on the Lee swatch Ball. Looks like Twickenham Green and 1 or 2 layers of their ND 1.2 may work if I can't find a 7B (but I haven't looked yet).

Murray

 

Jim Jones

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• May 3, 2008

• #6

Consider an LED. Dead Link Removed and probably many other sources have green LEDs with a peak emission near the center bandpass of the Wratten No. 7. They can be masked or filtered to reduce illumination level.