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Author Topic: Light source for large format film copying  (Read 313 times)

jwittes

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Light source for large format film copying
« on: February 11, 2020, 10:18:38 am »

I'm looking for recommendations for a light source (light table/box) for copying 8x10 negatives/transparencies using a copy stand. Evenness of light across the entire panel is extremely important as well as color temperature around 5000ºk.  Any advise or recommendations regarding this setup is greatly appreciated.  Thanks...
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Paul_Roark

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Re: Light source for large format film copying
« Reply #1 on: February 11, 2020, 11:32:54 am »

I once built an 8 x 10 head for my Beseler 4x5 enlarger by copying the design of a smaller enlarger head.  I used cardboard that I coated with titanium white paint to fabricate the head and used a 2 2/4 color head as the light source, so that I had the color filtration needed for variable contrast B&W paper.  It worked very well and cost almost nothing.  The 8 x 10 negative was simply put on a plain glass sheet that acted as the negative holder.  If found an Apo Rodagon copying lens that would cover 8 x 10 and was way cheaper than their 8 x 10 enlarger head.

FWIW

Paul
www.PaulRoark.com
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JaapD

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Re: Light source for large format film copying
« Reply #2 on: February 12, 2020, 06:27:10 am »

Out of the box thinking: what about using your (calibrated) monitor screen as light source for your 8 x 10 slides? Create a white window on your screen. Of course you’ll need to hang/mount the slide with a sufficient distance from the slide in order to de-focus the monitor screen.

Regards,
Jaap.
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digitaldog

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Re: Light source for large format film copying
« Reply #3 on: February 12, 2020, 12:48:56 pm »

5000K is a large range of possible colors of white so it’s kind of meaningless:
http://digitaldog.net/files/22Thecolorofwhite.pdf
Most important is the spectrum and ideally, one that’s smooth and devoid of spikes like seen in Fluorescent lighting.
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Andrew Rodney
Author “Color Management for Photographers"

kers

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Re: Light source for large format film copying
« Reply #4 on: February 12, 2020, 12:53:00 pm »

I am also thinking about that - for smaller negatives- Best thing would be a continu lightsource ( light bulb like Solux) - combined with a milk perpex/glass (at some distance from the film) that does not filter visible colour out...

I don't know if a led lightsource spectrum could be a big problem.
For evenness the ledlight source has to be as large as the film format and at some distance from the perspex.
you could measure the evenness with a lightmeter (- I use it nowadays only for this purpose)
« Last Edit: February 12, 2020, 12:59:54 pm by kers »
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Dale Villeponteaux

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Re: Light source for large format film copying
« Reply #5 on: February 12, 2020, 03:42:01 pm »

Just a random thought without any experience to back it up, but could you use a Fresnel lens to collimate and
enlarge the transmitted light beam? The plastic ones might work and they're cheap.

Regards,
Dale
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Chris_Brown

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Re: Light source for large format film copying
« Reply #6 on: February 12, 2020, 05:11:01 pm »

I used a clean 2'x2' piece of milk white plexiglass and mounted it horizontally (like a table top, making sure its flat) and placed clean, white foamboard under at about a 45˚ angle. I placed two strobe heads (Speedotron) with parabolic reflectors about 4–6' away from the foamboard, and flagged off any stray light. I created an 8x10 "window" on the plexi table with gaffer tape and flagged off everything outside that window. I spot metered the light, adjusting lights and foamboard until an even exposure was read throughout the window area. This setup allows for hassle-free copying once the camera is positioned and focused (but always check focus on every shot). I never had problems, but I've used/blended multiple exposures to help shadows or highlights if needed.

I used this system as an assistant in studios in Detroit and Los Angeles with good results. Best results come from a PMT drum scanner, but a good digital capture is second best, IMO.
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