Home-brew 8X10 enlargers and cold light heads

[Neal Chaves]

Since I first took up the 8x10 camera in 1988 (after considerable 4X5 experience), I have always wanted to enlarge to 11x14 and 16X20. I was doing this almost from the start with a variety of home-brew "enlarging cameras". The great benefit of using a view camera as an enlarger is that it can be precisely adjusted for alignment easily and quickly each time it is used. I always set up for vertical printing with a Bogen Expan Pole, the camera held in place with two Bogen Super Clamps.

My first "cold light head" was a Double Circuline kitchen light fixture fitted with daylight tubes. I blacked out all of the Lexan diffuser except for an 8X10 window on the bottom and I closed up the top with a disk cut from masonite. I replaced the ruled ground glass in my camera, an 8X10 B&J monorail, with a plain ground glass, and with Velcro on the diffuser and the camera ground glass frame, the head stayed firmly in place. I used two tape-hinged pieces of anti-Newton's ring glass cut to the size of a film holder as a negative carrier. That Double Circuline always flickered when it started, but the flicker was always the same and exposures were very consistent. Another nice thing about using a view camera as an enlarger is that you can focus from the rear. Anyone who has tried to do close-ups with a press camera, or make an 8X10 from an 8X10 in an enlarger knows what I am saying. When you focus from the rear, you don't change the lens to subject distance.

Eventually I converted a Beseler 45MCRX to accept an 8X10 Aristo cold light head and used that for many years until replacing it recently with a Beseler 810 VXL. I know that eventually LEDS will make the best light source, so I try to keep informed about what is out there. Recently I found this unit
http://www.allhydroponics.com/hydrop...dgrowlight.cfm
It's 12.25"X12.25", a quarter inch too big to fit in place of an Aristo, but should be fine for DIY projects as described above.

[ic-racer]

Nice but 28 watts!

Its still hot tungsten and quartz for me

[domaz]

Nice but 28 watts!

Its still hot tungsten and quartz for me

Hmm but do they mean 28 watts of equivalent tungsten light source or 28 watts of LED power? 28 watts of LED power is nothing to sneeze at if you consider a 3-watt Luxeon LED puts out about 80 Lumens.

[ic-racer]

Hmm but do they mean 28 watts of equivalent tungsten light source or 28 watts of LED power? 28 watts of LED power is nothing to sneeze at if you consider a 3-watt Luxeon LED puts out about 80 Lumens.

Yes, good point, but still probably under powered. With big enlargements I was up to 200 seconds or more with some denser negatives and an 8x10 Aristo head and contrast filters at f16.

[R Mann]

You may want to look into the folks that are making high output LED lights for their fish tanks - here is one that describes a DIY approach. 28 LEDs putting out 3 watts each - that is a lot of light in a small space with very little heat.

http://aquariums.seaspraydesigns.biz...-light-part-i/

[Jay DeFehr]

With more than four times the output of the original GrowPanel, the GrowPanel 45 uses only 28 watts of power and surpasses the output of a 250-watt HPS.

[Eric Woodbury]

These aquarium LEDs are pretty good (from R Mann's link)

http://www.cree.com/products/pdf/XLampXP-G.pdf

Page 3 shows the LED spectra. Relative power is indicated by the area under the curve. The V54 tube from Aristo

http://www.aristogrid.com/spd.htm

is a winner because it has strong blue and strong green. Most of the blue, at 440 nm is not even where the human eye sees well, but it is where the high contrast control of VC exists. Even shorter is better, but hard to see. LEDs, including those above, don't have enough strong blue, 400 to 440 nm, to push VC paper into high contrast. If you never need grade 4, then LEDs might be fine. Don't get me wrong, I love LEDs, but for now, high brightness LEDs aren't as good as a coldlight such as V54. Also, even though LEDs seem like low power, there are very small, concentrated heat. Power management is a problem. Lots of heatsinking is required to get the overall light power output that is easy for a cold cathode tube.

Bottom line is I'm buying a backup V54 while I still can.

[jon.oman]

Some interesting ideas here!

Jon

[Bill Kumpf]

I played with some Cree XR7090 colored LED back in 2007. I was looking at options to replace a Philips Tri Color head that died. I compared the contrast range produced by Kodak Polycontrast Filters and a 3 Watt LEDs: Royal Blue (455-465nm wavelength); Green (520-535nm wave length) and white LEDs. I counted the number of steps printed using a standard 21 step wedge. The Blue LED produced a 4 stop range while the green LED produced 5.5 stops. The white LED produced 3.5 stops. This compared to 3.0 stops for a Kodak #4 filter and 5.0 stops for a Kodak #1 filter.

I asked Ilford for their recommendation for Multigrade paper. They recommended a Blue light source (high contrast) in the 420 – 470 nm and a green light source (low contrast) at 520-530 nm. For best results, Ilford recommends blocking the green light source below 500nm. The Cree green LED will require a yellow filter to clip the lower frequencies.

I learned just enough to be dangerous.

http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

The potential is there.

[cosmicexplosion]

"My first "cold light head" was a Double Circuline kitchen light fixture fitted with daylight tubes. "

any photos of camera enlarger? i have been keeping an eye for a design.