we are currently building a 8 x 15 large format enlarger, we need a light source that works and has fast action on the switch power up procedure, i have viewed phil McCourts information, but i am looking mr-16 or anything new???? any thoughts and what type of air do we need to cool the unit ie fans blowers etc.
we are looking for any process photos of the construction or just dont's and do's.
thanks
For that size negative, first of all I would bulld it to enlarge 8X20 negatives because that is a much more common format and it would allow enlargement of 7X17 format as well. I am assuming here that you are thinking of a black and white enlarger...so here goes.
To save engineering considerations involved with incorporating dichroic filtration, since condensers would be difficult and costly to formulate and produce, I would opt for a design to allow above lens contrast filtration. I would look toward one of two light sources. The first would be four each of 1000 watt halogen lamps feeding each corner of a diffusion box with an 8X20 frosted (diffusion) acrylic panel on the bottom side. This will require a cooling fan capable of moving at least 450 CFM to cool the diffusion box. Each of the lamps will need to be filtered or in lieu of that you could use Rosco filter material as a single color filtration below the diffuse acrylic panel on the bottom of the diffusion box. The use of green and blue would allow you to split filter print.
The second design would use a bank of flourescent light tubes. This solves some problems of the other design but brings other problems to bear. Generally speaking, I would opt for the first choice because of the relatively lower light output of the flourescent lamps which may lead to inordinantly long print exposures.
The design of the diffusion box would need to be that the light path of each lamp must be reflected off at least two surfaces to gain even light distribution across the 160 square in negative area. The use of a whilte ceramic interior of the diffusion box would deal with heat and if of a rough surface will provide for greater light diffusion.
The use of both types of light may require the incorporation of a shutter on the lens to provide for more precise initiation and termination of the lamps output. A Packard shutter modified to use an electrical solonoid as the actuating mechanism would be a quick and easy fix. I would opt for 24 V on all control circuitry. If the first (4000 Watt lamps) are chosen than I would opt for 220 Volt since it would require a 20 amp branch circuit whereas at 115 volt it would require a 40 amp circuit. (# 12 conductors vs #8 conductors).
This will give you reasonable printing times and a design that will work.
Last edited by Donald Miller; 20-Oct-2006 at 20:57. Reason: Additional information
Dear jimmygcreative,
Here's an interesting approach: http://www.textklick.demon.co.uk/leden.htm.
Neal Wydra
The LED enlarger idea is cool. As the LEDS are quite efficient, you could probably run it off batteries... Or solar power if you live in a sunny place. At least when doing smaller formats.
Last edited by Jimi; 21-Oct-2006 at 07:51.
thanks for the help on this! great ideas so far!!!!!!!!! we might just go a bit bigger now11 x 20.
can anyone out in the group find any shots of home built enlargers in working spaces and post them?
thanks jimmy
This thread is a good starter, if you haven't seen it yet: http://www.largeformatphotography.in...ad.php?t=19820
Can't you just be happy with contact prints?
Okay, okay. I don't know what it is you mean by 'fast action'.
DM's idea of halogen isn't bad. I might use a bank of 20W or 50W halogens instead of the big whoppers. You could make it like Ansel's horizonal enlarger. Put them on tracks. Lots of heat. I don't imagine you will be enlarging by a big factor, so it would seem like you would not need tons of light. As an example, I think a 45 condenser enlarger uses 150 to 200W of tungsten to cover 20 sq in of film. This is an okay amount in tungsten for modest enlargements. My 1212 V54 tube is about 200W and covers 100 sq in of film and is fast. For 6x7 is it okay and for 35mm it is a bit slow. Of course for 35mm, the enlargement ratio is higher. Figure this in.
Be sure to do as Donald says about sizing this thing. 8x15 is not too common. You should go up to some 'normal' aspect ratio above what you have and then oversize a bit. Remember that the lens will 'see' beyond the diffusor a bit as diffusors are not perfect. Oversizing will give you more even light. Given all of this, if you decide to sell or rent it out, there will be a market.
If I were to do this, I would go with a cold cathode grid, such as Aristo V54. This wouldn't be cheap, but unless your time is free and your materials cheap, any other approach will bog you down and cost more. LEDs are out. Nice idea and maybe okay for small negs, but not here. Read other threads on this topic here and at APUG. LEDs have been around a long time and they haven't flooded the market. What does that tell you? And you will never get high contrast.
Given some form of coldlight and such large negs, you will have to use a glass carrier. Read the newton ring threads that have been so prevalant lately. Then make your carrier with clear glass on the bottom and the diffusor on the top---no other diffusor above. This is newton-ring-proof.
Now back to guessing what fast action means. If this is lamp startup worries, then the closed loop timer, whether Metrolux or RL, etc., will compensate for this. If you are projecting onto something fast and need short exposures, then you will need a shutter. Coldlight, halogen, everything has startup and decay issues. Compensating timers account for startup issues, Metrolux even figures the decay into the exposure.
Whatever you do, go with the most used, most known technology, and one that you are familiar with. This will make life so much easier when you run into problems. If you do something too weird, there will be nobody to answer your questions. Good luck.
-EW-
I have built 3 very large format enlargers when I had a photo business. My first one used 5 24" flourescent tubes and had the same exposure times as the previous owners homebuilt which used 6 500w photofloods as a source. Light output colour is not ideal for vc paper and if I were doing it for that paper, I would build a bank of low wattage quartz halogen lamps. A box with a fan and air filter connected with flexible hose would keep it cool.
contact prints are great I love them, and the best photographic work I ever viewed in person was a med format 6x9 contact print series printed around 1949.
okay , wow sounds like we will go with the low voltage system. we will go with the 600-1000 watt system, do you think thats over kill? what do you think the target wattage should be for vc max filter?
also, the bellows that we have is for a 8 x 16 camera so its smaller than the 11 x 20 target enlarger size. could we just add a hard bellows made out of wood the keeps the angle or should we make a new one out of fabric, it would be similar to a wide angle bellows.
any ideas???
thanks!
JG
What lens are you planning to use? Are you planning a vertical or horizontal design?
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