If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
DIY light source for 10X10" enlarger.
jjs wrote:
In return for the good input (and in the original spirit of Usenet) I will look into the LED array simply to get a realistic idea of what it would cost for enough light, what the proper power supply would cost, and try to get the actual color temp of so-called white LEDs and post back. It will take a while. http://www.elektor.com/magazines/200...s.350167.lynkx You have to pay for the article, but the free description has some links to manufacturer's web sites. Finally, I must test the electric shutter on B for a few minutes. It was not used that way in its original camera, but I have a fused box on the bench and welding gloves. It does not have to be a very sophisticated shutter, a solenoid with a spring return, or a 1/2 turn stepper motor would do. We are not looking for exposure accuracy here, the electronics will handle that (even if it is a pushbutton switch and you control it). Remember that a 1% variation in exposure is not going to be noticable, and that could easily be 1/2 second. It depends upon how much straight printing you want to do versus dodging and burning. :-) Tonight I will try to find time to do tentative drawings of a couple housings - one for traditional incandescents, and one for the external lights idea. Good luck. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM |
#12
|
|||
|
|||
DIY light source for 10X10" enlarger.
In article ,
jjs jjs.jjs.net wrote: This has been a terrific thread of brainstorming. I've learned a lot and also got pointers to things to explore further. In return for the good input (and in the original spirit of Usenet) I will look into the LED array simply to get a realistic idea of what it would cost for enough light, what the proper power supply would cost, and try to get the actual color temp of so-called white LEDs and post back. It will take a while. "White" LEDs don't have a color temperature; they are not blackbody light sources. You're going to have the same problems you would with a fluorescent lamp, color-wise... -- Thor Lancelot Simon "The inconsistency is startling, though admittedly, if consistency is to be abandoned or transcended, there is no problem." - Noam Chomsky |
#13
|
|||
|
|||
DIY light source for 10X10" enlarger.
In article ,
Richard Knoppow wrote: Cold light lamps are just fluorescent lamps. I think you Yes and no -- they've got a somewhat unusual spectrum and they have special ballasts and a large preheater. The latter two differences from your run of the mill fluorescent lamp are meant to make them more useful for enlarging by reducing the warm up time that causes problems for short exposures. These are worthwhile differences but with an enlarging timer that measures light output, like the Metrolux, much less so. -- Thor Lancelot Simon "The inconsistency is startling, though admittedly, if consistency is to be abandoned or transcended, there is no problem." - Noam Chomsky |
#14
|
|||
|
|||
DIY light source for 10X10" enlarger.
Thor Lancelot Simon wrote:
"White" LEDs don't have a color temperature; they are not blackbody light sources. You're going to have the same problems you would with a fluorescent lamp, color-wise... I did see an article somewhere for an enlarger head using LED's but a mix of I think blue and green were used*, their output or exposure times were variable to give a multigrade head. *Seems an odd choice to me but the chap knows more than I do. Pete -- http://www.petezilla.co.uk |
#15
|
|||
|
|||
DIY light source for 10X10" enlarger.
On Wed, 09 Apr 2008 10:43:19 -0700, David Nebenzahl wrote:
On 4/9/2008 10:19 AM Geoffrey S. Mendelson spake thus: As for incandescent bulbs, you may have to find ones with the lettering on the side instead of the bottom. There are ways to remove the lettering on the bottom. (Don't ask me how I know that.) Use acetone. Fingernail polish remover will do--It's mostly acetone--but you'll need to use isopropyl alcohol (NOT rubbing alcohol--it contains oil) after to remove the additives in the polish remover left on the bulb that keep the nails from becoming dry and brittle. Stef |
#16
|
|||
|
|||
DIY light source for 10X10" enlarger.
"Thor Lancelot Simon" wrote in message ... In article , Richard Knoppow wrote: Cold light lamps are just fluorescent lamps. I think you Yes and no -- they've got a somewhat unusual spectrum and they have special ballasts and a large preheater. The latter two differences from your run of the mill fluorescent lamp are meant to make them more useful for enlarging by reducing the warm up time that causes problems for short exposures. These are worthwhile differences but with an enlarging timer that measures light output, like the Metrolux, much less so. -- Thor Lancelot Simon Not all cold light heads have the heaters. They are mostly on Arista lamphouses and are meant to maintain the light output of the lamp when not run continuously. The phosphors may be different but there are at least two types of lamp offered by Arista, one being balanced better for VC paper. One can buy several types of flourescent lamps including at least one phosphor with a visual color similar to incandescent lamps. The spectral outputs for the phosphors are available from most lamp manufactuers so its possible to see if the spectra is suitable for VC paper. I have no idea of what differences there are in the balasts other than to withstand intermittent operation. All gaseous discharge lamps have outputs which increase with temperature so they like to run hot. In a diy lamphouse the only method of getting consitent light output is to run the thing continuously and use a shutter to control the exposure. -- --- Richard Knoppow Los Angeles, CA, USA |
#17
|
|||
|
|||
DIY light source for 10X10" enlarger.
"gr" wrote in message ... jjs wrote: To date I've considered enlarger light sources to be engineering well beyond my feeble capability, but I have used and examined only condenser enlargers such as the Leitz IIa and Omega condenser enlarger, but my task now is to make a diffusion thpe for the 10x10 enlarger. I want something with No built-in filtration. No fancy color mixing for VC papers. No electronics. No side-lit mixing chambers. Just a straight forward light source and a diffusing layer. I question cold light, mercury vapor, tubes, whatever they are because I just don't plain understand 'em. I can blunder head-first into this project, but this group has some smart people with impressive experience, so I'll put my blunder idea forward. First, I am limited to ~110V AC power although converting to DC is an option. How about a simple array of 'white' LEDs at the top, pointing down over the typical sheet of plastic translucent material found in home supply places? Or should it be fine ground glass? I am not concerned about the variability of LEDs over time unless they change during the time it takes to get an 8X10 negative-to-print just right - maybe a day or two. The power for the light will be run through a robust power-conditioner once set aside for a big minicomputer. Batteries not included. So far so good? Corrections would be most welcome. OR just let me blunder and if it goes badly I'll post pictures of the catastrophe. Forget florescent lamps unless you run then continuous and use a shutter; even then they can vary intensity quite a bit. Tubes have a warm up vs output curve of 30 minutes or so, CF type take at least 5 min to come up close to full output. An integrator would allow use. If I was making a quick light box for an 8x10 enlarger, I would use multiple bulbs (4 or 6) (prob small qz halogen to distribute the light more evenly and then 2 white plex diffusers spaced 1-2" apart between the bulb and the neg. gr The problem with incandescent lamps is heat. Dissipating the heat will make construction of the housing more complex. If one uses an enlarging meter the variations of flourescent lamps with temperature is of much less importance. Even though flourescent lamps like to run hot the heat involved is still much less than it would be for incandescent lamps of similar output. -- --- Richard Knoppow Los Angeles, CA, USA |
#18
|
|||
|
|||
DIY light source for 10X10" enlarger.
Nicholas O. Lindan wrote:
Ilford MGIV paper is a 3-emulsion paper, the third emulsion sensitized for cyan. For best control - especially at low contrast grades - the head would also have cyan LEDs. I've never heard of cyan LEDs. Green and blue will look cyan to the eye, but I have no idea if it will activate that layer, my guess is not. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM |
#19
|
|||
|
|||
DIY light source for 10X10" enlarger.
On Wed, 09 Apr 2008 12:11:47 -0500, jjs wrote:
"Thor Lancelot Simon" wrote in message ... A fluorescent light source of some kind -- a "cold light" source -- will give you the most light for the least power (and heat) unless you really want to use a *lot* of white LEDs. I'm not sure you can get enough output from a 10x10 grid of LEDs you assemble yourself to give decent enlarging times with a 10x10 negative, and I am also skeptical that it will be as even as you'd get with an array of fluorescent tubes. This is great, Thor. I appreciate your input. Are these flourescent sources in round tubes? Or would it be a line of short tubes? And I gather that they would be left on all the time and I'd use the lens shutter, correct? JJS, IIRC, one of the Ansel Adams Photo Series books from years ago had detailed instructions on how Adams built a diffusion head light source for a horizontal enlarger made from a salvaged 8x10 camera. It used an array of small incandescent bulbs, opal glass for diffusion, and a vacuum cleaner for heat removal. Very simple. I adapted the design to a vertical 4x5 enlarger, using below-the-lens VC filters. Worked quite well, but when I could afford it, I replaced it with an Aristo head color balanced for VC paper. Stef |
#20
|
|||
|
|||
DIY light source for 10X10" enlarger.
"Peter Chant" wrote
enlarger head using LED's but a mix of I think blue and green were used ... Seems an odd choice to me Blue and green are correct. Both emulsions are sensitive to blue light and one of the emulsions is sensitized so it will also respond to green light. The multi-contrast gel filters add red light for better visibility when dodging and burning - red + blue = magenta red + green = yellow A proper head would have red, green and blue LEDs - allowing it to produce 'white' light for focusing and graded paper, magenta and yellow light for VC paper, and red light for positioning sensitive materials. Ilford MGIV paper is a 3-emulsion paper, the third emulsion sensitized for cyan. For best control - especially at low contrast grades - the head would also have cyan LEDs. -- Nicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/index2.htm n o lindan at ix dot netcom dot com |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Durst L1000 4x5 Enlarger w/Aristo Cold Light Source | AK | Large Format Equipment For Sale | 1 | January 18th 04 05:47 PM |