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denverjims
16-May-2017, 14:22
In March I had the privilege to workshop with Alan Ross during which he spent time showing me the capabilities of the Ross Masking Technique. One of the things that became clear during our discussions was that this method would not work well with my D5 condenser lightsource. Not wanting to go back to the noisy and heat producing Chromega II head and having used a replacement LED source for the condenser head for some time, I began to search for a LED solution.

I am cold on cold light heads and, sadly, Modern Enlarger Lamps is not currently producing their Model 2. Finally, I was unable to convince my wife to sign the papers to take out a 2nd mortgage in order to afford the Heiland. As a result I went to Plan B which was to try to make one. Below are a couple of pictures of the Omega head so you can see what I needed to design to if I was going to build a replacement.

When I was in his darkroom, Alan showed me some details of his self-made LED head which we used a lot. The following design is adapted from many of the concepts and design ideas he so generously shared with me as to how it could be done.

My design parameters were: 1. It would be a ‘bolt-on’ replacement for my Omega Condenser head; 2. I would use filters (Ilford Multigrade, Rosco, [Arista] Color Printing Filters) for contrast control rather than a dial-in variable method; 3: It would use off the shelf LED components; 4) the negative holder for the Omega would still be used unchanged below the light source and 5. contrast filters would be above the negative.
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I have attached pictures to this post to illustrate my design and a spreadsheet to show the LED configuration and source.

Top to bottom the components are:

1. a simple box of wood which serves only to act as the place where the lever arms of the enlarger (which are used to raise and lower the condenser head) connect. This was made with 1x6 lumber (over kill but I used to work for AT&T when it was the phone company and we designed phones to last 100yrs).

2. the above is connected to the lid (7”x10”) of the contrast filter holder box. This lid has the LED strip lights mounted on it. I used 1/4 inch Masonite type board to which I glued a 1/32 inch sheet of sheet aluminum. Then I mounted the strip LED light to that. I used the aluminum to give a better surface for the strips to adhere to and to dissipate the LED heat more evenly.

The LED strip lights and the driver (power supply) I bought from FlexFire. Alan had used another vendor but I found that FlexFire had an ‘ultra-bright’ option which put out more lumens per foot. Alan’s head had 12x12 inches of LED strips for up to 8x10 coverage while mine was only going to be 6x8 inches for 4x5. I felt I would need the additional light output. The configuration of my strips and wiring diagram is included in the attached spreadsheet. Also on that spreadsheet is the call out for the FlexFire parts I used.

3. The filter box is mostly just that - a box. The bottom has a 5 1/4 x 5 1/4 inch hole which sits on top of the negative holder. Inside it, it has 2 components: a) at the top I mounted 3 sheets of .05 Mylar in between 2 pieces of window glass to act as the diffuser for the LED light coming down from the lid; and b) in the front of the box is a hinged door through which I introduce the 6x6 inch contrast filters which sit over the bottom hole.

Total cost of components, including LED lights and driver, < $300 US.

Put it all together and paint it black and you get the head shown. I works well so far (about 2 weeks into its use).

In testing, I found that the brightness was within 1/4 stop of the brightness my condenser head (using a Modern Enlarger Lamp 1a light source) so I was happy there.

The only place I was surprised was when I was doing my contrast calibration testing using the Steve Anchell methodology laid out in his “The Variable Contrast Printing Manual”. I first tested my Ilford Multigrade filters and found that, while they were spot on for grades 00 through 2 1/2, grade 3 to 5 filters were producing <3. When I switched to combinations of Rosco filters, I was able to achieve grades 3 - 5, however.

While the spectral output curves of the FlexFire look like they are adequate, apparently there is something missing in the part of the curve that Ilford uses to balance out the exposure factor for those higher contrast grades.

For me this will not be a problem as I was planning to change away from the Multigrade filters anyway. Using combinations of Rosco Magenta and Yellow filters and/or Color Printing Filters, one can achieve finer differences in contrast than the 1/2 grade steps using MG filters.

Hope this was not too confusing with pictures and feel free to PM me or ask questions through this thread about anything that was not clear.

denverjims
16-May-2017, 14:26
Below are some additional pictures of the final assembly on the enlarger. In the side view, the filter door is open with the light source on. PS, the light stripe over the door is not a light leak, it was part of the gray sponge material I used to seal the lid to the top of the filter box. I had not painted it yet.

Also, a couple of shots of the spreadsheet showing LED layout & wiring as well as the components I bought from FlexFire LED.

denverjims
16-May-2017, 16:37
I thought I'd add links to the FlexFire LEDs I used, their output spectrum and the power supply.
Also a useful YouTube video on how to cut and solder LED strips.

Strips:
https://www.flexfireleds.com/high-cri-93-series-ultrabright-led-strip-light-by-the-foot-natural-white/

Power Supply:
https://www.flexfireleds.com/12v-6-amp-72w-led-strip-light-power-supply/

Spectrum:
https://www.flexfireleds.com/content/UB-CRI-NW-12V-Test-Data-Summary.pdf

YouTube video:
https://www.youtube.com/watch?v=bTRLt-fzTwg&app=desktop

radii
19-May-2017, 07:11
Jim,

Very nice project and execution.

As far as the spectrum of the LED goes, did you look into using a mixture of green, blue and ultraviolet ones in lieu of the full spectrum ones?
Or would there be no benefit to it and the flexfire LEDs are the most even balanced ones out there?

How hot does the panel get, how far from the negative is it and how even is light at that distance?

Thank you

JP

denverjims
19-May-2017, 17:08
JP,
I did a cursory search but the color versions (at least for most I found) only had one color per strip and the lumens per ft. was less than the Ultra Brite's. Finally, I only had room for 11 rows of strips and I did not think I had enough room for each color to give a correct balance. (Translation: to do so would have required skills I don't have.)

As I said in my design spec, I was just looking for enough "white" light in the right area of the spectrum to be able to use Rosco and Arista Color Printing filters. The MG contrast filter issue did not bother me (although it did surprise me a bit). I tested them out of curiosity and I wanted to share this result with others in case they would plan to use them exclusively.

As far as being balanced, FlexFire advertises that they pick LEDs for each strip (up to 16') from a single mfg. batch so that they are balanced. Most of the other mfg. I queried specifically did not. It may be that some others do as well but I found FlexFire first and they had the Ultra Brite's with sufficient lumens at a fair price so I stopped looking.

The panel has not gotten hot or even very warm to the touch so far. Distance from the lid with the LEDs to the negative stage is almost exactly 4". I think if I were to make another, I would cut that distance down a bit. Using an Ilford EM-10 density meter, I could find no drop off anywhere in the illuminated field. That meter is not the most sensitive in the world but it is good to at least 1/4 stop. The 3 sheets of Mylar seem to have done the job in evening the light out. Also, I did several paper exposure tests with no neg and could discern no unevenness.

Hope that answers your questions.
Regards, Jim

Kirk Gittings
20-May-2017, 11:08
Sweet. Thanks for sharing this. Next time I am in Denver (some of my kids live there) I might want to see it first hand if possible.

Pere Casals
20-May-2017, 14:39
This lid has the LED strip lights mounted on it....

Thanks for sharing your project.

I'm also DIY making something like this. I plan to use RGB LEDs for contrast control, with 3 separate dimmers for each color, in order to avoid filters, and avoiding moving the head while exchanging filters for split grade, and later burning some areas with another grade.

I guess CRI is not important for BW contrast control, as you always end in some contrast grade, it's a matter of calibration.

The RGB LED source has the advantage that red filter is not necessary, just power on R channel...


Regards.

radii
20-May-2017, 18:50
JP,
I did a cursory search but the color versions (at least for most I found) only had one color per strip and the lumens per ft. was less than the Ultra Brite's. Finally, I only had room for 11 rows of strips and I did not think I had enough room for each color to give a correct balance. (Translation: to do so would have required skills I don't have.)

As I said in my design spec, I was just looking for enough "white" light in the right area of the spectrum to be able to use Rosco and Arista Color Printing filters. The MG contrast filter issue did not bother me (although it did surprise me a bit). I tested them out of curiosity and I wanted to share this result with others in case they would plan to use them exclusively.

As far as being balanced, FlexFire advertises that they pick LEDs for each strip (up to 16') from a single mfg. batch so that they are balanced. Most of the other mfg. I queried specifically did not. It may be that some others do as well but I found FlexFire first and they had the Ultra Brite's with sufficient lumens at a fair price so I stopped looking.

The panel has not gotten hot or even very warm to the touch so far. Distance from the lid with the LEDs to the negative stage is almost exactly 4". I think if I were to make another, I would cut that distance down a bit. Using an Ilford EM-10 density meter, I could find no drop off anywhere in the illuminated field. That meter is not the most sensitive in the world but it is good to at least 1/4 stop. The 3 sheets of Mylar seem to have done the job in evening the light out. Also, I did several paper exposure tests with no neg and could discern no unevenness.

Hope that answers your questions.
Regards, Jim

Yes, thank you for the thorough answer.
I had at some point thought about making a similar panel and was concerned about the spectrum, since traditional printing paper seems to be designed with incandescent light sources in mind. So a lot of work making a panel that will produce mediocre results ...and that the relative short distance to the negative would produce hot spots. It all seems to be working just fine though, as you have proven.

denverjims
21-May-2017, 12:19
Sweet. Thanks for sharing this. Next time I am in Denver (some of my kids live there) I might want to see it first hand if possible.

Sure Kirk, just let me know.
In fact come by on a 3rd Saturday of the month & join our LF group mtg. as well. We'd promise to be gentle. ;>}
Best, Jim

denverjims
21-May-2017, 14:42
Yes, thank you for the thorough answer.
I had at some point thought about making a similar panel and was concerned about the spectrum, since traditional printing paper seems to be designed with incandescent light sources in mind. So a lot of work making a panel that will produce mediocre results ...and that the relative short distance to the negative would produce hot spots. It all seems to be working just fine though, as you have proven.

Yes, I did consider distance for that reason but, inverse square law being what it is, I was trying to balance it out to keep it bright enough for reasonable exposures. With as many LEDs per inch as there were, and as tightly as I packed the strips, seemed to work.

Regards, Jim

Chauncey Walden
22-May-2017, 11:15
Jim! 2nd Saturday! Kirk, always welcome.

denverjims
22-May-2017, 19:52
Jim! 2nd Saturday! Kirk, always welcome.

Whoops! It's that thick Costa Rican air! Yes, 2nd.
(A contrite) Jim