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Thread: Omega 5x7 E6 LED Mod

  1. #1

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    Omega 5x7 E6 LED Mod

    BACKGROUND:
    This post is in response to a request made in post #25 in this thread.

    I found a thread by Bob Mann, describing an LED conversion of his Omega E3 5x7 head; it impressed me enough to try a similar version of it on my enlarger. It seemed economical enough to make the attempt worthwhile. Sprinkled throughout my report here are excerpts from some of my previous posts to keep this description compiled in one place.

    My enlarger is an Omega E6 5x7 with XL column, shown under “discontinued enlargers” here. It has an Omegalite lamphouse (aka, the “saucer”) that uses a Circline fluorescent bulb. I’ve only used it with graded papers obviously, and it has performed very well that way for many years, provided my negatives have an appropriate contrast range, but it's not compatible with modern VC papers, so this conversion seemed like a candidate light source that is compatible.

    PHOTOS
    I didn’t make pictures of the modification while doing it but I’m showing here what I do have, together with the MGIV paper test curves that resulted from my checkout of the LEDs and functioning of the mod.

    LED ASSEMBLY + INSTALLATION:
    To modify the E6, I used Bob’s concept, with a few differences after conversing with Bob via PMs. I used the same LEDs, at a 2-inch spacing, and also used the same solderless connectors to attach them to a heat sink. I was concerned about the heat generated since I didn’t want to add any holes (requiring light baffles) to the saucer for convection cooling, so I took a conservative approach and installed an aluminum heat sink with cooling fins available from the Cree LED source (reefledlights.com). I found the videos available on the source’s website to be very helpful and easy to follow – among other things in the videos I discovered that I needed to get a Sperry DM-4100A multimeter to make a simple check of the circuit for errors, as demonstrated, before applying power to it (my old Sears multimeter was not up to the task). So the list of items needed from this supplier looks like this (with current prices which have gone up somewhat since I bought them):

    12 - 3-watt Cree Premium XP-G cool white LEDs @ ~$5 Each
    Color temp: 7500K, Cree’s Data Sheet spectral power distribution is given on pg.4 in this PDF
    12 - Solderless BJB LED Connectors @ $.88 Each
    1 - Self-tapping Screws (Bag of 30) @ $4.00
    1 - Meanwell LPC 60-1050 Power Supply @ $20.20 (closeout price)
    1 - Leviton 2-prong Plug @ $2.95 (for Power Supply)
    Aluminum finned heat sink - 8.46” wide x 6” long (NLA in 6” length, so cut 12” current version @ $32.52)
    Heat Transfer Paste – Arctic Alumina, 14g syringe @ $9.95 (very little is needed)
    Solid Core 20-gage Wire (black @ $3.00, red @ $3.00) [Radio Shack may cost less]

    Note: The Carclo Optics available for each LED were not used because of the effect on the 125-degree beam spread of the LED.

    Total cost ~ $150.00 + multimeter

    The flat white surface inside the saucer was in good condition and did not need to be refurbished. The enlarger’s original diffuser had yellowed somewhat, so it need replacement. Using graph paper I made a scale drawing of the saucer’s measured internal dimensions, and used it to design a finished assembly. I used some 1/8-inch MDB board in my scrap pile to build a support for the heat sink to rest on (and precisely hold it from shifting relative to the format opening in the negative holder). This support included a slot to slip in an additional diffuser below the LEDs; it was then spray-painted flat white and connected to the flat bottom of the saucer with four nuts/bolts (drilled through the -inch foam rubber visible in the saucer pic that is bonded to the bottom of the saucer). Choosing the finned heatsink necessitated placing the LED driver on top of the saucer, by making an MDB span that attaches to the saucer’s lift arm brackets.

    DIFFUSION AND UNIFORMITY:
    I initially installed two diffusers (original replacement + one in the heatsink support) obtained from my local plastics supplier. They were both 1/8-inch thick GP acrylite in sign white color. However, when doing step tablet tests with Ilford under-lens filters later I found an apparent color issue that prevented results beyond Grade 3; also some LED hotspots were seen. After more research, I discovered a new diffusion material on the market that was developed especially for LED diffusion, also 1/8-inch thick (specifics on this material in a bit). After installing these two diffusers and step tablet re-tests, Grades 00-5 are attained and, with no negative in the carrier and no lens, illumination is uniform with no visual LED hot spots. This uniformity was apparent both visually and via measurement with my old AC-powered Gossen Labosix meter, using its on-easel sensor. Since each of the diffusers causes a full stop reduction in output, some day when it’s convenient, I’ll check to see if using only one of these diffusers may still be adequate for uniformity with a one-stop gain in output, because the output did seem marginal for the large print sizes. The faster paper speed of the new Classic papers will also ease this situation. Similarly, I checked the uniformity with each of my lenses (all Componons - 105/135/150/Durst 210) at apertures of 5.6/16/45 with enlarger setups for print sizes 8x10/11x14/16x20. As expected falloff in the corners was quite poor wide open, but improved quickly upon stopping down, indicating only ~1/3 stop falloff that would only need the usual edge burning of a print.

    HEAT UP AND TIME LAG
    During the foregoing and subsequent checkouts, the LEDs were powered up for considerable periods during checkout of enlarger light leaks. Since I don’t own the temperature checking equipment that Bob used, I found that, when placing my hand on the top of the saucer during these extended periods of ON-time, it was only barely warm, leading me to believe that there was really no need for the finned heatsink and that simply using the flat aluminum plate, as Bob did, would have been totally adequate. However, the question of negative flatness is still a concern, since I’m still using glassless carriers. I’ll be changing them in the near future. Regarding time lag on powering up/down the LEDs, no problem, it is instantaneous. My timer is a digital 2-channel GraLab 655 (no longer available).

    ILFORD MGIV FB CURVES
    Ilford has released the new MG FB Classic and Cooltone papers, now that I’ve completed my tests with the MGIV FB paper, so I’ll be re-doing some of the tests soon to confirm the mod’s performance with these new papers, but at least I’m now confident with the LED modification. Ilford says that the new papers have improved spacing between grades, and I'd like to see that.

    1) Tests were done with Ilford under-lens filters 00-5 (no half-grades), plus “no-filter”, using MGIV glossy fiber-based paper, MG developer 1+9, a Stouffer 31-step wedge projected onto 5x7 paper (to gather more data points for smoother curve plots). Results show that “no filter” contrast compares to G2 in the shadows and G2-2.5 in the midtones.

    2) Just for kicks, I also included tri-color blue (47B) and tri-color green (58) to see how closely the Ilford filters approached those results, even though the tri-colors’ large filter factors rendered them impractical for normal printing use with this mod. The individual curves were then slid along the RLE scale to intersect at a common reflection density value of .09 (Zone VIII) so the relative slopes could be more easily seen. See the plots of the MGIV FB test results in the “PHOTOS” link above. A good explanation of the peculiarities of these curve shapes has been published by Nicholas Lindan (Darkroom Automation) here.

    3) Similarly, just out of curiosity, I compared the slope of a projected wedge to a contact printed wedge, although in retrospect the thoroughness of the projected wedge masking to minimize flair may have influenced the result somewhat. This comparison is shown in the “PHOTOS” link above.

    DIFFUSION MATERIAL
    Each of the two diffusers is 1/8” (3mm) thick with 50% light transmission (one-stop loss). The distance from the top surface of the upper diffuser to the LEDs is 3/4” (19mm). The lower diffuser, which replaced the original, leaves an air space of .34” (8.64mm) between the two diffusers. The material is Makrolon LD in B48 white. I'm guessing LD stands for LED Diffusion. It's a new product designed specifically for diffusion of LEDs. It’s made by Bayer MaterialScience with distributors everywhere. I have about a half dozen distributors near me, so I got a sample sheet from one of them while I waited, enough for my diffusers and spares. Using a saber saw and blade with 40 teeth per inch, it left a smooth edge that required no further work. I clamped it between two thin sheets of MDB board when cutting, just to ensure a good cut. Here’s a blurb from the manufacturer on the material:

    Makrolon LD polycarbonate sheets deliver uniform light diffusion for today’s LED signage. They feature an advanced light diffusion technology that provides excellent light uniformity. LED hot spots and shadowing are eliminated in flat or formed applications.
    Call 800-254-1707 for samples or visit www.sheffieldplastics.com to locate your
    local, authorized distributor.
    Distributor search: http://www.sheffieldplastics.com/dis...nav_id=9,0,0,0
    Material properties: http://www.sheffieldplastics.com/web.../PDS097_LD.pdf

    Update 6/1/2017: Sheffield is now controlled by Covestro, the new owner. So any links for the Makrolon LD diffusion material will take you to their sites.
    Last edited by Jerry Bodine; 1-Jun-2017 at 12:58.

  2. #2
    Kevin Kolosky
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    Re: Omega 5x7 E6 LED Mod

    I do not know much about electronics, but I think the obvious question now is whether those white LEDs could be switched for colored ones so that you didn't need to use filters for variable contrast paper.

  3. #3

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    Re: Omega 5x7 E6 LED Mod

    Jerry,

    I have an E6 with both the saucer head and the dichroic head. I'm thinking of using the dichro-head on another enlarger, so your conversion may be something I'm interested in.

    Your link to the photos takes me to a Yahoo site where I have to create (yet another...) account to view the pictures. I really don't want to do this.

    Is there anyway you can post a few here? I'd appreciate it.

    Best,

    Doremus

  4. #4

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    Re: Omega 5x7 E6 LED Mod

    Doremus,
    Sorry about that. The length of the post was pushing the forum limit of 10,000 characters, so I chose to use the Flickr link for pictures. But I didn't think one would need to open an acct to see the pictures. Here you go:

    Click image for larger version. 

Name:	Omegalite Lamphouse.jpg 
Views:	146 
Size:	62.7 KB 
ID:	110593Click image for larger version. 

Name:	LED Driver on Omegalite Housing.jpg 
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Size:	170.5 KB 
ID:	110594Click image for larger version. 

Name:	MGIV Curves.jpg 
Views:	106 
Size:	81.2 KB 
ID:	110595Click image for larger version. 

Name:	Projected vs. Contact - Grade 2.jpg 
Views:	78 
Size:	48.5 KB 
ID:	110596

  5. #5

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    Re: Omega 5x7 E6 LED Mod

    Quote Originally Posted by Jerry Bodine View Post
    Doremus,
    Sorry about that. The length of the post was pushing the forum limit of 10,000 characters, so I chose to use the Flickr link for pictures. But I didn't think one would need to open an acct to see the pictures. Here you go:

    Click image for larger version. 

Name:	Omegalite Lamphouse.jpg 
Views:	146 
Size:	62.7 KB 
ID:	110593
    It has been a while since I've been in a conventional darkroom, but I must say that is one cool looking enlarger head! (sorry for the non-technical aside)

  6. #6

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    Re: Omega 5x7 E6 LED Mod

    The grouping of 12 LEDs gives you a good amount of light to work with, not too long or too short on the exposures? I'm thinking of doing something like this for a homebrew 4x5, the compactness of an LED panel like your great example is a great thing compared to an average mixing box setup.

    Thanks for the inspiration

  7. #7

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    Re: Omega 5x7 E6 LED Mod

    Jerry -

    Great job, glad I was of some help in getting your project going, but you have clearly taken it to the next level.

    Bob

  8. #8

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    Re: Omega 5x7 E6 LED Mod

    Quote Originally Posted by Bob Mann View Post
    Jerry -

    Great job, glad I was of some help in getting your project going, but you have clearly taken it to the next level.

    Bob
    Bob, I want to take this opportunity to thank you for your groundwork which saved me a lot of research time.

    Jerry

  9. #9

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    Re: Omega 5x7 E6 LED Mod

    Quote Originally Posted by Jerry Bodine View Post
    Call 800-254-1707 for samples or visit www.sheffieldplastics.com to locate your
    local, authorized distributor.
    Distributor search: http://www.sheffieldplastics.com/dis...nav_id=9,0,0,0
    Material properties: http://www.sheffieldplastics.com/web.../PDS097_LD.pdf
    I just discovered that the last two of these links have evaporated, but the first link is still good. Use it as follows:

    Bayer MaterialScience > Product Information > Sheet Products > Makrolon (Polycarbonate) > Makrolon LD > "Where to Buy" link is at the bottom. Other links are found here as well. The B48 White = Standard Industry Color #2447.

    I'd recommend calling first to make sure the distributor has it in stock, since it's a new product.

  10. #10

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    Re: Omega 5x7 E6 LED Mod

    Jerry that looks really nice. I like the saucer head. My first LED head was also based off of Bob's head. I even used the same E3 cold light head as he did, but mine was a bit more roughly constructed. My plan was to do some testing and then rebuild it when I found the optimal placement for the LEDs. As a stop gap measure I made a pencil shaded mask to even out the light. My next version for the Durst used a different layout for the LEDs (based on Huw Finney's LED head http://www.huws.org.uk) and I was able to get away with a single sheet of white plexiglass for the diffuser. But I would like to test out the Makrolon. It might be even better than what I'm using now.

    Quote Originally Posted by Kevin J. Kolosky View Post
    I do not know much about electronics, but I think the obvious question now is whether those white LEDs could be switched for colored ones so that you didn't need to use filters for variable contrast paper.
    Yes you can substitute green and royal blue LEDs for the white and get a variable contrast head. You need a way of dimming them relative to each other to be able to control the brightness. The easiest is with a dimable driver for each channel controlled by two potentiometers (like the old Zone VI VC head). I built a system that uses an arduino to control the LED brightness and integrates an fstop timer. It allows me to profile each paper so they all print very close to each other at the same grade. I have it somewhat detailed on my site http://www.trippingthroughthedark.co...ment/led-head/.

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