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> Light output of 240 W Enlarger bulbs |
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Light output of 240 W Enlarger bulbs
I have finally got around to trying an LED bulb in my enlarger - Durst M800 - attracted by the lower voltage and cooler running temperature.
I had been using a Phillips Tungsten 150w E27 Screw fitting mains bulb and above the bulb Ilford multigrade filters. Because of mains voltage variation I run this from a large 12v leisure battery and inverter about which I have posted on previously: http://www.film-and-darkroom-user.or...=Mains+voltage http://www.film-and-darkroom-user.or...=Mains+voltage Based on the recommendations on FADU threads particularly by Richard Gould, I tried a Paul Russels warm white (nominally 2700ºK) 15W LED bought through t'internet (B&Q was a waste of space in this respect) . This worked fine. The box said this LED bulb is equivalent to a tungsten 125W bulb. I was interested in exploring the availability of higher wattage LED bulbs to reduce the times of exposure when printing my maximum 12×16" Prints. The highest wattage suitable LED bulb (again 2700ºK) I could find on t'internet was 18W Bell bulb which they say on the box was equivalent to 100W Tungsten. To compare the light output of the bulbs in the enlarger I used my RH Zonemaster Enlarging Exposure Meter set to read in its densitometer mode. Once I had got my head round the way it zeros (and rezeros) and records relative densities on a logarithmic (base 10) scale, I compared a number of bulbs in my possession: The relative light output results as ‘f’ stop steps relative to the brightest: BULB ‘f’ Stop Steps 150w Tungsten 0 18w LED -1/3 15w LED -1/2 75w Tungsten -11/3 6w LED -11/2 NB the layout of the results is OK if I edit it but reverts when I save it...apologies if it has become confusing. I would be interested in hearing of any higher wattage LED bulbs and source. Mike Last edited by MikeHeller; 23rd June 2021 at 05:09 PM. Reason: Failed attempt to improve layout |
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If I wrap the text in #CODE# tags I get the following - is that the correct formatting Mike?
Code:
BULB ‘f’ Stop Steps 150w Tungsten 0 18w LED -1/3 15w LED -1/2 75w Tungsten -11/3 6w LED -11/2 |
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Thanks, Mike Last edited by MikeHeller; 24th June 2021 at 09:19 AM. |
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Due to health reasons he has since dismantled his darkroom and disposed of his equipment so I cannot photograph it for you. Bill |
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Interesting, but I think I will tolerate the increased exposure times and think about this type of workaround should it becomes a problem or I am feeling particularly adventurous. Thanks, Mike |
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Just out of curiosity, how does all of this workout in terms of lumens?
As I understand, watts have more to do with energy consumption rather than brightness.
__________________
MartyNL “Reaching a creative state of mind thru positive action is considered preferable to waiting for inspiration.” - Minor White, 1950 |
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Mike, how do you manage the spectral output of each of the LEDS, so they match the Y/M/C output of a bulb - or am I over thinking it ?
Martin |
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Efficiency is often quoted in lumens per watt, which really shows how bad tungsten lamps are. A rough estimate is to multiply the LED wattage by 6 to get the tungsten wattage for a normal bulb lamp and 10 for a directional lamp - but those are only a rough guide as efficiency of the power supply, how hard the LEDs are being driven and the beam directionality vary a lot. Basically, the only real way to tell is do what Mike has already done! |
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I think the best way to tell check out the brightness of your LED bulb is to make comparison prints.
I had a 75 watt tungsten pearl bulb in my Leitz Valoy 11 enlarger, and bought an 11watt LED bulb (2800K) to replace it. This was supposed to be the equivalent of 75watts tungsten. But it turned out to be brighter. With the tungsten bulb in place I made a print with a known negative. 26 seconds produced a nice print. When I switched to the LED bulb, and kept filters and Fstop the same, 20 seconds exposure produced an identical print. Alan |
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