Enlarger bulb burned after 30 min.

[bobwysiwyg]

Interesting. Keep us posted on how this goes. I have been converting our lights over from incandescent and CFL to LED's. I've installed several of the same Utilitech bulbs in household fixtures which had 60w incandescent bulbs. In particular, four in two ceiling fixtures in our upstairs bedroom. I never mentioned it to my wife, and the next day she asked, "is it just my imagination, or are the bedroom light brighter?" They were, but hardly a scientific evaluation plus the incandescent bulbs were fairly old, so I expect they had lost some "shine." LED bulbs have improved quite a bit in the past few years and the prices are finally coming down out of the stratosphere.

 

[bobwysiwyg]

..I would not count on these bulbs being available forever.

What bulbs are you referring to?

 

[Hatchetman]

What bulbs are you referring to?

incandescent enlarger bulbs

 

[mauro35]

There are places making LED heads (white light and variable contrast) for some enlargers. They are not cheap. Some people have made homebrew LED heads that work, too.

I'm early on in the process of testing an off-the-shelf 60 watt equivalent LED

I'm also interested. In here LED lamps are resonably priced, I'm not sure if because of european energy-saving regulation. But I could not find anything more powerful than 40W equivalent.

 

[MartinP]

The larger power LED lamps are available from any specialist lighting shop here (in NL) but they never seem to appear in a supermarket or normal high street place.

The larger LED lamps (yes, I don't mean CFL) I have used in light-fittings still seem to have a short but noticeable turn-on time, perhaps a tenth or a fifth of a second. I have no idea if that is consistent or not, but it may be an unwanted variable for short exposure times. Apart from the location of the illumination with respect to the condenser(s) of a black-and-white enlarger, the other question-mark would be about the spectrum of the colour temperature of these lamps and whether there are any peaks or troughs compared to incandescent lamps. The only thing to do is try them and see I suppose!

I'm half wondering about using one of the industrial, high-brightness LED's as a pseudo spot-source but I'm uncertain about the effectiveness of a pre-existing condenser in this case. Another thing that has to be tried out probably. Perhaps there will be a metal-work project swapping for my De Vere Varicon lamp-house this winter . . .

 

[bobwysiwyg]

Martin, I too have noticed the very brief delay in the start-up of LED's. I attribute it to the need to convert house current down to what is needed by the LED architecture. Nothing like the annoying delay (for me) of CFL's but not the instantaneous "on" exhibited by incandescents. They, LED's, are after all small electronic packages. In everyday life, the brief delay is barely noticeable.

 

[AgX]

Apart from the location of the illumination with respect to the condenser(s) of a black-and-white enlarger, the other question-mark would be about the spectrum of the colour temperature of these lamps and whether there are any peaks or troughs compared to incandescent lamps. The only thing to do is try them and see I suppose!

Meanwhile there are (expensive) LED cinematographic lights ready to substitute the classic incandescand or HMI fresnel light.

 

[mauro35]

Maybe I'm going a bit out of topic, but reading about people trying LED bulbs made me think about one point that is not so clear for me. Does one need to consider if the distance between bulb and condenser change, compared to the original design? Is this parameter very important, I mean does the distance bulb-condenser have to be fixed and what happens if it changes?

 

[AgX]

With every point light-source when employed in a condensor lighting system the distances lamp/condenser and condenser/lens have to adjusted.

 

[richard ide]

I might add: For every exposure for proper light balance.

 

[richard ide]

Should have said with every change in enlargement factor.

 

[Paul Glover]

I'll report back on print results as soon as I have them, depending on when I next get some darkroom time. Hopefully that'll be this week, finished making a lamp holder box of sorts yesterday.

On my enlarger (Beseler 23CII) moving the bulb too far up or down will cause light falloff, unevenness and formation of dark rings at the edges. There's some leeway here but I wouldn't want it too far from spec.

This particular LED bulb appears to turn on and off about as quickly as an incandescent does. I've heard of some of them having noticeable on/off times, possibly because of circuitry designed to smooth out the AC voltage supply. Perhaps the cheaper bulb skimps on that as a cost-cutting measure, which works in my favor here. Also, it claims to be OK for use in enclosed fixtures, which can't hurt.

 

[mauro35]

I'll report back on print results as soon as I have them, depending on when I next get some darkroom time. Hopefully that'll be this week, finished making a lamp holder box of sorts yesterday.

On my enlarger (Beseler 23CII) moving the bulb too far up or down will cause light falloff, unevenness and formation of dark rings at the edges. There's some leeway here but I wouldn't want it too far from spec.

This particular LED bulb appears to turn on and off about as quickly as an incandescent does. I've heard of some of them having noticeable on/off times, possibly because of circuitry designed to smooth out the AC voltage supply. Perhaps the cheaper bulb skimps on that as a cost-cutting measure, which works in my favor here. Also, it claims to be OK for use in enclosed fixtures, which can't hurt.

Sounds great! Looking forward to it. I´m very interested to see if the contrast is affected on VC paper. In your previous post you said you had to exclude many LED bulbs because of light unevenness. I´m curious on how exactly you selected the one you are testing. Is it possible to visually identify hotspots in the light source, when projected to the baseboard?

 

[Paul Glover]

Sounds great! Looking forward to it. I´m very interested to see if the contrast is affected on VC paper. In your previous post you said you had to exclude many LED bulbs because of light unevenness. I´m curious on how exactly you selected the one you are testing. Is it possible to visually identify hotspots in the light source, when projected to the baseboard?

I wrote up the process of finding a bulb and initial tests, with some photos, at http://www.paulglover.net/20140108-...ghtsource-part-1-investigating-possibilities/

TL;DR version: I ruled out any of the bulbs which look like mood lighting for a spaceship or otherwise had designs which weren't going to present an unbroken area of light on the end, where it's needed. Some of these things are pretty wacky looking! Then looked online for photos of the bulbs lit up. Read reviews to see what else might be a problem. That narrowed it down to the Utilitech.

At this point I walked into my local Lowes and by good luck they had a dimmer demonstration set up using one. To my eye it looked like there were no obvious problems with the way it lit, so I grabbed one.

Right now it's all visual assessment. I think it looks OK compared to the PH140 but I don't 100% trust it without some sort of testing on paper.

 

[mauro35]

Very nice web page! Waiting for part 2...I also found a cheap LED bulb which has actually a very similar shape as the PH-140 lamp and the same E26/E27 mount. It´s a Philips 25 W equivalent:

http://www.ledwholesale.eu/philips_corepro_led_luster_230v_4w__25w_e27_827_p45_fr_1337

Of course the power output is significantly lower compared to the 75W incandescent, so that might be a big limitation. But the light looks really even and of the same color temperature. Trying to look at the same negative projected on the baseboard I can only notice visually a reduction of intensity (obviously) with the LED, but no shadows or hot spots.

Can´t do a real life test yet, cause I´m waiting for my photopaper to be shipped.

 

[mauro35]

Just wanted to update on my last post. I tested both the LED bulb and the PH-1400 incandescent with my Beseler Cadet. Not a scientific test or anything quantitative, just printed the same negative with both lamps and looked at the results. Well, the LED lamp is absolutely fine. Actually, it´s so nice to work with it I´m not using the PH-1400 anymore. The contrast is maybe about 1 grade lower with the same filtration and multicontrast paper (which, for me, is even better), but cannot be sure cause I don´t have any real experience on that. And the exposure times are obviously longer, but that´s a plus, I can learn burning and dodging. Anyway, what I wanted to say is that the prints look just great and I am not going to worry anymore about enlarger bulbs burning.