What is special about enlarger bulbs?

[BetterSense]

When my bulb goes, why can't I just replace it with a 75 incandescent? I'm sure there must be a reason. Freestyle wants $12 for a replacement bulb.

[Toffle]

Well, for one thing, most incandescent bulbs have printing on the center of the surface... something that can result in uneven exposure on crucial areas of your print. Some of the more experienced printers here can give more precise replies, but it is also possible that regular light bulbs have a different colour temperature, or that their warm-up time is not as consistent as the real thing. On top of all that, I believe that enlarger bulbs are somewhat more robust than regular incandescent bulbs. Think of the dozens of times you may switch your enlarger on and off in a single session. I don't know that a regular light bulb would be up to the challenge.

Cheers,

[Removed Account]

I can speak from personal experience acquired with my first darkroom. Normal bulbs do work, although I'm not sure how long they would last. The printing on the center of the bulb can not only create uneven exposure, but depending on your focus it can even be readable! :o

[David A. Goldfarb]

Enlarger bulbs also seem to be more heavily frosted than regular bulbs. Some enlargers have parabolic reflectors that may require the filament to be in a certain location.

[dances_w_clouds]

When I was using my old Omega I just used a 60 watt bulb with the writing taken off with an eraser and alcohol. Worked in a emergency but it couldn't handle the off and on scenario and they weren't frosted as much as regular enlarger bulbs.

[Ian Grant]

This is the 2nd thread in about a fortnight on these enlarger bulbs.

The specialist enlarger bulbs are often powder coated inside the glass to give a better spectral response and more even distribution of light. Some people still use these enlargers/bulbs for colour printing so consistency is important, although most people now use colour enlargers with Dichroic heads.

Using other bulbs you run a big risk of poor illumination particularly with uneven corners.

Ian

[leicam5]

Enlarger bulbs are not frosted but opal (important difference) and, in certain cases, of a well defined dimension with the filament on the right place being of a certain form (no zigzag for instance). They give the same intensity all along their rather short life, short life because they are 'over tensioned' (I do no know if this is the right expression in English, sorry), this is why they are so consistent in output. The inner bulb coating is told to be special too, but this I do not know for sure.
It never crossed my mind to use anything else than the right enlarger-bulb in my enlarger. I think that when these bulbs are designed, their must be a good and acceptable reason, for a non engineer tough...
I trust Philips, Osram and G. E. to know more about (enlarger-) bulbs than I do.

I pay 19 EURO for a bulb, Freestyle is cheap.

Philippe

[digiconvert]

There is also the point that it will soon be impossible to buy household filament bulbs in many parts of the world (EU and Australia have already gone this way I believe) . Not sure how economic it is to make these enlarger bulbs now, I would guess that the last production run has already taken place and that we are living on warehouse stock.

[AgX]

The filament of that lamp has been designed that way that, relative to the similar houshold incandescent lamp, it is run on too high voltage.
Thus the part of photographically effective radiation is increased. With the disadvantage of, again in comparison with the household types, of a reduced lifetime. Which should not matter in amateur enlarging work.

The same technique has been employed in those (non-haloid) photo-lighting lamps.

[Ian Grant]

There is also the point that it will soon be impossible to buy household filament bulbs in many parts of the world (EU and Australia have already gone this way I believe) . Not sure how economic it is to make these enlarger bulbs now, I would guess that the last production run has already taken place and that we are living on warehouse stock.

I'm stocking up on enlarger bulbs for that very reason, although all my current enlargers use tungsten halide bulbs which are also being withdrawn.

Ian