500 Watt enlarger bulb?

[Sevo]

Indeed, but in the online catalog they use Watts OR Lumen OR Candela. There's no way to determine Lumen or Candela from Watts.

I'd assume that anything merely rated in Watts was not intended for applications where amount and quality of the light is critical - and probably will have correspondingly irregular illumination. Regular illumination is the key point for which I'd look in a enlarger lamp - original lamps used a opalescent white coating, at the loss of 70-80% of their light output. While substitutes won't be quite as good if you have a enlarger for which no opalescent bulbs are made any more, they'd be better as good as possible. We don't have quite the same issues over here (there still is a maker of proper enlarger lamps in Germany, within the 150-250W power range my enlargers take), but if I had, I'd settle for something fit for theatrical or showroom spotlight use rather than bulbs not made for any kind of optical system at all...

[StoneNYC]

Original style bulb.

[StoneNYC]

Found the info!!!!

This is the Phillips version of the GE bulb...

Appears to be 11000 lumens

http://www.donsbulbs.com/cgi-bin/r/b...125v~ansi.html


And detail sheet...

[Sevo]

In doubt I'd settle for 250W rather than use a fundamentally different lamp type - a smaller lamp might require a different rod to be properly positioned, and show some light falloff near the edges, but a lamp missing the white coating will be much worse. You might want to write Dr. Fischer (info@dr-fischer-group.com) whether they make or might make a lamp of the above characteristics - they seem to be the only current maker of white coated enlarger lamps.

[Jac@stafford.net]

Pardon my ignorance, but if a bulb has L luminance, then do three bulbs make 2L or 3L?

IOW, is it like flashbulbs where 3 bulbs = 1 stop increase (over 1) and 7 bulbs make 2 stop increase, or not?

[Larry Gebhardt]

Thanks, Sevo. Silly me: I equated Watts with brightness. I'll spend the rest of the morning learning up. Already it is clear that given only lumens, we cannot calculate watts, nor visa-verse.

I see from 1000bulbs.com such metrics as lumen, watt and candle power, but not all for each bulb so I must learn which metrics matter most and how to convert, if possible.

I bought a bulb by accident that is similar, but not frosted. It's also has specs for 130 and 120V. At 130V it's 500Watts, 5000 hours and 7800 lumens. At 120V it's 440Watts, 12500 hours and 5896 lumens. My guess is the ratio between your bulb and the one I have will be about the same. So it may not be too bad.

With a Variac you could run it at 130V, or 125V, or 110V (and make it last a lifetime).

Edit: Also, with a condenser enlarger the diameter of the bulb as well as the evenness of the frosting will be very important.

[Jac@stafford.net]

Larry, which Variac model do you use, please?
.

[Len Middleton]

Different voltages may result in a colour shift, hence the use of constant voltage transformers with enlargers.
An issue in colour printing but not certain if the colour shift would be enough for a problem with VC paper...

[ic-racer]

For a 500W enlarger lamp, a minimum 500W variac should work. I have an inexpensive Chinese 1000 Watt TDGC-1KM that seems to work well for my other projects. I have not used it with an enlarger, but I have used it to dim hot-lights between shots.

[Larry Gebhardt]

Larry, which Variac model do you use, please?
.

It's similar to this one off ebay: http://www.ebay.com/itm/Variac-Varia...item259821902c

It might be the same, but with this type of knock off gear I'm never sure. it works very well, but the marked voltages are not accurate. I used a meter and made marks at the voltages I'm interested in.