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Dimming Quartz Halogen Bulbs

Nathan Bladow , Jul 25, 2008; 04:02 p.m.

I know it can be done with regular dimmers but that it shortens the life of the bulb. what i am wondering is if their is a way to do it other than lighting controls (scrims, ND filters, ect) that will not shorten the life of the bulbs like if you get a dimmer that lowers amperage as opposed to voltage or some thing like that. thanks

Responses

Ellis Vener , Jul 25, 2008; 04:12 p.m.

I'm not sure lower voltage shortens the life of the bulbs but I guess that could be the case. Using scrims , ND gels etc. works fine and an addded bonus is that these methods also do not change the color temperature the way dimming does.

Charles Webster , Jul 25, 2008; 04:59 p.m.

There is no "magic" dimmer that lowers the amperage without lowering the voltage. Physics is physics.

As Ellis says, you can/should use scrims or diffusers or ND gels to lower the intensity without changing the color temperature, as happens when you use a dimmer.

<Chas>

Frank Skomial , Jul 25, 2008; 06:15 p.m.

"I know it can be done with regular dimmers but that it shortens the life of the bulb." - so you know, you know this is a nonse, right ? Dimming the light could extend the bulb life, but sudden temperature chances could cause unexpected damage.

What you seem not to consider is that the light temperature could change... but if you use black and white photography, then it does not matter for you. As long as you know possible color teperature changes and take care of the camera color balance properly ?

Kelly Flanigan , Jul 25, 2008; 06:34 p.m.

The results with diming a Halogen Bulb vary with its constuction; ie its thermal configuration; ie how it fares with still supporting the Halogen cycle.When the cycle drops below say 250 C the cycle tends to stop working.It depends on the variant of gas, ratio of gas to filament; thermal layout; ie size of the bulb; reflector etc.. Once the dimmed Halogen is dimmed to the point where the Halogen cycle is not working; one has sort of just a regular bulb that blackens with time; ie its light output drops. If you are an engineer; an experimenter or tooler one can drop the voltage than then make a lampholder/reflector that purposely throws in a mechanical shield/insulator ; etc to keep the bulb above 250C; and thus the dimmed Halogen still has its cycle going. ( sort of like truckers masking off alot of their radiators when in sub zero weather;)).

"life of a bulb can be burnout; or having a bulb its output below spec. Adrop might not matter for the garage lamp; but matter for a copys stand for artwork.

Kelly Flanigan , Jul 25, 2008; 06:46 p.m.

Even with a Halogen reducing the voltage makes the bulb run longer hours before burnout.Once you dim the bulb low enough where the Halogen cycle stops the bulg blackens slow with time;like a regular filament bulb. This blackening may go awayif one uses the bulbs at the normal voltage for awhile. ON a copy stand one often replaces the entire set of bulbs.Here with my Phase One scan back I use a series parallel switch; or a variac to drop the voltage; to not fry and fade the items.. When somebody says dimming reduces the "life of the bulb" it often means the bulbs are NOT burned out; but have darkened somewhat. "Life" of a bulb can be defined by the end usage; burnout; color temp; percentage drop in output. This might not matter in your family room with a mini Halogen aimed at a mantle; but matter to a studio settup for shooting images/movies etc.

Steve Levine , Jul 26, 2008; 07:06 a.m.

In the B&W days in Hollywood they would sometime have the power house lower the power to a soundstage to dim all the lights at once. When color came into vogue this stopped of course due to the color temp shifts that a dimmed light would produce.

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