Frosted or Clear Halogen Bulbs?

[Frank Petronio]

What is the purpose of frosting on a Halogen bulb? I mean at anything other than macro distances, it all becomes a point source so it can't be diffusing the light can it?

I just was at Lowes and saw they stock a lot of Halogens now, including 500W "Rough Duty" ones that will fit my Lowels. Only $8-9 too, compared to the bulbs I buy from B&H for double that. But I think all my bulbs I've purchased from photo concerns have been frosted.... what is point of the frosting though? If anything it should make them less efficient, right?

[Leigh]

... what is point of the frosting though?
I suspect its purpose is to reduce the hot spot of the filament, so folks don't damage their eyes if they look at the bulb.

- Leigh

[Mark Woods]

It might just be a marketing tool. I've seen things like this over years where opposing sides will stake out a position when it really doesn't matter. The source would be slightly larger because of the frost on the globe, but not enough to make a difference IMHO.

[Frank Petronio]

For what it's worth, the bulbs seem to work just fine and are a bargain compared to the photo-store bulbs. Same brands as the photo ones too, I guess they understand that housepainters and carpenters won't pay $18 for a bulb lol.

Well the frosting might help lessen the eye strain, if anything the craftspeople using work lights are getting fried eyes more than photo subjects, who usually have some diffusion between them and the light.

[Drew Wiley]

"Rough duty" refers to the alleged extra strength of the filament and surrounding glass, so the bulb is suitable for jobsite use and isn't so fragile. But it will still blow
up if it gets fingerprints on it, and will still easily start a fire. Frosting has long been
offered on techinical bulbs for a variety of reasons. It acts as a bit of diffusion, and
this is sometimes important to prevent a specular reflection of the filament per se.
It rarely makes a significant difference with studio lighting setups, since we tend to
provide our own diffusers and bounce materials. There are also cases when these
cheaper bulbs are less desirable for color photography. When in question check them
with a good color temp meter. Lots of the time you can save money, but generally El
Cheapo made-in-China bulbs don't last nearly as long as US, Japanese, or German
bulbs. Photo suppliers per se routinely overcharge, so I prefer to buy better quality
bulbs from a bulb specialist.

[Allen in Montreal]

In theory,
a softer more even light.

I almost always buy the hardware store 300 watt, 2 per $9.00 pack version of the bulb for my mini Lowel's.

Very quickly fixed with a small piece of Tough Spun (#216) or Half Tough Spun (#215) from your Mole Richardson dealer.




What is the purpose of frosting on a Halogen bulb? I mean at anything other than macro distances, it all becomes a point source so it can't be diffusing the light can it?

I just was at Lowes and saw they stock a lot of Halogens now, including 500W "Rough Duty" ones that will fit my Lowels. Only $8-9 too, compared to the bulbs I buy from B&H for double that. But I think all my bulbs I've purchased from photo concerns have been frosted.... what is point of the frosting though? If anything it should make them less efficient, right?