Received my first big flash yesterday, these are Profoto B1 and there is a thick glass in front of the flash and removing it is not easy but it is possible. What is it? Is it something like that built in diffuser we had in small flashes that when it was on the lens it was always setting the zoom to its widest? Should I take this out? or is it a pat of the flash system and I shouldn't mess with it?

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    -1 Because. Page 15 of the manual. We do expect you did basic research before asking a question. – inkista Jul 31 '15 at 18:14
  • @inkista I actually read that last night and that's how I found out this thing can be replaced but still isn't clear to me what is it currently doing and if I should take it out? – user1899082 Jul 31 '15 at 20:19
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    It says "optional" which means there is no "should." It's up to you whether or not you want to protect the bulb, use a dome, or do without. – inkista Jul 31 '15 at 20:36
  • @inkista But isn't "Why or when would I use this option?" a legitimate question? – mattdm Aug 22 '15 at 20:03
  • @mattdm, had it been worded it that way, then I wouldn't have downvoted. The words in the post are: "what is it?" and I think the manual answers that: it's an optional piece of glass you can remove. Simply using it answers how effective it is as a diffuser. Basic research. – inkista Aug 22 '15 at 21:51

I am surprised that nobody mentioned safety as a reason for the glass. (@user1899082 mentioned protection, but I am not sure if they meant protection of the flash or of its user.) Although it happens very rarely, flash tubes may explode, as may other incandescent photography light based on halogen bulbs or similar. A protective glass cover (which should be thick enough not to be shattered itself by an exploding bulb/tube) can protect yourself and the subject/model from broken bits of very hot glass flying around. At least in the EU, protective glass covers are even mandatory for halogen bulbs.

The possibility of the flash tube exploding is also mentioned in the safety instructions of the manual.

So, no, I would not remove it.


It is just a diffuser and also great protection, I haven't seen anybody take it off really. Left it be there.


It is probably there to cut down on UV light. High end flash tubes are made of quartz which passes UV light. If you are shooting color the UV will cause some objects to fluoresce, fabric in particular. If, for instance, you don't want wedding dresses to photograph as blue you want that filter.

If you want harsher light, they make a clear piece of glass to replace the frosted.

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