Whats the use of a diffuser on a flash?

[The Ever Optimist]

Hello to all

I have been noticing some pro photographers use various add ons with their flash guns....the two most common ones being a white card taped to the top of the flashgun and the other being a diffuser like the Sto-Fen Omni-Bounce ...

What is the difference between the two and do i really need them? Cant i just bounce the flash off the ceiling?

TIA

Kunal

[another view]

Basically, straight-on flash is pretty harsh and bounce flash is soft. These devices help you get some of the advantages of both.

The white card is a bounce card, which you would usually use when bouncing the light off the ceiling. That white card on the back side of the flash will reflect a little light and give you some highlights (like catchlights in your subject's eyes). The light will be soft but you'll get a little more punch to it this way. I've seen people (mainly photojournalists) shoot in big spaces and outside with a bounce card and the flash pointing straight up. You won't get much light out of the flash, but that's probably what they're after.

The Omni-Bounce works good inside because it will bounce light off the ceiling and walls. Perfect situation would be 10-12' white ceiling, white walls and a fairly small room (or at least you're close to the walls). The higher the ceiling, bigger the room, etc - the less it's effective.

[92135011]

some argue that diffusers do not soften the light because it is by all means the same light and the same meter that surveyed that light. I have used cards and havent seen too much of a difference at all. Some people do a -0.5 or -1 EV compensation on their meters instead. oh yeah you also need diffusers for super wide lenses

[OldSchool]

AV and 921... have covered this nicely. The only thing I'll add is that using a diffuser may reduce the hard shadows some that result from a direct flash because light is coming directly from the flash AND also bounced of the surroundings.

Personally, I do not use a bounce card much because I switch often from shooting landscape to portrait. Instead, I keep a diffuser on and then bounce the flash.

Tim

[Stephen Lutz]

I have used an omnibounce a few times, but didn't notice that much difference in my flash photos. I have also used the "pocket bounce" which is sort of like a cobra head on your flash. It redirects and diffuses the light straight ahead, rather than all over the place like the omnibounce. The pocket bounce, IMO, provides better results. Fewer hot spots on people's foreheads, nose, etc and the shadows are softer.

Still, direct flash is generally not THAT bad. The flash head itself is somewhat diffused, and once you're past ten feet the add-on diffusers don't have any effect. What works best, in my opinion is a bounce flash off a ceiling. Very even lighting usually results, though shadows under chins can be an issue, as well as the lack of a catchlight in the eyes.

What I've been doing the last year or so is dropping my flash power 2/3 of a stop when using flash indoors, and adjusting up or down depending on the histogram. As a rule, if the shot is a touch underexposed overall that means the important parts of the photo (people's faces) are usually correctly exposed.