How come flash shoots twice?

[shiggy]

Hello all,

I have been using my Nikon 2100 extensively and really have been enjoying it . My question is how come when I take a picture the camera seems to use the flash twice. A friend asked me why it does that and now it has peaked my interest.

Peace...

Shiggy

[tealblue]

some coolpix units will do this when the flash is set for anti-redeye

[djkothbauer]

I have an Olympus and I know someone who has a Coolpix 2000, they both do the same thing even with the red eye turned off. Im no expert, but what I read was that they fire a first flash to set the white balance, then the second flash. I find this annoying sometimes especially taking pictutures of my cat, he is too quick, he squints every time I take a picture!

[rych26]

djk,

Try setting the WB to "sunlight" instead of Auto WB...

It should be balanced properly for a flash shot, and maybe your flash won't go off twice (I'm not sure about that part).

[Mike_PEAT]

Just so you know the buzzword, it's called preflash. The red-eye flash fires off a few flashes before the main one.

[rych26]

I need all the buzzwords I can get!

I'll play with my camera tomorrow, but if the redeye reduction is off, and it's not on Auto WB, will that kill the preflash, so his kitty won't squint?

I hate squinting cats...my cats usually just give me the finger...especially when I catch one of them where they know they aren't supposed to be. :lol:

[Mike_PEAT]

I haven't found a way to turn it off yet. Try going into Google.com and typing in DISABLE PREFLASH and see what you come up with. The only real solution is to buy a camera that doesn't have a preflash, or a fast enough preflash that it's not noticable.

[voxmagna]

It should be balanced properly for a flash shot, and maybe your flash won't go off twice (I'm not sure about that part).

On my Fuji, I recently discovered that whilst it appears you can set an alternative white bal in the menu, and the preview shows it, the moment you enable flash internal or external, what you actually get is a default white bal for the flash anyway.

There's no external flash shoe on this cam, so I can't see an obvious solution.

[Mike_PEAT]

Also if you set a manual or preset white balance, your pictures will be too blue (usually) from the flash colour (although it can be corrected in a good photo editing program).

[NHL]

Originally Posted by shiggy

Hello all,

I have been using my Nikon 2100 extensively and really have been enjoying it . My question is how come when I take a picture the camera seems to use the flash twice. A friend asked me why it does that and now it has peaked my interest.

Peace...

Shiggy

In film camera there's a separate sensor in front of the camera (for point and shoot), and in SLR there's a sensor measuring off the film plane to meter the flash and modulates its output to provide the proper exposure with one exposure in real-time.
Most digital cameras use the CCD to accomplish this by using the same CCD that capture the image to meter the light, hence the pre-flash to determine the exposure/white balance, and then the real shot with the correct flash output and white balance setting. Some camera like the D7's for one can be programmed to disable this pre-flash since this is very annoying when taking picture in the studio with photoeye slaves where the external strobes all go off with the pre-flash instead of the main burst!!! ops: ops: ops:

The same thing apply to AF where former separate sensors like IR or phase detectors where used to quickly determine focus on film cameras. The CCD is now also double up (to save cost) for the same function, hence economical, but slow AF !!!