Question on Metering and Flash.

[jwbryson1]

When my detachable flash is turned off, the meter on the camera shows if I am overexposed, underexposed or the meter falls dead center which I will call "normally exposed." When I turn on the flash, suddenly the meter will light up all the way to the right and no amount of monkeying with the front or rear dials of my D90 will change that. I cannot get the camera to adjust back to dead center or "normal exposure."

So, I think I am not fully understanding how the on camera meter works or I do not know how to interpret the meter.

Can somebody enlighten me on this?

Thanks.

 

[Robin Usagani]

when you turn on the flash, your shutter speed is limited to your sync speed. Lets say your sync speed is 1/200 sec. Your camera is telling you that you are over exposed. The only way to fix this problem is use no flash or turn your flash to FP mode. But it is not really a problem, it is your camera limitation

 

[Big Mike]

At first I was thinking that your camera/meter shouldn't change just because you turn the flash on...but Schwetty is probably right. When you turn the flash on, the camera will limit the shutter speed to the maximum flash sync speed (or longer)....so that would change your metering if you had it on a faster shutter speed before you turned it on.

 

[KmH]

+3 ↑ ↑ ↑ What make/model/strobe light?

Plus the in-camera light meter is essentially useless when using flash, because it only measures reflected light.

The exposure of strobed light (flash) is controlled by the lens aperture, not the shutter speed. Shutter speed controls the ambient light exposure. Shutter speed is also no longer used to stop motion, becuase that is taken care of by the short duration of the flash of strobed light. A camera maker's flash unit at full power has a flash duration of about 1/1000 second. At less than full power the duration of the flash is even shorter.

If you're using the flash unit and camera in an iTTL mode, the camera electronics and software can use the light meter to monitor the light reflected from the subject, but the pre-flashes used to accomplish that are so short they are useless to you looking in the viewfinder at the meter display.

 

[scorpion_tyr]

I've found that unless I'm in Program Exposure and I have the external flash facing straight forward, the exposure meter isn't very accurate. If you're shooting outside it just takes A LOT of practice to know what to set everything at. If you're starting to do some inside studio stuff then get yourself a light meter.