Quick flash question... I RTFM :)

[Adam Hicks]

I was shooting some indoor shots last night with a flash, and when the ISO was high enough that it would go above the flash sync speed of 1/250, the image would be washed out. I was shooting in Av mode. What causes this? I expected the flash to operate as fill, and the camera to meter as if there was no flash there. I guess I was wrong.

I turned the flash off and was able to get the proper shots I neded, but I was a little puzzled by this and hoped I could get the boards input.

Also, I've ordered a 550 which is due in tomorrow from B&H, which I will use as my primary flash. Other than being able to adjust on-flash output, is there anything I should keep in mind? Is it still max 1/250 sync speed?

Thanks!
Adam

[jimlp]

I was shooting some indoor shots last night with a flash, and when the ISO was high enough that it would go above the flash sync speed of 1/250, the image would be washed out. I was shooting in Av mode. What causes this? I expected the flash to operate as fill, and the camera to meter as if there was no flash there. I guess I was wrong.

I turned the flash off and was able to get the proper shots I neded, but I was a little puzzled by this and hoped I could get the boards input.

Also, I've ordered a 550 which is due in tomorrow from B&H, which I will use as my primary flash. Other than being able to adjust on-flash output, is there anything I should keep in mind? Is it still max 1/250 sync speed?

Thanks!
Adam

If the shutter speed goes above the max sync speed the flash will not fire unless your flash is set to high speed sync. Are you using a Canon flash? If not have you ever run into this before? I am not sure why your photos would be over exposed, I am curious to see the replys.

[Adam Hicks]

I am using the 420EX. I know with the 550 I can just dial it down... I suppose I could have used FEC on the camera to reduce the flash output in higher than 1/250 exposures? I was using a bouncer so it was locked at 50mm on the flash.

It just seemed odd that the slower shutter times yield the correct results, while the faster shutter times result in a highly overexposed image.

It's scary how much easier it is to figure the camera out than it is the flash!

[Quinn Porter]

If I understand your situation, I believe your problem is that the shutter speed is reverting to 1/250 since the flash is up (even though the shutter speed should be faster given the ambient light). So the shutter speed aperture combination is going to result in over-exposure regardless of the flash strength.

Your solutions, assuming you want to use flash are:

1. Reduce ISO
2. Select a smaller aperture
3. Use high speed sync with your 420ex or 550ex (you may need to use manual mode to make sure the shutter speed doesn't revert to 1/250, though I'm not sure about this)

Reducing the power of your flash is not going to solve the problem because the ambient light is causing an over-exposure on its own, any flash will just add to the problem.

Good luck

[Adam Hicks]

Ahhh that makes perfect sense. I'll need to pull the camera out and play with is some, but I guess I didn't think about the fact that it would force the shutter to 1/250. It's obvious I'm learning the ways of flash-hood.

THanks for the response!

Adam

[Quinn Porter]

Adam,

Check out custom function 16. Its called Safety Shift, and if it had been enabled, it would have automatically shifted your aperture even though you were in Av mode. Safety Shift will adjust your aperture when you are in AV or your shutter speed when you're in Tv mode if a proper exposure can not be obtained with the aperture or shutter speed selected by the user. :D

[Adam Hicks]

Cool thanks! I'll check in to that... I assume this means it will shift the aperture or shutter if the exposure falls below or above the normal EC stops? I'd hate to be adjusting my EC +1 and have Safety Shift put it right back in the center!

Thanks!
Adam