Flash and high speed synchro

[yb98]

I have a 430EX and a digital rebel.
I tried the high speed synchronisation of the 430 EX but there is something strange. The difference in exposure between 2 shots, first one taken at 1/200 and second one at 1/250 is very high. I think this is not normal. I don't think that 1/50s will make such a difference in exposure. Do you have any explanation ? Am I doing something wrong ? Thanks.

http://bellik.free.fr/flash200.jpg

http://bellik.free.fr/flash250.jpg

[coreypolis]

when you enable high speed sync, the flash's duration is cut way down and as a result, the flash is much less powerful

[coreypolis]

its designed to be fill flash under bright days without having to compensate in exposure

[yb98]

I often do macro shots and would love to try to shoot insects when they are flying. So I need a high speed such as 1/500 or 1/640 to have sharp insect's wings. Is there any way to achieve that (except using natural light) ?

[coreypolis]

I personally know nothing about macro photog, but just in general your best bet is to use natural light with high speed sync for fill, but not as the key light

[Curtis N]

There shouldn't be a difference in flash exposure between 1/200 normal flash and 1/250 FP flash, as long as you have enough power.

Did you get the flash confirmation light when you took the second shot?

[PacAce]

Curtis is right, you really shouldn't be getting such a big difference in exposure between those two images. Does this happen consistently or did it only happen that one time. If it's doing it consistently, it may be time to take the camera and/or the flash to the shop.

[coreypolis]

the camera can't sync at that high of a speed with out high speed sync on the camera enabled, and flashes behave very differently with high speed sync on, its no surprise that theres a difference

[jrsforums]

If the EXIF info is correct, you are using a Digital Rebel. This camera was quite a bit down spec'd. Does anyone know if it supported FP flash?

John

[PacAce]

the camera can't sync at that high of a speed with out high speed sync on the camera enabled, and flashes behave very differently with high speed sync on, its no surprise that theres a difference
No, not really. Whether the flash is in normal sync or highspeed sync mode, it's still operating in ETTL mode so the camera has full control of the exposure.

Actually, I see two things wrong with the exposures. With the first one, shot at 1/200, the flash output is too high, thus blowing out some parts of the figurine.

With the 2nd one, it's obvious that the picture is well underexposed.

It's very possible that the AF points in the two images were at different points, such as one over the black rim of the eyeglasses above the nose and the other being just slightly below it on the white part of the nose. If there's nothing wrong with the camera and the flash, that's the only thing I can think of that can explain the drastic difference in the flash exposures.

[PacAce]

If the EXIF info is correct, you are using a Digital Rebel. This camera was quite a bit down spec'd. Does anyone know if it supported FP flash?

John
I'm pretty sure that it does but even if it didn't, the shutter speed difference is so small that it wouldn't have made a difference. Worst case scenario, the one shot at 1/250 would have had a narrow black bar along one of the long sides of the frame but the exposure shouldn't have been much difference from one shot at 1/200.

[Curtis N]

you are using a Digital Rebel. Does anyone know if it supported FP flash?Must you speak of my wife's beloved camera in the past tense? ;)

Yes, it's a Type A body that supports FP Flash with flash units that have it. There is a letter "H" that appears in the viewfinder next to the flash icon in this mode.

[yb98]

There shouldn't be a difference in flash exposure between 1/200 normal flash and 1/250 FP flash, as long as you have enough power.

Did you get the flash confirmation light when you took the second shot?

Yes.

[yb98]

I changed the batteries and removed the wide angle lid on the flash and now I have coherent results...
Thanks everyone.