Problems with Omnibounce

[thegrandpoohbah]

I just got my Stofen Omnibounce in the mail today so I threw it on the Sigma 530DG Super and what I got was definitely not what I expected.

SOOC. Both shots were at 50mm, f/4, 1/200 sec. and ISO 400. Flash set to ETTL mode.

Here is the first shot with just the flash at 60 degrees bouncing off the ceiling:


And here is the exact same shot with the Omnibounce:


Am I missing something here? How did the Omnibounce actually INCREASE the light output of the flash? I must be doing something wrong but for the life of me, I have no idea what...

[thegrandpoohbah]

Oh, and I'm pretty sure the flash is firing at full power when the Omnibounce is on as it takes longer to cycle than when the Omnibounce is off. Is that supposed to happen?

[zona5101]

If the exif data shows the same exposure then I believe what has happened is during the exposure with the omni had cut the light enough that the ttl sensor called for more light and increased the output of the flash.

[sybren]

This is very strange. The eTTL mode should have made the exposure of both photos more or less the same. Zona5101 is right in that the diffuser "eats up" light. It also sends light in all directions, so even less light will hit the subject. It's expected that your flash will have to do more work to get the same amount of light on the photo.

However, the flash can be increased in 1/3 stops. The difference you're seeing here is much more than just 1/3 stop. I would set the flash to manual mode and figure out how many stops of light is eaten up by the diffuser. And take some more shots in eTTL mode, just to see whether it's consistent behaviour or not.

[crunch]

How big was the room? All the bouncy flash (from all the walls) may be the cause.

[kencaleno]

Yes the "omnibounce" is meant to emulate the old "bare bulb" lighting-Flash should be vertical- (not 60 degrees) and you will get 360 degree lighting coverage. The omnibounce is not a diffuser, but a light modifier. Ken

[sybren]

Originally Posted by crunch

How big was the room? All the bouncy flash (from all the walls) may be the cause.

That can't be the cause, as the eTTL metering should have compensated for that.

[crunch]

Originally Posted by sybren

That can't be the cause, as the eTTL metering should have compensated for that.

Oh right, missed that one...

[inkista]

Just curious: when you had the Omnibounce on the flash head, was it still in the same position as you had it for the bounce shot? or did you tilt the head down so it was pointed directly at your plushie cow? I think that, more than anything would account for the light change.

Going from bounce to direct changes the distance the light has to travel, so you effectively upped the power of the flash if that's what you did.

[thegrandpoohbah]

The shots were identical except for adding the Omnibounce. It's not just these two shots, every shot with the omnibounce (regardless of what position its in) is overexposed. I don't get it, I've never heard of anyone having this problem with them when I was researching them...