topic Re: Speedlite 580 Exii with diffuser in Speedlite Flashes

Speedlite 580 Exii with diffuser

jdharford — Tue, 15 Mar 2016 18:31:48 GMT

My 580 EX II exposes properly when the diffuser is not on the flash. The diffuser is made for this Speedlite and yet when I use it there is a drop in the exposure by about one and a half stops. I have tried the flash with different manual settings on the camera, and the result is as indicated. Changes in the manual settings without the diffuser were properly adjusted for and properly exposed, but the diffuser seemed to cause some problem. The setting in these cases is ETTL.

Re: Speedlite 580 Exii with diffuser

TTMartin — Tue, 15 Mar 2016 19:16:42 GMT

@jdharford wrote:
My 580 EX II exposes properly when the diffuser is not on the flash. The diffuser is made for this Speedlite and yet when I use it there is a drop in the exposure by about one and a half stops. I have tried the flash with different manual settings on the camera, and the result is as indicated. Changes in the manual settings without the diffuser were properly adjusted for and properly exposed, but the diffuser seemed to cause some problem. The setting in these cases is ETTL.

Why not simply use about one and a half stops of flash exposure compensation when using the diffuser?

Re: Speedlite 580 Exii with diffuser

jdharford — Tue, 15 Mar 2016 19:19:29 GMT

That is, of course, a practical answer. But it troubles me that I do not know why an ETTL setting should not already compensate.

Re: Speedlite 580 Exii with diffuser

TTMartin — Tue, 15 Mar 2016 19:32:49 GMT

@jdharford wrote:
That is, of course, a practical answer. But it troubles me that I do not know why an ETTL setting should not already compensate.
Unless you are talking about the built-in pull out diffuser panels how is the flash supposed to know there is a diffuser attached and that it needs to give more power to compensate for its output being diffused?

Re: Speedlite 580 Exii with diffuser

kvbarkley — Tue, 15 Mar 2016 20:35:43 GMT

Because of the ETTL pre-flash - which is the whole point of ETTL. I doubt that he is putting the diffuser on in the instant between the pre-flash and the exposure flash!

Re: Speedlite 580 Exii with diffuser

jrhoffman75 — Wed, 16 Mar 2016 01:41:34 GMT

Right, E-TTL should compensate. But, perhaps the distance is now too great compared to the reduced light output.

Re: Speedlite 580 Exii with diffuser

kvbarkley — Wed, 16 Mar 2016 03:14:18 GMT

But when he switches to manual flash, he gets good exposure.

Re: Speedlite 580 Exii with diffuser

jrhoffman75 — Wed, 16 Mar 2016 03:27:40 GMT

I interpret his statement as manual camera settings, not manual flash settings.

Re: Speedlite 580 Exii with diffuser

TTMartin — Wed, 16 Mar 2016 11:15:20 GMT

@jrhoffman75 wrote:
Right, E-TTL should compensate. But, perhaps the distance is now too great compared to the reduced light output.

E-TTL is a tool not magic. Like any other automation on the camera sometimes it requires user input. Otherwise everyone should just be shooting on Green Square Auto.

Re: Speedlite 580 Exii with diffuser

kvbarkley — Wed, 16 Mar 2016 13:44:26 GMT

This is a wild shot, but try using second curtain sync. It might be the preflash is interfering with the main flash. Canon uses some wierd language about this point in the manuals - though it is usually in reference to wireless flash.

Re: Speedlite 580 Exii with diffuser

jrhoffman75 — Wed, 16 Mar 2016 13:46:22 GMT

The 430EX-III comes with a bounce diffuser. The manual warns that under exposure can occur because the guide number is reduced.

Re: Speedlite 580 Exii with diffuser

kvbarkley — Wed, 16 Mar 2016 13:51:51 GMT

I am talking about this note:

"Even if you disable the built-in flash from firing, it will still fire in order to control the slave unit via optical transmission. The flash fired to control the slave may therefore appear in the picture depending on shooting conditions"

Re: Speedlite 580 Exii with diffuser

jdharford — Fri, 18 Mar 2016 21:56:36 GMT

Thanks to everyone for the comments. To clarify, I was using the 580EXii with a 100mm macro lens with the camera on manual settiings and, for the test, shooting at one of my prints about 6 to 8 feet away. Ambient light was too low to be a factor. THe settings were at an intermediate f-stop and with the time around 1/60 second. It did not seem that power limitations were the problem. I was beginning to think that the pre-flash came from a different part of the flash than the exposure flash, but that does not seem to be the answer. I tried the experiment with two different kind of diffusers, one which is a designed to bounce the light, and the other just a milky fitting on the flash head, but the results were much the same: the loss of more than a stop of exposure with the diffuser. I should probably try the same experiment with a lens set around 50mm.

Thanks again to all.

Re: Speedlite 580 Exii with diffuser

RobertTheFat — Fri, 18 Mar 2016 22:35:02 GMT

@jdharford wrote:
Thanks to everyone for the comments. To clarify, I was using the 580EXii with a 100mm macro lens with the camera on manual settiings and, for the test, shooting at one of my prints about 6 to 8 feet away. Ambient light was too low to be a factor. THe settings were at an intermediate f-stop and with the time around 1/60 second. It did not seem that power limitations were the problem. I was beginning to think that the pre-flash came from a different part of the flash than the exposure flash, but that does not seem to be the answer. I tried the experiment with two different kind of diffusers, one which is a designed to bounce the light, and the other just a milky fitting on the flash head, but the results were much the same: the loss of more than a stop of exposure with the diffuser. I should probably try the same experiment with a lens set around 50mm.
Thanks again to all.

In my experience, E-TTL is nearly useless when ambient light is not a factor. E-TTL is exceedingly averse to blown highlights and therefore exposes for the brightest elements in the scene. In effect, it takes the attitude that all flash is fill flash. If you don't have enough ambient light to support that notion, there are two alternatives: bounce flash or manual (not E-TTL) flash. Otherwise, underexposure, sometimes severe underexposure, is practically guaranteed.

Re: Speedlite 580 Exii with diffuser

Waddizzle — Sun, 20 Mar 2016 15:14:16 GMT

This sounds like an excellent scenario where a good light meter will guide you to good exposure.

Re: Speedlite 580 Exii with diffuser

digital — Fri, 15 Apr 2016 19:56:32 GMT

ETTL is a geat tool but ball park. I have seen this conversation many times. I long ago stopped trying to figure out why it will or won't copensate for a diffuser even if it is suppsed to. I just do what needs to be done to get the shot.