Canon 20D Flash Issue

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Fotoz - 02 Mar 2006 14:16 GMT

My 20D works great in daylight. When using a flash, the images always
seem underexposed. This happens with the on board flash or an external
unit. (Sigma EF-500 DG Super)
I have to adjust the flash compensation up to +2 to get a proper
exposure.
I can shoot in RAW, but that requires a lot of additional work.
When used manually with my studio equipment it's not an issue.
My old G3 and SD400 have better flash lighting with their tiny built in
flashes.
Does anyone have any ideas what's going on??

Reply to this Message

JPS@no.komm - 02 Mar 2006 15:10 GMT

>My 20D works great in daylight. When using a flash, the images always
>seem underexposed. This happens with the on board flash or an external
>unit. (Sigma EF-500 DG Super)
>I have to adjust the flash compensation up to +2 to get a proper
>exposure.
>I can shoot in RAW,

Then you should probably be using +3. RAW is not a safety net for poor
exposure. Poorly exposed RAWs are almost as bad as poorly exposed
JPEGs. Much of the problems of under-exposure happen at the RAW level
itself, and most of RAW's benefit is more highlights, so you can expose
higher.

>but that requires a lot of additional work.
>When used manually with my studio equipment it's not an issue.
>My old G3 and SD400 have better flash lighting with their tiny built in
>flashes.
>Does anyone have any ideas what's going on??

The 20D assumes light flash fill in Av and Tv modes (and probbly P as
well). You need to be in manual mode in the camera, with TTL in the
flash, to get an honest result from your EC setting.

Signature

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>

><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

Reply to this Message

Peter - 02 Mar 2006 15:46 GMT

>>My 20D works great in daylight. When using a flash, the images always
>>seem underexposed. This happens with the on board flash or an external
[quoted text clipped - 8 lines]
> well). You need to be in manual mode in the camera, with TTL in the
> flash, to get an honest result from your EC setting.

Av and Tv modes expose for background, P mode for foreground (subject). Are
you always in P mode? (I'm not sure, maybe A-Dep works the same). Your
exposure/aperture settings in Av and Tv modes as determined by the camera
will always be the same regardless of flash presence, P will expose lower.

Peter

Reply to this Message

tomm42 - 02 Mar 2006 17:35 GMT

Also flash specs are generall for smallish rooms with 7.5-8ft ceilings.
If you have a big room, high ceilings, lots of people with dark
clothes, this can all change your flash settings. Also if you are
trying to use the on camera flash for more than 10ft distance, this
could cause exposure drop off.

Tom

Reply to this Message

C J Southern - 02 Mar 2006 23:22 GMT

NK Guy has (practically) written a free book on EOS Flash ... you can find
it at:

http://photonotes.org/articles/eos-flash/index.html

Hope this helps!

Reply to this Message