EOS Rebel XTi and flash Sigma DG-500 DG SPUPER

[michal_pokorny]

Hello,

I have question about subject. I have this - EOS Rebel XTi and flash Sigma

DG-500 DG SPUPER and when I flash directly, the image is quite dark. I have to

set +1EV flash composition. The second problem is, that the image is less sharp.

Does anyone the same experiences? Please, do you have any idea what shall I do?

Thanks for your answer. Best regards Michal

[mike_s10]

Please post some more details on your Camera and flash settings as at the moment they're quite vague, you don't say which mode you're shooting in or the flash mode either.

Ensure that your flash is set to ETTL only not the linked slave flash or manual, (manual will tell you how to).

If you want a fully auto flash experience than set camera body to 'P' and flash top ETTL, it will do the rest for you, you may need to increase the FEC or in some cases decrease but certainly not by mcuh and you should be getting very sharp clear images, (Lens dependant of course).

Whilst thinking of the settings to post take a look at the video link, I use the same flash unit and this card and it works superbly.

 

Cheers,

 

Mike

 

http://www.youtube.com/watch?v=RNCmuExlHvM

[michal_pokorny]

I'm sorry.

I tried it of course on M,P,A settings. Without any corrections. I'm not beginner in photo. I understand full how it works. But the experience is not well with the flash. My opinion is that the flash is not coordinated with the lens. When I set zoom to 50, flash show 50. But we have to count the crop factor. It means, I have zoom 50*1,6 but the flash think that 50.

 

example of bad exposition and bad sharpnes:

<a href="http://www.volny.cz/pokorny.m/flash/IMG_1029.JPG">Foto</a>

[mike_s10]

The crop factor shouldn't be an issue as these modern flashguns are designed for digital SLR's and accordingly as most are crop bodies this should reflect in the design of the flashguns.

Your image doesn't look too bad just a little soft at 100%, Some USM should help there and exposure isn't bad.

In P mode the camera should do the lot for you with ETTL metering in AV it should do likewise but use the flash as fill meaning you'll have a slower shutter to capture background ambient.

Do you know anyone else that has a flash unit the same that you could try to see if there's an obvious difference.

Also re the zoom, you can manually zoom the head to see if this makes a difference to your pics?

It's difficult to pinpoint the exact issue unless you carry out some samples and post images with the full info.

Try a set of shots in P mode with FEC and without at completely default settings and post them up with EXIF data to see if anyone else can see an issue.

 

Mike

[jimstrutz]

Actually, the EF 500 DG Super is not designed with digital in mind. At least not with the common digital crop factor in mind. It's designed for full frame cameras, and spills extra light off to the sides when used with cameras like the XTi. Not that that is a bad thing. It generally results in more even lighting since the camera allows for a narrower field of view, and some of the side light gets reflected back into the scene, possibly resulting in better lighting.

 

That is obviously NOT happening in the picture you linked. Unless you had inadvertently put the flash head into manual zoom, and selected a significantly longer length than the lens, your flash is not working correctly. At least not the auto zoom part of it.

 

But the included image shows glare right near the middle, so assuming the center AF sensor was the one active, the flash meter probably saw that glare and reduced flash power so far that the main scene is under lit. Canon's E-TTL II system is not foolproof. There are lots of times when you will have to actively use FEC to fix what it does. Fortunately, this is easy and quick to see with digital. Also, Canon digital SLRs are commonly noted for using less flash than most people want. The camera may just need flash exposure recalibration. Less flash is better than more since too much will blow out the highlights, and they are not recoverable.

 

Also, your lens is obviously not focusing correctly. Could be a lens problem or a camera problem. It looks rather dim in the room, so accuracy should be improved with the use of the AF assist light from the flash. I assume you did not have AF assist turned off by way of a custom function? Also, one of the chief failings of all third party flash units is that their AF assist light only works with the center AF sensor, so if you did not use the center AF point there would be no AF assist. That might account for poor focus in dim light.

[ci_p]

The photo was taken at 17mm f2.8. It isn't going to be perfect. I'd second the suggestion to investigate what the AF and the AF assist light is up to.