Help Needed: Flash Problem : Canon EOS 7D & 580 EX

[philperry]

Help desperately needed. I have just returned from a once-in-a-lifetime trip to Brazil’s Pantanal. While there I experienced some flash problems. I am sure that I have done something really stupid and will kick myself. But for the moment I cannot work out what the problem is.

I have not deliberately changed anything to the way I normally use my telephoto flash for night-time photography. But somehow things have gone wrong.

I am using a Canon EOS 7D with a 580 EX flashgun and a Better Beamer – for night-time photography using a spotlight to focus. As far as I can tell from the manuals the 7D and 580 EX are supposed to be compatible for ETTL shooting.

For as long as I can remember the flash synchronization speed has always been 1/250^th second. However on this trip I have been getting shutter speeds of anywhere between 1/10^th second and 2 seconds. I have had to use much higher ISO ratings than I have ever used before – up to 6400 – despite modest subject distances. As a result a lot of my pictures have blur due to two images being recorded – one from the flashgun and one from the spotlight.

My settings were :

Canon EOS 7D Settings : e.g. Tv (or C1, C2, C3); 1/250^th ; Flash Control Enabled ; 1^st Curtain sync

580 EX Settings : ETTL ; Manual Zoom at 50mm ; Better Beamer

If I do a test using manual metering – then lo and behold I get 1/250^th shutter speed. But any of the TTL systems give me a weird range of shutter speeds.

I did not even realize you could change the default 1/250^th setting – and no I did not accidentally set 2^nd curtain sync.

Any ideas anyone ?

[James Prudente]

Go to Custom Function 1 and see how you have the flash set up. Auto, variable or 1/250 sec. That may be your problem.

Jim

[philperry]

Many thanks for the comment James. I looked at the CF I settings (two bodies) and they were on Auto. I have changed them to a fixed 1/250th.

But that only appears to affect Av mode - and I was always using Tv mode. I will have to run a test to seem if the CF I function also affects Tv mode.

So there may still be a problem.

[philperry]

James

I have just tried checking my EXIF data and notice that it does not seem to show whether the metering modes are Tv or Av. I had set up a custom setting that did use Av and I guess some of my flash photos were taken on that mode. But I am still sure that most would have been taken on Tv (shutter speed priority) (Memo to self: In future use Aperture priority for flash !).

I did manage to find one set of pictures that were all taken at 1/250th - so that is a relief. But a mostly the photos show a range of shutter speeds.

So still not absolutely sure what the whole problem was caused by.

[Dave Blinder]

Not sure on how to resolve your metering problem, but I would use both the camera and flash in full manual mode if needed.

[philperry]

Thanks Dave. If I had discovered the problem earlier in my trip I would have had to go manual. The problem is amending the settings as the subject distance changes - a bit hit and miss. And sometimes you only get one shot !

[Chris Ober]

moving to the photography gear forum

[Christopher C.M. Cooke]

I have had the same problem myself so I look forward to an answer. (any explanations should be simple enough for someone with an inability to understand Manuals problem) :)

[Geraldo Hofmann]

As at night the flash will be the only light source you could use the camera on manual. Maybe you have CFN I-6 enabled (safety shift) ... in this case the camera will override the TV-setting of 1/250 and try to achieve a correct exposure using a much longer exposure time and an open apeture...

Hope you had a good time in Pantanal

Geraldo

[Christopher C.M. Cooke]

Thanks Geraldo, I will try it.

[philperry]

Geraldo

Thanks so much. That is the answer. I changed the CFN I-6 enabled (safety shift) setting to enabled after I went through Artie's 7D users guide. Unfortunately I did not realise the impact of this particular setting. For my night-time telephoto flash with spotlight (for focussing) work I need to have a fixed sync speed of 1/250th.

At least I know for the future.

Thanks again.

[Geraldo Hofmann]

Phil,

Your welcome ... I will be out in a little Forest patch south of Sao Paulo at night all next week. When I return I tell you what I forgot to set back to 0 ... sometimes I hate this modern cameras with all their bells and whistles too many things to change... but then I love them for the same reason :-)

Good luck let me know when you come to Brazil again

Cheers Geraldo

[philperry]

Thanks Geraldo. Had a great time in the Pantanal. Saw Puma and 5 Jaguars. Including mating pair of Jaguars at close distance in the open on a sandbank. Despite flash problems I just about managed to get some pics of them, though not up to my usual standard. C'est la vie.