Flash Issues

ishamy · 7 Jul 2011 at 14:07

HI all,

I just recently bought an external flash, Yongnuo YN467 to go along with my Canon 500d. Playing around with it last night and noticed now and again the flash goes off photo taken is white...way over exposed. I have camera set to e-ttl and flash is at ttl, I though the camera picked up what aperture and shutter is needed to go with flash. Certainly it did alright 90% of the time.

I was shooting on the 'P mode' as well as aperture priority mostly. Is there something I'm not doing? Or something I should be doing?

I've got to say though when it does work fine the images are really good, so much better than built in flash, being able to angle it to bounce gives so much more creativity

Zogger · 7 Jul 2011 at 16:39

I could be totally off here because I can't remember how P works with the flash, but it could be something to do with high-speed sync. If high-speed sync is off you can only take pictures slower than a certain speed e.g. 1/250th. If the camera is trying to do fill-flash (I think it does in P, but again not sure) it will try and expose the scene normally, just with the addition of flash. The aperture will open wide but the shutter speed won't go faster than the sync-speed. If you're in a bright place then that means it will end up hugely over-exposed....

What were the conditions / shutter speed / aperture like? I'm not exactly sure what you would need to do to enable it if this is the case

edit: just read you were using aperture priority as well so the above would definitely apply if high speed sync is off or not possible on the 467(?)

ishamy · 7 Jul 2011 at 16:48

Yea I wasn't really taking note of the settings when it happened, more 'och' then deleted the photo. As for sync-speed not sure what that is or is the camera has it or what so will have to get more info on that.

Was in the living room dimly lit with a few lamps, not low light though.

A hand full of the ones that turned out ok to good are in my Flickr (ones of chessmen) if anyone want a gander.

Scam · 7 Jul 2011 at 18:57

How funny. I've just got myself a Nissin flash for my D50 and was playing about with it and had exactly the same thing happen. I'm sure I've seen some great links for beginner guides for using flashguns, can anyone point us in the right direction? I know of Strobist but that's a bit advanced for now

An Exception · 7 Jul 2011 at 19:58

Firstly I'd stay away from 'P mode', and learn how to use your camera properly.
Learn how to expose using 'M mode' along with ETTL.
Av mode may also be a good mode to use when using flash.

For the two modes mentioned above I would disable Auto ISO when using flash.

Below is an example of how to correctly use flash ETTL in 'M mode'.
First identify the desired ambient exposure by selecting your desired working aperture (control's DOF) then set your desired shutter speed, i.e. not too slow that you get ghosting or soft images (unless that's what you want), or not too fast that you lose allot of light hitting the sensor, somewhere in the region of 1/60 - 1/125 works well for me indoors.
Take a shot, is it really dark? If yes then increase your ISO (but not too much as it increases noise).
Are you outside and the image is it too bright? if so, increase the shutter speed to it's maximum sync speed (if you don't have HSS), and if it's still too bright and you can't lower your ISO down further, then you need to increase you 'F' number which will increase your DOF as well as lower exposure.

Now that you have your ambient exposure set where you want it, you can then turn on your flash and set it to ETTL. Take a shot and determine if the flash exposure seems a little under or over exposed, then adjust FEC to suite your taste.

Generally I try to balance ambient and flash exposure, by exposing the ambient light about a stop less than the flash exposure, as this helps keep the image looking natural in larger spaces, where flash fall-off can look ugly, and the ambient portion of the exposure stays consistent.