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A Flash Headache……….
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Hi maybe someone can explain this to me. Firstly I very rarely use camera mounted flash, mostly i use studio flash heads. I had occasion the other day to have to use camera mounted flash. I was using a Canon 550ex along with a Canon 10D camera. I had the camera set on “P” mode and the ISO at 400. The flash unit was set to E-ttl. For some strange reason some of the shots were way overexposed, to a point of parts being “blown out”. I let the unit recharge and retook the shot, on a few ioccasions the shot was fine on others the shot was still way over exposed. Why would I have had such a varing result? Anyone any ideas? It’s driving me crazy as to be able to use the camera mounted flash would make life a lot easier for me………
Derek………..
Sounds very unusual. You dont specify whether inside or out, or what you were photographing? Maybe post the results. Did you try using any of the creative modes?
(Wasn’t it me who recommend this site to you? Hope you mantioned my name as a referrer! :lol: )Was the lens a Canon or an off-brand? Any off-brand lenses I’ve used have been fine performers but some (mostly sigmas) had odd interactions with flash…
This may be unconnected but in our last term one of our students was finding that his Canon 350D and 420EX flash (the one without the LCD panel at the back) were consistently UNDERexposing. I figured out that this particular combination needed some bumping on the flash compensation setting in the camera. That solved the problem
Hi Ross, yes it was you guided me to this site, thanks it’s a great site.
I was photographing a bridal party outside a church, it was about 16:15hrs so it was starting to get dark, sorta dusk. I was using a Canon 28-135 is usm lens which i have just bought a short time ago brand new. I also got non-consistant results inside the hotel at the reception at which point i reverted back to studio flash heads to save the rest of the day. I tried different things withe the flash, I used it straight on whth and without the diffusser, bounced it off the ceiling and also reduced the power ( which then under exposed the shots ).
I was wondering if the metering pattern would make any difference to flash exposure, i.e. if i was using say centre weighted, partial or average. Would this give me any difference or indeed would one be more accurate that the other?
Derek…….
DerekLaverty wrote:
I was wondering if the metering pattern would make any difference to flash exposure, i.e. if i was using say centre weighted, partial or average. Would this give me any difference or indeed would one be more accurate that the other?
Derek…….Certainly on the Nikon flashes it makes a HUGE difference. When using flash as the primary light source, as opposed to fill, and operating in TTL mode, the only way to get nice balanced exposures is with Matrix (evaluative). Going with spot and/or centre weighted will always blow the exposure. Also doing things like putting the diffuser on can “trick” the exposure. Again, coming from a Nikon world, putting the diffuser on automatically tells the flash you are using a 14mm focal length. So if in fact you’re using 200mm and you put the diffuser on, the exposures can be both off and inconsistent. I’m not sure how familiar you are with your flash Derek, but it’s worth reading back through the manual and basically playing with the settings.
I’m by no means a flash expert, but for the one wedding where I knew I’d be using flash, I refreshed my memory on the manual and all in all I was pleased with the shots on the day, because I knew how to drive the flash correctly.
Thanks Ciaran, I was wondering about that i have attached an image taken here probably the worst of the batch. It seems to be the only one I got a shadow behind the subjects for some reason. I had been through the manual and test fired shots with friend posing for me and it all seemed fine. I was confidend on the day, then once the light went and i was relaying on the flash totally it all went pear shaped for me. Thank god my studio heads were in the car or it may have been a real disaster……………
This is as it came from the camera, i have cropped it slightly and resized it for the web, apart from that i have not touched the levels at all……..
Have a look at this and see what you think, i would love to get this problem sorted out…………….
Derek……………
One possible explanation is that you first focused your image using the central focusing sensor and then you recomposed your image for a more pleaseing composition (for example you may have wanted your main subject to the left of the frame). Doing that moves the focus point away from the main subject and in most cases it’s now pointing at some place in the distance. The flash, when it fires, will then try and light whatever it is that’s in the distance, leaving your subject overexposed, as the flash measurement is based on the selected focus point. Where the shots were not overexposed, you may just have been lucky enough and find that the focus sensor remained on the subject. The flash will base it’s exposure on the area that is under the active focus sensor at the time of the flash exposure. The best thing to do is to select the focus sensor according to the type of composition you are planning on, so if your subject is on the left hand side of the frame, select one of the focus sensor on the left hand side, that you know will remain over the subject when you expose.
The best advice I can give, however, is to try and force yourself never to use “P”-mode. I’m guilty of using this on occassion myself but the problem is that you simply do not know what the camera is deciding. Far better to use manual mode and adjusting exposure accordingly (the flash can remain in E-TTL mode though, especially if you become familiar with how it works).
I would highly recommend anyone that uses EOS Flash units to have a read of Flash Photography with Canon EOS Cameras. It’s a long read but it’s very thorough and will give you a solid grounding in the use of Canon EOS Flash units. And once you’ve read and digested that, you should have a read of Neil van Niekerk’s Techniques for Better On-Camera Flash. If you read and understand these two resources, you’ll be very well equiped to handle any situation and will no longer be one of the many people complaining that Canon Flash technology is useless – it’s not useless at all, just mis-understood! :)
To be honest, the image you posted is exactly what I would have expected you to get given the type of setup you describe. There are two reasons you have such a harsh shadow on the background. The first is that your flash was much more powerful than the ambient light and the second is that your subjects were so close to the background (and there is a third – your flash being on camera and pointing straight at them). To get rid of such a shadow you need to take action on each of those items – move the subject further away from the background, so there is nowhere for the shadow to fall; decrease the ratio of flash to ambient light so that the ambient light effectively fills in the shadow, making it less noticeable; move the flash off the camera to one side, so the flash shadow falls to the side as well.
ciaran wrote:
…I was pleased with the shots on the day, because I knew how to drive the flash correctly.
Knowing how your flash works and how it interacts with the camera really is the key to success. Understand that and you can begin to take control of the situation instead of letting the camera take (unpredictable) control for you! Easier said than done, I know, because flash technology has become so complex these days, which is why I often resort to using the camera in manual mode and shooting with a Vivitar 285 flash (and it’s why you had better success using your “dumb” studio flash units – you were in control, not the equipment!).
Thorsten you are a star…..!!!! How you described the “focus, recompose” technique is exactly how I take photographs ! I focus with only the middle point and then recompose the shot. I do this with nearly all my shots. This is possibly the reason my 300D and the 380EX flash gave me so much trouble. It goes back to my manual days, when taking portrait shot we were always taught to focus on the eye and then recompose the shot. That is probably why my test shots with the 550EX were fine as I just shot them off to get a bench mark……..
Thorsten I thank you from the bottom of my heart………………………
Derek……….
And everyone else who helped with the problem…………. :D :D :D :D :D :D :D
Now I think I have this, if i am taking a shot i should then use a focus point closest to the point of exposure, i.e. the face say i would use the far right focus point, then i keep that over the face while i shoot. This by all intense and purpose should then give me a correctly exposed image. Is that right?
Oh, and by the way, am i the only daft edjit that still uses the focus recompose type of shooting????( Come on be honest )
Derek………………
DerekLaverty wrote:
Now I think I have this, if i am taking a shot i should then use a focus point closest to the point of exposure, i.e. the face say i would use the far right focus point, then i keep that over the face while i shoot. This by all intense and purpose should then give me a correctly exposed image. Is that right?
That’s pretty much the way to do it alright. And there’s another good reason aside from flash, to do this as well – see my next comment…
DerekLaverty wrote:
Oh, and by the way, am i the only daft edjit that still uses the focus recompose type of shooting????( Come on be honest )
You mean whilst utilising the central focus point only? Yes, I still do, but I no longer use it blindly. It depends on the circumstances. There’s a strong reason in favour of using it and that’s the fact that the central focus point is the generally the most sensitive (and therefore more accurate) BUT…
…aside from the flash issues that this can cause, there’s a simple physical fact that will almost gaurantee you out of focus images, particluarly when working at close distance with a minimal depth of field. Rather than me explain it, I’ll point you to a page that explains it better than I could – http://visual-vacations.com/Photography/focus-recompose_sucks.htm So for for these two reasons, I now try whenever possible to use the focus point nearest my subject. I don’t focus using the shutter button, preferring instead to set the custom function that allows me to use the * button under my thumb to focus. This gives me much more control and is much quicker too although if you’ve never used it, it may take some getting used to. And I use the joystick to quickly set the active focus point.
Some useful tutorials I stumbled across here http://images.photoworkshop.com/rebelxtlessons/interface.html – I think someone linked to the site in another thread about the Sports Illustrated articles. Lesson 18 – Beyond Basic Flash Photography very clearly explains how the E-TTL system works. It may start out a bit basic for you, since you’re already doing weddings, but it explains well what the flash does in each of P, Av, Tv and M.
re: focus recomposing – “even an inch of error in that case is about as significant as a fart in a tornado.” and I quote thorsten’s link. Cracking piece. You have to read to the bottom.
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