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Thread: Using ETTL flash in low light

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    Using ETTL flash in low light

    Hi all - I just got a 430EX II and am getting to grips with it.

    In a couple of weeks there's a family wedding - I'm not The Wedding Photographer, but I am taking some candids at the reception which will be indoors in the evening.

    In my experimentation with the new toy, I've noticed that the way it works with ETTL is that the camera tries to expose the background with ambient light, while lighting the subject with the flash. Unless I go to really high ISO, this results in the camera (in Av mode) choosing a shutter speed that is too slow for handholding (eg 1/13) with obvious results.

    Anyone have advice on how to handle this? Tripod is not an option here, since I'll be mobile at the reception. As far as I can see, I either have to live with high ISO, or switch to manual and have an underexposed background. Thoughts? I can't see any other way around it, but perhaps those experienced in wedding/event photography might have some sneaky trick...

    Canon 5DmkII + stuff

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    In theory the flash lights both the subject and background, but in practice because the background is generally further away than the subject, light falloff will mean that the flash has a negligible effect on the background.

    How the flash works in ETTL mode is that it will output enough flash to light up, but avoid blowing out the areas that are affected by the flash using zone metering

    If you had no foreground subject, it would output enough flash to light up the whole background (if it can), but when you have a foreground subject, it will get a huge wallop of light, and the flash will cut off that light before it blows out the foreground subject, so that's why the background is relatively unaffected (it's because the flash cuts the power to save the highlights in the closer objects, but this lower power will not be effective on the subjects further away)

    If you really want to shoot at a fast shutter speed, you can simply override the camera's ambient light exposure by using AV (with -EC), M, or TV

    Keep in mind that flash is a very fast burst of light...in theory you could get a sharp image from an exposure that lasts for an hour, let alone something relatively fast like 1/30 of a second. The issue is the ambient light. When you have the shutter open too long to expose the ambient, that is what causes the motion blur. If you want absolutely no motion blur, you have to make sure the flash is overwhelming the ambient exposure. The shutter speed duration will affect the ambient exposure, but not the flash (since the flash is so fast it will fully expose whether you have a 1 sec exposure or a 1/100 sec exposure - it makes no difference (until you get to the camera's Xsync speed which is the fastest shutter speed you can use and still catch the flash)

    But I recommend upping the ISO so that you get background exposure, otherwise your results become point and shoot like

    Also I highly recommend bouncing the flash as this will give a better exposure to the background too (the flash will reflect off the roof lighting up a large portion of the room)

    I always use my flashes either bounced, or not at all. Direct flash is terrible indoors (outdoors it's ok). I rather use no flash if I can't bounce it (which only happens when the venue is too large and there are no nearby walls or ceilings)

    If you'd like I can show you some indoor flash shots vs non flash shots...it's the venue that makes me use either one, not any "preference"
    Last edited by pollen; 19-12-2009 at 12:42am.

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    This doesn't really make sense to me, when I do event work unless it's a dungeon if yiu use say 1/150s, iso4oo and f5.6 the flash is more than powerful enough to light the subject and these settings usually register ambient also

    maybe try matrix metering and put in manual, iso400, s/s 1/150 and then use the apperture to control the ambient?

    Or even p mode just works, or should
    Darren
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    1/150 shutter speed, ISO 400, f/5.6!!!!!!!!!!!!!!! :O :O :O

    Oh wow I wish I was photographing at the venues you are at Darren, that would be awesome!

    With my own work I always get the dundeon types, here's a typical ambient exposure from me:

    f/1.4, 1/60, ISO 10,000 pushed (this is about 9 stops brighter than your settings :O)



    Last edited by pollen; 19-12-2009 at 12:53am.

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    Quote Originally Posted by Jimbo View Post
    I've noticed that the way it works with ETTL is that the camera tries to expose the background with ambient light, while lighting the subject with the flash. Unless I go to really high ISO, this results in the camera (in Av mode) choosing a shutter speed that is too slow for handholding
    Actually, no. What you are seeing is how the camera operates in aperture priority mode. This is what aperture priority means: the camera sets a shutter speed to correctly expose the scene in front of it. If you are in a dark place at f/5.6 and ISO 400, then yep, you will get 1/5th and 1/10th of a second all the time if you select aperture priority. That just shows that it's working correctly.

    Your problem. Jimbo, is that you need the FLASH to look after correct exposure, but you are in a shooting mode that uses the CAMERA to decide exposure. If you set the camera to aperture priority (or shutter speed priority for that matter), the flash "knows" that the camera is looking after the overall exposure calculations, and its job is just to provide a little fill flash.

    Aperture priority is brilliant for full natural lighting (e.g., in broad daylight) and equally good where you want to expose in the normal way, but brighten up the foreground subject a little with some fill flash. But it's exactly the wrong mode for dark scenes where flash is the primary lighting.

    The Canon flash system is actually very, very good at calculating correct exposure. It really doesn't matter at all what camera settings you have - any combination of shutter speed, ISO and aperture is just fine, as the flash system will figure it out and provide just the right amount of light to give you a good exposure. There are only two things it can't do - both of them obvious:

    1: the flash system can't take away light, only add more.
    2: the flash system can only put out a certain amount of light - you are not going to light up the entire MCG with a single 430EX! In practice, you will rarely have trouble with this: they are pretty powerful.

    The answer is simple. For flash photography, set the camera to MANUAL mode, and let the flash system figure out the exposure. You don't have to set a correct exposure! The flash system takes care of correct exposure. All you have to do is make sure that the flash is adding light and that it never needs to take light away. So, set the camera to an aperture and shutter speed that, IGNORING THE FLASH, will be a bit too dark. How much? Entirely up to you. You are controlling the background with the manual settings on the camera, and the flash does the rest.

    Didn't I already write this up in detail somewhere here? I'm sure I did. Now I can't find it.
    Tony

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    pollen, yeah, i see the issue with your shots, i mainly do indoor corporate work

    tannin, nice write up

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    Tannin, a really useful explanation - very clear. Thanks heaps. I've just seriously started playing with flash and this has been very helpful.

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    Thanks everyone, really helpful.

    Pollen - your shots are really what I hope to achieve - do you use dedicated noise reduction software? The 5d is really good with noise, but I'm always looking to keep my ISO as low as possible - your ISO10,000 shots look fine!

    I'll be endeavouring to bounce where I can - unfortunately I haven't been able do it experimenting at home, as my ceilings are bare wood and about 5-6m high, and my walls either have stuff on them or are brick!

    I have a cheap diffuser, which will be handy. Does anyone use CTO gels in this situation, to add warmth?

    Quote Originally Posted by Tannin View Post
    Your problem. Jimbo, is that you need the FLASH to look after correct exposure, but you are in a shooting mode that uses the CAMERA to decide exposure. If you set the camera to aperture priority (or shutter speed priority for that matter), the flash "knows" that the camera is looking after the overall exposure calculations, and its job is just to provide a little fill flash.
    Whilst I completely understand how Av works, I hadn't twigged to the fact that in this mode the flash was defaulting to a secondary fill function as you describe - but now it seems obvious! Thanks

    The answer is simple. For flash photography, set the camera to MANUAL mode, and let the flash system figure out the exposure. You don't have to set a correct exposure! The flash system takes care of correct exposure. All you have to do is make sure that the flash is adding light and that it never needs to take light away. So, set the camera to an aperture and shutter speed that, IGNORING THE FLASH, will be a bit too dark. How much? Entirely up to you. You are controlling the background with the manual settings on the camera, and the flash does the rest.
    Thanks Tony - this makes it very clear to me now what I need to do. In fact, I've sort of done this previously with my SB28 in manual mode via sync cable - I'm actually probably more comfortable putting into M mode and banging away, probably underexpose ambient by 1-1.5 stops.

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    Quote Originally Posted by pollen View Post
    Also I highly recommend bouncing the flash as this will give a better exposure to the background too (the flash will reflect off the roof lighting up a large portion of the room)

    I always use my flashes either bounced, or not at all. Direct flash is terrible indoors (outdoors it's ok). I rather use no flash if I can't bounce it (which only happens when the venue is too large and there are no nearby walls or ceilings)
    Actually, out of interest, when bouncing how much +FEC do you find you need (if any) ?

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    Is there something weird with this thread? It keeps showing up in "new posts" and there are supposed to be 8 posts in it (9 now, counting this one) but no matter how many times I refresh, there are only 6 showing. The last post I see is Kiwi's at #6. All other threads are working normally.

    EDIT: my posting pixed the problem. This is weird stuff. BTW, I viewed the source code earlier, and it was consistent with the error I described - i.e., it did not contain the missing posts.

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    Quote Originally Posted by Jimbo View Post
    M mode and banging away, probably underexpose ambient by 1-1.5 stops.
    That is usually the perfect amount!

    I found where I wrote this up before, by the way: http://www.ausphotography.net.au/for...ad.php?t=29707 Might be worth a look.

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    Quote Originally Posted by Jimbo View Post
    Pollen - your shots are really what I hope to achieve - do you use dedicated noise reduction software? The 5d is really good with noise, but I'm always looking to keep my ISO as low as possible - your ISO10,000 shots look fine!

    I'll be endeavouring to bounce where I can - unfortunately I haven't been able do it experimenting at home, as my ceilings are bare wood and about 5-6m high, and my walls either have stuff on them or are brick!

    I have a cheap diffuser, which will be handy. Does anyone use CTO gels in this situation, to add warmth?
    haha the ISO 10,000 looks ok at this size, but gets messy quite fast. I think it's usable for 8X12 at most I'm a bit lazy with noise reduction, I generally just use setting (1,3) or something in DPP even though I have noise ninja etc. (too slow to use)

    Diffusers only work when you can bounce, otherwise they are no different to using direct flash. I use CTO gels when there is tungsten lighting, it helps avoid the white subjects, orange background look.

    You can bounce off wood and brick, but you will need to colour correct. As an experiment, what I recommend is to take a photo of a grey or white piece of paper by bouncing off the wood or brick using RAW mode or RAW+JPG. Then go to Canon DPP or something and for the raw file, select "Click white balance". This will give you an eyedropper tool which you can click on the piece of paper on the photo, and your image should be colour corrected. Use "Tune" to finetune the colour.
    Whilst I completely understand how Av works, I hadn't twigged to the fact that in this mode the flash was defaulting to a secondary fill function as you describe - but now it seems obvious! Thanks
    The flash works the same as how it would work in Manual - what's changing is how the ambient exposure is being managed, either by the camera, or you manually.

    Imagine you had a bucket of paint to throw at a guy standing 10 metres in front of a wall. If you threw enough paint so that the guy is just lightly splattered, it is unlikely any will hit the wall at all. If you wanted to throw enough paint so that the wall is filled, so much paint will hit the guy standing closer to you that he will be fully drenched like crazy.

    What ETTL flash does is that it will detect the point where the guy is about to be drenched, and emit an amount of paint so that it hits the guy, but does not over drench him. The result is that the wall in the background won't be hit by the paint because of the lower output.

    This is the reason it's sometimes said "Flash only affects the foreground", it's not actually true - it's just that when you get the proper exposure of a foreground object, the laws of physics dictate that the light output won't hit the background at the same intensity due to the increased distance. To hit the background you have to increase the power, which will overexpose the foreground object.

    Bouncing flash is different because you're pretty much throwing a whole heap of paint against a reflective area, diffusing its output, but distance backgrounds will still be dark

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    You can counter the camera choosing a low shutter speed (because it is pushing ISO way down) is to use the custom function in your camera. You should be able to choose the Image Flash exposure setting (or something like that) to let the camera choose a shutter speed between 1/60 and 1/250 (or whatever the max sync is). This way even in AV mode your camera will choose a more handholdable shutter speed
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    My two cents worth...

    Ive been shooting nightclubs for years and my typical settings would be..

    - Shutter speed usually around 1/5th to 1/50th.
    - Aperture of 2.8
    - ISO usually 400-800
    - one or two external flash units (get them off camera as much as possible)

    The flash is there to freeze the action, and by dragging the shutter a bit you bring up the background atmosphere a bit more.

    Something I tend to do now with nightclubs, is bump my ISO real high. Like what pollen has showcased, with an ISO of 10,000. I feel so dirty when i do it, I feel like I need a shower and a spanking, im so against it, but for nightclubs.. the reality is... Facebook doesnt care about noise.
    Nightclubs predominately use the photos for small newspaper features, facebook and their websites, and the quality doesnt matter, and you will never see the noise at this level anyway.
    The photos come out amazing because you kill a lot of shadow and illuminate the whole scene really nice.

    For formal events and weddings I would keep that ISO down though. If you have a 5D or a nikon D3 or something then be generous with your iso, just stay away from the levels where noise comes in.
    Brodie Butler (Perth, WA)
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    Bit confused

    Your signature says you have a 400D but your photo was taken at ISO 10,000

    400D only goes up to 1600 (right?)

    So, I'm guessing you used another camera..?

    Scotty


    Quote Originally Posted by pollen View Post
    1/150 shutter speed, ISO 400, f/5.6!!!!!!!!!!!!!!! :O :O :O

    Oh wow I wish I was photographing at the venues you are at Darren, that would be awesome!

    With my own work I always get the dundeon types, here's a typical ambient exposure from me:

    f/1.4, 1/60, ISO 10,000 pushed (this is about 9 stops brighter than your settings :O)



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    Hi Scotty, sorry those photos were taken with my 5D Mark II and 35L

    I used to have my full gear in my signature but there were some insinuating remarks in this thread: http://www.ausphotography.net.au/for...gear+signature
    that listing gear in signatures was only an avenue to engage in a peeing contest, rather than have any informational benefit, so I thought I should remove them

    It is possible for the 400D to photograph at ISO 10000, but you need to shoot at ISO 1600 and then push your exposure 2.67 stops in a RAW converter

    haha agree with Brodie, downsizing for Facebook is the cure for all noise
    Last edited by pollen; 23-12-2009 at 3:24pm.

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    Keep in mind that flash is a very fast burst of light...in theory you could get a sharp image from an exposure that lasts for an hour, let alone something relatively fast like 1/30 of a second.

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