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Thread: Having trouble with flash outdoors at night

  1. #1
    terrib's Avatar
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    Terri

    Having trouble with flash outdoors at night

    A bear visited out bird feeder the other night. My husband got some fun video but I was unable to get any still shots due to the low light. Later, the bear came back and I tried using the flash with camera on automatic exposure, manual focus (auto would not work) and flash in ETTL mode. The first picture below is the result. The camera chose f/2.8, 1/60 and ISO400. It is out of focus because I really couldn't see to focus.

    The next night, anticipating his return, I set up the camera on a tripod with my 50mm lens, aperture priority at the widest f/1.4, and ISO 1600 and flash in ETTL mode. We also turned on the outside light. While it was still light enough to see, I focused in the area I expected him to be and took a test shot which is the second one below.

    About 15 minutes later, the bear did return. The third shot is what I got. Can anyone tell me what went wrong with the shot technically. Obviously, the bear ran before I got the shot off, so it wouldn't have worked anyway.

    And other than that, should this have been set up differently in the first place? As you can probably tell, I know very little about using the flash.

    Having trouble with flash outdoors at night

    Having trouble with flash outdoors at night

    Having trouble with flash outdoors at night

  2. #2
    steve40's Avatar
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    Steve Owen

    Re: Having trouble with flash outdoors at night

    looks like you were not using a shutter release, and got camera shake. Also I think if you check your camera manual, your flash did not fire in sync with your shutter. Looks like incandescent light only, your external flash sync is only 1/200 of a second, if I remember correctly. The test shot looks like it did sync?, but either the flash did not fire, or on the last shot the flash and shutter did not sync ?.

  3. #3
    inkista's Avatar
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    Kathy Li

    Re: Having trouble with flash outdoors at night

    Your second and third shots, the EXIF information tells us the following:

    1. You were in Av mode.
    2. Your ambient exposure settings were: iso 1600, f/1.4, 1s
    3. You used the same metering mode (pattern) on both shots, and the flash fired on both shots.

    My guess as to why they look so different is that the camera chose to set the flash power output differently between the two shots (you've got more flash in the second shot than the third one).

    The main problem here, though, is that your flash was in eTTL so we have no idea exactly what power output level your flash got set to.

    If you want the effect of the second shot, which is mostly lit by flash, and not so much by the ambient (you can tell, because there's no motion blur--the ambient, if you were handholding, would definitely be motion blurred with a 1s exposure), there are two simple ways to accomplish this. Switch from Av to P or full Auto mode. Or, mess about in your XSi's custom settings, and switch Custom Fn. III.2 ("Flash sync. speed in Av mode") from Auto to 1/200s.

    Here's why. In P or full Auto mode, your camera treats flash much the way a P&S camera will. If light levels are not low, fill flash is assumed, and the exposure settings of the camera will be pretty much what you'd use without the flash, and a little extra light is flicked out from the flash to "fill" in the shadows. Your flash/ambient balance is assumed to be mostly ambient. But when the light meters as very low levels, the balance will flop the other way, and the balance is assumed to be mostly flash, and forget about the background.

    In Av or Tv, however, the camera always assumes fill.

    In M mode, you can specify exactly what balance you want with your exposure settings, and primarily your shutter speed.

    When you take a flash image, you're basically adding together two different exposures. One is the ambient exposure, which is all the light you gather that isn't the flash. And the other is only the light from the flash. You can think of it like adding two different layers in Photoshop together.

    Your ambient is controlled by iso, shutter speed, and aperture.

    Flash, however, is controlled by iso, aperture, flash power/light output, and subject distance.

    Note how shutter speed wasn't in that second list. The flash burst is so fast that it's actually faster than your top shutter speed. No matter how much longer you leave your shutter open, you're not going to gather any more light from your flash, only the ambient. So how long you choose to leave your shutter open for is going to help determine your flash/ambient balance: the faster the shutter speed, the more flash and the less ambient.

    1/200 is used because that's your maximum sync speed. The way that shutter speed works is that you have two shutter curtains, and it's the size of the "gap" between the two curtains as it passes over the sensor that determines your shutter speed. Up until 1/200s, that gap is going to be as big or larger than the sensor itself. Faster than 1/200s, and the gap will be smaller than the sensor. Remember that earlier bit about how the flash burst is faster than your top shutter speed? If you use a faster shutter speed than 1/200s, you'll end up with a black bar at the top and/or bottom of the frame, unless you use high-speed sync (I know your head's probably exploding around now, so I'll just link and not go into it).

    So, that's why the setting you have is to force your shutter speed to be 1/200s when you're in Av mode and using a flash will force the flash/ambient balance in the image to be mostly flash.

    In your third shot, something different happened, and the camera assumed you wanted fill flash (mostly ambient), so that's why you see the yellow and the motion blur: that's the ambient light from the 1 second exposure dominating in the image, and not much flash at all.

    That's my guess.

  4. #4
    William W's Avatar
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    William (call me Bill)

    Re: Having trouble with flash outdoors at night

    My expectation is:

    In the second shot there was still some daylight and / or the outside lights were NOT yet turned on – more likely the Outside lights were NOT turned on.
    Also it is very likely that the AMBIENT daylight was very SOFT and acting as OPEN SHADE, and there was no FOREGROUND DITRECTIONAL LIGHTING that the camera measured to consequently make the 'Flash as Fill'

    In this shooting scenario the AMBIENT light level was metered as COMPARATIVELY low (dark) and 'overall light' - and when the camera made the computations made for “Flash as Fill” (see Kathy’s explanation of how Canon Flash works as “fill flash” when the Camera is Av Mode) - the Flash exposure the Camera computed was to use the Flash "as Fill" but it was "as Fill" for a "very dark hole"

    So, in frame two, the Flash exposure therefore is very DOMINATE, compared to the Ambient Exposure of the very soft and dying daylight and even though the Flash was acting as “fill” it appears for all purposes to be a “Flash Photo”.


    ***

    In the third shot, there are definitively strong and directional Tungsten / Incandescent Lights which are illuminating the scene, in the FOREGROUND: in this shooting scenario the Camera’s Light Meter picked up on what it thought was a “well lit scene” and used the “Flash as Fill.

    I think it was just happenstance that the camera used 1second as the shutter speed for the Ambient Light levels both times.

    ***

    Another likely explanation is - and this also relates to the Camera’s Light Meter – I would bet a Mars that IF you did not have your eye to the camera – you also didn’t have the Eye Piece cover over the Viewfinder?

    If this is so, then any bright ambient light from behind the camera (like the floodlights) will also confuse the Camera’s Light Meter when attempting to make the automatic computations and when it is reading the ambient exposure.


    WW
    Last edited by William W; 1st August 2012 at 06:51 AM.

  5. #5

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    Re: Having trouble with flash outdoors at night

    Terri. When I first moved from an old fixed output film camera flash to a modern 'thinking flash' I also totally failed. Then I finally realised that there are too many variables and the camera doesn't know what sort of scene I am photographing Hence the totally incorrect settings which it was auto selecting.

    Previous replies have gone into this in great detail, particularly Kathy.

    So now, I set the camera using manual controls to suit the scene. Concentrate on things like subject movement and required focus depth. Forget about flash for now. Decide on the best settings for shutter speed and aperture based on the actual scene. But bear in mind the limitation on shutter speed, as previously mentioned, or use high speed flash if appropriate.

    Set a suitable Iso value. Here you can take into consideration the ambient light; but don't set your Iso solely based on this, remember that flash will be used so you need to set Iso to give a rather darkish scene.

    Then adjust the auto flash setting as required. Use the ETTL option and vary the flash output exposure compensation as required. The flash output becomes the only variable element in your shot.

    It does take a bit of experimentation to get these settings to work at optimum performance but after a while you will simply look at the scene and know what actual settings to use.

    Some experts like to use fixed output flash which they adjust to suit the scene based on their considerable knowledge. And with care, that would allow you to work in the same manner as the old film camera flashes.

    But for normal everyday use I manually set the camera then auto vary the flash which is the easiest option.

  6. #6
    terrib's Avatar
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    Re: Having trouble with flash outdoors at night

    Thank you Geoff, Bill, Kathy and Steve for your detailed responses! There is much here for me to absorb and I will spend some time trying out and considering all that you have said. Last night after reading Steve's & Kathy's posts, I did try setting up the camera in P mode and used a remote shutter release. The remote not only took out the camera shake possibility but also allowed me to set up the tripod on the porch so I didn't have to open the glass door and risk scaring off the animal. I managed to get these shots - not of a bear and not exactly National Geographic moments, but fun, nonetheless.

    I will work through everything else you all mentioned and see where that takes me. Thanks so much for the time you all put in to these explanations!

    Having trouble with flash outdoors at night

    Having trouble with flash outdoors at night

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