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Old Apr 21, 2010, 8:27 AM   #21
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despite of fear of sounding really stupid:
I dont understand exactly what you mean by having the cameras exposure lower than the ambient. My understanding for this particular situation is that the fighters would be the foreground objects and everything else the background. so would the "everything else" be the ambient in this case? I suspect this is what you were trying to explain in your PM as well, so i am sorry i am not getting this yet
thanks for you help regardless of course.


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Actually, HSS is best used OUTDOORS when the flash is being used as fill. It dramatically cuts down on the range of a flash. The key to stopping action with flash is NOT high shutter speed - it's having a camera's exposure lower than ambient - by about two stops. A flash burst is anywhere from 1/1000 - 1/4000 of a second. By having the camera's exposure about 2 stops below ambient, even if the shutter is open 1/100 there simply isn't enough light let in for a proper exposure - accept when the flash is firing. So there really is only 1/1000-1/4000 of time when there is enough light to record a proper exposure.
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Old Apr 21, 2010, 8:37 AM   #22
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Quote:
Originally Posted by ronin2307 View Post
despite of fear of sounding really stupid:
I dont understand exactly what you mean by having the cameras exposure lower than the ambient. My understanding for this particular situation is that the fighters would be the foreground objects and everything else the background. so would the "everything else" be the ambient in this case? I suspect this is what you were trying to explain in your PM as well, so i am sorry i am not getting this yet
thanks for you help regardless of course.
Don't worry about what people might think, if we don't admit we don't know everything then we will never learn... I have lots to learn, I'm happy to admit it

Ambient is the light supplies by lighting that you are not putting on a subject, so in this case it is the gym lighting any any additional spot lights etc.

The quick and dirty way to get the rough ambient exposure is to shoot in Av with your desired aperture and ISO then the camera will meter and change the shutter speed. Take a shot, is it exposed correctly? If so this is your ambient exposure. Now dial in -2 stops of exposure compensation, shoot the same scene and you should have the 2 stops under. As you can see everything is very dark. Now when you put the flash on, the flash will bring out the detail. As John says, by doing this it doesn't matter that you have a slow shutter speed, it's the flash pulse that does the freezing and that pulse if faster than the shutter speeds we are using in a lot of daylight sports so it is plenty fast enough

There, hope that works.... not the best explained but I'm about to shoot out and wanted to give you some info, normally I would have shot some examples but time isn't on my side.

Let us know if you need more info.
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Old Apr 21, 2010, 8:41 AM   #23
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Mark, this makes perfect sense now. thank you very much for the explanation.

Actually, just to verify: so in Av mode i set the aperture and ISO and shoot. If i am underexposed and the lens is wide open, that pretty much means i am out of luck, since that is the most light the lens will let in from the ambient?
Or will the shutter speed slow down to something i cannot use without a tripod?

thx again for everything
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Old Apr 21, 2010, 9:24 AM   #24
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Actually, just to verify: so in Av mode i set the aperture and ISO and shoot. If i am underexposed and the lens is wide open, that pretty much means i am out of luck, since that is the most light the lens will let in from the ambient?
Or will the shutter speed slow down to something i cannot use without a tripod?
In AV mode, the camera adjusts shutter speed. It will go to very slow speeds if necessary. If you are underexposed in AV mode it is because the camera's metering is being fooled (by something bright in the background or even in foreground - like light reflections). That is why in indoor shooting, manual exposure is preferred - so the camera doesn't get fooled.

It is TV (shutter priority) mode that can lead to underexposures because the camera can't open the lens up any wider to accommodate the shutter speed and ISO you've chosen.
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Old Apr 21, 2010, 9:43 AM   #25
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JohnG I understand that part.
to continue that train of thought:
according to Mark, i would use the Av mode to figure out the proper exposure, knowing that my shutter speed may go to a really slow speed, where it may not be possible to handhold the camera without blurring the shot.
so then i would switch over to manual exp and use the settings from Av mode + shutter speed and compensate for -2 stops.
My concern is that if the shutter speed is very slow, even with the flash, wouldnt i get a blurry picture still? or how would i go about adjusting the shutter speed in M then?

I am really sorry if i am being dense. I truly do appreciate all the help you guys are giving me
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Old Apr 21, 2010, 9:54 AM   #26
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NO you won't get blur. As I explained in my PM, the FLASH stops the motion, NOT the shutter speed. The flash burst is only 1/1000-1/4000 long. If you have a shutter open for 1/60 but there isn't enough light being let in for the camera to record a proper exposure you don't get motion blur. There is only enough light hitting the sensor when the flash is firing. That burst is 1/1000-1/4000 long. Not long enough for motion blur.
Here's a shot at 1/60. No way is 1/60 enough to freeze motion. But without the flash, the photo would have been completely dark. There was only enough light to record an image while the flash was firing. Thus there is no blur:


Now, the closer the camera's exposure is to ambient, the more there is enough light when the flash is NOT firing for the sensor to record an image. Then the more chance there is of blur - or "ghosting" as it is called with flash use. Here's a shot where you can see the ghosting because the camera's exposure was too close to ambient:


That's why I talk about making sure the camera's exposure is around 2 stops below ambient. At that point you get dark enough WITHOUT flash for the sensor to record an image. Go to far below that point though and you start needing more light than the flash can provide.
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Old Apr 21, 2010, 10:23 AM   #27
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i think i finally understand now. thank you all very much for your patience and help
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Old Apr 21, 2010, 10:29 AM   #28
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since i dont have my camera with me now, i am reading through the XSi manual. just to be clear: are you talking about FLASH exposure compensation or just exposure compensation? According to the manual regular exposure compensation cannot be used in M mode on the XSi, for whatever reason.
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Old Apr 21, 2010, 10:38 AM   #29
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since i dont have my camera with me now, i am reading through the XSi manual. just to be clear: are you talking about FLASH exposure compensation or just exposure compensation? According to the manual regular exposure compensation cannot be used in M mode on the XSi, for whatever reason.
If you are referring to this statement by Mark:
Quote:
If so this is your ambient exposure. Now dial in -2 stops of exposure compensation, shoot the same scene and you should have the 2 stops under.
He's talking about the camera's exposure compensation IF YOU WERE STILL IN AV MODE. AV mode allows exposure compensation.

I think you would get a lot out of reading a book on PHOTOGRAPHY. Not a manual. Grab a book like Undrstanding Exposure by Bryan Peterson. A lot of this becomes much easier when you understand the basic components of photography. I don't mean this as a knock on you at all. It's just that when you have an understanding of the underlying principles it is much easier to understand how to change various parameters to shoot in a certain situation. Right now you're kind of jumping into a big lake without completely learning how to swim yet.

If you already know how to swim, jumping into the middle of a lake isn't nearly as difficult.
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Old Apr 21, 2010, 10:49 AM   #30
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JohnG, no offense taken at all. I am very aware of my lack of knowledge, so any advice is welcome.
i was just referring to the fact that you said i should shoot in M and use the 2 stops of compensation. Then i read the manual and it seems i could not use that setting.
i'll get the book though. dont want to bug people here that much
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