photosbysexton wrote:
KG, I think you have been given some bad information. There are not two physical curtains in your shutter. 1st curtain refers to the opening of the shutter, 2nd curtain refers to the closing of the shutter. So, when you are setting your flash to 2nd curtain, you are actually forcing the flash to activate just before the shutter closes. This is very effective when using slower shutter speeds to blur the action but freeze one subject in the image. Try taking a shot of someone walking towards you in the evening with a 1 second shutter speed using 2nd curtain flash. You will see the them nice and clear with an action blur behind them. Or try first curtain and you will see the blur in front of the clear image. This is what I've perceived from the turorials that I've read.
M
br br KG, I think you have been given some bad i... (
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Wrong, wrong, wrong - there are two curtains, you cannot now, nor is it possible to get an even exposure with only one nor will one be able to open and close at the speeds that a DSLR will go to (1/8000+).
Consider, the curtain begins to open and those first pixels start to expose; as the curtain continues each successive vertical line of pixels start to expose so through the whole process of opening each line starts to expose at a different time; when the curtain is fully open that last line of pixels has just started to expose while the first line has been exposing for a long time (relatively speaking); now, if what you say is true and there was only one curtain it would have to start its closing cycle and that would mean stopping the last row of pixels that started during the opening cycle from exposing while the first is still exposing. Can you see what I am saying, in such a case the end result would be a picture that would be properly exposed on that first row of pixels while each successive row of pixels would be progressively underexposed until, on the other side of the picture, there would be nothing but black. It takes a shutter speed of less than 1/250th of a secont to achieve a fully exposed sensor (first curtain fully open before the second starts to close) at which time the flash can fire without shutter shadows.
You must also consider the mechanical limitations, there is no way that a physical shutter can open and close in 1/8000th of a second, it is just not possible, that is why the Iris shutter in a hasselblad can only reach speeds of 1/800th of a second and that is a camera with technology costing $20,00+.
To achieve an even exposure at the speeds a DSLR can attain the first curtain has to be opening followed closely by the second curtain closing behind it. That is why the concept of Flash sync is important, so important that most cameras will not allow you to set shutter speeds above 250 to 350 because only a narrow vertical line of the picture will be exposed because the flash is much faster than the curtains leaving the only part of the picture exposed to the flash being that part that was open between the front physical curtain and the second physical curtain.
At exposures of 1/8000th of a second the opening between the two curtains would be extremely thin and moving as fast as the physical properties of the camera will allow leaving each column of pixels to have the exact same exposure time.
quote=photosbysexton br br KG, I think you have... (