 F C |
Shutter Speed, Flash, Indoors, Etc. I know that at 200mm focal length, the rule of thumb is I should use a 1/200 shutter speed. The question is: When I do this, do I always need flash to be on? I tried using high shutter speeds - 1/300-1/800 - and without flash, all of my photos were extremely dark or just black. I did this in a fairly well-lit room. Is this true? Do I need a flash all the time at such high shutter speeds?
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Christopher A. Vedros |
No, it's not necessarily true. But even when a room looks fairly well-lit to you, unless you have a lens with a large aperture, you will probably need to use a flash when shooting indoors. You need to read the section in your manual about how your camera's light meter works. Then you need to use it. If you increase your shutter speed without increasing your aperture, your picture will be too dark (underexposed).
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Kerry L. Walker |
Chirs is correct. If you increase your shutter speed, you will need to use a larger aperture. Unless the place you are shooting is lit up like it's sunlight, the chances are you won't be able to use such a fast shutter speed without flash. Now to add a couple of things: 1. If you use flash and shoot faster than your maximum shutter speed, part of the picture won't be lit since the shutter curtain will not be open throughout the exposure. 2. If you are shooting with flash, the rule of thumb goes out the window since the speed of your flash becomes your shutter speed (in effect). For most flashes, the slowest speed is 1/1000 sec. going up to 1/50,000 sec. (depending on the flash), which is determined by the amount of light you need (how far you are from the subject) so you can shoot at slower shutter speeds. In fact, you will probably want to do so to get some ambient light in the picture (or not, if you want everything but the subject to be in shadows).
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robert G. Fately |
F, allow me to elaborate on the previous answers. First, the rule of thumb to which you refer relates to 35mm film shooting - and basically states that the slowest shutter speed you should use - hand-held, without external flash - is 1 over the focal length of the lens. So, in available light shooting with a 200mm lens and a film (or "full frame" digital) body, the slowest speed you should use is 1/200th of a second. With most DSLRs, though, the imaging chip is smaller than the 24x36mm rectangle of 35mm film, so they talk about the "cropping factor" - eg., 1.5 times the focal length. So that 200mm lens suddenly behaves like a 300mm lens - and you should raise the shutter speed accordingly. That said, unless you're in a well-lit room and have a very fast 200mm lens (like a f2.8 or f2), it's quite possible there won't be enough light to expose the shot properly. So flash comes into the picture (excuse the pun). When you use flash, the rules may change a bit. This is because if the bulk of the light illuminating the subject is coming form an electronic flash, the shutter speed you use is less critical (on the slow end) because the duration of the flash burst itself is from 1/1000th second down to 1/50,000th of a second. So, any concerns about motion-related blur are probably unnecessary - the flash light itself will freeze the action. On the other hand, using a flash with a camera that has a focal-plane type shutter brings up another issue. Focal-plane shutters work by the use of two 'curtains' - the first one exposes the film or chip when you press the shutter button, and the second one follows the first after the designated shutter speed time. So, if you set the shutter speed to 1/2 second (to be ridiculous) and click the shutter, what happens inside the body is curtain 1 zips open, and after 1/2 second, curtain 2 zips behind it to close and stop exposing. And if you have a flash attached, it will fire at the time that the shutter is fully open and the film or chip is completely exposed. However, the mechanics and physics involved impose an upper limit on how fast the shutter speed can be before curtain #2 starts traveling closed even while curtain #1 is mid-way through its opening move. The effect of this is that, counter to intuition, at high shutter speeds the entire chip or film is not being exposed exactly at once, but instead is being exposed by a moving slit (between the curtains). And the reason that means anything at all is because if you use too high a shutter speed with electronic flash, when the flash pops off it will properly expose the slit being exposed in that instant, but the surrounding areas will remain black or dark. This could be top/bottom or left/right, depending on the mechanical nature of the focal plane shutter mechanism. So, the moral of the story is, if you're using electronic flash, do not go above the highest flash synchronization speed (it's one of the specs in the camera manual).
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F C |
hey thanks a lot guyss. Its been very helpful indeed. Appreciate it loads. Understand a bit more about it now. THe reason I ask this is because I enjoy wildlife photorgaphy, thats why I got it in the first place. But if I am using a high shutter speed and I am in a jungle full of trees, it will be too dark and if I were to use flash, it would probably scare the animal away. So, I always wondered how those wildlife photographers manage to freeze motions of runnin cheetahs or flying humming birds but their exposure is still so excellent.
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