Sunday 22 February 2009

Techniques-Image Elements

Too many times i have seen what could be a very good image ruined by careless technique and instead the image is soft or not critically sharp, A good sharp image is made up of various elements that must be taken into account before the shutter button is pressed, The exposure is made up of Aperture/shutter speed and ISO value-focal length of the lens also plays a big part and must be taken into consideration if the image is to be sharp,The weather is not always kind to us and on a miserable day high shutter speeds may not be available so what do we do, Say our guy has a 300mm f2.8 lens (lucky guy) he is handholding on a grey day, He sets the aperture to f8,He takes a test shot and checks his histogram which is good so he starts shooting but his images are soft and blurry-why because he is only getting 1/100 of a second and handholding a heavy lens with that focal length at a slowish speed is going to end in tears,What can he do to resolve the situation-he has choices, Firstly he can go to F4 which will give him an extra stop in speed (doubles it) so he gets 1/200 which could work or go wide open to F2.8 now his shutter speed doubles again and he is getting 1/400 now this should be good for handholding a 300mm lens but he now ended up with a shallow depth of field and will not get the effect he wanted-like all the bird in focus now he only has the head in focus-so what can he do-he sets his aperture back to F8 and adjusts his ISO,He looks and has set it to ISO 100 so but going to ISO 200 he has added an extra stop in speed so buy going to ISO 400 he will end up with 1/400 which is what was needed to get a good sharp image,The compromise here is that by upping the ISO it will add more grain or noise to the image,But as i say a grainy image is better that a blurry one and there are main noise reduction software packages on the market that can help eliminate noise, Many lenses now have image stabiliser/Vibration reduction which can give up to 4 stops of reduction so an image that needs 1/400 could be taken at 1/50 but this is only in theory-yes it definantly helps but should not totally be relied upon,When you are setting up think aperture,shutter speed,ISO and focal length and set up accordingly-Always try to use a tripod as that way you can use a lower shutter speed/ISO and get away with it


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