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Help! Need more understanding on camera ISO speeds


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Old 09-08-2010, 00:13
Markjuk
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I have recently taken some photos which have unforunately suffered from "motion blur". I have since read on the internet that a "higher speed" setting is required to prevent this from happening. Does a "higher speed" mean ISO 400 and under or ISO 800 or higher?
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Old 09-08-2010, 00:47
dodgygeeza
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Higher speed in photography can mean a few things, but usually the sensitivity or shutter speed. Higher ISO numbers are more sensitive, so ISO 200 needs half the shutter speed compared to ISO 100 for any given aperture. ISO 400 is twice as fast as ISO 200, so four times the speed of ISO 100. Raising the ISO allows you to use faster shutter speeds for the same exposure, but the trade-off is moisier images. Similarly if you open up the aperture buy a full stop, say from f/8 to f/5.6 you can then use a shutter speed twice as fast for the same exposure but the trade-off is shallower depth of field.

"Fast lenses" are ones which allow you to select low f numbers, usually f/2.8 and lower, corresponding to larger apertures which therefore allow more light to enter which allows faster shutter speeds for the same ambient light. The trade-off in this case being shallow DoF again, plus the fact that fast zooms are usually VERY expensive. Fast prime lenses (fixed focal length, no zoom) can be quite affordable though

As a rough guide, you want to be using shutter speeds of 1/200th or faster if you're trying to freeze fast human motion, and higher still for things that move even faster. Increasing ISO speed is often the only way to achieve this if the light is not great. I'd suggest putting your camera in shutter priority auto with ISO set to auto adjust, picking a fairly fast shutter speed such as 1/200th and taking some shots then checking what ISO the camera chose to get an idea of how high you need to go.
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Old 09-08-2010, 02:11
PrinceGaz
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What sort of camera do you have? The only way to use a faster shutter speed to reduce motion blur is to do one or both of using a wider lens aperture (does your camera allow you to do that? - SLRs will but most compacts won't) or a higher sensitivity (all digital cameras will let you do this, but at a cost of reduced image quality, especially if you go above ISO 400 or so on compact cameras).

At the end of the day, the best way to get a good photograph is being a good photographer. Making the best use of the camera you have is what matters, and knowing when the emphasis needs to be on shutter speed (fast to freeze motion, or slow to give a desired motion blur), aperture (narrow for maximum depth of field, or wide for concentrating on one object or in low light conditions), and sensitivity (the lower the better, but in lower light conditions it often needs to be increased to meet the shutter speed and aperture requirements).
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Old 09-08-2010, 04:17
pocatello
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Iso is a hold over from film, where more sensitive films had higher iso ratings. The very nice iso 100 standard film didn't work that well at night for instance, 400 or higher and you started to get noisy pictures.

Digital cameras only have one sensor, so cranking the sensitivity is all its doing. On small cheap low tech sensors they are extremely prone to noise, so cranking the iso will give you a picture..but also a massive amount of noise. In automatic mode the camera will do this automatically. Once you get to slrs you can have usable 1600-3200 iso settings even.

Bigger sensors, bigger senses aid in gathering more light, its all about more light, less noise. I somehow doubt you are setting everything manually, so it should have been done automatically. But theres only so much you can do with a cheap camera.
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Old 09-08-2010, 16:44
Markjuk
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What sort of camera do you have? The only way to use a faster shutter speed to reduce motion blur is to do one or both of using a wider lens aperture (does your camera allow you to do that? - SLRs will but most compacts won't) or a higher sensitivity (all digital cameras will let you do this, but at a cost of reduced image quality, especially if you go above ISO 400 or so on compact cameras).

At the end of the day, the best way to get a good photograph is being a good photographer. Making the best use of the camera you have is what matters, and knowing when the emphasis needs to be on shutter speed (fast to freeze motion, or slow to give a desired motion blur), aperture (narrow for maximum depth of field, or wide for concentrating on one object or in low light conditions), and sensitivity (the lower the better, but in lower light conditions it often needs to be increased to meet the shutter speed and aperture requirements).
Thanks for everyones replies so far.
I have an old and now classed as rubbish Finepix s5000 zoom that I am hoping to upgrade in the near future. The Camera has an Auto setting, ISO 200, 400 but at 800 it only allows 1 Megapixel images. So in order to prevent motion blur on this antiquated model I would need to set at ISO 200 or 400?
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Old 09-08-2010, 18:37
rjb101
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400 will give you less blur than 200. Bigger the number the less blur.
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Old 10-08-2010, 05:49
pocatello
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Thanks for everyones replies so far.
I have an old and now classed as rubbish Finepix s5000 zoom that I am hoping to upgrade in the near future. The Camera has an Auto setting, ISO 200, 400 but at 800 it only allows 1 Megapixel images. So in order to prevent motion blur on this antiquated model I would need to set at ISO 200 or 400?
Woah, 1mp thats getting ancient.
http://www.imaging-resource.com/IMCOMP/COMPS01.HTM
For some reference images from modern cameras of different makes.
Theoretically you can increase iso, it boosts the sensitivity of the sensor, but you get a whole lot more noise, early cheap sensors would get pretty bad very fast. More sensitivity at higher iso lets the camera use a faster shutter speed, which would counter blur from camera movement. It only goes so far of course. The thing is..you shouldn't have to set iso, it should have done it automatically in a low light situation, normally it takes manual over ride to choose a longer exposure by force, which would require a tripod to prevent blur. But a camera that old might have its oddities. Iso should always be related to shutter speed in automatic mode, its the faster shutter speed that prevents blur, not the iso alone.
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Old 10-08-2010, 12:56
GetFrodo
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I have an old and now classed as rubbish Finepix s5000 zoom that I am hoping to upgrade in the near future. The Camera has an Auto setting, ISO 200, 400 but at 800 it only allows 1 Megapixel images. So in order to prevent motion blur on this antiquated model I would need to set at ISO 200 or 400?
Let's start from the beginning. When you get blurring problems, what are you trying to photograph? Is the object stationary or moving? Near/far? Indoors/outdoors? Time of day?

Increasing the ISO will definitely reduce blurring, but to the detriment of other factors. Let us know what you want a photograph of, then we can give you some tips on how to create a sharp image.
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Old 11-08-2010, 07:06
kyussmondo
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If your camera is in auto then it is detecting limited light. To let in more light it is slowing the shutter speed so without a tripod you will get motion blur. Increasing the ISO will increase light sensitivity so it will help. However your camera is quite old so increasing ISO too much will result in terrible noise in your pictures. A nice digital SLR will cope much better. Take a look at something like the Nikon D40 or D5000 or Canon 400D, all good entry level SLRs. If you want to go crazy something like the Nikon D3 will take good pictures even at ISOs of 16,400 but that is proper pro level stuff.
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