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Old Oct 31, 2003, 4:48 AM   #1
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Default Whats the purpose of Higher ISO values??

hey there everybody.
im still gettign to learn the ropes of serious digital photography and was just wondering about the purpose of ISO.

i see that there is a lot of focus on the ISO Range of a camera, and diff people use diff settings of ISO for different shots.

from what i can see, the more ur subject is movingm, the higher ISO u need to get a better shot....unless im confusing the action pics with shutter speed needed.

could someone please give me a dummies intro to what iso does for ur picture quality.

thanks a million.
cheer for now.
Bryce.
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Old Oct 31, 2003, 5:01 AM   #2
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It is similar to film iso. With film, the higher the iso, the more sensitive the film is to light. With a digital camera, higher iso settings increase amplification of the signal from the sensor which in a sence, makes the sensor more sensitive. The effect of a higher iso setting is that you will get a brighter exposure with the same shutter speed and apature. You can kick your iso up to a higher setting to help with night shots as the camera is boosting the signal more. It also allows for faster shutter speeds. You can have a fast shutter speed which would normally give too dark of a picture. When you increase the iso though, it brightens the picture and allows for the faster shutter speed. A fast shutter speed can be good for action shots to freeze the scene and minimize motion blur from a moving object.
The draw back is that more amplification increases noise. Higher iso settings will produce pictures with more noise. In general, the biger the ccd, the higher the iso you can use with acceptable noise. A dslr's huge sensor makes iso 1600 usable. The tiny sensor in my a70 has a lot of noise at it's maximum setting of iso 400. The a80 which has a larger sensor, performs beter at higher iso than the a70.
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Old Oct 31, 2003, 5:05 AM   #3
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ISO, it makes the CCD more sensitive to light (turns up the gain). On film it describes the light sensitivity. But in the case of both CCD and film, higher ISO means more noise (grain). Because it makes the camera more light sensitive, you can use a faster shutter speed, or it might mean the difference from having to use the flash, and not having to use the flash (in a situation where you're not allowed to use the flash, or if you're too far away from the subject).

Many people don't actually touch the ISO or let the camera select it for them, but if you ever see a camera where you can't select ISO or it has limited settings, watch it be panned for that reason!

If you're serious about learning more digital camera basics, check out the following site where there's a free online "book" covering things like this, http://209.196.177.41/
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Old Oct 31, 2003, 5:23 AM   #4
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hey ther eguys.
thanks for the swift reply.

so i had it all wrong.
i thought that the u used the HIger ISO to get rid of motion blurr.

the fuji 40i that im using at the moment doesnt have iso or shutter speed settings thats why im gonna chenge it, and its a very old camera as well.

Mike_peat, i will definately have a look at the link that u suggested.
thanks a mill.
i am very keen to learn as much as i can before i go and buy the dslr.

so to conlcude this topic.......my conclusion on ISO...
if u want a brighter picture, increase the iso, but expect some more noise to appear. right??

thanks a gain for the replies.
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Old Oct 31, 2003, 5:52 AM   #5
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Quote:
Originally Posted by snakeman
i thought that the u used the HIger ISO to get rid of motion blurr.

the fuji 40i that im using at the moment doesnt have iso or shutter speed settings thats why im gonna chenge it, and its a very old camera as well.
Well, the higher ISO means you can use a higher shutter speed to attain the same light level, so in that regard you can reduce blur (usually in daylight you'd be shooting 100ISO). Camera's are like a pan balance...if you increase one setting you have to decrease another setting to keep the same light level. But each control has its own effects on the picture, like shutter speed can freeze the action or blur it, f-stop can have the background of a subject sharp or out of focus (depth of field), etc.

All this takes practice and experimenting (the good thing about digital is you can experiment with little cost, and see if the results are to your liking right away...if not make the required changes).

Here's a site where you can play with shutter speed and f-stop, and see the results (based on a 35mm camera), http://www.photonhead.com/exposure/simcam.htm
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