Have you ever taken a shot, and noticed some 'noise' or 'grain' in the photo? Perhaps, you have. Nope, it has nothing to do with the camera, the player behind it is the camera's ISO setting.
So, what is ISO?
In film photography, ISO (also called ASA) was the measurement of the film's sensitivity to light. The lower the number, the lesser is the film's sensitivity to light. And the amount of grain in the photo, what we also call noise; increases with the increase in ISO number, and decreases with the decrease in ISO.
In digital photography, the ISO is the measure of the light-sensitivity of the image sensor.
Take a look at the two images of the same subject shot with different ISO.
Notice how the amount of grain increased in the 3200 ISO image.
Higher ISOs are generally chosen in low-light conditions for faster shutter-speeds. In slower shutter-speeds, there remains an increased chance of camera shake, and to eradicate that, you'll need a tripod. So, if you have a tripod, there's no need to shoot in higher ISO, and make the image noticeably noisy.
But, there are cases where tripod might come to no use. In indoor sports events; for sports events at night, there's no point of choosing slower shutter-speeds. In sports photography, the players' actions are frozen in shots, so slower-shutter speeds will do nothing but screw up the image. Those cases require higher ISOs. Also there are ways to overcome those, I'll discuss about it as I advance into later topics. Generally, it's best to shoot in the lowest ISO your camera offers, for Canon DSLRs it'll be 100 ISO, and for Nikon DSLRs it'll be 200 ISO. Maybe some point-and-shoots offer even lower ISOs. I had a Canon SX30IS; the lowest ISO possible in it was 80. Many Canon DSLRs have an ISO up to 25600, which is further extendable to 102400 ISO. There's nothing to get mesmerized about it, they will screw the image up pretty bad.
So, what is ISO?
In film photography, ISO (also called ASA) was the measurement of the film's sensitivity to light. The lower the number, the lesser is the film's sensitivity to light. And the amount of grain in the photo, what we also call noise; increases with the increase in ISO number, and decreases with the decrease in ISO.
In digital photography, the ISO is the measure of the light-sensitivity of the image sensor.
Take a look at the two images of the same subject shot with different ISO.
 |
| 100 ISO 3200 ISO |
Higher ISOs are generally chosen in low-light conditions for faster shutter-speeds. In slower shutter-speeds, there remains an increased chance of camera shake, and to eradicate that, you'll need a tripod. So, if you have a tripod, there's no need to shoot in higher ISO, and make the image noticeably noisy.
But, there are cases where tripod might come to no use. In indoor sports events; for sports events at night, there's no point of choosing slower shutter-speeds. In sports photography, the players' actions are frozen in shots, so slower-shutter speeds will do nothing but screw up the image. Those cases require higher ISOs. Also there are ways to overcome those, I'll discuss about it as I advance into later topics. Generally, it's best to shoot in the lowest ISO your camera offers, for Canon DSLRs it'll be 100 ISO, and for Nikon DSLRs it'll be 200 ISO. Maybe some point-and-shoots offer even lower ISOs. I had a Canon SX30IS; the lowest ISO possible in it was 80. Many Canon DSLRs have an ISO up to 25600, which is further extendable to 102400 ISO. There's nothing to get mesmerized about it, they will screw the image up pretty bad.
From a tutorial of a renowned photographer, I learned that four things should be asked to one's self while choosing the ISO.
- Light: Is the subject well lit?
- Grain: How much grain do I want in my photo? Will it be grainy or a no-grain image?
- Tripod: Am I using a tripod?
- Moving subject: Is the subject stationery or moving?
If the subject is in dark conditions, you want grain purposely (which most people don't want normally), you don't have a tripod and your subject is moving; then you might have to go for higher ISOs.
But, if possible keep your ISO within 1000. I have taken images at night with 800 ISO, and even though I got the image with much greater light, it had so much noise that I had to discard it. Remember, while shooting well-lit or even medium lit subjects, always go for lower ISOs.
There was a time when I didn't have a tripod; but I used supports to keep the camera on it; and shoot. Of course for exposures greater than 2 seconds, you'll need something to keep the camera on.
There are cases where you have to pump your ISO higher. I had already mentioned two: Indoor sports events and night sports events.
Also in indoor parties, concerts, places where flash is not allowed, you need to push you ISO high. There will be grain in the image, but a grainy shot instead of no shot at all is better, isn't it?
Shutter-speed, Aperture and ISO; together form "THE EXPOSURE TRIANGLE". These three are the basics of a camera, mastering these will help a lot. After you have mastered these, you can move on to specializations of photography. Every specialization involves these three only.
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