I'm a bit confused what ISO could be used for. Don't you always want to minimize the noise in a photo so it looks more crisp?
sandykzhang
IMO we usually do try to minimize ISO, but a higher ISO might be necessary in low-light situations where higher sensitivity is necessary to capture the details in the scene.
henryzxu
To give an example of another high ISO use case, say you want to minimize motion blur, e.g., at a sporting event or capturing a bird in flight, a high ISO will allow you to maintain a fast shutter speed otherwise not possible with a lower ISO. This link was helpful in understanding the ISO/noise tradeoff.
kingdish
Another example is taking pictures of the starry night. Since the earth is moving, you have to use a relatively high shutter speed (usually need to set high ISO) to capture the light of the stars. Otherwise, you are taking pictures of star trails.
henryzxu
That's a very interesting point about starry night photography! This may be referring to another technique, but Nikon's website on the subject recommended shutter speeds of 20 seconds in addition to a high ISO and widest f-stop available.
Reading a little bit further into the topic, these long exposures introduce additional noise since the sensor gets warm, so a common technique used to address this issue is Long Exposure Noise Reduction (LENR), which takes a duplicate image immediately after the first, except this time the camera effectively pretends the lens cap is still on. The resulting image, called a dark frame, is compared to the original image, and the ambient noise is subtracted out. More information about LENR can be found here.
I'm a bit confused what ISO could be used for. Don't you always want to minimize the noise in a photo so it looks more crisp?
IMO we usually do try to minimize ISO, but a higher ISO might be necessary in low-light situations where higher sensitivity is necessary to capture the details in the scene.
To give an example of another high ISO use case, say you want to minimize motion blur, e.g., at a sporting event or capturing a bird in flight, a high ISO will allow you to maintain a fast shutter speed otherwise not possible with a lower ISO. This link was helpful in understanding the ISO/noise tradeoff.
Another example is taking pictures of the starry night. Since the earth is moving, you have to use a relatively high shutter speed (usually need to set high ISO) to capture the light of the stars. Otherwise, you are taking pictures of star trails.
That's a very interesting point about starry night photography! This may be referring to another technique, but Nikon's website on the subject recommended shutter speeds of 20 seconds in addition to a high ISO and widest f-stop available.
Reading a little bit further into the topic, these long exposures introduce additional noise since the sensor gets warm, so a common technique used to address this issue is Long Exposure Noise Reduction (LENR), which takes a duplicate image immediately after the first, except this time the camera effectively pretends the lens cap is still on. The resulting image, called a dark frame, is compared to the original image, and the ambient noise is subtracted out. More information about LENR can be found here.