Photographer
Mad Hatter Imagery
Posts: 1668
Buffalo, New York, US
It is my understanding that 400 and below these days produces very little noise. Maybe even not noticable. But how about 800? Is there a way to measure the added noise for each doubling of the ISO? I am doing long exposure star timelapse and at 400 the exposure is a bit too long combined with an equal amount of time to process each shot before the next can be taken. I don't want to compromise quality too much, but would like to get more frames and time before the battery dies.
Photographer
Shadow Dancer
Posts: 9775
Bellingham, Washington, US
Every camera is different. In addition to ISO, length of exposure time can affect the noise level. So a shorter exposure at a higher ISO might not be much different in terms of noise.
Take some photos in low light on a tripod.
Shoot at ISO 400, 800 and 1,600.
Then, zoom way into the screen when you have them up on your computer and compare the noise.
If others have different cameras, their results will be different.
Photographer
Art Silva
Posts: 10064
Santa Barbara, California, US
As Shadow Dancer said, Each camera is different in how it handles ISO ratings.
It all depends on the image processor chip in the camera, the converter and of course the signal to noise translation in the motherboard.
It has Nothing to do with optical (lens) performance but the better the lens the better the total IQ. Noise is a byproduct of "gain" of the captured image. The camera will always capture in it's native (lowest) ISO but when you "up" the ISO setting, you are telling the processor to add light gain to be visible. In a sense each stop of ISO gain will basically break down the already captured image into lower resolution group of pixels as it works together to appear you are seeing in the dark.
Just like in a radio or guitar amplifier when you turn up the volume or gain it gets more and more distorted, same with image sensors.
It is always wise not to depend so much on high ISO settings but instead find ways to set your exposure to preserve as much native ISO as possible no matter What camera you chose.
But to answer your post, I always try to stay below 800 ISO, sometimes using 1600 ISO if I have to. Star trails and Star time laps can be done in low ISOs but anything above 1/60th of a second and you are going to start to see movement in the sky when zooming in 100%, which could be a good thing if that's what you want. However some cameras can and will let you go higher [ISO] without much noticeable difference.
Photographer
Eye of the World
Posts: 1396
Corvallis, Oregon, US
You might find this technique helpful. https://fstoppers.com/photoshop/stackin … pro-162857 He is using 8 images in the stack, but even just 3 or 4 would be helpful in reducing the noise, and if you can shoot when there are no clouds that would make auto alignment more likely to work. Then for each time lapse interval, you would take the group of shots and not use the long exposure noise reduction setting. So for example, instead of a 20 second image at ISO 1600 (plus the blank long exposure frame for a total of 40 seconds), try doubling the ISO to 3200 and take three, 10 second long exposures and use the stacking technique to reduce the noise. Test it out to see if it gives a better result with the noise. And, there should be a side benefit of sharper stars due to there being less movement during each 10 second exposure (and then aligning them) vs. a 20 second exposure. The downside is more work in Photoshop to process each group of three shots to create each frame in the time lapse.
Photographer
Instinct Images
Posts: 23162
San Diego, California, US
Art Silva wrote:
As Shadow Dancer said, Each camera is different in how it handles ISO ratings.
It all depends on the image processor chip in the camera, the converter and of course the signal to noise translation in the motherboard.
It has Nothing to do with optical (lens) performance but the better the lens the better the total IQ. Noise is a byproduct of "gain" of the captured image. The camera will always capture in it's native (lowest) ISO but when you "up" the ISO setting, you are telling the processor to add light gain to be visible. In a sense each stop of ISO gain will basically break down the already captured image into lower resolution group of pixels as it works together to appear you are seeing in the dark.
Just like in a radio or guitar amplifier when you turn up the volume or gain it gets more and more distorted, same with image sensors.
It is always wise not to depend so much on high ISO settings but instead find ways to set your exposure to preserve as much native ISO as possible no matter What camera you chose.
But to answer your post, I always try to stay below 800 ISO, sometimes using 1600 ISO if I have to. Star trails and Star time laps can be done in low ISOs but anything above 1/60th of a second and you are going to start to see movement in the sky when zooming in 100%, which could be a good thing if that's what you want. However some cameras can and will let you go higher [ISO] without much noticeable difference. "anything above 1/60th of a second and you are going to start to see movement in the sky when zooming in 100%"???
What focal length are you shooting???
The 500 Rule says divide 500 by your focal length to get your maximum exposure time before star trails become apparent.. So at 20mm that's a 25 second exposure.
No way you can capture stars at 1/60 of a second at an ISO below 6400!
Basic exposure for shooting the Milky Way is 14mm 30s f2.8 ISO 3200
Photographer
Art Silva
Posts: 10064
Santa Barbara, California, US
Instinct Images wrote:
"anything above 1/60th of a second and you are going to start to see movement in the sky when zooming in 100%"???
What focal length are you shooting???
The 500 Rule says divide 500 by your focal length to get your maximum exposure time before star trails become apparent.. So at 20mm that's a 25 second exposure.
No way you can capture stars at 1/60 of a second at an ISO below 6400!
Basic exposure for shooting the Milky Way is 14mm 30s f2.8 ISO 3200 That was meant for those wanting tack sharp star images at what ever ISO and focal length they chose. Yes it's less noticeable with wide angle compositions but that's not what I was referring to.
The earth rotation speed at the equator is about 1000 mph, that is 16 mp/second, That is not much time to get a sharp freeze frame of a particular star. That comment also had noting to do with what I said earlier about the effects of high ISO noise, however you do want to make sure you saturate your sensor pretty well in any event.
I know what star photography settings are. I just got back last week from my annual Eastern Sierra trip where once again I did Milky Way photography... usually and again using my 12mm f/2 at about f4 to f5.6 [the sweet spot] shooting a range between 30" to 50" at ISO 1600 to 3200. It all depends on atmospheric conditions, and using my trusty 12mm I don't have to worry about shutter speed effects much.
Photographer
Instinct Images
Posts: 23162
San Diego, California, US
Art Silva wrote:
That was meant for those wanting tack sharp star images at what ever ISO and focal length they chose. Yes it's less noticeable with wide angle compositions but that's not what I was referring to.
The earth rotation speed at the equator is about 1000 mph, that is 16 mp/second, That is not much time to get a sharp freeze frame of a particular star. That comment also had noting to do with what I said earlier about the effects of high ISO noise, however you do want to make sure you saturate your sensor pretty well in any event.
I know what star photography settings are. I just got back last week from my annual Eastern Sierra trip where once again I did Milky Way photography... usually and again using my 12mm f/2 at about f4 to f5.6 [the sweet spot] shooting a range between 30" to 50" at ISO 1600 to 3200. It all depends on atmospheric conditions, and using my trusty 12mm I don't have to worry about shutter speed effects much. I use a star tracker so I don't have to worry about star movement at all 
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