Iso and shutter speed noise

plumberdp69 · Feb 27, 2021

Impressed with the many stars behind the moon in a photo I took the other night (after enlarging the image and also some editing). Asked myself were they really stars or noise. Read about the iso and shutter speed noise (due to the heat with slower shutter speed). Thus a test I did. Sharing some results below. Taken using lens cap on and all settings were the same except the shutter speed.

My takeaway from this test is the rapid increase in noise for shutter speed slower than 1 sec.

Interested to compare the above with other cameras and see which ones are better.

I will share the ISO noise results later.

Jeffry7 · Feb 27, 2021

Why are you taking long exposures of the moon?

plumberdp69 · Feb 27, 2021

Jeffry7 said:
Why are you taking long exposures of the moon?

Good question. Ha. The slow shutter speed test was secondary, added to my iso test after reading about the iso and shutter speed noise.

Nonetheless, good awareness for me when I am using slow shutter speed for other uses.

plumberdp69 · Feb 27, 2021

82Virago · Feb 27, 2021

High ISO values will always come with a noise penalty. Some cameras better than others.

The 'shutter speed' noise is demonstrating what happens when you capture nothing.

When doing actual time exposure of object, milky way etc, you are capturing photons that will overwhelm the noise and therefore take the place of the noise. Will see conversations about the data signal (your image) swamping the 'read noise' of a particular camera. This signal to noise ratio is what impacts your final image.

More exposure is typically better, up to the point where light pollution gets to be too strong of 'data' compared to the image data. At that point it is the light pollution doing the swamping. A balance is found for any particular set up, or conditions at hand.

Unless you are out somewhere very dark, it is unlikely you will see a zillion stars behind the moon, with your eyes or captured with the camera.

When you hear or see the term 'dark frame', the purpose is to actually record the noise you are seeing in blank frame, and the processing software can use that as a reference to process out some of that noise.

Ideally a dark frame would be equal in exposure length to your images, and also same ISO, AND temperature. As sensor temperature affects it's noise level. Dedicated astro cameras are often cooled to minimize this type of noise.

Your images here are of no surprise, but it is good to see the 'wheels turning', as there is much to learn, and some of the best answers come from trying stuff.

Hope some of this is useful. Never hurts to post a pic and ask for advice.

Cheers

Tristimulus · Feb 28, 2021

Do not quite get the point.

Obviously stretching under exposed images to the same level as well exposed images will increase noise. The more under exposed the more apparent the noise.

Star brighness is a key factor when recording stars. Simply a 5 mag star needs 100 times longer exposure than a 0 mag star to become visible in a similarily exposed mage (same aperture and focal lenght). ISO will not change that.

Exposure is about time and aperture, not ISO (which only brighten the image). In this case you compare different exposures.

So basically just trying out under exposure? Or?

plumberdp69 · Feb 28, 2021

82Virago said:
High ISO values will always come with a noise penalty. Some cameras better than others.

The 'shutter speed' noise is demonstrating what happens when you capture nothing.

When doing actual time exposure of object, milky way etc, you are capturing photons that will overwhelm the noise and therefore take the place of the noise. Will see conversations about the data signal (your image) swamping the 'read noise' of a particular camera. This signal to noise ratio is what impacts your final image.

More exposure is typically better, up to the point where light pollution gets to be too strong of 'data' compared to the image data. At that point it is the light pollution doing the swamping. A balance is found for any particular set up, or conditions at hand.

Unless you are out somewhere very dark, it is unlikely you will see a zillion stars behind the moon, with your eyes or captured with the camera.

When you hear or see the term 'dark frame', the purpose is to actually record the noise you are seeing in blank frame, and the processing software can use that as a reference to process out some of that noise.

Ideally a dark frame would be equal in exposure length to your images, and also same ISO, AND temperature. As sensor temperature affects it's noise level. Dedicated astro cameras are often cooled to minimize this type of noise.

Your images here are of no surprise, but it is good to see the 'wheels turning', as there is much to learn, and some of the best answers come from trying stuff.

Hope some of this is useful. Never hurts to post a pic and ask for advice.

Cheers

Noted and many thanks!

Good to know more about the light "inside story"! Beside high ISO noise, I did not know until recently there is this heat induced noise (eg slow shutter speed).

Below are my iso noise results. As expected, higher noise with higher iso. My takeaway from this study is, the max ISO I will use on my Z6ii is 3200. Maybe the real max is 6400 with post noise reduction later. Surprisingly, I got 3200 as well in another check by comparing chart images taken at different iso.

Z6ii has high iso noise reduction (low, normal, high). I will try these and see how good is this high iso noise reduction. A potential penalty with post noise reduction is some of the actual image pixels may be unintentionally deleted in the process. So ....

Cheerio.

plumberdp69 · Feb 28, 2021

Trollmannx said:
Do not quite get the point.

Obviously stretching under exposed images to the same level as well exposed images will increase noise. The more under exposed the more apparent the noise.

Star brighness is a key factor when recording stars. Simply a 5 mag star needs 100 times longer exposure than a 0 mag star to become visible in a similarily exposed mage (same aperture and focal lenght). ISO will not change that.

Exposure is about time and aperture, not ISO (which only brighten the image). In this case you compare different exposures.

So basically just trying out under exposure? Or?

Thanks.

I may be wrong here, when one increases the ISO, this increases the sensor's electronic signal amplification. One negative effect of this signal amplification is, electronic noise will be generated and they end up as noise in the image.

I think for film iso, different light-sensitive chemicals are used for the iso range.

Cheerio.

Kazmarov · Feb 28, 2021

Interesting - long exposures of the moon. Perhaps you could investigate "dark subs" in astrophotography. They together with bias, flats & dark flats contribute to improving the quality of the final image. You could also look at Bill's "Photonstophotos.net" site for additional information.

plumberdp69 · Feb 28, 2021

Kazmarov said:
Interesting - long exposures of the moon. Perhaps you could investigate "dark subs" in astrophotography. They together with bias, flats & dark flats contribute to improving the quality of the final image. You could also look at Bill's "Photonstophotos.net" site for additional information.

Thanks. Ha ha.

One thought came to mind the other day, has anyone photographed the flag planted on the moon in the 70's? Or other items we left behind on the moon?

Lyle Aldridge · Feb 28, 2021

plumberdp69 said:
Kazmarov said:

Interesting - long exposures of the moon. Perhaps you could investigate "dark subs" in astrophotography. They together with bias, flats & dark flats contribute to improving the quality of the final image. You could also look at Bill's "Photonstophotos.net" site for additional information.

Click to expand...

Thanks. Ha ha.

One thought came to mind the other day, has anyone photographed the flag planted on the moon in the 70's? Or other items we left behind on the moon?

I don't think any of the manned missions went back to the same places, so the only images I know of that show what was left on the moon have been taken from satellites in orbit around it. Here's a 2011 article showing some taken from roughly 13 and 15 miles up:

Apollo moon tracks, trash in never before-seen images

NASA orbiter sends back photos of astronauts' tracks, trash left between 1969 to 1972

www.cbsnews.com

There are probably more recent images by now, but that was the story I remembered seeing.

plumberdp69 · Feb 28, 2021

Lyle Aldridge said:
I don't think any of the manned missions went back to the same places, so the only images I know of that show what was left on the moon have been taken from satellites in orbit around it. Here's a 2011 article showing some taken from roughly 13 and 15 miles up:

https://www.cbsnews.com/news/apollo-moon-tracks-trash-in-never-before-seen-images/

There are probably more recent images by now, but that was the story I remembered seeing.

Many thanks.

I was wondering whether someone has taken a photo from the earth of things left behind on the moon. Come to think of it, maybe not possible even with high-tech gadget we have now. Earth to moon distance is 384,000,000 m. A 1 m flag on the moon from earth will appear as 1/384,400,000 = 0.000,000,003 m = 0.000,003 mm. With a 100x magnification lens, it will appear as a 0.0003 mm dot.

Even with Hubble's 5800 magnification power, the flag there will appear as a 0.02 mm dot.

So, I will not try to hunt and shoot the flag on the moon photo. Ha.

bclaff · Feb 28, 2021

plumberdp69 said:
Impressed with the many stars behind the moon in a photo I took the other night (after enlarging the image and also some editing). Asked myself were they really stars or noise. Read about the iso and shutter speed noise (due to the heat with slower shutter speed). Thus a test I did. Sharing some results below. Taken using lens cap on and all settings were the same except the shutter speed.

My takeaway from this test is the rapid increase in noise for shutter speed slower than 1 sec.

Interested to compare the above with other cameras and see which ones are better.

I will share the ISO noise results later.

This is a worthwhile test but the reason for this effect might not be as you imagine.

You are probably aware of something called Dark Current which increases linearly with exposure time (and is dependent on temperature).

What you are seeing is a related effect called Dark Current Non-Uniformity.
This means the individual pixel accumulate dark current and very different rates.
So when Dark Current is significant then a random pattern appears that reveals those pixels that are more subject to Dark Current than their neighbors.

This isn't noise per se because the pixels still have pretty uniform read noise it's just that that read noise in centered on higher values.

(I've been gathering data on this for an as yet unpublished article for PhotonsToPhotos)

--
Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

plumberdp69 · Feb 28, 2021

bclaff said:
This is a worthwhile test but the reason for this effect might not be as you imagine.

You are probably aware of something called Dark Current which increases linearly with exposure time (and is dependent on temperature).

What you are seeing is a related effect called Dark Current Non-Uniformity.
This means the individual pixel accumulate dark current and very different rates.
So when Dark Current is significant then a random pattern appears that reveals those pixels that are more subject to Dark Current than their neighbors.

This isn't noise per se because the pixels still have pretty uniform read noise it's just that that read noise in centered on higher values.

(I've been gathering data on this for an as yet unpublished article for PhotonsToPhotos)

Thanks.

Good to know more. Didnt know there is Star War Dark force in camera. Ha.

Please let me know once your paper is ready.

bclaff · Feb 28, 2021

plumberdp69 said:
plumberdp69 wrote:

...

I may be wrong here, when one increases the ISO, this increases the sensor's electronic signal amplification. One negative effect of this signal amplification is, electronic noise will be generated and they end up as noise in the image.

...

You are right that most cameras implement the ISO Setting (at least for non-extended ISO settings) by using a variable gain amplifier between the pixel and the Analog to Digital Converter (ADC).

That amplifier amplifies both the Signal and the Noise so this is why noise is increased.

Paradoxically, because some fixed amount of noise is added after the amplifier input-referred read noise, noise expressed in electrons, goes down as the ISO setting goes up.

More terrestrial photographers don't pay attention to this but it's important for some astrophotography.

For example, Read Noise in DNs

b23e6b8c2e0641cfae8962ad91bc01ec.jpg.png

Input-Referred Read Noise in electrons

d13dcd72f8034554a70baa42aa440c23.jpg.png

Depending on your situation you might judge the "sweet spot" for astophotography to be about ISO 1280/1600 since input-referred read noise doesn't drop much after that.

--
Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

plumberdp69 · Feb 28, 2021

bclaff said:
You are right that most cameras implement the ISO Setting (at least for non-extended ISO settings) by using a variable gain amplifier between the pixel and the Analog to Digital Converter (ADC).

That amplifier amplifies both the Signal and the Noise so this is why noise is increased.

Paradoxically, because some fixed amount of noise is added after the amplifier input-referred read noise, noise expressed in electrons, goes down as the ISO setting goes up.

More terrestrial photographers don't pay attention to this but it's important for some astrophotography.

For example, Read Noise in DNs

Input-Referred Read Noise in electrons

Depending on your situation you might judge the "sweet spot" for astophotography to be about ISO 1280/1600 since input-referred read noise doesn't drop much after that.

Excellent! Thanks for sharing. Interesting and useful graphs.

Happy to see that my iso 3200 is close to your stated iso 1280/1600.

Cheerio.

Jared Willson · Mar 1, 2021

plumberdp69 said:
Kazmarov said:

Interesting - long exposures of the moon. Perhaps you could investigate "dark subs" in astrophotography. They together with bias, flats & dark flats contribute to improving the quality of the final image. You could also look at Bill's "Photonstophotos.net" site for additional information.

Click to expand...

Thanks. Ha ha.

One thought came to mind the other day, has anyone photographed the flag planted on the moon in the 70's? Or other items we left behind on the moon?

From Earth, a one meter object on the Moon would subtend 0.000537 arc seconds. A telescope that could just resolve that (barely—no details, just a point) would need to be about 150m in diameter. That assumes no blurring atmospheric effects here on Earth. To be able to see any details, you’d need something perhaps ten times that size, a lens/mirror diameter of about a mile. Again, assuming no atmosphere here on Earth to blur the result. And, of course, the colors on the flat have all been bleached out to white by UV light, so you can forget seeing stripes or colors. Throw in the blurring effects of our atmosphere, and the task becomes all but impossible. Perhaps, if we ever figure out a way to do very long baseline optical interferometry (where the resolution is determined by calculating interference patterns in smaller telescopes spaced a known distance apart) even with Earth’s atmosphere it could be done. With equipment currently available? Not even close.

However, many of the objects left behind on the moon—particularly crash sites of “hard lander” probes and descent stages from lunar landers—have been photographed from lunar orbit. This includes pictures taken by, in particular, Chinese orbiters, not just NASA orbiters, so those who have suggested conspiracies, well, it would take wider involvement than just the U.S. government and NASA.

plumberdp69 · Mar 1, 2021

Jared Willson said:
plumberdp69 said:

Kazmarov said:

Interesting - long exposures of the moon. Perhaps you could investigate "dark subs" in astrophotography. They together with bias, flats & dark flats contribute to improving the quality of the final image. You could also look at Bill's "Photonstophotos.net" site for additional information.

Click to expand...

Thanks. Ha ha.

One thought came to mind the other day, has anyone photographed the flag planted on the moon in the 70's? Or other items we left behind on the moon?

Click to expand...

From Earth, a one meter object on the Moon would subtend 0.000537 arc seconds. A telescope that could just resolve that (barely—no details, just a point) would need to be about 150m in diameter. That assumes no blurring atmospheric effects here on Earth. To be able to see any details, you’d need something perhaps ten times that size, a lens/mirror diameter of about a mile. Again, assuming no atmosphere here on Earth to blur the result. And, of course, the colors on the flat have all been bleached out to white by UV light, so you can forget seeing stripes or colors. Throw in the blurring effects of our atmosphere, and the task becomes all but impossible. Perhaps, if we ever figure out a way to do very long baseline optical interferometry (where the resolution is determined by calculating interference patterns in smaller telescopes spaced a known distance apart) even with Earth’s atmosphere it could be done. With equipment currently available? Not even close.

However, many of the objects left behind on the moon—particularly crash sites of “hard lander” probes and descent stages from lunar landers—have been photographed from lunar orbit. This includes pictures taken by, in particular, Chinese orbiters, not just NASA orbiters, so those who have suggested conspiracies, well, it would take wider involvement than just the U.S. government and NASA.

Wah, noted and thanks for the Telescoping 101 lesson! Interesting to learn.

plumberdp69 · Mar 2, 2021

The final part of my test on using high iso noise reduction ...

A. Convincing reduction in the noise. But feel the affected images do not look right, too smoothed (if there is such a word).

B. My earlier ISO max is 3200, maybe push it to 6400 when required. Now looking at this, maybe even 12800 but with high iso noise reduction (low) or post noise processing.

C. One question comes to mind, are noise colored? If so, why? The noise reduction seems to remove the colored noises, leaving behind some of the white noises. Why are most of the noises pink-colored?

Cheerio.

bclaff · Mar 2, 2021

plumberdp69 said:
The final part of my test on using high iso noise reduction ...

...C. One question comes to mind, are noise colored? If so, why? The noise reduction seems to remove the colored noises, leaving behind some of the white noises. Why are most of the noises pink-colored?

White is roughly equal amounts of red, green, and blue.

But the sensor is much less sensitive to red and blue than green.
So the red and blue will have more noise and when they are increased to "match" the green any imbalance will show.

--
Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

Iso and shutter speed noise

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