Shot Noise and Read Noise - Noise in Astrophotography Ep1 

Thanks Kayed! Will definitely keep going!

Thank you! I like the small details of the hobby, even if I don't understand them all (far from it)...

@ Christian , i was so hopping some one would say that out loud...

Glad this was useful!

I totally brought the buckets out in the rain first (not) :-)

You are right, have a look at how that darn read noise stacks in the total stack here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3RH93UvP358.html

Thank you! The bucket analogy is not new, but I think the surface tension as read noise is :)

Hahaha, excellent to hear! NINA is an upgrade in so many respects (frame to frame overhead, AF, etc.) although it is somewhat of a downgrade for the sequencer as it is. I do hope it will help you capture great images!

Hahaha that is pretty cool! Almost wondering whether it has been inserted intentionally :) I should ask around. Bummer on the Celestron thing.... I hope it gets fixed - I used to have an account on their test/dev forum, and the devs were very reactive, so it may be worth asking.

Celestron has released a updated Unified Ascom driver.

That's awesome to hear!

Hahaha I know man, sorry lol - you can also check my recent videos (within the last couple of months) on the topic!

Oh no, I missed such a great opportunity!!! I hadn't even though of that :D Thank you!

Read noise is reduced with increased ISO!

@@CuivTheLazyGeek thank you for always replying to my questions . I really like your channel and think the content is amazing . I am learning a lot from you .

Thank you! Those videos about technical details and PixInsight are much less popular, but I like making them as it's all valuable information.

Well, ISO is just an amplifier. Higher ISO isn't intrinsically noisier than lower ISO in terms of SNR. In fact, higher ISOs typically have LOWER read noise (very important for astrophotography), but sacrifice dynamic range to some extent. Higher ISOs appear to have more noise, simply because normally higher ISO is associated with something like faster shutter speed (to freeze the moment for instance), but in that case everything, including the shot noise, gets amplified by the high ISO to achieve the same brightness level as a longer exposure with lower ISO. With a shorter exposure (regardless of ISO) you will achieve less signal, less shot noise (sqrt(signal)) and worse Signal to Shot Noise Ratio than a longer exposure. If you used higher ISO to achieve higher overall brightness you'll have LESS read noise, but also less dynamic range than an exposure with lower ISO. With bracketing you have: - an underexposed low ISO image with high dynamic range and high read noise (read noise is usually inconsequential in well lit conditions, but very important in astrophotography) - a well exposed normal ISO image with good DR and "normal" read noise (sweet spot is usually around 800 for a lot of cameras in terms of read noise). Maybe the normally exposed image could have clipped highlights somewhere. - an overexposed high ISO image with low dynamic range, potentially clipped highlights, low read noise. Because all share the same parameters besides the ISO (which is just an amplifier, nothing more nothing less), they have sensibly the same SNR (low ISO slightly worse because of high read noise). But each covers a different dynamic range (say 14 stops for low iso image, 13 stops for medium iso image, 12 stops for high iso image), centered differently. Depending on how the bracketed images are combined (as assume some kind of HDR replacement + averaging), you will have better SNR by increasing signal more than shot noise, because square root function (although the LOW ISO image does introduce slightly more read noise), AND an HDR picture that covers a lot of dynamic range. It makes sense to me in a lot of cases!

@@CuivTheLazyGeek That was a very helpful response (and thank you very much). I'm had a feeling you could answer it. That said, while I do the research, can you explain why high ISO has "lower" read noise? And are we talking about upstream (pixel level) or downstream of the ISO amplifier to card? I guess I don't understand the mathematical formula (yet) on how with higher ISO there is less read noise and lower ISO high read noise. Take your time, but if I understand that piece to the puzzle, I think I can make it the rest of the way. BTW: Enjoyed the video a lot. Helped immensely.

Thank you David - once I manage to build a time machine, I'll make sure to go back 32 years into the past and replace your instructor for the introduction to the topic ;) That's awesome though, did you end up working in the field you studied?

@@CuivTheLazyGeek I became a medical physicist, but instead of working in diagnostic imaging I work in therapeutic radiological physics, radiation oncology. I still use much of my knowledge of digital imaging in my work, but most of my passion for imaging is in my hobby. Thanks for producing these videos. You have a wonderful way of explaining things.

Thank you for the feedback! It's always nice to know the details :)

Hahaha, at least my difficulties with English can entertain :D :D Glad this is useful!

Yep, I have a problem with conciseness but I do my best!

@@CuivTheLazyGeek that's totally okay!

Thank you!

I had such a light bucket... But ended up not using it enough and said farewell... :)

@@CuivTheLazyGeek yea mine was a 16 inch F-4 it weighted a ton....................... LOL