If the sensors have the same pixel size, a larger sensor does not gather a stronger signal, the signal is the same per pixel, If you crop in on a galaxy on the larger sensor it's gathering the same amount of light as on the smaller sensor since the pixel size is the same. The same goes for read noise, even if the camera has less pixels you expose long enough to make the read noise insignificant compared to the shot noise, the stacking process takes care of the shot noise. If you compare the famous IMX533 and IMX571 sensors they have the same noise characteristics , same sensitivity to get above the noise floor. There are experts in imaging that can explain this better/ in more detail on Cloudy Nights though.
Good video, thanks. I remember from a few videos back you got the ASI585mc planetary camera (as I did) and are using it for DSO. astrophotography. Just wondering, what gain setting you've been using with that camera? I've pretty much been sticking with the HCG setting of 252 which works pretty well but being an uncooled camera (and warm summer nights), I do have a fair amount of noise in my images and I was wondering if maybe a lower gain setting might help. Thank you.
I have the same camera (ZWO ASI585MC). I used the same gain settings and sometimes even higher to overcome overall noise. Although you need to identify what kind of noise is impacting you most, if its dark current then you need to capture darks after your astrophotography session (to make sure the darks were taken at the same temperature as your lights) You could also do what I did....I got myself a cheap USB powered fridge (one of those that only have space for a soda can, off of amazon or ebay) and took it apart to get the peltier cooler inside. Then I attached the peltier cooler to the back of my ASI585MC camera with a little double sided tape and thermal paste between camera and cooler plate to make contact :) With this setup I can get my camera to 10 C below ambient, it makes a LOT of difference to dark current noise.
Hey barnaclewatcher! I stick to 252 as (going by the graphs) it provides the lowest read noise to highest dynamic range ratio. I know this sounds counter intuitive, but dropping the gain will increase the read noise. On the flip side, increasing gain past 252 will slightly reduce the read noise further, but the dynamic range drops by much more, so basically stick to 252 and dither and take darks if you are finding the noise to be a little too much. I'm lovin ziggyfrnds mini fridge Peltier mod though, maybe we should all be doing that! :D
Thanks a lot for your contributions. I usually really enjoy your videos. In this specific case, I feel the need to react. These comparisons are at same ISO and same f-number. It's like mounting a micro four third camera on a 6" f-7 telescope, and comparing it to a full frame camera mounted on a 12" f-7 telescope. Sure you get the same angle of view and the same f-number, but obviously the 12" telescope will collect 4 times more photons, making the comparison unfair (and perhaps not very meaningful).
I appreciate you taking the time to provide your thoughts. Maybe we are just looking at this from different angles. I'm looking at it from the angle of someone who is often asked which camera to choose for a specific telescope, so that part of the equation is fixed much of the time (I'm asked this at least a few times a day through my day job) The part of the video I think you are referring too is meant to highlight some of the unforeseen difficulties with choosing a larger sensor camera, such as requiring a larger image circle to avoid vignetting, and the extra fine tuning of back spacing and tilt required. You are of course right that a 12" f/7 will collect more photons than a 6" f/7. I specifically gave the example of 200mm f/4 camera lenses to keep large aperture differences out of the discussion as that's not the point of the video. The relationship between sensor size and noise, and the practical implications of choosing a larger sensor if you want lower noise, was.
@@Astrolavista my point is that the relationship between sensor size and shot noise is at best weak, if any. When shooting the same scene, with the same shutter speed, pictures from my phone (crop factor 3.6, 25mm equivalent, f-1.9) have the same shot noise as pictures from my full frame camera with a 25mm lens at f-7.1 (using f-7.1=f-1.9*3.6 to have the same aperture diameter). On the other hand, if I vary the aperture diameter on my FF camera, shot noise (and more interestingly SNR) will vary proportionally to the aperture diameter. Same if I vary the shutter speed. So, between shutter speed, aperture diameter, and sensor size, if I vary only one of the three, sensor size is the only one that doesn't have a significant impact on shot noise.
Well presented, great video…👍🏻
Great explanation Chris thanks for sharing your wisdom
Cheers Tony :)
Thanks Chris.
🙂
If the sensors have the same pixel size, a larger sensor does not gather a stronger signal, the signal is the same per pixel, If you crop in on a galaxy on the larger sensor it's gathering the same amount of light as on the smaller sensor since the pixel size is the same.
The same goes for read noise, even if the camera has less pixels you expose long enough to make the read noise insignificant compared to the shot noise, the stacking process takes care of the shot noise.
If you compare the famous IMX533 and IMX571 sensors they have the same noise characteristics , same sensitivity to get above the noise floor.
There are experts in imaging that can explain this better/ in more detail on Cloudy Nights though.
Good video, thanks. I remember from a few videos back you got the ASI585mc planetary camera (as I did) and are using it for DSO. astrophotography. Just wondering, what gain setting you've been using with that camera? I've pretty much been sticking with the HCG setting of 252 which works pretty well but being an uncooled camera (and warm summer nights), I do have a fair amount of noise in my images and I was wondering if maybe a lower gain setting might help. Thank you.
I have the same camera (ZWO ASI585MC). I used the same gain settings and sometimes even higher to overcome overall noise. Although you need to identify what kind of noise is impacting you most, if its dark current then you need to capture darks after your astrophotography session (to make sure the darks were taken at the same temperature as your lights)
You could also do what I did....I got myself a cheap USB powered fridge (one of those that only have space for a soda can, off of amazon or ebay) and took it apart to get the peltier cooler inside. Then I attached the peltier cooler to the back of my ASI585MC camera with a little double sided tape and thermal paste between camera and cooler plate to make contact :) With this setup I can get my camera to 10 C below ambient, it makes a LOT of difference to dark current noise.
Hey barnaclewatcher! I stick to 252 as (going by the graphs) it provides the lowest read noise to highest dynamic range ratio. I know this sounds counter intuitive, but dropping the gain will increase the read noise. On the flip side, increasing gain past 252 will slightly reduce the read noise further, but the dynamic range drops by much more, so basically stick to 252 and dither and take darks if you are finding the noise to be a little too much. I'm lovin ziggyfrnds mini fridge Peltier mod though, maybe we should all be doing that! :D
@@ziggyfrnds Very cool ziggy 😎 no pun intended.
Thanks a lot for your contributions. I usually really enjoy your videos. In this specific case, I feel the need to react. These comparisons are at same ISO and same f-number. It's like mounting a micro four third camera on a 6" f-7 telescope, and comparing it to a full frame camera mounted on a 12" f-7 telescope. Sure you get the same angle of view and the same f-number, but obviously the 12" telescope will collect 4 times more photons, making the comparison unfair (and perhaps not very meaningful).
I appreciate you taking the time to provide your thoughts. Maybe we are just looking at this from different angles. I'm looking at it from the angle of someone who is often asked which camera to choose for a specific telescope, so that part of the equation is fixed much of the time (I'm asked this at least a few times a day through my day job) The part of the video I think you are referring too is meant to highlight some of the unforeseen difficulties with choosing a larger sensor camera, such as requiring a larger image circle to avoid vignetting, and the extra fine tuning of back spacing and tilt required. You are of course right that a 12" f/7 will collect more photons than a 6" f/7. I specifically gave the example of 200mm f/4 camera lenses to keep large aperture differences out of the discussion as that's not the point of the video. The relationship between sensor size and noise, and the practical implications of choosing a larger sensor if you want lower noise, was.
@@Astrolavista my point is that the relationship between sensor size and shot noise is at best weak, if any. When shooting the same scene, with the same shutter speed, pictures from my phone (crop factor 3.6, 25mm equivalent, f-1.9) have the same shot noise as pictures from my full frame camera with a 25mm lens at f-7.1 (using f-7.1=f-1.9*3.6 to have the same aperture diameter). On the other hand, if I vary the aperture diameter on my FF camera, shot noise (and more interestingly SNR) will vary proportionally to the aperture diameter. Same if I vary the shutter speed. So, between shutter speed, aperture diameter, and sensor size, if I vary only one of the three, sensor size is the only one that doesn't have a significant impact on shot noise.
Above my pay grade.