Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

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AJamesB
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Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by AJamesB »

Edit - seems there's likely something else going on, since others don't have any quality degradation in 8bit, so I'll just leave this up as an example of caution when drawing conclusions from small sample sizes:)

The following is good and common knowledge had all ready by many here, but I was curious exactly what the different would be since files captured in 16bit ser can take up a lot of disc space, even more so when capturing 100+ of them for a time lapse.

So, I'm kind of lazy and don't like to do 2 separate captures to make a solar image that has both the disc and the proms visible, so I prefer to expose to the disc, and then stretch that single image in post processing to bring out the prominences that way. The following photos were taken back to back to back on the asi294+4x telecentric in bin2 mode. All videos were the same ROI of 2072x1410. No sharpening/deconvolution or anything else has been done to them. Seeing wasn't great so they are the best 15% of 500 frames. Final images were cropped down to the prom.

First, the 8bit avi capture, who's total size was 1.36GB:

Image

Stark and harsh cutoffs in gradient are easily noticeable in the prom, and not much detail is visible in it, its just sort of uniformly blandly grey with a blotchy appearance. Decent mount of noise visible as well. Disc looks as it normally does when exposed correctly-ish.

Next, the 8bit in ser format, with total size of 1.37GB:

Image

Pretty much identical to the 8bit avi, a touch blurrier but that's likely due to rapid variation in moment to moment seeing. So, if you are set on recording in 8bit, avi can save you a little (but not much) disc space.

Lastly, the 16bit ser, with total size of 2.72GB:

Image

Hugely noticeable different in the prom. The blotchy, greay bland gives way to subtle detail that just wasn't seemingly captured in 8bit. Transitions and gradients are much smoother, and overall noise levels are lower as well. While the file is twice the size, you have much more detail out the gate to work with, and less noise to deal with as you sharpen/process the image.

So, for those newer to h-alpha imaging or for those wanting to try the singlecapture+stretch method for getting images with both disc and proms visible, its recommended to capture in 16bit mode if you can, since the really faint proms you'll be stretching into view really benefit from the extra depth captured in 16bit mode.

And caveat, I'm not an expert, so I could have completely missed something that completely undermines this entire post, lol. So also feel free to comment/add/clarify as well. Truest info is always the goal!
Last edited by AJamesB on Wed Apr 14, 2021 8:02 am, edited 1 time in total.


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Re: Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by Carbon60 »

These types of comparisons can be tricky unless you run the tests in rigorous way as there are so many other factors at play. I always capture in 8 bit mode (SER) and can capture disk and proms at the same time and in quite some detail. It depends on the image capture settings (speed, gain, gamma) as much as anything. Also, the degree of detail captured depends so much on the seeing conditions, as we know. As you switched between 8bit, AVI, 8bit, SER and 16bit SER the seeing conditions could have changed slightly and also you probably needed to change other settings, particularly between 8 and 16 bit imaging. You’d need to repeat the test several times to show that the improvement is consistent. There will no doubt be some differences between 8 and 16 bit imaging from a grey scale perspective, but does this translate to the degree of image improvement you’ve demonstrated, I’m not sure.

It’s going to be an interesting debate..... thanks for starting the discussion.

Stu.


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Re: Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by AJamesB »

Ah, good info to know, thank you. No, if others like you are able to have equal success with 8bit as with 16, then there's something else going on instead, probably small changes in seeing that affected the smoothness of the gradients, since I kept all other settings the same. Like I said, I'm not well educated on this stuff, so I'd rather learn what's true!


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Re: Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by Jordan Konisky »

Hoping for a robust discussion on this topic, especially how it relates to CAK imaging.

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Re: Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by Montana »

I too have found this difference, you are not alone. When I used 16 bit SER on my white light images I suddenly has so much more dynamic range to play with. The images were like night and day.

However, nobody else ever seemed to get the same results as me. I always capture 16bit SER even if it does mean I halve my frames per second, keeping the dynamic range outweighs the loss in fps in my images.

Alexandra


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Re: Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by Radon86 »

Thank you AJamesB! for showing this.
I wonder what capture program you use, because SharpCap 3.2 does only allow 8 bit avi, and 16 bit SER files only on my ASI120mm-S.
It is also reassuring to see that my images may even be only slightly more blurred than yours on the images you showed!

Has anyone worked out how many actual frames you really need to process an image, because I found, the longer you take a video file, the less reliable it is. So accounting for movement of the sun through the camera sensor during a long video, you can therefore stack less than you would expect and quality is not as good as a shorter video.


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Re: Comparison between 8bit avi, 8bit ser, and 16bit ser when doing single capture of proms and disc

Post by christian viladrich »

Hello,
Here is a comparison between 8-bit and 12-bit acquisition. It takes very special high dynamic range targets to make any use of 12-bit acquisition.
http://astrosurf.com/viladrich/astro/te ... ndree.html
Hope this helps.
Christian


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