Question on capture settings

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Question on capture settings

Post by rigel123 »

I always do my settings for capturing AVI's on the fly, playing with Gain, Gamma and exposure until I like what I see on the screen. Particularly for animations since I want to capture the image close to how I would like the end product to look so I can do a minimal amount of processing. I’m curious though as to how others do captures. Do you use specific settings for all captures or do you adjust for each session?


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Re: Question on capture settings

Post by Montana »

I do exactly what you do, for minimal processing. That is probably not correct but that's what I do. I don't tend to change the gamma too much though as I end up with terrible artifacts in processing otherwise. I have never found a standard method, it always seem to be ad hoc, sometimes I win, sometimes its a lose. I do feel very out of practice at the moment though :(

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Re: Question on capture settings

Post by rsfoto »

Hi Warren,

I do adjust is the exposure and only when I see that there are some crackling solar spots in order to not to overexpose them too much ...

I also adjust from time to time the tilt of the etalons but since a year I open the roof, point onto the Sun, go to the kitchen for a coffee, read the newest gossips online and after 30 minutes everything warmed up. I check the image and then acquire my videos.

The more you move, the more your raw material will change and the more headstands and somersaults you will need to do when processing ...

From my experience over many years what changes is the seeing e.g. the sun moves more or less and that is unavoidable.

Of course a permanent set up makes everything easier as the etalons are not touched, specially that silly golden wheel or the pressure tuner. I do not understand how pressure tuner works but IMHO those have a disadvantage over tilt tuning because of everytime adjusting the pressure and that will never be equal everytime ...

Read this posting if you have time viewtopic.php?p=330077&hilit=remote+eta ... er#p330077

The first images are my first version and they have a resolution of 0.155 microns. Now I have seen that moving let me say 64 steps I already see a change in the image. The lead screw has a pitch of 32 tpi or 0.79375mm. Now you can calculate the angle change for 64 steps ... IMHO such an adjustment is not achievable by turning the golden wheel or pressing the air pump ...


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Re: Question on capture settings

Post by Rusted »

In SharpCap I aim for Gain no higher than 100. Preferably much less.
I push the exposure as short as it will go. Though usually end up with 7ms for 88fps.
3ms improves highly mobile seeing conditions in my experience over 7 ms. Which needs much more Gain.
I aim for a rather dull {dark] image on the 27" monitor to avoid glaring highlights.
I rarely use Gamma after being told off for using it.


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Re: Question on capture settings

Post by rsfoto »

Rusted wrote: Thu Sep 15, 2022 3:49 pm In SharpCap I aim for Gain no higher than 100. Preferably much less.
I push the exposure as short as it will go. Though usually end up with 7ms for 88fps.
3ms improves highly mobile seeing conditions in my experience over 7 ms. Which needs much more Gain.
I aim for a rather dull {dark] image on the 27" monitor to avoid glaring highlights.
I rarely use Gamma after being told off for using it.
Hi Rusted,
I aim for a rather dull {dark] image on the 27" monitor to avoid glaring highlights.
You are killing subtle details in the dark areas. Check the histogram and just keep the white exposure at about 240 ...

https://photographylife.com/exposing-to ... -explained

https://en.wikipedia.org/wiki/Exposing_to_the_right

https://www.creative-photographer.com/e ... ing-right/

just a few explanations ... of thousands in Internet


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Re: Question on capture settings

Post by Rusted »

Thank you Rainer.

I moved to slightly darker [video] images on the monitor because I found it produced more detail in the final image. Not less. ;)


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Re: Question on capture settings

Post by rigel123 »

Always interesting to read how others approach their captures!


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Re: Question on capture settings

Post by rigel123 »

Of course a permanent set up makes everything easier as the etalons are not touched, specially that silly golden wheel or the pressure tuner. I do not understand how pressure tuner works but IMHO those have a disadvantage over tilt tuning because of everytime adjusting the pressure and that will never be equal everytime ...


I thought I was the only one that wondered about pressure tuners being more fidgety than a tilt tune that just seems to stay the course, but I understand all systems are not created equally!


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Re: Question on capture settings

Post by Martin_S »

I bracket my exposures to between 80 to 95% histogram in the area I am imaging in. I then compare my raw stacks and do final processing on what looks the most promising.


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Re: Question on capture settings

Post by pupak »

Several times I read here the opinion that it is useless to shoot in 16 bits, that 8 is enough. I dare to disagree. If you have SW that can use the potential of 16 bits, then you won't get artifacts, but existing details, as 256 levels vs 65535 levels is a big difference. In the sample, the image is taken in 16 bits with good seeing, and apart from the overlap of the granulation into H-alpha due to the inaccurate band setting, there are no artifacts, but the SW can highlight even the finest details also because I shoot with minimal Gain for the highest possible dynamics.
Attachments
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ss3a.jpg (1.72 MiB) Viewed 2002 times


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Re: Question on capture settings

Post by Radon86 »

Hello Pupak,

What camera is this and what is SW.

I do not understand why imagers are still using 8 bit avi for capture. Unless you are capturing to display on a 1 inch screen for Twitter or something similar, it will be inadequate.


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Re: Question on capture settings

Post by rsfoto »

Radon86 wrote: Fri Sep 16, 2022 2:48 pm Hello Pupak,

What camera is this and what is SW.

I do not understand why imagers are still using 8 bit avi for capture. Unless you are capturing to display on a 1 inch screen for Twitter or something similar, it will be inadequate.
Hi,

I guess SW is software. BTW, most of the cameras we use are not real 16 bit imagers more around 10, 12 or 14 ...
I do not understand why imagers are still using 8 bit avi for capture.
Yes you are right IMHO. Having 65535 shades of grey helps us more to stretch the image rather then only 256 shades of grey. Unfortunately I have to capture in 8 bit due to the feature I use in my acquiring software which is applying a false colour mask onto my raw image in order to get prominence and surface with one shot. The author decided not to pursue further the development of the software and did not implement this to 16 bit ...


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Re: Question on capture settings

Post by pupak »

The assembly is AR150/F6, LS80, TV 5x PMT, Apollo IMX432. SW is my own product, built on fractal libraries I wrote about 30 years ago for a license plate recognition SW for a large SW company. It was designed for small camera resolutions (640x480). For a higher resolution, it requires a very powerful PC (24 cores / 256 GB RAM) and even so it takes more than an hour to process an image from the IMX 432 in 16 bits. If the source data is of good quality, it can get incredible detail, but it is not suitable for mass processing. It can't even be used commercially, because I sold the copyright to the libraries. I think commercial AI SW can achieve similar results and much faster.
Unfortunately, my technology is 30 years old.


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Re: Question on capture settings

Post by pupak »

rsfoto wrote: Fri Sep 16, 2022 3:18 pm
Radon86 wrote: Fri Sep 16, 2022 2:48 pm Hello Pupak,

What camera is this and what is SW.

I do not understand why imagers are still using 8 bit avi for capture. Unless you are capturing to display on a 1 inch screen for Twitter or something similar, it will be inadequate.
Hi,

I guess SW is software. BTW, most of the cameras we use are not real 16 bit imagers more around 10, 12 or 14 ...
I do not understand why imagers are still using 8 bit avi for capture.
Yes you are right IMHO. Having 65535 shades of grey helps us more to stretch the image rather then only 256 shades of grey. Unfortunately I have to capture in 8 bit due to the feature I use in my acquiring software which is applying a false colour mask onto my raw image in order to get prominence and surface with one shot. The author decided not to pursue further the development of the software and did not implement this to 16 bit ...
Many people use Impg, PSP and various commercial postprocessors. It should be noted that the basis is quality data in 16 bits, even if the cameras are 14 bits. I see a lot of beautiful pictures here that have huge potential, but it's not being used. It's a pity.


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Re: Question on capture settings

Post by torsinadoc »

I do exactly the same as you. My basler camera requires that I adjust the black point otherwise it will clip the left side.


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Re: Question on capture settings

Post by christian viladrich »

Hi there,
My process flow is pretty much stabilized :
- I only use 8-bit acquisition. In 20 years of solar imaging, using quite a lot of different cameras, I've never seen an advantage to 12-bit (or more) acquisition, except for total solar eclipse imaging. On top of that, using 12-bits (or more) reduces the frame rate, i.e. the amount of captures good images.
- For Ha imaging (double-stack): light is missing, so I use 7 ms exposure time to saturate the USB3 link (155 fps with the B1920-155). The gain is set accordinly (from 15000 to 20000 according to sky condition). Gamma is left to 1. I use gamma (more precisally curves in Photoshop) in post-processing only for prominences).
- For white light imaging, I've got plenty of light, to gain is set to the minimum value in order to maximize S/N ratio and minimize the number of frames to stack. Exposure time is set accordingly. Gamma is left to 1, even in post-processing.
- Ca K imaging, the situation is a bit in between. Light is limited in double-stack configuration. I keep exposure time lower to 7 ms, and set the gain accordingly.

My processing is basically always the same, it is nothing fancy : unsharp mask (one or two levels), with sometimes very limited RL deconvolution, no noise reduction.


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Re: Question on capture settings

Post by pupak »

christian viladrich wrote: Fri Sep 16, 2022 4:31 pm Hi there,
My process flow is pretty much stabilized :
- I only use 8-bit acquisition. In 20 years of solar imaging, using quite a lot of different cameras, I've never seen an advantage to 12-bit (or more) acquisition, except for total solar eclipse imaging. On top of that, using 12-bits (or more) reduces the frame rate, i.e. the amount of captures good images.
- For Ha imaging (double-stack): light is missing, so I use 7 ms exposure time to saturate the USB3 link (155 fps with the B1920-155). The gain is set accordinly (from 15000 to 20000 according to sky condition). Gamma is left to 1. I use gamma (more precisally curves in Photoshop) in post-processing only for prominences).
- For white light imaging, I've got plenty of light, to gain is set to the minimum value in order to maximize S/N ratio and minimize the number of frames to stack. Exposure time is set accordingly. Gamma is left to 1, even in post-processing.
- Ca K imaging, the situation is a bit in between. Light is limited in double-stack configuration. I keep exposure time lower to 7 ms, and set the gain accordingly.

My processing is basically always the same, it is nothing fancy : unsharp mask (one or two levels), with sometimes very limited RL deconvolution, no noise reduction.
You will see the advantage when you use the appropriate SW. It depends on what the author wants from the picture. If it's just confirmation that the Sun is still there, or if he wants to see details that are hidden by normal image processing techniques.
If I cover one eye, I see basically the same thing, but we still have two eyes.


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Re: Question on capture settings

Post by ffellah »

A very interesting thread, thank you all, I learned something here.

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Re: Question on capture settings

Post by Sumpy »

I use various presets to get me in the ballpark, then tweak depending on what I see. I do try to standardize my histogram day to day, and will generally tweak exposure to a point, gain only if necessary.


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Re: Question on capture settings

Post by rigel123 »

Great input everyone!


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Re: Question on capture settings

Post by Bob Yoesle »

My processing is very similar to Christian's, and in my own non-expert experience I have found no significant difference between 8 bit avi and 12 bit ser files and processing. Moreover, compared to most people it seems I generally under-expose my images so as to not blow out active region details, yet I'm still able to bring out the fainter prominence details when using the histogram (gamma), curves, or HDR images produced from a single underexposed image or mosaic. For me the results are quite acceptable.

The image posted above to my eye shows "detail" which is not observed visually at any level of excellent seeing with 150 mm of aperture. Nor is it realistic to what is seen in high-resolution professional solar telescopes with huge apertures and using state-of-the-art adaptive optics. It therefore appears to me a more fanciful than an accurate portrayal of reality.

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Re: Question on capture settings

Post by Alto »

An interesting thread, thanks everyone.


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Re: Question on capture settings

Post by Dennis »

My imaging is also similar to Christians, i tried with more then 8 bit and it looks a bit better (subjective), but i also went back to 8 bit due to technical restrictions mentioned. Now i think a drop in framerate is not acceptable for high res imaging. A bigger hard drive is easy aquirable though.
I never touch the gain during imaging, keeping the data as raw as possible.

H-a: I keep the exposure time at maximum 7ms (or lower in single stack mode when gain is already 0) and gain as low as possible according to this.
Histogram at 85-90%

WL: i have a lot of light there, so i always use the camera with the largest full well capacity (imx432) to keep the stacked images to a minimum (~20 images), exposure time will be at minimum (in my case ~0,3ms) and gain of course at 0 to be able to use the full well.
Histogram at 70-80%

Ca-K: here i reduce the exposure times to 5ms or less with gain at around 200 (imx432). Histogram usually at 75%, here the bright areas can quickly be blown out in postprocessing if i use more. But: if flaring is happening then i need to raise the Histogram to 80-85% otherwise the rest gets too dark.

If i was focused on animations of course i also would do like you Warren, as long as you keep the exposure times not too high.


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