When to use RGB multipliers

While you're waiting for Mabula to answer...Sometimes you need a secondary program for post-processing like Lightroom and Photoshop. Another way to fix things like this is in pre-processing Via Adobe camera Raw. There you can import your raw images remove chromatic aberration vignetting on a single sub then it will batch process all of them save them back in raw format and bring them into app afterwards. I'm finding there's too many ways to do something. In Photoshop you could open curves and play with just a green Channel or red Channel pull those out or you can use the plugin called hasta Lavista green (HLVG) which I use cuz I have a cannon. Usually stacking software doesn't address these things it just makes the best it can out of what it's fed, but with a PP there's more customization than just that.

I hope I have not clouded the issue just thought I'd give you something to play with if you're equipped with those programs.

Hi GW, 

Thanx for you're reply. In your opinion al my recordings should be pre-proccesd to make the curves overlap to each other?

The only thing is that I shoot FITS files, and as far as u know these files can not be loaded into photoshop or lightroom because there aren't raw files. 

Do you an other way to match the curves to each other. Or am I on the wrong way? Because when I proces al the files in APP, APP makes by itself the adjustments to match the curves to each other?

Kind regards,

Jan-Willem

No, I thought I would confuse you. The pre-processing of Subs is kind of an advanced technique in Adobe camera Raw I would work on standard techniques first. It's easy to line up your RGB peaks in Photoshop but I've always had them come up lined up in app or very close. I have never used the RGB multipliers feature in app. It is a simple thing in Photoshop to open up your image after converting it to a tiff and lining up the individual Peaks using levels.

Fits give me fits. I downloaded a little app with you right click on your file and it will convert it to a tiff from a fit. I'm sure there are many that are free but I use something called rhea convert.

If by curves you mean the individual RGB Peaks, you can do it using curves or levels I prefer levels in Photoshop. Image /adjust , levels, then in the histogram select the individual RBG channels rather than all of them and adjust each one.

Hope I'm understanding you right and that that helped

Hi GW,

Now i'm a little bit confused. I understand the pre-processing but is it nessecery?

What i mean is this: this camera, it has a RGGB pattern, so it is natural that it collects more green data in stat of red and blue. With normal DSLR's the software inside of them would correct this additional green data (so i understand it with the "white balans" etc.) But with a cmos cam i get real rough data (so thas why i think it is so greenish). Normaly when i shoot with my DSLR i would use lets say "White balans, Daylight settings" most of the time the colors are real nice and somtimes i tweek al little on the colors (like you said in photoshop) and than process them in APP. But i'm fairly new with this kind of camera so i don't know what to do with the additional green data?

Should i increse more Blue and Red bij using multipliers in APP, or first run them through Photoshop adjust the colors and than put them in APP, or is it not necessary to incres the red and blue data at all?  Because APP will always create a neutral background color?   

I am not familiar with your camera and we'll wait for my Mabula to give advice on that. You are getting into some complicated areas, my thought is Occam's razor don't do anything but run it through APP and correct it in Photoshop. Maybe set up a Dropbox links to your problem image

Posted by: Jan-Willem

Hi Mabula,

 

I've got a question about the when to use the RGB multipliers, i'm currently using the ASI071mc-c pro but when i see my recordings they are al verry greenish. (see file)

Now i can use the rgb multipliers to create a better view but is that the way?

When i proces the recordings (multipliers as default) i will be able to get a neutral backgrond, but when i do this shoudn't this result in a loss off red and blue data?

Could you explain to mee how to work with this?

One image as it came out of APT,

the other image i used the rgb multipliers, 1,3 red, 1,0 green, 1,9 blue (so the histogram has equel overlapping curve's)

 

Kind regards,

 

Jan-Willem Duijndam

Hi Jan-Willem and Greg,

Apologies for the late response to your question and your discussion.

 I have read the whole topic until now.

My advise would be to never use the RGB multipliers actually, the option is there though so you can experiment and other applications do offer it as well. I never do myself with Canon, Nikon Dslrs or color cmos camera;s like yours. Let me explain why:

If you start to use a multiplier higher than 1, you immediately start to throw away data that is on the right side of the histogram (so the highlights) giving you quicker burnt out stars at a stage in processing where it's not needed at all.

Furthermore, the color of the initial light frames, can be all sorts of color and it just depends on a lot of factors actually. I have seen all sorts of colors and all can be easily corrected after integration of all the frames.

Some factors that play a role:

• moon phase has a big influence
• sensor response in R,G & B broadband wavelengths (which is different for different camera models)
• your local light pollution
• the quality and transmission of the filters that are used ( in this case the CFA filters on your sensor)

In a nutshell, a lot of factors determine what color your sensor actually sees for the night sky. That's no problem and perfectly normal. A thing like chromatic abberation doesn't play a role in this sense (and APP can correct for that as well by the way).

After integration, you should correct the data for gradients and then perform background calibration. Then the sky background is corrected in a scientifically correct manner. Star Colors are a different subject but need to be corrected using the star color calibration tool after background calibration since it needs to know the background levels.

So I recommend to use the linear data as it is recorderd by the sensor, the colors can and should be corrected after integration I think.

For DSLR data (regular consumer camera's not initially created for linear data processing) , the discussion is more complicated and warrents a separate topic if you are interested ;-). Non-linear raw processing versus linear raw processing is a matter of hot debate currently and I have 2 development priorities to actually solve and counter the debate (I think).

Jan-Willem, does this answer your questions on this subject? Let me know if anything is unclear.

Mabula

Hi Mabula,

Thank you for this extensive answer. Now it has cleared all. I didn't realise that by using the multipliers I actually was throwing away data. Next time I set the multipliers as default. And use you're advise first l.p. removal and than background calibration. 

When I've got some new results I will share them on the forum.

Succes with the new version :)! I`m curious about the new version.

Kind regards, Jan-Willem

Posted by: Jan-Willem

Hi Mabula,

 

Thank you for this extensive answer. Now it has cleared all. I didn't realise that by using the multipliers I actually was throwing away data. Next time I set the multipliers as default. And use you're advise first l.p. removal and than background calibration. 

When I've got some new results I will share them on the forum.

Succes with the new version :)! I`m curious about the new version.

 

Kind regards, Jan-Willem

 

Excellent Jan-Willem 😉

and thanks!

Mabula