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LRGB Processing?

Astrosurf

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D4N

D4N

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Nice image but I don't see any colour at all, I would have expected at least some red / blue stars. Something probably went wrong in the processing, you might get more replies in the imaging section.

Sent from my iPad using Tapatalk

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ollypenrice

ollypenrice

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I take an RGB and L into Ps separately and stretch/process them before combining. The L I process for sharpness, contrast, detail. The RGB does not need processing for detail and is best without it since it will add noise. I go for good strong colour saturation because the L will dilute it.

Often the L overwhelms the colour but ne panic pas!

Paste the L on top of the colour and set the blend mode to Luminosity. Reduce the saturation to maybe 30%.

Slightly increase the saturation in the colour layer.

Put a slight Gaussian Blur into the L layer (say 0.6) and flatten.

Repeat this process until with the L getting progressively higher levels of opacity, until you can apply it at full opacity and on the last application you don't apply the blur, so restoring all the detail.

Olly

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ollypenrice

ollypenrice

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Great! Thanks Olly. I'll have a go at that.

What do you use to saturate? Just the Saturation tool??

At the stage I describe, yes. However, there are better ways to boost saturation before you get to the stage of applying the L layer.

Briefly, you can take your stretched RGB and make sure you have left lots of room to the left of the histo peak then go to Image, Mode, Lab colour.  Then go to Image, Adjustments, Brightness and Contrast and, in Channels, activate first the 'a' channel and then the 'b' channel and increase the contrast equally in both by a whacky amount, say 30 to 40.

Re-convert the image to Mode RGB after that.

Olly

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Uranium235

Uranium235

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Briefly, you can take your stretched RGB and make sure you have left lots of room to the left of the histo peak then go to Image, Mode, Lab colour.  Then go to Image, Adjustments, Brightness and Contrast and, in Channels, activate first the 'a' channel and then the 'b' channel and increase the contrast equally in both by a whacky amount, say 30 to 40.

Must try that one! :)

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ollypenrice

ollypenrice

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Must try that one! :)

It's a classic.

Here's another one;

RGB or LRGB, make two copy layers. Set the top one to Blend Mode Soft Light and flatten it onto the middle layer. Set the blend mode now to colour, add a slight Gaussian blur (say 0.6) and flatten. Repeat if you like.

These are low noise ways to increase saturation.

Olly

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dazza1639

dazza1639

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I'm new to LRGB processing after using a dslr for years. I'm finding the processing a bit confusing I have posted these questions in another thread but it seems more appropriate here, my questions are

Do you combine the RGB in Photoshop straight from the alignment/stacking software or do you stretch each channel 1st ?

Do you process the combined RGB as you would a dslr image then add the streched/processed ha to the red channel?

Do you process the lum image then add it to the RGBHa image as a luminance layer?

All tips would be very helpful as at the moment I'm finding it harder to process ccd images than dslr ones. I think that it's just the order of the operations that I'm getting wrong

Thanks for your help

Darren

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Twitter: @SalAstroSoc @Astronut1639 www.salfordastro.org.uk

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johnrt

johnrt

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Do you combine the RGB in Photoshop straight from the alignment/stacking software or do you stretch each channel 1st ?

No load them in to photoshop first and then after they are applied to the correct colour channel begin stretching.

Do you process the combined RGB as you would a dslr image then add the streched/processed ha to the red channel?

Yes apply the processed Ha image to the red channel and set blend mode to lighten.

Do you process the lum image then add it to the RGBHa image as a luminance layer?

Yes

:)

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dazza1639

dazza1639

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Cheers I've been stretching the individual RGB files before combining. I was getting some very strange results. So once I've combined I can use similar processing to my dslr process

Thanks that helps a lot

Darren

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Twitter: @SalAstroSoc @Astronut1639 www.salfordastro.org.uk

Nexstar 8 GPS ADM MDS Rings & Counter Weights, Skywatcher ST80 & Synguider, Canon EOS 1000d,

Dew Heaters & 4 Channel Controller, Orbit Wedge, Observatory and not enough clear nights

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ollypenrice

ollypenrice

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If you stretch the colours separately you'll never keep them consistent - as you've found!

In stretching RGB, keep an eye on the top left of the histo peak in each colour channel and use the black point to keep this top left aligned in each channel. Also use the colour sampler to check your background sky. Personally I like parity, so about 23/23/23 in each channel but sometimes an image seems to demand something a little different from that.

When stretching and processing your colour I would not process it quite like a DSLR image myself. You don't need detail in your colour layer so don't push for it. Concentrate on low noise and high saturation. The luminance will bring in the detail and dilute the colour.

Olly

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Uranium235

Uranium235

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No advice required really, as I think youve done quite well for the amount of exposure. However, the lanes in this galaxy do respond well to a bit of high pass. The only other thing I can think of is the star colour (a bit of cyan creepng in).

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Astrosurf

Astrosurf

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Thanks Rob. I couldn't get rid of the cyan. This is soooo different from DSLR imaging!

I did a soft light High Pass Filter on it and it looks nice. But had to G Blur the stars. The only thing I could think of to lose the cyan was to use the sponge tool on the stars, but it's not that good.

post-1704-0-42176300-1429562056_thumb.jp

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ollypenrice

ollypenrice

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Stars are even on the green side to my eye but the galaxy has good strong colour. Image-Adjustments-Selective Colour is a good place to fine tune your colours. I might try Colour Balance, highlights, and lowering the green, too.

Olly

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Fordos Moon

Fordos Moon

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Cheers I've been stretching the individual RGB files before combining. I was getting some very strange results. So once I've combined I can use similar processing to my dslr process

Thanks that helps a lot

Darren

------------------------------------------------

Twitter: @SalAstroSoc @Astronut1639 www.salfordastro.org.uk

Nexstar 8 GPS ADM MDS Rings & Counter Weights, Skywatcher ST80 & Synguider, Canon EOS 1000d,

Dew Heaters & 4 Channel Controller, Orbit Wedge, Observatory and not enough clear nights

Me too! This is very helpful info well done for asking the question!

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