LRGB combination for nebula

François Guiot

Hi everyone,

I start processing this nebula I took few days ago. L and Ha datas are 600 seconds exposure and each color are 200 seconds exposure.
I actually blend Ha and Red together and then RGB. On both L and RGB I used BlurXTerminator.

Now I'd like to combine the L and RGB data together but this gives me a result that I don't like much.
In fact, eveytime I tried LRGB, I ended up with a result like this, It seems the colors lost their contrast, became kind of desaturated. I like the details L brings but I like colors of RGB data; is there a better way to combine all that stuff together?

Above, on the top left is the Luminance, top right is RGB and bottom left is LRGB combination (default settings).

BlockHead

Yes, this is the LRGB challenge. I talk about this in a number of places in my videos. They key is to not have the luminance too bright initially and adjust the contrast of the color image. In your case your color image is too dark. You must have every color showing... even if the image is "flat" looking. The luminance will control the correct tonal value... so the color image can have a whatever brightness profile is necessary to color the luminance. You might consider, for example... using masked stretch on the color data and raising the color saturation. Then blend with the luminance. Things like this can help. There are also some minor adjustments you can make with the LRGB Combination sliders to help too... but it is better to get the two images to "marry" each other nicely.

You watched this one?

https://www.adamblockstudios.com/articles/Fundamentals_LRGB

-the Blockhead

François Guiot

Good evening Adam,

Thank you for replying. I actually watch the video a long time ago; so I almost have forgotten, to be honest :)

So I rewatched it and I have a better understanding of how LRGB work but it's not obvious yet.

I started reprocessing from scratch and made a quick test and I've been able to get a closer result of what I want to do with the datas.

Colors are exagerated but I guess I can see the direction I have to take. Tahnk you ! :)

BlockHead

Yes...I think you are on the right track now...

-the Blockhead

François Guiot

Juste a quick update, here's what the result looks at the end of the day.

Thank again for your help :)

BlockHead

This is GOOD. I personally think you can stretch it more (mid-tones) and bright things up a bit. You have some nice faint nebulosity and the bulk of the nebula could be a bit brighter! You can do this on the combined LRGB image itself I think. 

-the Blockhead