Difference between luminance and NB accent?

[BrendanC]

Hi,

I'm making my first steps into narrowband, using the Compose module, and I don't understand the difference between these two options.

Could someone explain please?

Thanks
Brendan

[hixx]

Hi BrendanC,
Star Tools features 3 independent but parallel processing streams:
1) Luminance: responsible for Detail/ Brightness. Use a stack with max exposure time for minimal noise.
2) Chrominance ( RGB ): responsible for coloring / hue: Use individual stack shot with colored filters or OSC / DSLR
3) Narrowband Accent: responsible to accentuate details in RGB images using narrowband datasets (i,e. H-II regions in galaxies etc.

You'll find details for COMPOSE, Color and NBA modules in the documentation or check the User Notes by Guy here in the forum for an excellent comprehension. Also the Inofficial manual on download page may help you along operating these
cheers,
jochen

[BrendanC]

Thanks, I've been through all the docs and I still don't quite understand the difference between 'responsible for Detail/ Brightness' and 'responsible to accentuate details'.

I understand how luminosity works, having used it in Photoshop layers in the past, but I'm just not sure what the NB accent is all about. It seems to be a more subtle version of luminance.

This page explains what it is, but not what it does or how to use it: https://www.startools.org/modules/compo ... nd-accents

This page goes into more detail, but is entitled stage 2 and I couldn't find stage 1: https://www.startools.org/modules/narro ... 2?tts=true

Eventually I found stage 1 by typing into Google 'startools narrowband stage 1': https://www.startools.org/modules/narro ... age-1?tts=

So, I'll go through these and see they make things clearer for me.

Thanks,
Brendan

[hixx]

NBA is able to provide a selective boost of details, i.e narrowband details. E.g. you may boost Ha regions in Galaxies only, without impacting overall brightness. You need to use stages 1&2 to specify which details you want to enhance. stage 1 works much like Autodev module. Make sure to cut off noise here, to not have large NB contribution in the coloring / luminance. Stage 2 will then limit the detail size and determine, which coloring applies
A good step by step instruction and more tips can be found in the user notes:
viewtopic.php?f=12&t=2300
cheers,
jochen

[hixx]

viewtopic.php?f=12&t=2300

[Mike in Rancho]

Brendan,

Based on your initial post, what is it you are actually doing when you say taking first steps into narrowband?

If you mean an original, full NB stacks from different filters that you want to create an image from (for example Ha, OIII, and maybe SII to create an HOO or SHO), that is going to just be your normal Compose usage to bring those all together.

While there are multiple ways to creatively use ST, including the NBAccent, in general the NBA is to take a single extra NB file (possibly duoband, which is an option), and use that to augment your main data combination - often RGB.

Anyway, let us know what kind of data you have in front of you that is ready to process, and we should be able to better take you through the steps or point to more specific locations of the various documentation and notes.

[BrendanC]

Thanks!

What I'm actually doing is using a 7nm Ha narrowband filter to augment my RGB images. I know, I know, it's wrong to use narrowband filters with a DSLR, but I don't care - I'm enjoying the results, and it's my first step towards learning more about the narrowband world.

I'm currently experimenting a lot with different approaches. I'm using the Compose module to use the Ha instead of red; also as a luminance channel; and have tried using the NB accent too. I'm also experimenting with processing the RGB and Ha images separately and then layering them, mostly in Photoshop because I just know how layers work in that package better.

So, I was just interested in what NB Accents was all about.

Thanks, Brendan

[Mike in Rancho]

Hi Brendan,

Well, if your 7nm Ha with a DSLR is "wrong," what does that say about my 6.5nm SII?

So now that we know what your combo is, indeed there is voluminous documentation on the many, many (many!) ways of going about this. Even the Compose user notes here in the forums is loaded with special techniques steps. But it all boils down to experimenting and seeing if you get what you want. Colors can be changed up quite a bit, in ways you might not like, when the luminance and color get disconnected. So just a lot of trying and balancing.

The NBA module is really tailor made for this though, as you can adjust so many parameters between the two screens without having to go back to the beginning to recombine. Or you could also split things up -- add some Ha to R to make a new R, but also then use the Ha via NBA.

For various weighting possibilities of Ha and RGB, there's also this post on CN last year by Ivo, where he notes a few nuts and bolts of how ST works internally for these things, and also gives some example calculations that also help explain how it all works. Or can work. Depends on your plan.

https://www.cloudynights.com/topic/7496 ... ry10849588

I'm not sure if all of this ever made it into the special techniques. Might have. But good stuff anyway for learning.

Let us know what you come up with!

[BrendanC]

Brilliant. Thank you so much!