When to combine Ha with RGB?

[joelshort]

When is a good time to combine Ha data with R(GB)?  Linear or non-linear?  Earlier in the process or later? 

[JoLo]

I extract the RGB components after background / color calibration while in the linear state.  In my workflow, i have already performed non-linear noise reduction at this point.  The extracted R component is then combined with the Ha narrowband, and the RGB image is recomposed using the R/Ha hybrid in the red channel.

Joe

[lucchett]

If you are adding ha to R, I would do this in the linear stage. If you want to mix also ha in
L you have better to do this after stretching. This because I think the Cie Lab space is non linear.
I know it is possible to do the same in the linear stage but you should first apply a linear color space, which is something I couldn't personally master till now
Andrea

[jerryyyyy]

You may want to compare your results using the AIP and NBRGB scripts.  I think both allow linear versus nonlinear inputs.  This gives you a 2x2 matrix of possibilities x the various settings of each script for a lifetime of processing.... 

[JoLo]

In my experience, it is much better to hybridize Ha with R, rather than a standalone channel in RGB combine, or with a luminance image.  This produces much better color in the final result, the others tend to produce the sickly salmon color you often see in Ha combined images.  I always normalize the color space with RGBWorkingSpace prior to splitting into R, G, B and combining the Ha with the R.  I never use L*a*b color space in this process.

It varies from image to image, but play with the percentages of Ha and R in the hybrid, then recombine to form the new HaRGB and assess.  Sometimes more Ha, sometimes less....

[topboxman]

Hi Joe,

I am interested in your procedure. I see that you do this:

1) RGB Combine
2) Background Neutralization
3) Color Calibration
4) Extract R, G and B from RGB combined

Then I am curious is whether you do any processing of Ha before blending it with R? Do you do LinearFIT of Ha with R first before blending Ha with R? Do you Pixel Math for Ha combined with R? If so, what are your typical Pixel Math equation?

Thanks,
Peter