blending mode question

[Rkonrad]

I am trying to blend an HA layer with an Oiii to get an acceptable luminance file (Heart and Soul nebula). The HA is quite strong whereas the Oiii is just the core of the subject. I would like to blend the Oiii into the the HA but I don't want the darker parts to influence the HA. Which blending mode / technique should I use?

Thanks in advance!

Richard

[admin]

Hi Richard,

Though the darker OIII parts may "bring down" luminosity of the Ha parts, is there any reason you cannot simply stretch the resulting blend harder when processing it? You can always use the HDR or Contrast modules on the highlights if needed?

Presuming the OIII and Ha are weighted properly in terms of exposure time ratios, you are not really "losing" any signal by creating a weighted average - it's just darker but not appreciably noisier (the noise component is also "darkened").

Does this make sense?

[Rkonrad]

So you mean do a second stretch after the blend? I will try that. In such cases I usually just push the gamma under develop module - assuming that is the best way to go?

Thanks Richard

[admin]

So you mean do a second stretch after the blend? I will try that. In such cases I usually just push the gamma under develop module - assuming that is the best way to go?

Thanks Richard

To clarify, I meant creating a new synthetic luminance frame of the two linear datasets. Then, process the synthetic luminance frame.
Does that make sense?