LRGB & DBE Processing.

[ribuck]

Hi All,

I've read a few tutorials and i'm a little confused about the correct method to apply DBE, as the 2 different tutorials seem to conflict each other.


So when Processing LRGB, is it best to apply DBE to each of the channels individually  or  is recommended to combine RGB and then apply DBE to the combined RGB and then Lum.

Lastly, is it better to Combine LRGB early in the processing stage, before noise reduction etc or, should i process the RGB and Lum Seperately and then combine near to the end of the process when i'm ready to do curves / saturation etc ?

Many thanks,
Rich.

[pfile]

as for dbe you can do either, but if you just do the channel masters you'll probably see that there are residual gradients in the RGB - they are easier to spot because the background appears to have colors due to the gradients.

one issue with doing dbe only on the RGB is that the brightness of the 3 channels could be quite different, and then you'll be forced to push the tolerance really high to capture the background of the brightest channel. you can linear fit the B and R to G to overcome this if it turns out to be a problem.

with LRGB it's best to stretch both the RGB and L images separately to similar levels and then do the LRGB combine.

rob

[ribuck]

Hi Rob,

I'm struggling to understand your reply as i'm still a little confused.

One the DBE side of things, do i :
A)  combine RGB channels into a single RGB image and then apply DBE to it.
or
B) Apply DBE sperately to each R,G,B channel then combine RGB into a single RGB Image.


In regards to the Lum channel,  do i :
A) Combine with RGB at start of processing workflow before i apply noise reduction processes etc
or
B) apply noise reductions process to RGB Image and then seperate to Lum Image and combine L & RGB near the end of the processing workflow.


Sorry to have to ask again.

Regards.
Rich.

[pfile]

for dbe i'm saying that you can do B followed by A, or you can do just A.

for LRGB combination i'm saying to process the L and RGB separately. after each has been stretched, you can then do the LRGB combine (replace L of RGB with L image) and then continue processing the LRGB image from there.

rob

[eganz]

Hi Rob,

I'm struggling to understand your reply as i'm still a little confused.

One the DBE side of things, do i :
A)  combine RGB channels into a single RGB image and then apply DBE to it.
or
B) Apply DBE sperately to each R,G,B channel then combine RGB into a single RGB Image.


In regards to the Lum channel,  do i :
A) Combine with RGB at start of processing workflow before i apply noise reduction processes etc
or
B) apply noise reductions process to RGB Image and then seperate to Lum Image and combine L & RGB near the end of the processing workflow.


Sorry to have to ask again.

Regards.
Rich.

Rich,

it's easier to do DBE on the combined RGB image. If this works, it is much faster. only when this fails would you want to do each channel separately.
Similarly, it is often more effective to attack the noise after the L RGB combination. You can use TGV (or MMT) after the image is stretched quite effectively most of the time. TGV allows you to separate luminance and chrominance filtering operations and works very well. MMT is easier to use.

These are just general rules of thumb, and processing usually must be adapted to your specific images and noise. You can always go back and try filtering the noise at the start as an alternative.

Eric

[ribuck]

Hi Eric,

Many thanks, that makes it a lot clearer to understand. Was following Harry's video tutorials and also reading the very comprehensive guides from lightvortex and the 2 take very different approaches so can get a bit confusing for a PI newbie like myself.

Rich.