Luminance Mask

[russ.carpenter]

I'm an astro photographer and frequently use Affinity Photo to fine tune images I've produced in specialized astro imaging programs, such as PixInsight. I have a question that's probably painfully naive, for which I apologize in advance.

 

Astro imaging constantly uses masks, because elements such as background, stars, galaxies and nebula present completely different processing problems. One of the most common types of masks is known as the "luminance" mask. I've attached a typical luminance mask, which was produced from an RGB image, using the "extract CiE L*" command in PixInsight. In this case, the purpose of the mask is to manipulate the brighter parts of the galaxy, while leaving the faint details and background relatively untouched. To work properly, many of these masks need to include a full range of shades of grey.

 

My question is: can this kind of mask be produced and/or used in Affinity Photo? Thanks for helping a newbie.

 

Russ

 

 

[Frank Jonen]

You could try the following:

1. Duplicate the layer 
2. Run a couple of transforms to get the best edges, use Black and White to dial it towards the colours you want the mask to focus on most.
3. Layer > Rasterise to Mask
4. Nest the mask to the original layer.

 

You can go back and repeat till you've found the balance that gives you the best mask.

[rmar]

Can you use this method for your astro image? https://www.youtube.com/watch?v=FVtnMuHsFig

https://www.youtube.com/watch?v=nKIlckVCCF0

 

If not, you can make luminosity layers using Silver Efex https://www.youtube.com/watch?v=qDrAn9883Ik&feature=youtu.be&t=329

[Marimo]

Hello

 

There is a Action for LM

https://forum.affinity.serif.com/index.php?/topic/30523-luminosity-masks-for-adjustment-filter-layers/

 

and

 

https://forum.affinity.serif.com/index.php?/topic/27214-luminosity-masks/

[kirkt]

You could try the following:

1. Duplicate the layer 
2. Run a couple of transforms to get the best edges, use Black and White to dial it towards the colours you want the mask to focus on most.
3. Layer > Rasterise to Mask
4. Nest the mask to the original layer.

 

You can go back and repeat till you've found the balance that gives you the best mask.

 

This approach is amenable to working with with 32bit images (curve, B+W, etc. tools are all 32bit compatible) so consider using a 32bit image as source when you apply your edits.  Also, when isolating a luminance range, the Curves adjustment layer permits you to specify the input range of the curve, so that the curve affects a specific portion of your unbounded 32bit data.  This can be helpful in producing/avoiding clipping in the mask.

 

kirk

[anon1]

You could try the following:

1. Duplicate the layer 
2. Run a couple of transforms to get the best edges, use Black and White to dial it towards the colours you want the mask to focus on most.
3. Layer > Rasterise to Mask
4. Nest the mask to the original layer.

 

You can go back and repeat till you've found the balance that gives you the best mask.

guess how much better this would be in a node based environment  :wub:

https://forum.affinity.serif.com/index.php?/topic/15873-coming-2016-32bit-hdr-editing-sneak-preview/?p=81085

[russ.carpenter]

Thanks for all your interesting thoughts. For now, it seems that the most efficient solution is using blend options, although I will need to retrain my brain. I will be glad to have immediate visual feedback on the impact of changes to the blending curve in adjustments and live filters.

 

Russ