GIMP processing - analog to PS layer masking method?

[aparker]

Hi,

Question for anyone who is experienced with GIMP (I am cheap and trying to use this instead of photoshop).  Olly pointed me towards this PS method: http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM for blending two different exposure length images.  I can see that many of the same features seem to exist in GIMP, but I can't work out how to copy a BW image in to be used as a semi-transparent layer mask.  Any advice will be much appreciated!

 

[alexbb]

Hi,

There's a tutorial for gimp 2.8 on their site: https://www.gimp.org/tutorials/Layer_Masks/
For the newer beta version 2.9, which allows 16 and 32 bit integer image processing, there might be an extra step as I remember. After you add the layer mask as described in tutorial, you can immediately apply it to the layer (right click and click on apply mask or merge down, I don't remember the order). You can then choose what to be visible in the layer's context menu: the layer, the mask or the result of them combined. After you finish with editing the mask, you can proceed to the next step (merge down or apply layer, the ones that I didn't remember theirs order before) and in the end you can merge all layers in a single image.

If you need more help, I can take a look later this evening.

Edit: by the way, make sure you select from image - processing something - 16bit or 32bit integer instead of real. When you use real with layers and masks, the highlights will look somehow black when combining the layers.

HTH,

Alex