Mask not available

[hbeing]

Pretty new to this, so be gentle and bear with me 

I am using Kayron's DSLR workflow to process some data in PI 1.8
However when I do PixelMath to combine two images to use as a mask the image generated is not available in the dropdown.
This also happened at the second round of noise reduction earlier in the tutorial.
I have tried saving and closing and reopening which has worked in a couple of other unrelated instances, but no joy.

I am probably missing something here , but it escapes me.

Thoughts

Peter

[pfile]

this probably indicates that (for some reason) the image you want to use as a mask either has the wrong # of planes (if you are masking a mono image, then the mask should also be mono; however, you can mask an N-plane image with an N-plane or 1-plane image), or the image you want to choose as a mask has the wrong x/y dimensions. PI will probably refer to either problem as "incompatible geometry" since the # planes (as well as the X/Y dimensions) are part of the image's "geometry".

you can mask an image by dragging another image's "name tab" (along the left side of the image window) to the area *below* the name tab on the target image. if you try to do this with an incompatible image you'll at least get a dialog box saying so...

rob