Different lightness levels when alignining with dynamic align vs star align

[gvanhau]

Hello

I'm not sure if this is a bug or something I'm doing wrong.
I'm using the last PI version (1.8....1092).  on windows 7 64bit.
I'm working on a mosaic.
Last night I noticed that the images aligned using the standard star align module (with frame adaptation flag on) are generating different lightness levels of the image in the output file. This doens not hapen if I aling the same image using dynamic align.
Is there any flag or parameter that could cause this?

note:
I had to realign a tile using dynamic align because it had some artifacts introduced by the standard star align.

edit: I added a screenshot of the StarAlign settings and a screen shot of the results wit either algorithm.  (Above is using dynamic align, below is using StarAlign.  Both images are auto stretched. you can clearly see that StarAlign is doing something wrong.


Geert

[gvanhau]

Hello

What I am also seeing that the output of Star align is not linear anymore (levels are stretched).

Geert

[pfile]

is the reference image stretched? i wonder if star alignment just applies a linear function with a crazy slope if the ref image is nonlinear.

rob

[Juan Conejero]

I'm not sure if this is a bug or something I'm doing wrong.

As always: We can't say or do anything useful without the images. Can you upload them?

What I am also seeing that the output of Star align is not linear anymore (levels are stretched).

This is physically impossible: StarAlignment's frame adaptation applies a purely linear transformation.

[gvanhau]

I'm not sure if this is a bug or something I'm doing wrong.

As always: We can't say or do anything useful without the images. Can you upload them?

What I am also seeing that the output of Star align is not linear anymore (levels are stretched).

This is physically impossible: StarAlignment's frame adaptation applies a purely linear transformation.

  Ok, may be that is the answer... Does frame adaptation mean that there is a linear stretch?  I tought that it only enlarged/croped the frame to fit the reference image.
Here, it has no sense to "linear fit" the SII image  to a Ha reference  .
As I said, there could be something I was doing wrong, I apologize for this.

Geert

[pfile]

yes linear fit is meant to help match the brightness of two linear images being built into a mosaic…

rob