Questions on DBE and Pixel Math

[LD]

I am having trouble using DBE in Pix LE.  Once I generate the new image I then try to divide it into the original. I have the original image window active (the Target in Pixel Math, I assume) and divide it by the newly generate image (the Operand), I get a mostly black image with a bit of color on the sides. This happens often. Here is an example:

http://www.freewebs.com/drivewayastronomy/dbeimagepixinsight.htm

I imagine I'm not doing this right. For instance, before doing the operation, I get a window asking which images I should be using, and both the target and operand are present with check boxes. Do I check both?

In essence I feel like I am creating an artificial flat then dividing the image by it. But you can see my results.

Thanks for any input and ideas,
Larry

[Carlos Milovic]

Hi

Could you upload a pi-psm file, containing the process icon with the PixelMath instance?

Did you correctly set the image identifier of the sinthetic flat on PixelMath? How are you applying it to the original image?


Meanwhile, try this:

Calculate the median value of the sinthetic flat image. Now, desactive the "rescale" check box. Put the median values calculated for the flat as the scaling factor for the result. This would yield a result very similar to the original image, in terms of the mean brightness.

I guess that you have some zero valued pixels in the flat imagen, and then, when you divide, those pixels in your original image become totally saturate, with great value, and when you rescale, all the information is hidding at very low intensity values. Please verify this. To avoid that, create more sample boxes in the DBE instance.

[LD]

Carlos,
Thank you for your reply. Can you tell me how to upload? I have done another session and saved the process icon, but don't know how to get it to you. I have also done a screen grab of the Pix workspace to show you my procedure--I am sure I'm doing things wrong! Note that the images have been reduced 1:2 to fit them all on the page.

In this case I have taken an old image of mine and attempted to flatten the gradient. After doing the DBE and generating the background image or "flat" I reactivage the original image before calling up Image Math. At that time, I assume the active image is the "target" and select "new" selecting the operation "divide" and the background images as the "operand." My assumption is that this will divide the original image by the background image. Before I can do the operation I get a box asking me to choose which images to use, with both the original image and the background image available to check. I generally check them both since I don't know which one to select. You can see the result--again I get a black image with some sort of "ripping" effect on the upper right corner.

Sorry to go on so long, but I am really stumped on this one. I also know, when it comes to computers and computer applications, almost all problems can be attributed to user error...particularly if I am the user!

Screen capture can be found at
http://www.freewebs.com/drivewayastronomy/dbeimagepixinsight.htm

Best regards,
Larry Durst

PS: How can I add images to these messages--I seem stumped on that one, too!