Fixing Vignetting

 

 

After taking your picture you may notice that you do not have even background, this is called Vigentting. Note the center is gray and the outer corners are more black

Figure 1

Figure 1

Using Photoshop you use a rubber stamp to blot out all bright sources, nebula, galaxy, clusters. No need to be perfect, just get the brightest ones.

figure 2.

Figure 2

Now I do a Gaussian Blur, I used a radius of 20 to get a smooth filter.

figure 3.

Figure 3

 

Now open both the filter and raw image. Make the Raw image active by clicking on it. Then go to the Image menu, and choose apply image. Make the source file the mask, and the target image shoudl be the raw image. Set blending method to Subtract and the offset value to 20. High will make the background more gray, lower will make the background to dark. You can experament.

figure 4.

 

Figure 4

 

 

Finished image. Things look more even. Total work time, only a few minutes