non-uniform illumination

Hi all,

I am calculating homogenization in a series of images (taken every 20 seconds) by computing standarized STD (how far off each pixel stands compared to mean intensity of bright green regions in each image). However, non-uniform illumination (UV light) preveals in almost all sets. Thus, I am having difficulties comparing STD values for different image sets. Please see the links to the images below (my apologies for too many links). Any insight would be much appreciated.

Many thanks,

https://imagizer.imageshack.com/img923/5295/ylzMPs.jpg

https://imagizer.imageshack.com/img924/413/C3Lu9z.jpg

https://imagizer.imageshack.com/img922/8544/yGqnrn.jpg

https://imagizer.imageshack.com/img924/5865/Ilq6bU.jpg

https://imagizer.imageshack.com/img922/8126/S1EMOB.jpg

https://imagizer.imageshack.com/img924/2200/z3t7qE.jpg

https://imagizer.imageshack.com/img922/9892/yxxSLo.jpg

https://imagizer.imageshack.com/img923/7674/CDDAYu.jpg

https://imagizer.imageshack.com/img923/2491/BdJ3Ov.jpg

https://imagizer.imageshack.com/img924/7222/NyB4tT.jpg

https://imagizer.imageshack.com/img923/8258/mCh03x.jpg

https://imagizer.imageshack.com/img923/953/fCbbHb.jpg

https://imagizer.imageshack.com/img922/9325/SUSIln.jpg

https://imagizer.imageshack.com/img924/8440/Tvyidi.jpg

https://imagizer.imageshack.com/img923/9140/0oUHEQ.jpg

Answer 1

[Image Analyst]

See my answer in your other question:

https://www.mathworks.com/matlabcentral/answers/1593039-non-uniform-illumination-scenes-are-changing#answer_839519