Thanks guys
You're quite correct Mike. I've been using the Multiscale Median Transform process tool in PI for noise reduction. Its very effective, but I have noticed it has a tendency to produce a blotchy background with my data and the typical settings i've been playing with. I'm still learning the ropes there with how to get the most out of the tool without those negative artifacts.
I wonder if the 12bit AD converter and low QE of my uncooled DSLR is also partly to blame here - not really enough depth to the data or the requisite SNR to pull out the *really* faint stuff. Doesn't stop me trying though!
(Here's a greyscale comparison with an
enhanced luminance image you might have seen before Mike...
)