Hi Dave,
You will also notice that the 'background' image that is 'created' by DBE (the image that will subsequently be 'subtracted' from the original) is usually presented as a 'half-size' image. Don;t worry about this - this is just a 'space-saving' feature of PI - whereby PI knows that it does not need a 'full-resolution' image in order to be able to perform the DBE, so it doesn't bother creating one - and, it also knows how to 'subtract' a half-size image from a full-size image. Clever, eh!!
It can also be very useful to 'hold on' to the 'background image' - I do, even if only briefly. I like to throw a strong STF onto the 'background' just to 'see' what PI is actually subtracting. I like to make sure that there is little (in reality, nothing) in the way of 'real structure', and I also like to see just what the gradients looked like.
Sometimes I will 'double STF' the background image.
I do this by selecting the background image first - the 'title bar' goes 'blue' to confirm this
Then I select the STF window (mine is ALWAYS open, usually on my RHS auxiliary monitor, or resized right along the bottom of the main window)
I then make sure the <Track View> tick mark is 'active' on the STF window (bottom RH corner - it should be 'green')
Now, any changes made in the STF window will automatically 'update' the screen view of the (currently 'active') DBE 'background 'image.
Once I have this image looking the way I want it to look I click on my HistogramTransform window (which, in my case, is 'always open' on my RHS auxiliary monitor)
I make sure that it also has the <Track View> tick mark checked 'green'
Now, I drag the blue triangle <New Instance> icon from the STF window over to the bottom bar of the Histo window
When the floating icon eventually has the 'cross' change to a 'box', I know that I can 'drop' it on the Histo window, and the Histo process 'learns' the slider positions from the STF process
Note that the actual image has still NOT yet been changed permanently - all we are seeing is the 'screen view' transformation as a result of the applied STF
However, I can now click the <Apply (F5)> icon, the little blue square, on the HISTO WINDOW - and the copied STF parameters will be used to CHANGE the actual image data
(Remember, because the Histo process is running in the <Track View> mode, it is FAR EASIER to click the little blue box (or hit the F5 key) rather than dragging the blue triangle all over the screen)
At this point the image will look 'horrible', because it now effectively has the STF transform 'applied twice' - once by the Histo process (where ACTUAL data has changed), and then again by the STF process itself.
I will usually then <Reset> the STF sliders, and then give them a second 'tweak' to help me better visualise the Background Gradients that have been extracted
Obviously the above process is equally as applicable if you just want to quickly set the Histo sliders themselves - for any image. Just set the sliders in STF first, and then 'copy over' the STF setup to the Histo box, most likely then applying final adjustments in the Histo box, before applying the changes to the image.
And, perhaps less intuitive, is the fact that the 'copy over' process is reversible. You can set the sliders in the Histo windo, and 'copy over' the Histo setup to the STF process - which allows the transform to be 'soft' (i.e. only affecting the 'visualisation' of the image data.
Basically, I copy slider positions back and forth between STF and Histo quite a lot as I work through my processing workflow.
And, remember to make good use of the <Track View> check-box, as well as using the 'blue square' or <Apply (F5)> icon to save the hassle of dragging the <New Instance> (blue triangle) to an active image - and these two shortcut suggestions apply to 'most' PixInsight process dialogues.
Hope this helps.
