Why does STF do this?

[UlteriorModem]

I am working with a linear image. All that I had done to is so far was crop it, made a Luminance mask (which was NOT applied), some noise reduction with MLT.

I then went to do a Photometric color calibration. When that was done I hit the Stretch button on the STF and Kablooe a big mess, and apparently it cannot be undone!

At first I thought it might be PCC so I loaded the project again and applied the STF to the image before color calibration and, well see the attachment.

I dont understand I thought you could apply an STF to any unstretched image?

Oh this is OSC RGB by the way

[UlteriorModem]

I did a little more 'research' and learned that this happens after MLT noise reduction has been applied.

[ngc1535]

Hi,

I guess I am not certain what the "mess" is here. I see what appears to be a poor flat field calibration result and slightly green result in color. These are two different things. The part that is confusing... what does an STF stretched raw image look like?

Your application of MLT acts like a low pass filter (I think this is safe to say) and will make noise faint structures *easier* to see (against a more evenly smoothed background/sky). But the stuff that MLT makes easier to see after stretching..was always there. After MLT the stretch is probably going to be a little more dramatic in terms of brightness.

Can you add a little more info on what the issue is?

-adam

[UlteriorModem]

I dont have access to the machine right now but a stretched 'raw' image looks perfectly fine. Sharp with good contrast with a small amount of gradient.

After applying The MLT (Using a Luminance mask) it still looks good. But if you apply an STF stretch again it turns into that blotchy mess shown above.

I know I could just not use auto stretch anymore after that point, but still I forget on occasion and POOF I have that blotchy mess and cant seem to be able to undo it resulting in me having to chuck the progress I had made to that point.

[ngc1535]

I understand.
At the moment, it is my guess that the "mess" was already there and your smoothing with MLT just made it easier to see.
This is one of the examples that looking at the data itself is probably necessary (which is why this kind of question is tough to answer).
-adam

[chris.bailey]

integration_clone_ABE ?

What does an image look like that hasn't had ABE applied to it?

[Geoff]

Two things to try:
1. Save the autostretch as a process icon before applying MLT. Then use that process icon to apply to the image after using MLT
2. Alternatively, just adjust the STF sliders when stretching the image you have applied MLT to.

[UlteriorModem]

Two things to try:
1. Save the autostretch as a process icon before applying MLT. Then use that process icon to apply to the image after using MLT
2. Alternatively, just adjust the STF sliders when stretching the image you have applied MLT to.

Right like I said at some point just stop using the auto stretch. The problem is when you 'forget' and do the autostretch there is seemingly no way to un do it and your stuck.

Here is an example.

STF mess 1 by Tom Whit, on Flickr

Image top left is 'raw' except for an ABE applied, Top right is after MLT is applied, and bottom left is the ABE-MLT image auto stretched.

So to answer a previous question, yes ABE was applied.

Here is what the 'master' looks like un-cropped and no background extraction applied.

Master by Tom Whit, on Flickr

I should also add that it is not just this image. I run into this time after time on as far as I know all of my images.

[pfile]

you have some problem with the way your flats are being acquired. or you have some reflections inside your and/or stray light entering your OTA. this can be a very difficult thing to debug...

there's not much that can be done about what STF does after ABE/DBE, short of modifying STF's default behavior (which can be done by clicking on the wrench icon in the interface.) if you want to "undo" the autostretch just follow what Geoff said in his point #1 - save the autoSTF configuration from the original image as a process icon and then apply that to the ABE/DBE'd image. it won't look so ratty, but the problem is real; the ABE/DBE just reveals it better.

rob

[wvanreeven]

You could either save the resulting image after each applied process/script (this is what I do but it generates a LOT of images which consume a LOT of disk space) and then load the image of which you'd like to apply the STF of (first apply STF on the image that you loaded and then apply the SAME STF on your latest image) OR press ctrl-z several times until you're back to the step where you got a good STF and then press ctrl-y again to apply the processes/scripts again (not sure if this always works since I don't know if all processes/scripts allow for this).


HTH, Wouter