Nnnnope. Don't understand Auto Dev in StartTools at all.

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Nnnnope. Don't understand Auto Dev in StartTools at all.

Postby BrendanC » Sun May 17, 2020 12:45 pm

I've been using StarTools for a while now.

At first I tried to use it 'properly' after following tutorials, starting with Auto Dev. I sort of got it to work, but I've just decided - I really don't understand it.

I've been bypassing it and just using the manual Develop option, but I feel I should really understand what I'm doing wrong, if anything.

Whenever I use Auto Dev, I just get a horrible, overexposed mess, no matter if I select a ROI or not. I understand that it's supposed to show me the errors in my image, but it's unusable. I've noticed that if I then use Wipe, it gets even worse - but then, when I click 'Keep' after the wipe, it goes back to how it looked when I opened it, before the Auto Dev!

It's completely counterintuitive. There's no progression from 'bad' image to 'good', and frankly I don't get it. 

Can anyone shed some light on this?
BrendanC
 
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Re: Nnnnope. Don't understand Auto Dev in StartTools at all.

Postby admin » Sun May 17, 2020 1:42 pm

Hi!

BrendanC wrote:I've been using StarTools for a while now.

At first I tried to use it 'properly' after following tutorials, starting with Auto Dev. I sort of got it to work, but I've just decided - I really don't understand it.

I've been bypassing it and just using the manual Develop option, but I feel I should really understand what I'm doing wrong, if anything.

Whenever I use Auto Dev, I just get a horrible, overexposed mess, no matter if I select a ROI or not. I understand that it's supposed to show me the errors in my image, but it's unusable. I've noticed that if I then use Wipe, it gets even worse - but then, when I click 'Keep' after the wipe, it goes back to how it looked when I opened it, before the Auto Dev!


This is a separate thing and doesn't have much to do with AutoDev. Wipe operates on the linear data. It uses an exaggerated AutoDev (e.g. completely ignoring your old stretch) stretch of the linear data to help you visualise any remaining issues. After running Wipe, you will need to re-stretch your dataset. That is because the previous stretch is pretty much guaranteed to be no longer be valid/desirable. That is because gradients have been removed and now no longer take up precious dynamic range. Dynamic range can now be allocated much more effectively to show detail, instead of artifacts and gradients. As a matter of fact, as of version 1.5, you are forced to re-stretch your image; when you close Wipe in 1.5+, it will revert back to the wiped, linear state, ready for re-stretch. Before 1.5 it would try to reconstruct the previous stretch, but - cool as that was - it really needs your human input again, as the visible detail will have changed dramatically.

It's completely counterintuitive. There's no progression from 'bad' image to 'good', and frankly I don't get it.

Can anyone shed some light on this?


You can actually see a progression by gradually making your RoI larger or smaller; as you make your RoI smaller you will notice the stretch being optimised for the area inside your RoI. E.g. detail inside the RoI wil become much more easy to discern. Conversely, detail outside the RoI will (probably) become less easy to discern. Changing the RoI gradually should make it clear what AutoDev is doing;
a.jpg
a.jpg (192.11 KiB) Viewed 679 times

b.jpg
b.jpg (160.89 KiB) Viewed 679 times

c.jpg
c.jpg (120.43 KiB) Viewed 679 times

d.jpg
d.jpg (75.08 KiB) Viewed 679 times

Confining the RoI progressively to the core of the galaxy, the stretch becomes more and more optimised for the core and less and less for the outer rim.
(side note, I'd probably go for something in between the second and third image :) )

E.g. AutoDev is constantly trying to detect detail inside the RoI (specifically figuring out how neighbouring pixels contrast with each other), and figure out what histogram stretch allocates dynamic range to that detail in the most optimal way. "Optimal" being, showing as much detail as possible.

TL;DR In AutoDev, you're controlling an impartial and objective detail detector, rather than a subjective and hard to control (especially in the highlights) bezier/spline curve.

Having something impartial and objective is very valuable, as it allows you to much better set up a "neutral" image that you can build on with local detail-enhancing tools in your arsenal (e.g. Sharp, HDR, Contrast, Decon, etc.);
Image
Notice how the over-exposed highlights do not bloat *at all*. The cores stay in their place and do not "bleed" into the neighboring pixels. This is much harder to achieve with other tools; star bloat is unfortunately still extremely common.

It should be noted that noise grain from your noise floor can be misconstrued by the detail detector as detail. Bumping up the 'Ignore Fine Detail <' parameter should counter that though.

I hope the above helps some, but if you'd like to post a dataset you're having trouble with, perhaps we can give you some more specific advice?
Ivo Jager
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Re: Nnnnope. Don't understand Auto Dev in StartTools at all.

Postby BrendanC » Sun May 17, 2020 2:49 pm

Hello Ivo, thanks for such a comprehensive reply (and I can see you posted on SGL too, I didn't know you were on that).

I'll go through what you've said and see if I make more progress with it.

:)
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