Possible to control strength of OptiDev?

[cytan299]

Hi everyone,

I'm wondering whether there is a way to control the strength of OptiDev after Wiping?

One cosmetic problem that I've noticed is that the first diffraction ring around bright stars show up after OptiDev is applied after Wiping:

startools_optiDeV_zoomed_small.jpg (384.87 KiB) Viewed 2669 times

However, if I use FilmDev and set Digital Development to 98.07%, I get this:

startools_FilmDeV_zoomed_small.jpg (364.63 KiB) Viewed 2669 times

The ring around the bright stars is a lot less visible probably because the shape of the stretch function is different between OptiDev and FilmDev.

I really, really dislike the ring around bright stars, so is there a way to control the strength of OptiDev so that I can get something similar to the effect of FilmDev on stars? These rings persist throughout the StarTools workflow and there's no easy way of getting rid of them later.

Thanks!

cytan

P.S. I'm using the latest beta 1.9.577 beta 2. I have also attached a zip file of the StarTools log files for comparison.

[decay]

Hi, this is (most probably) not the first diffraction ring showing up there. Last year Ron started a thread about 'Donut stars' (viewtopic.php?p=15522#p15522) and your stars do look very much the same. The dark ring is more of an optical illusion, in fact it is a plateau and an enormous spike in its middle, which is caused by non-linear sensor response in combination with stacking. At least I think Ivo put it this way. As a result of this discussion and this analysis Ivo introduced the [Brightness Tranches] parameter in OptiDev. Please see the above thread for details.

In short, please try increasing the [Brightness Tranches] setting. If it helps, you may notice that the stretch becomes darker in general, you can try to counteract this by increasing the Gamma setting.

I hope this helps.

Best regards, Dietmar.

[cytan299]

Hi Dietmar,
You're exactly right. By increasing the Tranche bitness from 12 to 16, the diffraction ring is greatly reduced and the stars look a lot better. Here's the result:

startools_ngc3165_16bit_tranch_cropped_small.jpg (347.52 KiB) Viewed 2279 times

Thanks for the pointer. Now I'm a lot happier

cytan

[dx_ron]

You don't always need to go all the way to 16-bit tranches - play around and see what you like best. Pay attention both to the bright stars and to the main subjects (galaxies in this case).

[cytan299]

You don't always need to go all the way to 16-bit tranches - play around and see what you like best. Pay attention both to the bright stars and to the main subjects (galaxies in this case).

Thanks for the reminder. I eyeball every step in the workflow to make sure the image looks good.

cytan