Night Sky Shooting / Astrophotography on X-T2 : ETTR? ISO 1600?

Sebastien Guyader wrote:

tradesmith45 wrote:

Thanks for sharing this & your previous pointers on RT. Looks like you nailed the focus - well done. Got questions & maybe a pointer or 2.

During RAW conversion for this in RT, did you apply any highlight reconstruction or compression or exposure compensation? I read the instructions for Sequator & disagree w/ their statement: "Any processing except vignetting correction should be avoided." Highlight recovery & several other adjustments are best done during RAW conversion.

No I didn't apply any highlight recovery, no exposure compensation, no tone curve (in fact I exported 16-bit tiffs in linear, so there's no input color profile, just WB and demosaicing, and the export profile I chose is ACES-P1 with gamma=1.0. And also profiled chromatic aberration (based on lensfun) and manual vignetting correction (I find the profiled vignetting to be too strong).

Did you try a version of your stack w/ Reduce LP & Enhance Stars off? You have variable color (look at upper right vs lower left corner - lower left is almost devoid of color), perhaps too many blue stars & nearly uniform size for brighter stars. Hard to tell if these effects are from RT or Sequator.

Sequator Enhance stars may be brightening the brighter stars causing an increase in their size. The blue stars may be the result of your WB adjustments or uncorrected fringing & will limit how much color enhancement you can apply. The LP correction may be zapping color in parts of the image. There's more color in there.

Yes I tried LP off, enhance stars off, I tried a fair number of combinations. Enhance stars doesn't change things too much, but I compared with and without, I preferred when it is on (subjective). There was light pollution the result was better with the correction. Part of the color wash out in the lower left could be due to the vignetting correction.

Couple things you could try to bring back some of the sense of depth in the star field. Remember when you were looking at this area w/ your eyes, there was an obvious 3D sense to what you saw. That's been somewhat lost here. This is a big struggle for me too & many factors are involved.

This sense of 3D is difficult to convey on a 2D screen. I think a lot of it comes from the field of view of our vision, we see or sense things beyond what is shown by the 23mm, and with 2 eyes with see naturally in 3D. If we were to use only one eye, and view a narrower portion of the sky, I'm pretty sure the 3D sense would vanish.

Consider a couple things if you haven't done these. Look on YouTube for tutorials on how to reduce star size using PS. Try out applying RL Deconvolution sharpening to the final stack in RT.

I've tried RL deconvolution sharpening in RT on the final stacked image, and I didn't like the result. Actually I tend to prefere USM in general over RL, even more so for X-Trans images (when sharpening in RT). I don't use Photoshop, I don't know how to reduce stars.

How much have you cropped out of this image? The edges look much sharper than I'm getting from my XF23. Given the high astigmatism, its not easy to pick best focus for this one due to the astigmatism.

Below is a screenshot showing the whole image and the crop area:

Last but not least, there are plenty of dark stellar dust trails in this region & they are almost completely lost in this image. They are really hard to tease out. Like nearly all Sony sensor cams, the Fuji Xs slightly clip blacks to reduce noise at high ISO. That's why shadow improvement as ISO is increased is so limited. Take a look at the shadow improvement curve for the Canon 6D.2. The LP correction in Sequator may also clip blacks.

Several steps might help bring the dust trails out better. Bring up blacks a bit during RAW conversion so these aren't lost at the start. Instead of going for a completely black blank sky, aim for a luminosity of a few percent above black. Apply a contrast increase to shadows using your tool of choice to your stack. If you use curves to stretch the stack, make sure blacks are not being clipped further.

I saw that I can make dark parts darker by moving the Black slider up, or by playing with the L* curve to increase the contrast (in the final stacked image), but I just prefer the overall look of the image like that. It's subjective.

I may have questions for you about some detail about RT DCPs later in a PM.

No problem.

Cheers,

Thanks!

A few tips that may help. There is a slight green colour bias in the image. Green bias is not uncommon for 2 reasons, one is light pollution often hits the green channel the worst. The other is there is thing called airglow. Which is a chemical reaction in the upper atmostphere to UV light that then emits at night often as a greenish glow. I used to be surprised that my deep sky telescope images would sometimes have excess green despite being taken in a very dark site. It was airglow.

HALVG is a free Photoshop plugin that gets rid of excess green. I use it a lot with my deep sky CCD telescope images. It makes getting a nice colour balance much easier to achieve.

I take it that this is a crop and so the stars do look a little large despite being in focus.

There are techniques to reducing star size. Deconvolution sucks big time so I would avoid that (worm effect is often the result or dark rings around stars if done too hard).

Russell Croman sells a plug in for Photoshop called Star Shrink and that's about the best out there. The other techniques usually involve selecting the stars and then expanding the selection a little to include the whole star and then reducing brightness using curves or levels.

Boosting dust lanes can be done using a brush and dodge tool (or is it burn, no I think burn brightens and dodge makes dimmer) just brush over the dust lanes only.

As far as blue stars go, to me it looks fine. There is one person who contends blue stars are the minority and there are hardly any. Not my experience looking and taking thousands of astro images. Depends on the area in the sky. Some areas have lots and lots of blue stars. The denser regions near the galaxy core tend to be the older stars and are more yellow types other areas have younger stars that are bluish. You seem to have a fair spread there and I can't imagine what processing could make stars go blue that were originally yellow.

3D effects can be enhanced by brushing the dust lanes as above and also brightening other areas that would have been brighter in the original scene. Also you can use the sponge tool set to saturate and say 5% and then brush over areas that have pinkish nebula to enhance or star fields to bring out the colour. You could brush it over that area where the colour has been weakened to restore the colour.

I am full of "tricks" so feel free to ask away.

Fuji X cameras are excellent astro cameras in my experience. Only made better by the long exposure choices, no star eater filtering, built in intervalometer - ooh I better stop typing or I may order an XT3!!!

Greg.

Greg.