Eclipse shots: Workflow for HDR photos that need aligning

So, even after drastically scaling back my original eclipse photography plans, I ended up with several decent corona/diamond ring shots. Whoopie!

Except now I need to figure out how to process them. I’m pretty solid on GIMP, but a newbie with most of the more advanced tools. The most HDR I’ve done is combining two images in GIMP with a gradient layer mask.

I see that LuminanceHDR has a nice easy UI for combining images … but it relies on the images being already aligned, or at least nearly aligned, and doesn’t work for a sun that changes position from shot to shot. When I try it, hugin crashes during the auto-align step. (That’s pretty typical of my experience trying to align anything with hugin, sadly.)

I could preprocess each of the raw Canon .cr2 images in rawtherapee or darktable, then align them in GIMP (2.9, so as to keep the bit depth as high as possible), crop and export the layers, then open those in LuminanceHDR. But in that case, what format could I use that wouldn’t throw away bit depth? LuminanceHDR doesn’t seem to be able to read either XCF or 16bpc PNG.

Is there a better way when you have raw images that are way out of alignment? Is there a better tool for this than LuminanceHDR?

Thanks for any suggestions!

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Did you use a tripod? Do the foregrounds line up?

Can we see the images :stuck_out_tongue_winking_eye:

I think it’s hard to say exactly without seeing the images. But if you have still foreground and a moving sun/moon, you can use the masking tool in hugin to mask out the parts that you don’t want. I’ve had pretty good luck doing this.

Hey Akkana, nice to see you here. :slightly_smiling_face:

The understatement of the year.

That being said, as @paperdigits said, it depends on what is in the frame I guess. So seeing a sample image would help a lot. And satisfy our curiosity. If the shots were taken with the telescope seen in your blog post about the DIY finder I assume that not a lot of foreground is to be seen in the shots?

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I would try aligning manually in Hugin and output an exposure blended image. Or if there is a specific LuminanceHDR TMO you want to use, output to EXR and load that into Luminance for tone mapping.

My workflow typicaly goes like this:
Convert RAW to 16 bit TIFF with Darktable (remove base curve, add profiled NR and TCA correction)
Load the TIFFs into hugin and align, save to EXR
Load the EXR into LuminanceHDR for tone mapping.

Awesome, an akk!

Sweet merciful poop that is too funny. :stuck_out_tongue: (For those that don’t know Akk, she knows a little more about GIMP than she’s letting on…)

Could you manually define a handful of alignment points in Hugin? In the past when I’ve had poor results in Hugin I find that it sometimes helps to manually place a small handful of points for each image pair if needed. (Basically skip the auto-align step completely).

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Thanks for the suggestions!

Combining replies:

Yes, it was on a tripod – but just a tripod, not a tracking mount, so it’s in a different place in each shot. (Long story about things gone wrong during the practice sessions beforehand.)

I used a 250mm lens rather than the 500mm scope in the blog post, but that still means there’s nothing in the foreground: the only things in the frame are the eclipsed sun and, in some shots, a ghost image of the sun from internal reflections in the lens.

I might be able to find alignment points in Hugin, but it would be tedious. Aligning the images in GIMP is easy, and I could probably find some way to figure out the offsets (e.g. img_1501 needs to move 24 pixels left and 14 pixels up, img_1502 need to move 41 pixels left and …). I could also add a “then crop the result to (w, h) starting at (x, y)” but if that’s too hard I could always crop it later. Is there a way to turn those into something I could put into Luminance to pass through to Hugin?

Here’s a sample image.