Handling ultraviolet overexposure

The attached image is a Buffy Helmetcrest - a species of hummingbird found in the high Andes.

I shot this photo last November, at altitude 5000m in Colombia’s Los Nevados National Park. It was cold and misty, so the conditions were not good for photography, but the Helmetcrest was happy to pose very close to the cafe/National Park Welcome Centre.

As you can see the bird is feeding on a pretty purple flower with whitish petals, however the flowers appear to be a uniform purple to human eyes. The DT colour picker shows the blue channel is maxed out at 255 and the vectorscope suggests the petals are rendered as white because they are out of gamut - which I am pretty sure is due to ultraviolet light.

So the challenge is to find the best strategy of modules masked and blended to show good, natural colour and detail on both the Helmetcrest and the flowers.

A 2nd instance of Color Calibration maybe?
ER6_0629.CR3 (27.5 MB)
ER6_0629.CR3.xmp (7.2 KB)

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In rawproc, the linear RGB with just the regular color primaries supplied by libraw makes nice purples. I then added my default filmic curve, and it blew out the colors as is depicted in your rendition. So, I threw out that curve and put in a regular control point curve, where I shaped the contrast to occur in the lower third of the histogram. That pulled the shadows very low, making the flower and bird stand out more. No high shoulder on the top end to blow out the lighter parts of the flowers… In rawproc:

Edit: Oh, most Nikon cameras for which I’ve seen SSF data show a pretty hard cutoff at 400nm, which is just above the lower end of the visible spectrum at 380nm. It’s UV, but you can see it, so you want it…


ER6_0629.CR3.xmp (9.6 KB)


theres clipping in the petals - you can tweak highlight reconstrcution to reconstruct in color instead of clipping
here a quick edit with upcoming guided laplacian highlight reconstruction


ER6_0629.cr3.xmp (10.4 KB)


Yes I guess clipping is clipping regardless of the cause.

When do you think the new reconstruction module will go into the main branch?

Also if you are using filmic be sure you try all the color preservation modes…they can give quite different results with color and saturation…

Indeed - RGB Euclidean norm was a bit better but not much.

I’ll have to test this with AP’s new version in the works for filmic dubbed v6

ER6_0629.CR3.xmp (14.7 KB)

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Ya…sometime no is the best and sometimes its the worst… :blush:

ER6_0629.jpg.out.pp3 (14,3 KB)


I tried to leave the upward-facing petals lighter.

with Filmulator:

  • Highlight Recovery 2
  • Exposure Compensation -1 2/3
  • NR on
  • NR Strength 20.46
  • Speckle NR strength 1.7
  • Chroma NR strength 17.25
  • Highlight Rolloff Point 0.31
  • White Clipping Point 0.835

bit lighter

ER6_0629.CR3.xmp (16.5 KB)
I forgot to make a duplicate…history stack should be in jpg or back a few steps from the lighter version…



Nice - a decent amount of recovery of colour and detail in the petals, whilst keeping great detail on the bird!

Traitement avec Art.

Demosaicing : VNG4
Exposure/Highligth : Color Propagation
Log Tone Maping
Noise reduction and Sharpening and some other…

ER6_0629.CR3.arp (20.6 KB)


Fun to play with !

dt 3.8.0

ER6_0629_02.cr3.xmp (19.1 KB)

Essentially highlight reconstruction->reconstruct color, fiddling with filmic rgb reconstruct, LAB tone curve to enhance the blown out violet (excluding the bird)

ER6_0629-1.jpg.out.pp3 (15.6 KB)
RT-5.9 highlight reconstruction with color propagation. Exposure boost locality on the tiny dinosaur. Copious false color suppression and chromatic aberration correction applied (I think this enhanced the natural iridescence a bit).

Interesting - good reconstruction - and it set me thinking about what I saw of the flowers and the bird when I was taking the photo.

The location was about 4000 m up in the Colombian Andes. It was overcast and rainy, with the sun occasionally breaking through. So not the best lighting.

I think the bird looks like I remember, but maybe the flowers are a touch too bright. Maybe its time for me to reprocess with the latest DT modules to see if I can use your ideas.