Heavy fog today morning up on Kopparhatten (Copper Hat), then shot a wild hound just as it started clearing up.
One reason I stitched this panorama was to try out how today’s software versions handle working with unclipped 32-bit floating-point images. I was pleasantly surprised that there was only one snag.
- Using RawTherapee 5.5-137-g05bc7b245, I only applied a custom DCP input profile (it made no difference from the one RawTherapee already ships), used chromatic aberration correction, bumped exposure compensation +1EV and disabled out-of-gamut clipping (which didn’t appear to make any difference either, since there are no out-of-gamut colors in this foggy morning scene); no curves or anything to make the image look nice, that’s done last.
- I exported to 32-bit floating-point TIFFs.
- I stitched them using Hugin 2018.0.0.5abfb4de7961. Opening these 32-bit TIFF files took perhaps twice as long as opening 16-bit files, which is to be expected. Automatically creating control-points, geometric and photometric optimization went smoothly. However, the OpenGL viewer is not your friend. It does not handle 32-bit images correctly - this is the one snag. It shows them far too bright and so is difficult to use:
The slow viewer shows them properly:
- Finally, back to RawTherapee to make the image look aesthetically pleasing. When saving the stitched panorama in Hugin, I selected the “high dynamic range” option, in TIFF format. The resulting TIFF lacks an ICC profile, so when opening it in RawTherapee it has wrong colors and wrong gamma:
You must apply the same profile as was used when exporting the raw files to TIFF, which in this case was sRGB. So I applied sRGB, bent a curve here, made a tweak there, cropped to where it matters, and done.
More testing needs to be done, specifically seeing whether 32-bit floating-point TIFFs with no out-of-gamut clipping of a high dynamic range scene retain data in the highlights, and whether the resulting 32-bit panorama hasn’t lost any data on the way, but so far things look promising.
