How do I processing RAW images in the same way my camera processes JPEGs?

Started 3 months ago | Questions thread
knickerhawk Veteran Member • Posts: 7,509
Re: How do I processing RAW images in the same way my camera processes JPEGs?

stephband wrote:

knickerhawk wrote:

stephband wrote:

The application RAW Power tells me the red channel clips in the river, but the other channels do not.

The JPEGs you included tell a different story. In the OOC JPEG, the red and green channels are both blown in yellow areas of the flow. In the reddish areas the green channel isn't blown but the red channel is blown or close to blown. The blue channel is generally not blown at all in the flowing lava but it's blown in the white erupting part. (You get white when all three channels are blown).

In the version you edited the big problem is that the blue channel is mostly blown as well as the red and green channels in the flowing lava. The difference is quite clearly illustrated by looking at the blue channel only:

Yes. We are getting our wires crossed a little bit, and it's partly my fault. Neither of these are edited.

Poor wording on my part to refer to the one you processed from raw as "edited". "Converted" or "processed" would have been more precise terms to use.

The second is a screenshot of a preview of the raw file, showing how it displays (blown out) on my screen.

That should make no difference. The preview (and, hence, your screenshot) is using the same RGB values as is generated when you save the previewed file to an output file (e.g. as a JPEG or TIFF). If you're skeptical, just save a JPEG from the same file/settings as you were using when you do a screengrab. The RGB values in both the JPEG and the screengrab also saved as a JPEG will be the same. If they're not. Something very odd is going on.

The actual raw file is here (sorry, I didn't post it earlier)
stephen.band/test/PANA4186.RW2

The raw file says only red clips,

I checked the raw in Rawdigger, which is the best way to readily tell what's going on at the raw level. The histograms and clipping warnings you see in most converters are based on gamma corrected and profiled data. They also often apply a certain hidden amount of automatic highlight recovery so that it may appear to you that some highlights aren't clipped when they actually are. Per Rawdigger, quite a bit of the flowing lava is blown in raw in both the red and green channels and most of erupting area is completely blown in the red channel. There's only a very tiny bit of the erupting area that's blown in the blue channel and virtually none of the flowing lava is blown in the blue channel.

yet it displays as white, until I switch those switches.

Any of the neutrally colored lava is neutral ("white" as you refer to it) precisely because all three channels are roughly the same (i.e., similar numeric RGB values). The mystery is why those switches should need to be switched at all in order for the lava to appear yellow. It definitely wasn't necessary to do anything extraordinary in ACR (the Adobe converter) and others in the thread have reported success with other converters. With default ACR settings, I'm not really seeing anything wonky with the blue channel like what appears in your screengrab. There may be some relatively minor out of gamut issues in sRGB but they're not the type that would result in the lava looking less yellow. It's still something of a mystery to me why things are so far off for you as a default/starting point in the converters you've tried.

This appears to be because of the way the gamut is mapped to my screen.

As I probably unsuccessfully explained, it has nothing to do with your monitor. Those roughly equal values in all three channels tell us that the monitor is behaving perfectly correctly to display the lava flow as white on ANY reasonably well-calibrated monitor or print. The problem is further upstream than how the data is being fed to and interpreted by the monitor.

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