Lightroom Classic, Apple ProRaw slider

This may be an ignorant question, but I can't find the answer anywhere:

In Lightroom Classic in the Develop module, working on an image in Apple ProRaw from and iPhone 13 Pro, there is a slider at the top labeled "Amount" which goes from 0 to 200.

Can anybody tell me exactly what this slider controls? "Amount" of what??

Al Evans wrote:

This may be an ignorant question, but I can't find the answer anywhere:

In Lightroom Classic in the Develop module, working on an image in Apple ProRaw from and iPhone 13 Pro, there is a slider at the top labeled "Amount" which goes from 0 to 200.

Can anybody tell me exactly what this slider controls? "Amount" of what??

I edited an Apple-RAW file with that slider the other day. It appeared to offer a faster averaged-out method to lift or lower the extremes within the exposure. This seems to be the Apple Color Profile slider and it raises and lowers the basic core brightness within the image as though the Gamma is being altered. You still have other alternatives with all the other sliders. I was editing an image of a thundercloud and the usual Contrast/Brightness sliders would wash out the highlights in the white areas, even though I was being cautious... so then I tweaked the Highlights slider ...but I was still getting some material washed out in the extreme highlights of the image. Yet when I activated the Apple Color Profile (V2) slider, it assisted in recovering those highlights for me. I don't think the function of the slider is specified and it's main use is quite limited. But it's the Color Profile that this slider alters.
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Here's a webpage on the subject that explains how the slider really works:

https://jkost.com/blog/2018/12/using-the-amount-slider-with-creative-profiles-in-lightroom-and-camera-raw.html

MonstieurVoid wrote:

I've found the correct answer to this. The Apple ProRaw Amount slider is a compression plus tone mapping slider for the brighter-than-SDR values recorded by the camera sensor. If you have a HDR monitor, you can see how the slider truly behaves by enabling the HDR Output Technology Preview in Camera Raw.

When the slider is set to 0, tone mapping is disabled and the histogram shows values well into the HDR range, as captured by the camera sensor.
When set to the default of 100, the values are tone mapped into the SDR range, and the dark & light areas are compressed as well. With raw files from other cameras, you would need to do this manually by tweaking the other sliders in Camera Raw.
When set above 100, the values are tone mapped even lower than the SDR range. I see no reason to do this.

When exporting as HDR, set this to 0 to get the original dynamic range of the raw file.
When exporting as SDR, use a value between 0 and 100 as a starting point before tweaking the other sliders.

This is an amazing explanation - thank you. I have recently upgraded from a 2013 Retina Macbook Pro with perpetual Lightroom 6.14 to a new M2 Macbook Air with Lightroom Classic, and was completely confused as to why an iPhone 13 ProRaw photo looked completely blown out in LRC (same DNG imported into both versions of LR). The culprit turned out to be this Amount slider - setting it to 0 (from its default of 100) made LRC look nearly identical to 6.14 (insofar as anything so many versions apart can look the same). I wish that 0 had been the default - that would have saved me from making posts on the Adobe forum about this! Thanks so much for the post (and I'm glad dpreview is still around for me to have seen your reply!)