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0 pointsAaargh203188y ago0 comments

> In other words, it's compression for images.

No, it’s not.

There are two parts to this. First is capturing a HDR image, either by stacking photos or using a sensor with a good dynamic range (and capturing in raw). This is a good thing as you are capturing more information.

The compression you talk about is called tone-mapping and is used to make it possible to view HDR images on a non-HDR display. It can either be (over) done intentionally or it can just be an unfortunate consequence of HDR displays not being mainstream yet. Fortunately HDR is becoming a thing now for TV’s so computers are sure to follow.

Now, viewing HDR material on an actual HDR display, that is something different and can look absolutely stunning.

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munificent8y ago

> The compression you talk about is called tone-mapping and is used to make it possible to view HDR images on a non-HDR display.

Yes, and it's exactly how audio compression works. You have a fixed dynamic range and in input signal that doesn't fit in that range. So you attenuate the values near the endpoints (shadows and highlights in the case of imagery) to fit within the range while still leaving values in the midrange with their original spread.

> Now, viewing HDR material on an actual HDR display, that is something different and can look absolutely stunning.

Yes, but that's not what I'm talking about.

Aaargh20318OP8y ago

> Yes, and it's exactly how audio compression works. You have a fixed dynamic range and in input signal that doesn't fit in that range.

Not exactly. Audio compression is usually used to compress to a much smaller dynamic range than the output format or playback equipment can support. Some recordings compress to within just a few dB. With HDR pictures it's usually because the display is physically incapable of reproducing the image without compression.

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