Exactly. This is huge, and I was wondering why people didn't do it already. Or, for example, why don't cameras currently take multiple snapshots of the sensor? For example, if I'm exposing for 2 seconds, read the sensor at 0.1 sec (for the very bright lights) and again at 2 seconds, for the darker parts. That way, I can make an HDR image without having to take another photo.
Is reading the sensor destructive to the data, somehow?
A sensor with per-pixel reset to zero on readout would seem to be ideal — then you could get cumulative counts without wasting valuable photon landing space on the die.
Of course - that's the current standard way to produce HDR photos. The advantage here is being able to do it all in a single image, which prevents mismatches between images due to subject or photographer movement.
Yes, but if I understand correctly, unless those images occur at the same time (or really, really close) you run into issues involving subject and camera motion.
Because the images would look funny. Imagine you're capturing someone running - at frame 1, they would be at position x, and at frame 2, they'll be at position x + 1. If you try to stack them together, you'll get a weird ghosting effect.
Motion blur, but different parts of the image would be exposed differently due to the nature of HDR, resulting in an odd look. Imagine instead of a runner, that you're panning from a dark to light scene.
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Exactly. This is huge, and I was wondering why people didn't do it already. Or, for example, why don't cameras currently take multiple snapshots of the sensor? For example, if I'm exposing for 2 seconds, read the sensor at 0.1 sec (for the very bright lights) and again at 2 seconds, for the darker parts. That way, I can make an HDR image without having to take another photo.
Is reading the sensor destructive to the data, somehow?
Readout of a CCD is destructive. There are types of sensors that have non-destructive readout (Charge Injection Devices being one example: https://www.cis.rit.edu/research/CID/a_cid_is.htm).
A sensor with per-pixel reset to zero on readout would seem to be ideal — then you could get cumulative counts without wasting valuable photon landing space on the die.
Okay, but can’t I take 8 raw images and merge them into one image with 8 times higher dynamic range?
Of course - that's the current standard way to produce HDR photos. The advantage here is being able to do it all in a single image, which prevents mismatches between images due to subject or photographer movement.
Yes, but if I understand correctly, unless those images occur at the same time (or really, really close) you run into issues involving subject and camera motion.
Yes, that's what modern cameras with the built in feature do. (although I'm not sure about 8 times) The article talks about this feature.
Yes, but why can’t the camera do it continuously? Film at 240fps and provide a 60fps output with 10bit color depth.
Because the images would look funny. Imagine you're capturing someone running - at frame 1, they would be at position x, and at frame 2, they'll be at position x + 1. If you try to stack them together, you'll get a weird ghosting effect.
Well, that ghosting effect is also called motion blur. If I integrate continuously, that is.
Motion blur, but different parts of the image would be exposed differently due to the nature of HDR, resulting in an odd look. Imagine instead of a runner, that you're panning from a dark to light scene.
Not necessarily.
Assume we say an 8-bit image is taken every 0.1 second, if I merge 4 of them, wouldn’t I just get a 10-bit image with 0.4 second shutter time?
Because I essentially just take the RAW image, load them into a 10-bit colorspace, add them up, and then store the image.
Very interesting, thank you.