How many of you have phones that save photos in PNG format? My Android phone doesn't even have that option. Must be an IPhone thing.
When Q posted those pics from their holiday to Google HQ last week an anon was suspicious of hidden extra data due to the unusually large file sizes. They were about the right size, given what they are (1125x2436 16-bit PNG); so I didn't think anything of it. But it's been bugging me. Why that format?
iPhonefags, is this a normal option for your phones? Could you switch from normal JPEG files to PNGs by accident?
I know Apple makes some snazzy stuff; but there's no way a puny little camera sensor can legitimately quantize the light at 16 bits. That's high-end scanner territory. So I separated the low 8-bits and made them into their own 8-bit image. As expected, this is mostly just noise. And the histogram is what I expected. It looks like the sensor is actually 12-bits, and it stores 8 in the upper byte and the 4 least significant bits in the lower byte. Hence the spiky histogram. The smaller spikes look like the result of combining multiple light sites or multiple captures in time and averaging them to get finer depth resolution. And there are complete gaps. So I'm 95% sure there is no stenography going on. But without anything to compare it to I can't be sure what is "normal" for this sensor.
Would one of you iPhone owners snap a pic of something in full rez 16-bit PNG mode and post it here?
And if you're wondering, the two new Oval Office pics are also 16-bit PNGs. But the LSB histograms are flat, presumably due to resizing and inter-pixel interpolation. Looks like pure noise. I think it's a different sensor too. But, still, why this format? Hmm.
(The files aren't garbled. They're supposed to look like that.)