Archives for 2015

I was asked if the spatial filtering mentioned in the previous post that takes place in bulb mode at ISO 6400 also happens at other ISOs. I tested three of them. It looks like the filtering is nonlinear, since it has different effects at the different read noise levels of different ISOs. I assume, but… [Read More]

The other alpha 7 cameras switch from 13-bit to 12-bit precision when the shutter is set to bulb, even if the shutter mode is single shot. Is that the case with the a7RII? Yes, indeed. Here’s the histogram of a 6-second single shot, ISO 6400, dark-field exposure made using the camera’s shutter timing mechanism: Every… [Read More]

Earlier, we saw indications that the Sony a7RII was doing spatial filtering of raw images at ISO 32000 and above. In such situations, I find it instructive to look at spatial frequency graphs. Assuming that some of you do as well, here is a graph of the horizontal and vertical spectra of a 1000×1000 pixel… [Read More]

Some of you asked for this: The red, green, and blue raw channels are all on top of each other. The D810 curve is the one that starts at ISO 32 and goes to ISO 50K. The a7RII  curve is the one that starts at ISO 50 and goes to ISO 100K. These curves are… [Read More]

I set the shutter to single shot, the ISO to 6400, turned off all the noise reduction options that the a7RII exposes to the user, and made a series of dark-field exposures at shutter speeds in 1/3 stop intervals from 1/2000 until boredom set in. Here’s the way the read noise varied: You can see… [Read More]