[FFmpeg-user] Demystifying Digital Camera Specifications (was Glossary: Nyquist)

Mark Filipak (ffmpeg) markfilipak at bog.us
Sun Oct 4 17:27:14 EEST 2020

Demystifying Digital Camera Specifications

is a blog by Jim Feeley that mentions a video presentation by John Galt of Panavision and Larry 
Thorpe of Canon titled "Demystifying Digital Camera Specifications".

The link that Jim Feeley provides is dead. I've searched for a current link so that I could share it 
here but I couldn't find the video.

I have it, either complete or as 7 parts.

20-08-10  19:04       397,590,171 Demystifying Digital Camera Specifications .mkv
20-08-10  18:51        76,493,280 Demystifying Digital Camera Specifications, Pt 1 .mkv
20-08-10  18:54        43,846,576 Demystifying Digital Camera Specifications, Pt 2 .mkv
20-08-10  18:56        46,831,671 Demystifying Digital Camera Specifications, Pt 3 .mkv
20-08-10  18:57       106,638,385 Demystifying Digital Camera Specifications, Pt 4 .mkv
20-08-10  18:57        45,627,889 Demystifying Digital Camera Specifications, Pt 5 .mkv
20-08-10  18:58        28,933,720 Demystifying Digital Camera Specifications, Pt 6 .mkv
20-08-10  18:58        49,218,650 Demystifying Digital Camera Specifications, Pt 7 .mkv

Anyone who wants one or all should contact me.
Part 1 is on youtube: https://www.youtube.com/watch?v=gqq8QKMmtYg
I assume the other parts are there, too.

On 10/04/2020 05:00 AM, Anatoly wrote:
> On Sat, 3 Oct 2020 21:22:38 -0400
> "Mark Filipak (ffmpeg)" <markfilipak at bog.us> wrote:
>> Here's what I visualize:
>> Imagine a heat map -- one of those colorful images ...reds and
>> yellows and greens and blues. Then, imagine a screen in front of it,
>> between you and the heat map. The screen is the final samples (ex:
>> 720x480).
> Now write down temperature for every cell of your screen and draw x-Y
> plot: temperature vs cell number in grid line.

That's sampling.

>> I think you'll agree that neither the screen nor the underlying heat
>> map are serial in nature. Oh, they're transported as a sort-of raster
> That doesn't really matter. Now you have x-Y plot of some function and
> you can process it mathematically as you wish.

I totally agree.

>> -- that's for sure -- but that's not how they're made and I don't
>> think that Fourier applies.
> Then you must dont't think that you can JPEG compress your screen
> image, because all JPEG/MPEG-like things works that way.

Compression and resolution aren't related. Compression that is lossy spoils resolution, but that 
doesn't mean that there's a functional relationship between them.

You know, I'm going to remove reference to Nyquist. I don't think spacial image resolution is 
related to frequency at all. I don't think that the photons that fall on one pixel affect the 
photons that fall on nearby pixels in any way -- I'm discounting quantum mechanics for the 
pixel-to-pixel distances involved. That 'said', if the resulting image is scanned, rastered into 
lines of pixel values and sent as a serial analog signal, then Nyquist definitely applies. But 
that's not what's happening in a CCD or in the human eye.

There is an exception. If a CCD's photosensors are 'read' and analog-to-digital converted serially 
(one photosensor at a time) -- and that is probably the case -- then Nyquist most definitely 
applies, but it applies to the analog-to-digital conversion, not to some fictional analog 
'frequency' within the image.

I think people have taken a temporal channel concept (Nyquist) and have tried to stretch it to fit a 
spacial situation. I don't buy it. Photons that are broadside loaded into a camera (or into an eye) 
is not a serial stream (i.e. not a raster). Nyquist doesn't apply.

>> Thank you. Do you think I should just post the whole thing? I can't.
> Not here, but maybe on github?

Not github. I'm a human being. Github is for Martians.

What if you woke up and found yourself in a police state?
African-Americans wake up in a police state every day.

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