Let me try to explain it non-mathematically.
Imagine you are weighing something. You are given a scale. The scale
has 100 notches that you can balance the thing you are weighing against.
So you put on a small object, and it falls between 0 and 9 (out of
100). So there are only 10 slots it can be measured against. Now
suppose you have a magic button, that accurately increases the "weight"
of the object so that you can use the full scale, now it can read
between 0 and 99 (you mentally have to divide by 10). Which would you
rather have, the reading where you have only 10 possible values for the
weight, or the one with 100 possible values. Older scales actually work
like this, but there is no magic button, there is just different rails,
each with their own weight on it, that corresponds to the appropriate
range you are trying to weigh.
The magic button is the amplifier within the camera that increases the
effective iso, and the slots are the "quanta" that the camera can
measure the light levels with. Quantitization is the process of
converting the light level of each pixel to a discreet value between 0
and the maximum value in fixed value increments, just like the scale.
Except the camera uses powers of two instead of 10.
rg
Shel Belinkoff wrote:
You've lost me completely. I don't understand the "math of photography."
Just snap the shutter and see what comes out. Push a few buttons in
Photoshop, or adjust the light in the darkroom. If it works one way or not
another, then the answer is clear.
Anyway, I don't even understand terms like "quantization," or what a
"chunkier quantization" might be, or why or how you'd amplify a
quantization..
I love how photography has become a numbers crunching exercise for some
people. Pick up the camera, focus, press the shutter, and see what
happens, see what you get.
Shel
[Original Message]
From: Gonz
This does not make sense to me. Assuming a perfect amplification and a
perfect digitization for a moment, then a shot that would have a
complete dynamic range at ISO 1600 would only go up to 1/4 the dynamic
range at ISO 400. So when you amplify this quantization (for 12 bits
this would be 2^12/4 = 1024) to the full range, you have "chunkier"
quantitization, as if you only had a 10bit sensor instead of 12. That
leads me to believe that there would be more noise associated with this.
This is similar to the arguments of keeping your image in 16 bit mode
when editing as much as possible, until the final conversion to JPG and
8 bits. Converting to 8 bits first then editing is going to cost you
alot of information.
I'm not taking into account the effects of Bayer interpolation or other
interpolation such as uprezing, etc. That just complicates the way the
information is interpreted, but it does not change the absolute
underlying numbers.
--
Someone handed me a picture and said, "This is a picture of me when I
was younger." Every picture of you is when you were younger. "...Here's
a picture of me when I'm older." Where'd you get that camera man?
- Mitch Hedberg
