Why 'more or less stopped using ISO'?

Started Feb 19, 2014 | Questions thread
xpatUSA Forum Pro • Posts: 13,670
Re: Why 'more or less stopped using ISO'?

D Cox wrote:

xpatUSA wrote:

I would take the data in a "raw" file to include everything in the file, such as anything in the header that tells the raw converter to multiply all the numbers by some constant.

That would be your privilege.

At the risk of repeating myself, I said "raw data" which specifically means raw image data and nothing else. I did not say "data in a raw file" which means any data, including meta-data, headers, jpegs, image raw, checksums, the kitchen sink and whatever else you might want to add.

The problem with your concept . .

It is not a concept; I did not conceive the workings of my camera. Sigma did.

. . .is that if the header includes an instruction to multiply all the image numbers by 3, that is how they are intended to be read. The instruction is as much part of the raw data as the numbers it applies to.

The header includes no such instruction. That instruction is part of the converter. In fact, using a RawDigger as a converter, no multiplication takes place.

Likewise the header includes the X and Y dimensions of the file. Without those numbers, the array cannot be displayed as an image.

For your restricted meaning, we should say "the data in the file body".

For my "restricted meaning" I recommend that we do not, for fear of PO.

In my post, I said "With my camera, if shoot a scene at ISO 100 and 1/100 sec and then at ISO 400 and 1/100 sec, the raw data is the same in each image."

In a later post, I published histograms which proved that statement to be true.

Perhaps I should have said "the same for each image". Is that what confused you?

To keep widening the discussion into other parts of the raw file is simply diverting attention from the intent and obvious meaning of my post.

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