Blenheim Orange Loc: Michigan

My TIFF files are much larger than raw files.

Mike

mjmoly

Nice explanation.

selmslie Loc: Fernandina Beach, FL, USA

I have shown that ISO is not just "associated with" changes in the raw file. It has a direct effect.

Doubling the ISO doubles the numerical values stored in the raw file and halving the ISO halves them.

The values stored in the raw file are the direct result of exposure (aperture and shutter speed) and ISO. Exposure defines the analog value and ISO the digital value.

The ISO standard has no practical meaning until it is implemented. All digital cameras are subject to the same basic science even though their performance and software needs to accommodate sensors that perform differently.

Remember Occam's razor, "when presented with competing hypotheses that make the same predictions, one should select the solution with the fewest assumptions." In other words, the simplest explanation is usually the best one.

bleirer

I believe the tiff has already been demosaiced and the result baked in. It is lossless but forever disconnected from raw. Where the raw file one pixel stores one monochrome value, red or green or blue, so one number, but tiff is after a raw converter/editor has looked at all the neighboring pixels and wrote out red and green and blue for that pixel. Plus is luminosity another value or just extracted from the rgb? So I would think tiff has to be bigger since it stores all 3 colors. Probably showing I know just enough to be dangerous.

imagemeister Loc: mid east Florida

smf85 Loc: Freeport, IL

The interpolation is part of the demosaicing process so the output raw file contains RGB values for each location. Raw files, however, are often compressed via a lossless algorithm and is the default (usually); TIF files can also be compressed but aren't usually. TIF is a highly flexible image storage standard - that makes it hard to generalize about it.

smf85 Loc: Freeport, IL

Not always, in invariant designs its not. The ISO value is stored in the RAW file and is always used in the rendering implementation. If you alter it the file is re-rendered using the updated value.

Only if they're doing digital amplification - and that's rare now.

Implementations are different from one another. So everything you said can be true in a given implementation and not true in a different implementation. Kind of like Schrödinger's cat - its indeterminate until you open the box or, in this case, the camera. The point here is all of this is implementation dependent.

In grad school I had to implement a working microprocessor. The details of the processor design were left up to the grad students. In a class of about 20 there were at least 4 different major implementation types used with multiple variants of each. All of the designs would get the job done. Thats the point - there are many ways to get to the output file.

MichaelH Loc: NorCal via Lansing, MI

Now that was a good and illuminating read! Thank you for posting it.

bleirer

I'm not sure about that, I thought the raw converter/editor did the demosaicing in the computer, not the camera (unless a jpeg is saved in camera). The camera does the analog to digital conversion but that is turning voltage generated by the photons into numbers, but if you look at a raw file in rawdigger all you see are the separate red or green or blue. My camera in rawdigger has 2 greens, one red, and one blue, I assume all cameras do it that way. Willing to be corrected of course.

smf85 Loc: Freeport, IL

Implementations vary - the camera could output a mosaic file. It could just as easily output a hybrid that has full demosaicing but also keep enough of the mosaic data to reconstruct the mosaic image.

Blenheim Orange Loc: Michigan

I think that is right, yes.

Mike

Ysarex Loc: St. Louis

Implementation of ISO values can have a direct effect on raw files but it doesn't have to have a direct effect. Both options, A) direct effect and B) no direct effect, are possible and both options are implemented in various examples in today's cameras. That's already been proven in this thread. One proof that you're wrong in this post was provided by you in your first post in this thread: https://www.uglyhedgehog.com/t-630446-9.html#10914576 You identified an exception to your claim of a direct effect. You've been inconsistent in how you've presented your assertion. Here you insist ISO has a direct effect on raw files but earlier you made the claim and tagged on your exception: "ISO above base ISO affects the raw file but below base ISO it only affects the JPEG." https://www.uglyhedgehog.com/t-630446-9.html#10914705

I had already identified another exception, and there are more exceptions. Sigma makes and sells cameras that implement only option B) no direct effect. There are too many exceptions to "be exceptions" which is recognized in the ISO standard by a direct statement saying you're wrong: "ISO speed and ISO speed latitude values shall not be reported for raw images, however, because with raw images processing that affects the values has not been performed" (ISO 12232:2019).

Your error is insisting that only option A) is possible. That's wrong and has been proven wrong both in this thread and in previous threads: https://www.uglyhedgehog.com/t-609317-1.html

There are multiple ways to implement ISO value changes. Some of those implementation methods alter the data in raw files and some do not.

Joe

ken_stern Loc: Yorba Linda, Ca

Great "STUFF"
Have zero concept & absolutely NO IDEA how it all works ---
But glad it does & operates about as well as film asa did

Ysarex Loc: St. Louis

Yes, exactly. If you try and define ISO by implementation or insist on a single implementation you're going to trip up. The ISO standard does not address implementation which leaves the camera designers and engineers free to do whatever suits there fancy as long as the end result is achieved. The end result in the ISO standard is defined as the camera's final output image and not the intermediate raw data. The camera manufacturers wrote the ISO standard.

Joe

bleirer

In this post the poster is not talking about iso, but is saying that demosaicing happens in camera and the raw file is already demosaiced. You agree with that?