RAW-Tiff what happens to the ISO value?

[Big Pete]

Maybe a banal question but I'm looking for an answer anyway! When I transfer images from RAW to Tiff and need to increase the brightness one step what happens in the process? Will there be a higher ISO number or where will the change take place? An example, I set my flash to a lower value and compensate it in the image processing RAW by increasing the exposure value in the computer, but it must be done at the expense of some other value, otherwise you can deceive the exposure by underexposing and then compensating?

[rjlittlefield]

Turning up the brightness setting in raw development is essentially telling the conversion process to imagine that the image had been shot with a higher ISO setting, and you want it to estimate the pixel values that would have produced by that higher ISO, given the same amount of light.

The result may be almost equal to setting a higher ISO when shooting, or it may be noticeably noisier. That depends on details of the camera's electronics. For much more about this, see https://photographylife.com/iso-invariance-explained .

But in either case, capturing less light will give you worse pixel noise. That is because the main source of pixel noise is just the random arrival of photons. Collecting more photons gives you lower relative noise, roughly in proportion to 1/sqrt(#photons). There are several ways to hide the increased noise, but really no way to recover from it.

--Rik

[Big Pete]

Thank you for your explanation!