ETTR is a fallacy.

The thinking is that because each successive f/stop records double the number of photons recorded during an exposure, by overexposing the image, (OK then, subjecting the sensor to a greater number of photons than is normally necessary to accurately register any given light value in order to record an image), we gain the advantage of doing our image processing using a vastly greater volume of data.

Utter nonsense.

The facts………

The camera sensor converts the quantity of photons striking it during the exposure and stores the result as a voltage.

That voltage is read and converted to say, a 12bit binary number.

A binary number is to the base 2 which means that there are only two possible values for each successive entry.

Each entry is a multiple of 2, or double the value of the previous one in the line.

A 12 bit number is equal to 4096 to the base 10.

Consider a 12 f/stop sensor.

Each successive f/stop represents a doubling of the light that “it” will pass.

F/stops are not values. An f/stop in isolation is not quantifiable; it has relevance only when in reference to a known value.

Each successive f/stop represents a doubling, (or halving, all else being equal), of the volume of photons that it will pass reference its neighbor.

Voila! That’s the same deal as that binary number….Isn’t it?

Well, no, it isn’t.

The numbers of photons passed by different f/stops increases logarithmically whereas the binary description of the equivalent tonal values the progression is linear.

By the time we can gain access to the data recorded by the sensor it has been irreversibly divided into 4096 steps of tonality ranging from black to white.

There is now the same number of steps for each of the f/stops regardless of where they “fall” and the actual number of photons involved takes no further part or has any further influence.

In RAW PP all you are doing is changing the value of the binary number which describes the tonal value of each pixel in the image.

The notion that by ETTR we gain the advantage of doing our image processing using a vastly greater volume of data is therefore invalid.

Rob.

I have a problem that I can't seem to resolve. A polarizing filter is stuck on a UV filter so tight that I can't separate them.
Can anyone suggest a way to loosen them?

Would using cold water help? Possibly putting them in the freezer section of the refrigerator is another possibility (like we used to loosen a tripod in the winter after it was brought indoors and the heat swelled up the leg locks--actually we just put the tripod outside on the porch for an hour our so depending on the temperature). The two filters were given to me by someone with "very strong" hands! I don't want to damage them as they cost quite a bit to replace.