ETTR theroretical doubt

[coldplug]

Hello;

Can anybody confirm (or deny) this thinking:

Let say you have mid grey card with some fine black texture on it. Let texture does not change colour of card significantly from being mid grey card.

Now, we need to capture it, get most of camera sensor capabilities and maximally retain fine texture on card. In other words, we need to get best possible image quality of that card. Also, in final image, card must retain mid grey (18% of grey).

You can use two techniques:

1.) Use automatic camera metering and let card be captured mid grey as it is.

2.) ETTR exposure so that you bring card as bright as possible but not clip any channel, and then lower exposure in RAW editor in postprocessing to get card back to mid gray (18% of grey).


I would choose (2.) Am I correct? But then, I'm little worried about fine texture that must be retained, is it in danger assuming ETTR technique is done correctly? This is just theoretically question, I don't have to shoot any card, I just need correct answer to better understand theory about ETTR.

TIA,
Ivan

[number six]

The card fills the entire frame?

If so, there's no reason to ETTR. ETTR and subsequent PP reduces noise in the shadows. If you have no shadows, there will be no improvement.

-js

[Panopeeper]

I'm little worried about fine texture that must be retained, is it in danger assuming ETTR technique is done correctly?

I don't really understand your worry. The fine texture in your scenario is darker than the card, so it needs rather more light than the card.

Generally, you can not go wrong with higher exposure as long as it does not cause pixel saturation.

Added: a black texture does not need extra illumination, for you would tweak it anyway until it appears black. However, if it is not black writing but dark texture, then it needs light in order to make the texture clear.

[coldplug]

Thanks both of you;

If you have no shadows, there will be no improvement.


But, couldn't I got better S/N ratio, if I "push" ISO to below 100 using this technique?

Thanks again!

[tzalman]

Technically there should be less noise, practically it would not be significantly better.