How to determine the best exposure for raw files

I've written an article on how to get well-exposed raw files for the Lensrentals blog. It's being published in two parts. The second part, which will be published next week, has examples, some more technical discussion, and a glossary.

The article is pitched at intermediate photographers who are already shooting raw and want to know how to get the best exposure settings. It's not aimed at beginners, nor is it targeted to experts.

Here's a sample paragraph:

"Raw exposure is like the game of Blackjack. In Blackjack, you want the highest score possible as long as it’s 21 or less, and if your score is more than 21, you lose. In exposure, you want the most light possible as long as significant highlights are not clipped. Like Blackjack, you can win if your exposure produces electron counts a bit under your target, but you lose if it goes over your target. As in Blackjack, if you get greedy, you are likely to pay a price for your greed. "

www.lensrentals.com/blog/2023/05/how-digital-cameras-determine-exposure-part-1/

If you have any questions or comments, I can deal with them in this thread.

Jim

Well written - especially with respect to ISO. :-)

Will you be mentioning how to review the raw capture in order to determine the quality of it's exposure?

Not pushing it but I use the global and selection histograms available in RawDigger for such a purpose.

That's in part 2. Stay tooned.

A wise decisioin.

I like the differentiation between thinking and non-thinking photographers :).

Woo! :-)

I think a square root got lost here:

Later, we get:

"ISO settings aren’t part of exposure, and ISO settings don’t determine exposure for the thinking photographer." - I'd still write : that after exposure settings are decided the next decision shall be about nominal ISO settings to dial in ( before the actual exposure process starts )

Jim,

Thanks! I find this a more easy to absorb explanation of exposure than I ever got from the big thread here. However, I get lost in the ISO part, as it doesnt tell me why I should set any particular value for it in order to get a better raw file. I hope that this will come out of the maths in the second installment -- or, even better, out of a Feynman-like analogy! So far, it seems to me that your funnels are like transformers.

David

Interesting. So, if I decide that f/5.6 at 1/60sec is a perfect exposure setting for my sensor and that lighting, why would I have to decide a different "ISO setting to dial in"?

you have to have some ISO dialed in so what did you dial in ( setting auto-ISO count as such decision too ) and WHY ? may be your exposure settings were bare minumum to keep subject motion blur acceptable and get whatever you want into acceptable DOF - but your exposure was in the best exposed channel like 5 stops to clipping ? are you dialing in lowest nominal ISO ? 2nd base nominal ISO in dual gain camera ? max ISO using some auto-ISO range.. surely you are not flipping a coin... more so - I argue that you decide about a nominal ISO even before deciding about exact exposure parameters in a situation when you after some action ( not like shooting static scene w/ plenty time to spare), not after ...

I think you will probably be best off simply considering exposure and ISO independently. Make every effort to maximize the exposure (Light+Aperture+SS) - always satisfying any DOF, and motion blur requirements, and then consider ISO.
Whether you’re shooting full manual or semi-Auto with exposure compensation, once exposure is dealt with, if base ISO is going to result in some shortfall in brightness, you will then need to decide how much additional ISO is needed to get the job done…
For jpeg shooters, if there isn’t enough light to fully saturate the sensor at base ISO, you’re going to want to increase the ISO value to achieve the desired image brightness in-camera without clipping any important highlight detail. There are also some other options to consider - DR modes etc., but those are best left for a separate discussion.
For raw shooters, it could be much the same thing, but as most sensors are largely “ISO invariant” these days, you also have the option (for numerous reasons that we can discuss separately) of deferring some, or all, of the in-camera “brightening” (for lack of a better word) that the ISO setting represents, and applying (again, some or all) of any necessary “brightening” in post instead.

once you settle on exposure parameters , a nominal ISO controls S/N in deep shadows ( where photon shot noise does not overwhelm the rest of noise sources ) + room to clipping in raw channels + what happens in raw converter later ( hue twists and such - even Ai NR might work differently w/ the same exposure parameters, but different nominal ISO... so you can't avoid testing how your raw converter of choice and your conversion of choice in there behaves based on a nominal ISO , no matter how absolutely not part of exposure it is )

actually they are NOT ... there was a short time ( between ADC off sensor and advent of dual-gain sensors), but not anymore

What would make it a darn sight easier would be raw histograms. Here we are in 2023 and I cannot think of one camera company that has given this. It is pretty lazy of them, but as far as i can see they are more often than not about small evolutionary changes rather than revolution. We are still seeing a histogram based of if a jpg on the back of our cameras in this day and age. Hardly a great tool for data collection...

Jim...the blackjack analogy perfectly describes the situation.

Many cameras a pretty invariant after the dual conversion gain bump.

I would appreciate it if you would expand on that.

Rich

I was using Canon R5 recently. With the same exposure, at ISO 200 setting the noise in shadows was worse than at ISO 100. Raw files become fully manageable at ISO 800.