Average Spot Metering Question

[Pere Casals]

how will the tones be distributed.

Ian, this is quite easy... once you select an exposure (using any method...) you know how many stops will we under or overexposed any spot in the image.

If you have 6 stops range you first have to decide at what zone you are to place your shadows, it can be Z-III or Z-IV depending on the detail you want to conserve in the shadows. Let's say that you place the shadows in Z-III, then your highlights will be in Z-VIII or in Z-IX, depending on how you calculate your 6 stops range.

You shoud always expose enough to preserve your shadows, then it can happen that you burn your highlights, Z-IX can be too much... but you solve that with development !!!! So with a high range scene you expose to preserve the shadows and then you develop less to prevent burning the highlights. Well, we have the highlights in the Z-IX, we may want it in Z-VII, so 9-7 = 2, an N-2 development plaves your highlights in Z-VII !!!! Solved !

Note that N-2 development does not modify much the shadows, while it limits the excessive density in the highlights.

So this is the classic recipe for a high dynamic range: expose to have your shadows in Z3 or 4, then develop less to place the highlights in Z7 or 8. Using Z3/4 or 7/8 depends on the film you use an on the detail what you want to obtain.

This is for negative film... slides are another animal.

[IanBarber]

I was going to mention in my post above about scenes that are beyond normal SBR (subject brightness range.) EV 18 clouds?! Wow!! I've never measured a cloud value beyond EV 17 and I live in the desert!! I guess when y'all get clouds in the UK them frickin things are BRIGHT!! Are you sure your meter is accurate?

It was hovering from 17 to 18. I am wondering if I was also getting flare because the sun was just outside the meters viewing area

[IanBarber]

Let's say that you place the shadows in Z-III, then your highlights will be in Z-VIII or in Z-IX, depending on how you calculate your 6 stops range.

Is there no set method for this. What I mean is, do you include zone 3 and count from there or do you start counting from zone 4. Doing the latter will give you N-1 whereas the other one would give you N development, if you know what I mean

[interneg]

I was going to mention in my post above about scenes that are beyond normal SBR (subject brightness range.) EV 18 clouds?! Wow!! I've never measured a cloud value beyond EV 17 and I live in the desert!! I guess when y'all get clouds in the UK them frickin things are BRIGHT!! Are you sure your meter is accurate?

Anyway, based on these readings you're looking at a tremendous brightness range. Forget holding all that with transparency film. Color neg might be OK; those with experience shooting color neg might weigh in. For B&W, if you placed the 10.5 on Zone III or IV, then you would definitely need minus development if using a standard film developer. Using pyro and some sort of compensating development technique, you might be OK as it stands.

I suspect that it's not 'actual EV' which is correct for ISO 100, but has been shifted two stops for an ISO 400 film. In other words, it's an EV of 16 in absolute terms, but the meter reads out 18 as it's been set to ISO 400 - my Minolta meter does this & it's quite annoying!

[IanBarber]

I suspect that it's not 'actual EV' which is correct for ISO 100, but has been shifted two stops for an ISO 400 film. In other words, it's an EV of 16 in absolute terms, but the meter reads out 18 as it's been set to ISO 400 - my Minolta meter does this & it's quite annoying!

My meter is a Sekonic L758. Should the EV value not reflect what ISO you have the meter set to ?

[Leigh]

What I mean is, do you include zone 3 and count from there or do you start counting from zone 4.

Hi Ian,

If your shadows meter to Zone V, and your highlights to Zone VI, your SBR is 1 stop.

- Leigh

[IanBarber]

Hi Ian,

If your shadows meter to Zone V, and your highlights to Zone VI, your SBR is 1 stop.

- Leigh

Thanks

[Drew Wiley]

The whole point of spot metering is to know exactly what specific scene values are, so you can give threshold shadow values correct placement in relation to highlights and degree of development. Averaging has nothing to do with it. What "zone" the shadows should fall on differs relative to the specific film, contrast range involved, and your esthetic goal with the negative. So no, there is no set method, and never will be. But it's easier to learn staying with one film and developer to begin with, to minimize the variables.

[Alan9940]

I suspect that it's not 'actual EV' which is correct for ISO 100, but has been shifted two stops for an ISO 400 film. In other words, it's an EV of 16 in absolute terms, but the meter reads out 18 as it's been set to ISO 400 - my Minolta meter does this & it's quite annoying!

I can tell you for fact that the Pentax Digital Spot meter that I've used for many a year reads out EV values based on the luminance of the object the spot is on...period. I'm pretty sure the Sekonic works the same way, but now that you've brought it up I'm definitely going to test it.

[Doremus Scudder]

Averaging the meter readings between high and low is what an averaging meter does. This works for scenes without excessive contrast for the most part as far as exposure is concerned. It has its shortcomings, which is why there are so many other (better) metering methods. Using your spot meter to, in essence, replicate what an averaging meter does defeats the whole reason for having such a meter, IM-HO.

The problem with basing your exposure on an average is that if the contrast range in the scene exceeds "normal," then the middle value you end up basing your exposure on is pretty high. This results in underexposing the low values and the corresponding loss of detail. In other words, you are no longer "exposing for the shadows," which is a better method than averaging.

To ensure you have the shadow detail you desire you have to base your exposure on an important shadow value, placing it so it has the amount of detail/separation you want. This determines exposure. Then you check the highlights to see where they will end up and make adjustments to development, choice of paper grade, filtration, etc. at that point.

Best,

Doremus