using a zone chart to determine PEI

[Tim Meisburger]

I was recently reading a description of the process for determining personal exposure index for various film. It seemed complicated, and I wondered why I could not merely do this:

- meter zone five on a zone card and set the appropriate exposure using the film's standard ASA
- photograph the zone card
- process normally

Then, if zone five was the center of the spectrum, you would assume your PEI matched the film rating. If zone five was shifted one or two stops in either direction, you would re-rate the film accordingly.

I don't know much about this sort of thing, so I'm sure its not that simple, but I cannot figure out why...

[pocketfulladoubles]

Sounds reasonable, but like you, I'm a novice. I'm not sure what type of film you are using, but what I've found in my unscientific try-it-and-let's-see approach is that you don't necessarily get the same # of zones above and below 5. For that reason, I sometimes bias my exposure down so as not to overexpose the brighter parts and lose color.

[ic-racer]

If PEI means Personal Exposure Index, then it is simple.

Photograph a uniform target with an exposure that places it at zone I using a guess at exposure index.

Process the film. If the density on the film is 0.1 d ( 1/3 of a stop ) then your guess was correct. You can use a densitometer or place the film over you exposure meter and look for a 1/3 stop drop of the needle. (If you have a densitometer, look for a density of 0.1 log d).

[Bruce Watson]

I was recently reading a description of the process for determining personal exposure index for various film. It seemed complicated, and I wondered why I could not merely do this:

- meter zone five on a zone card and set the appropriate exposure using the film's standard ASA
- photograph the zone card
- process normally

Then, if zone five was the center of the spectrum, you would assume your PEI matched the film rating. If zone five was shifted one or two stops in either direction, you would re-rate the film accordingly.

I don't know much about this sort of thing, so I'm sure its not that simple, but I cannot figure out why...

Because finding your personal EI is about shadow detail, not midrange detail. Midrange will vary (a lot) more with development (time, temp, agitation, etc.), so midrange is not a good indicator of EI.

To find out more I recommend finding a copy of Fred Picker's Zone VI Workshop. Mr. Picker explains Zone System testing in very easy to understand terms. Nice and simple, yet complete.

[ki6mf]

This was from an earlier post from Gem Singer

Re: Multi-spot metering in b&w landscape from Gem Singer http://www.largeformatphotography.in...ad.php?t=56334
Aim the one degree spot at the darkest area in the scene where you still want to see some detail. Close down two stops.

You have just placed the shadow area in Zone III.

That's usually the proper exposure for the scene.

Now, aim the spot at the brightest area in the scene.

If it's a five stop range between the darkest and brightest reading, use normal development.

Less than five, increase development.

More than five, decrease development.

No need to take a whole series of meter readings and average them. That's defeating the purpose.

Just make certain that you have given enough exposure to get some detail in the shadows. Then, develop for the highlights.

That's the Zone System in a nut shell.

A good tutorial on line that will step you through exposure and film speed is located at
Film Speed Test and Developing Test from Jerry Orabona Photography http://www.jerryo.com/teaching.htm

[Lachlan 717]

This was from an earlier post from Gem Singer

Re: Multi-spot metering in b&w landscape from Gem Singer http://www.largeformatphotography.in...ad.php?t=56334
Aim the one degree spot at the darkest area in the scene where you still want to see some detail. Close down two stops.

You have just placed the shadow area in Zone III.

That's usually the proper exposure for the scene.

Now, aim the spot at the brightest area in the scene.

If it's a five stop range between the darkest and brightest reading, use normal development.

Less than five, increase development.

More than five, decrease development.

No need to take a whole series of meter readings and average them. That's defeating the purpose.

Just make certain that you have given enough exposure to get some detail in the shadows. Then, develop for the highlights.

That's the Zone System in a nut shell.

I'm not sure this is what is being discussed here...

[Tim Meisburger]

ic-racer (what does that mean anyway?) - That looks like an interesting way to measure density, but if I guess wrong, do I still need to make more test prints to determine the EI, or is their a scale or table that will tell me how far off I am based on a meter reading (I don't have a densitometer).

Bruce - I don't really understand, To hold detail in zone 3, you need to be able to differentiate areas that are zone two and one in the shadow area. If I can differentiate these zones on a photo of a chart, wouldn't that mean I could see detail in shadow in a regular negative?

Wally - That's a pretty succinct summary of the zone system, but Lachlan is correct in that what I am really asking is about film testing. I had a look at the link you posted, and the method described is the normal one where up to ten separate exposures are made. In the third method described he seems to be looking for a neutral gray, which is the same reference I would be using looking at one shot of a zone chart.

[ic-racer]

ic-racer (what does that mean anyway?) - That looks like an interesting way to measure density, but if I guess wrong, do I still need to make more test prints to determine the EI, or is their a scale or table that will tell me how far off I am based on a meter reading (I don't have a densitometer).

Radio controlled internal combustion racing. But also just way to maintain anonymity.

Yes, repeat the test with multiple exposure index guesses and find the one that gives you 0.1 density. That is basically the "Zone I" test. You can search for other variations on doing the test.

[percepts]

Tim there are many anomalies in the zone system. Forget about zone 5 and throw your 18% grey card away. It causes more confusion than just about anything else.
What you want is enough exposure to give you some shadow detail which is adjusted through setting personal EI and enough development to retain highlights detail.

So just follow the advice given above.

read the following thread which explains why your grey card is useless amongst other things.

http://www.largeformatphotography.in...ad.php?t=56334

[percepts]

I was recently reading a description of the process for determining personal exposure index for various film. It seemed complicated, and I wondered why I could not merely do this:

- meter zone five on a zone card and set the appropriate exposure using the film's standard ASA
- photograph the zone card
- process normally

Then, if zone five was the center of the spectrum, you would assume your PEI matched the film rating. If zone five was shifted one or two stops in either direction, you would re-rate the film accordingly.

I don't know much about this sort of thing, so I'm sure its not that simple, but I cannot figure out why...

doesn't matter what kind of card you point your light meter at. The result will be the same which is an exposure which will make the result middle grey.
Problem is you think a "Zone Card" is a true middle grey but they never are. I assume you are thinking of a kodak 18% grey card. Well 18% is not the middle of a 10 zone system and your light meter is not calibrated to 18% even if 18% was the middle of a 10 zone system where each zone is 1 stop.