Grey card wrong?

[Bill Burk]

http://dpanswers.com/content/tech_kfactor.php

This article looks like a better summary than usual...

[Bill Burk]

I'm using a very new Sekonic L758DR.

There is plenty of Internet information that explains 18% gray card is not the equivalent of incident mode. Meters are not calibrated to 18%.

I use the same meter and have the Sekonic gray card which includes patches in 1/3 stop intervals so I can find the patch that does give the same spotmeter reading as incident mode in the same light. I find the reading is closer to 12%, which agrees with correspondence I've had here and on APUG, and it agrees with Internet lore*.

Instead of confirming exposure with a gray card, I satisfy my "sanity" by taking a spotmeter reading of the palm of my hand. When I "place the reading on Zone VI," my readings agree well with the incident mode, and then I feel more reassured.

*But of course that doesn't prove the Internet lore is correct.

[Kirk Gittings]

There is plenty of Internet information that explains 18% gray card is not the equivalent of incident mode. Meters are not calibrated to 18%.

I use the same meter and have the Sekonic gray card which includes patches in 1/3 stop intervals so I can find the patch that does give the same spotmeter reading as incident mode in the same light. I find the reading is closer to 12%, which agrees with correspondence I've had here and on APUG, and it agrees with Internet lore*.

Instead of confirming exposure with a gray card, I satisfy my "sanity" by taking a spotmeter reading of the palm of my hand. When I "place the reading on Zone VI," my readings agree well with the incident mode, and then I feel more reassured.

*But of course that doesn't prove the Internet lore is correct.

However not everyones palm should be placed on ZI as pigmentation varies. Just saying as mine never reads one stop brighter than middle grey. But do I meter off it and place it on ZI in a pinch? You bet. Always gets me in the ballpark. In changing light with rapidly moving clouds etc. It gets me a quick relatively accurate exposure right off. Then for the next exposure I can take more time.

[Bill Burk]

However not everyones palm should be placed on ZVI as pigmentation varies. Just saying as mine never reads one stop brighter than middle grey.

Haaa, yes I keep forgetting people differ, and this is just what works for ME.

swmcl, if reading YOUR palm and placing on ZVI matches the reading from incident mode... Then, like me, you'll have a confidence-building quick check.

At least you will catch BIG mistakes like incident metering the light falling on your ear when you think you are spotmetering.

I went through the same doubt when my meter was new, and I was about to remove the K factor from the meter (because you CAN).

Until I found this much better plan... By USING the Zone System meter-and-place technique to confirm the Incident Mode.

I gave up the confidence-shaking result of working with a Gray Card and trying to remember the exact relationship.

[Leigh]

...USING the Zone System meter-and-place technique to confirm the Incident Mode.

Sorry, Bill.

Incident metering is significantly more accurate in all cases than using the ZS.
Of course this assumes that you haven't mucked with the meter's calibration.

The ZS relies on your perception of tonality, which is imperfect even in a highly experienced practitioner.

The perceived reflectance (tonality or "zone") of a surface varies due to many factors.

Human perception of reflectance can be influenced by color, angle of incident light, angle of surface to line of sight, and reflectance of adjacent areas.

It's easy to demonstrate this fact by simply spotmetering a gray card at different angles.
That's why the instructions tell you to position it quite specifically relative to incident and lens axis.

- Leigh

[Bill Burk]

Sorry, Bill.

Incident metering is significantly more accurate in all cases than using the ZS.
Of course this assumes that you haven't mucked with the meter's calibration.

The ZS relies on your perception of tonality, which is imperfect even in a highly experienced practitioner.

The perceived reflectance (tonality or "zone") of a surface varies due to many factors.

Human perception of reflectance can be influenced by color, angle of incident light, angle of surface to line of sight, and reflectance of adjacent areas.

It's easy to demonstrate this fact by simply spotmetering a gray card at different angles.
That's why the instructions tell you to position it quite specifically relative to incident and lens axis.

- Leigh

Incident metering has its strengths, among which are speed of work and accurate results. Nobody need ask more than that.

And I agree suppose you meter a random object, and plan it for a particular Zone, say Zone V... I would expect inaccuracies for all the reasons you stated.

But my "Zone System" readings usually agree with incident readings. Maybe it's because I have been practicing. I make multiple readings of the scene with the spotmeter (or reflective reading meter) and mentally "place" each reading in an intended Zone. Making multiple readings gives me the opportunity to favor some readings or throw out readings I think don't fit in. The reading I most often throw out is foliage. Palm of my hand is the most favored.

I get what Kirk Gittings says too, I was out not long ago with a meter (Sekonic TwinMate) that only has Incident and Averaging reflected light modes... But I was facing into the light and would have appreciated a spotmeter reading.

[Leigh]

Incident metering has its strengths, among which are speed of work and accurate results. Nobody need ask more than that.
And I agree suppose you meter a random object, and plan it for a particular Zone, say Zone V... I would expect inaccuracies for all the reasons you stated.
But my "Zone System" readings usually agree with incident readings. Maybe it's because I have been practicing. I make multiple readings of the scene with the spotmeter (or reflective reading meter) and mentally "place" each reading in an intended Zone. Making multiple readings gives me the opportunity to favor some readings or throw out readings I think don't fit in. The reading I most often throw out is foliage. Palm of my hand is the most favored.
I get what Kirk Gittings says too, I was out not long ago with a meter (Sekonic TwinMate) that only has Incident and Averaging reflected light modes... But I was facing into the light and would have appreciated a spotmeter reading.

Hi Bill,

My comments were based on the use of "Zone System" metering without truly using the Zone System as a complete controlled process.

For the ZS to be used correctly requires an awful lot of calibration of every step from scene selection to the final print. I know of few people who have actually taken the time to do the required tests, and who then follow their process definitions religiously.

It can be easily demonstrated that any fully-defined process will yield consistent results if followed without deviation.

My comment about errors in ZS exposure are based on the fact that the human eye cannot perceive white as a defined value. The iris adjusts based on scene brightness, and the mind interprets the results by scaling the values.

True ZS practitioners can certainly achieve outstanding results.
I suggest that those who pick and choose aspects of ZS to be used while ignoring others are deluding themselves.

This is not to say that they can't achieve proper exposures. Anyone can do so if they do the same thing the same way every time. The point is that they're not using the ZS as defined by our friend Ansel, or any of its derivatives.

- Leigh

[Drew Wiley]

Leigh - the Zone System is actually crude. It's basically just a set of pigeonholes a stop apart, making it convenient to classify individuals shots for normal, plus,
or minus development. And different film & developer combinations can behave quite differently, so you'd hypothetically need a whole different ZS for every
significantly different set. Some people make a religion out of all this. No need. Black and white exposure isn't all that difficult unless you're doing something like
color separation negatives, in which can the Zone System is itself insufficient, and no substitute for plotting actual curves. So yes, I do pick and choose what applies to the shot, regarding ZS technique, and don't think I am deluded. More often, I'm visualizing in my mind, often intuitively and spontaneously from experience - but nonetheless visually the shape of the specific film curve, especially with regard to placement of readings on the SHAPE of the toe and highlight portions, so in this respect am a step ahead of what the ZS offers. But then I might label the shot plus or minus or whatever. If it works, it works. No need to
examine the entrails of an owl every shot.

[ROL]

More often, I'm visualizing in my mind, often intuitively and spontaneously from experience - but nonetheless visually the shape of the specific film curve, especially with regard to placement of readings on the SHAPE of the toe and highlight portions, so in this respect am a step ahead of what the ZS offers. But then I might label the shot plus or minus or whatever. If it works, it works. No need to
examine the entrails of an owl every shot.

That's hilarious Drew. Can I have your phone number for the next time I forget my spot meter? All kidding aside, I actually do appreciate what you mean though. Sometimes, I find myself slavishly and somewhat embarrassingly metering new scenes throughout the day where the light has not appreciably changed. I could have just taken the shot knowing either my previous aperture or speed. Doh! What fun is that?

[Bill Burk]

Instead of confirming exposure with a gray card, I satisfy my "sanity" by taking a spotmeter reading of the palm of my hand. When I "place the reading on Zone VI," my readings agree well with the incident mode, and then I feel more reassured.

I'll have to re-think this. I'm beginning to think that there is a 2/3 stop shift between Zone System calibration and standard meter calibration. Maybe my palm at Zone VI agrees with incident. But if I place shadows on Zone II... I don't think I can expect agreement.

I think I should NOT expect different metering techniques to agree. I should expect a 2/3 stop difference. When metering Zone System style, I would need to use Exposure Index 250 and I should expect that to agree with Incident reading when used with Exposure Index 400.

In practice this is kind of what I have been doing: I set my meter at 250 where I use it for everything until I "need" the 400 speed for some reason, like if I want to do indoor candid photography and I want to shoot handheld. Then I'll set the meter for 400 and use it in a more standard way.