Feedback Please: The Kodak 18% Grey Card and Metering, a new look.

[Stephen Benskin]

There's a difference between how to and why. RobC misinterpreted what K was and instead of getting into a unsubstantiated he said, he said discussion, I went to the source material.

 

[BrianShaw]

Oh Rob, I don't totally disagree with you. But that extreme position and the "disagreeable" way of expressing yourself may limit your ability to focus on the windmill you desire to tilt. Not everyone before you got it wrong.

Im interested in both your thesis and your paper but growing weary because I understand it less and less as the discussion continues.

 

[Stephen Benskin]

Rob, didn't you use formulas in your paper? I guess you misinterpreted them because you weren't really interested in using them. BTW, it was Jones, not Mees. Mees edited the first two editions of The Theory of the Photographic Process, but Jones wrote the papers and wrote the chapter on Tone Reproduction Theory. And the definition of plagiarism is when someone takes credit for another person's work. I reference and quote the papers I use. Don't you get tired of always being wrong?

 

[BrianShaw]

Chill, Rob... Please.

 

[markbarendt]

You were specifically asked not to

APUG resides in a public setting, you have the right not to listen to or not take advice from any of us, but he/we have the right to reply to publicly posted threads.

... flare theory which no one is interested in.

You are wrong Rob. There are lots people that care about flare because it's real and needs to be considered to make a good exposure decisions. They may or may not specifically care about how it works, but they are pragmatic and do want metering ideas and systems that give them better exposures and that needs to consider all the facts involved.

Brian's right, you need to chill Rob.

 

[BrianShaw]

So before this thread comes to a crashing halt, I think I'll stop caring also. So far I've learned a lot about K and a lot about C and a lot about 18% gray. Bottom line, its all interesting and necessary to the design of photographic light meters but the differences are not significant enough to really inspire any changes to photographic exposure. Also learned that gray cards can be used in an unintended manner - erroneously positioned when using them to take a reflected light measure. That effect is about one-half stop... which is enough that folks might want to take notice and correct their erroneous procedure. That's about it. I may need no more than that. Thanks folks.

 

[Old-N-Feeble]

I'll just use a spot meter and not worry my feeble brain with complex formulas. Complexities give me headaches. Arguing gives me diarrhea.

 

[wiltw]

Why do we continue to come back to the 18% grey card for metering, when multiple analyses confirm it is NOT a good target for that?!

Why not simply use the grey card for the 'middle of the range of white to black' when printed or in a photo, when an example (like these) is photographed?

 

[BrianShaw]

Why... well, probably because Kodak gave us gray cards.

But lets face it, when was the last time any of us used a gray card for metering. I know I haven't since the 1980's. I have seen or heard of anyone using one for metering since then either. That is when I was taught "the wrong way to use a gray card" and have done quite good with photographic metering without it using reflected, incident, or spot metering and a bit of intuition.

Seriously... how prevalent is this problem or are nits being picked?

 

[Old-N-Feeble]

Picking at my nits will get you slapped.

 

[Bob Carnie]

Boy oh Boy - this is unbelievable - I have actually learned some new insults I can use on a daily basis..
I pop on this thread every once and awhile to learn a bit , boy you densitometry geeks can really go at it.

This is bringing me back to the days of Jorge- who I do miss.

 

[BrianShaw]

I miss Jorge too. A real piece of work but there was some residual value to his input.

When was the last time you used a gray card, Bob... or worried over a K/C constant?

 

[wiltw]

Even if I take the same grey card and spotmeter, and the same incident meter, and I take readings with both in different situations,

• sometimes they agree
• sometimes they are about 0.3EV apart from agreement
• and I have even gotten 0.1EV difference and 0.2EV differences, too

...so the debate outcome is not even consistent from moment to moment, given the above outcomes.
The only thing which is proven is "your results can vary".
But one cannot dispute that midtone grey (18%) is mid way between 'black' and 'white' (and look at the Tone Curve histogram from my earlier post to prove this to yourself).

 

[BrianShaw]

Yes... But so what (written with the most polite intentions)? For 99% of photography (a completely made up number) that amount of deviation is irrelevant. Why the fixation on fixing a problem yet the problem isn't being well stated and the magnitude of the problem is being ignored. Who does this really matter to, I ask again. Most politely... of course.

EDIT: Scientific and a lot of engineering photography is excluded from my comment above.

PS: I can validate your deviation values. I got the same deviations when I did my measures yesterday wit the same gray card and the same spot meter.

 

[Bob Carnie]

I think years ago as I pretty much use the same materials so when I set up I balance in my process.

I think I understand the practical applications of flare and its effect on film.
For my Lambda work I am constantly balancing in a 21 step wedge to laser output so I can stay in process.
In Photoshop I am always adjusting curve shapes - but I don't believe its useful to this discussion.

I remember Jorge calling me up on a claim I made about how much silver I recovered in a year.
John Callow and I also asked him to participate in the first APUG conference held at my shop- he decided against itl

I miss Jorge too. A real piece of work but there was some residual value to his input.

When was the last time you used a gray card, Bob... or worried over a K/C constant?

 

[RobC]

Boy oh Boy - this is unbelievable - I have actually learned some new insults I can use on a daily basis..
I pop on this thread every once and awhile to learn a bit , boy you densitometry geeks can really go at it.

This is bringing me back to the days of Jorge- who I do miss.

plenty more where they came from

 

[Bob Carnie]

plenty more where they came from

Could you include some in French for me.. I have a show in Montreal next month and if someone doesn't like my work I want to be prepared.

 

[Stephen Benskin]

I think years ago as I pretty much use the same materials so when I set up I balance in my process.

I think I understand the practical applications of flare and its effect on film.
For my Lambda work I am constantly balancing in a 21 step wedge to laser output so I can stay in process.
In Photoshop I am always adjusting curve shapes - but I don't believe its useful to this discussion.

I remember Jorge calling me up on a claim I made about how much silver I recovered in a year.
John Callow and I also asked him to participate in the first APUG conference held at my shop- he decided against itl

Bob, the example with flare that I gave shows how 12% scene reflectance is the middle of the Illuminance range at the film plane. Part of the topic is what is the middle, and that addresses it. I also quoted Jack Holm as a source to support the idea.

 

[BrianShaw]

Say all the same stuff, just wear a beret!

 

[Bob Carnie]

Say all the same stuff, just wear a beret!

thanks not sure if that will fly in Montreal but will give it a go.

 

[Stephen Benskin]

You've got the intellectual capacity of a fart. You still think this topic is about you and what you say. I have repeatedly told you its meant to be a simple method of undertstanding what a grey card really is and what it means and yet in your moronic and delusional state of mind you think I'm in the slightest bit interested in proving you right or wrong? You are sick or a complete arsehole. I thought the latter but I now begin to think both. No, on reflection I think an arrogant and delusional little shit who hasn't offered anything to the discussion except confusion.
Keep going and you'll get me kicked off the forum...

Correct me if I'm wrong but didn't you write this?

My response defining what K really is was a response to what you wrote. Let me get this straight. Your using the calibration equation from the exposure meter standard is the simple method but anybody else uses it, it's not?

 

[markbarendt]

Even if I take the same grey card and spotmeter, and the same incident meter, and I take readings with both in different situations,

• sometimes they agree
• sometimes they are about 0.3EV apart from agreement
• and I have even gotten 0.1EV difference and 0.2EV differences, too

...so the debate outcome is not even consistent from moment to moment, given the above outcomes.
The only thing which is proven is "your results can vary".
But one cannot dispute that midtone grey (18%) is mid way between 'black' and 'white' (and look at the Tone Curve histogram from my earlier post to prove this to yourself).

Part of what is happening with this is that the gray card and the incident meter aren't necessarily seeing the same thing.

The lumidome sees 180 degrees pretty darn well, the gray card does a progressively worse job of reflecting light to the meter as the light is coming to the card varies from perpendicular to the card. The difference can be huge, compare a mid-day scene to a campfire scene. In the campfire scene the lumidome is seeing lots of black, in the day scene it see a lot more light sources throwing light at the subject.

Meters, incident and spot, are truly dumb, they can't tell the difference. We have to make that judgement.

 

[RobC]

Could you include some in French for me.. I have a show in Montreal next month and if someone doesn't like my work I want to be prepared.

You can translate yourself.
And if my aunt had balls she'd be my uncle.

 

[Diapositivo]

I bought my first and last grey card when I was around 20, that's 30 years ago, and I could not afford an incident light meter. I had a meter in my camera, and the grey card was a complement for it. "One makes the fire with the wood he has".
As a way of measuring incident light on a subject, the grey card is certainly a clumsy method and prone to errors.

Yet, I do consider all reflected light meters to be calibrated to a shade of grey, and I consider interesting and relevant to know which shade it is. Before attending this very informative and very polite forum I would have taken that light meters are calibrated to an 18% grey as more gospel than gospel itself.
In my real photographic life I use spot meters to place the high light and I don't track middle tones, or I would have noticed some problems earlier, as 0.5 EV, as I stubbornly insist, is quite noticeable on a slide.

I think we should leave this discussion and find an appropriate one where we can discuss the question: what reflectance do light meters consider the subject to have when they give us an exposure value?

 

[Old-N-Feeble]

I bought my first and last grey card when I was around 20, that's 30 years ago <snip>

Yet, I do consider all reflected light meters to be calibrated to a shade of grey, and I consider interesting and relevant to know which shade it is. Before attending this very informative and very polite forum I would have taken that light meters are calibrated to an 18% grey as more gospel than gospel itself. In my real photographic life I use spot meters to place the high light and I don't track middle tones [transparencies] <snip>