Meter recommendations

BMbikerider · Nov 25, 2016

On the rare occasions when I have thought a grey card was best for my needs, I have always used a 6x8 section of card cut out from the box previously holding breakfast cereal. That is as close as makes no difference. Or if you are in an urban area, the surface of a roadway is also a pretty good substitute. Although my Minolta Spotmeter F has a multi spot facility and then being able to average the readings, I regularly use this method and I have never had a problem.

Or use a meter which has an incident light facility, they are almost fool (sorry, profound idiot) proof. Especially the now discontinued Weston Master or Euromaster with a selenium cell, Cold weather hs no effect on the workings.

trondsi · Nov 25, 2016

moto-uno said:
Didn't Ctein write that originally these cards were to be held at about 45 degrees , which brought it's reflectance down to about 12 % ?
Peter

I don't get why that should work. I never used a card, but have used my grey jacket a couple of times. All I do is put it in the sun if the subject is in the sun, or in the shadow if the subject is in the shadow. Then I set the camera half a stop faster, because the jacket is slightly too dark.

Bill Burk · Nov 25, 2016

Leigh B said:
Where did you find a 12% reflectance gray card?

All the ones I've ever seen are 18%, because that's what the "average" of photographic scenes is supposed to be.

- Leigh

There are many discussions about this, you probably know some of the points that have been made.

As MattKing said, 18% is the middle of a range from black to white that a flat target can easily show.

The statistical average scene reflectance comes not from the middle of black to white, but from the typical pictures that people take, and people usually include some things in the shade that they still want to see, and the middle of that range, from something white in the sun to something dark gray in the shade (we don't really need to go as far as capturing something black in the shade)... draws down the statistical average from middle gray 18% to something a bit darker.

I have a Sekonic "Exposure Profile Target" which has a 12.7% patch.

Stepping down in sixth-stops from 18% (density 0.74), the target visits 16% (0.80) -1/6 EV, 14.3% (0.84) -1/3 EV, 12.7% (0.90) -1/2 EV

benjiboy · Nov 25, 2016

BMbikerider said:
On the rare occasions when I have thought a grey card was best for my needs, I have always used a 6x8 section of card cut out from the box previously holding breakfast cereal. That is as close as makes no difference. Or if you are in an urban area, the surface of a roadway is also a pretty good substitute. Although my Minolta Spotmeter F has a multi spot facility and then being able to average the readings, I regularly use this method and I have never had a problem.

Or use a meter which has an incident light facility, they are almost fool (sorry, profound idiot) proof. Especially the now discontinued Weston Master or Euromaster with a selenium cell, Cold weather hs no effect on the workings.

This is a popular fallacy, the inside of a Kellogg's corn flakes box is exactly one stop lighter than a Kodak Grey Card which will make a significant difference.

Leigh B · Nov 25, 2016

moto-uno said:
Didn't Ctein write that originally these cards were to be held at about 45 degrees , which brought it's reflectance down to about 12 % ?

By a very extensive set of research, the average scene reflectance is 18%.

That's why grey cards are 18%.

The actual reflectance of a card depends critically on the light's angle of incidence and the angle of view of the spot meter.
The magnitude of the error will vary from one product to another due to variance in manufacturing methods and materials.

As much as it pains me to agree with Ctein on anything, his 45 degree comment is correct.

- Leigh

macfred · Nov 25, 2016

Leigh B said:
...As much as it pains me to agree with Ctein on anything, his 45 degree comment is correct.

- Leigh

I agree !
How to use KODAK Gray Cards http://eclass.teiion.gr/modules/document/file.php/CULTURE208/Συνάντηση 2/Kodak Grey Card manual.PDF

Bill Burk · Nov 25, 2016

Leigh B said:
By a very extensive set of research, the average scene reflectance is 18%.

That's why grey cards are 18%.

The actual reflectance of a card depends critically on the light's angle of incidence and the angle of view of the spot meter.
The magnitude of the error will vary from one product to another due to variance in manufacturing methods and materials.

As much as it pains me to agree with Ctein on anything, his 45 degree comment is correct.

- Leigh

In Exposure-Speed Relations and Tone Reproduction, Jack Holm said it could be anywhere from 10 to 18% (he used 14%).

"...the mean log luminance of a statistically average scene ... result in the mean luminance correlating with a Lambertian scene reflectance of 12% for 100% highlight reflectance or 14% for 128% highlight reflectance. Values ranging from 10 to 18% have resulted from various experimental determinations."

http://beefalobill.com/benskin

Speed Relations and Tone Reproduction - 05.03.2014.pdf

Leigh B · Nov 25, 2016

Bill Burk said:
...or 14% for 128% highlight reflectance.

Hmmm...

128% reflectance.

That's quite an achievement. Not likely achievable in the physical realm that exists on this planet.

- Leigh

Bill Burk · Nov 26, 2016

Shine a flashlight at a piece of white paper, say for example it has 90% reflectance...

Now think about shining the same light at a mirror...

It can easily be 38% brighter since now you are seeing specular reflection.

I want to also point out that the "average scene reflectance" does not necessarily equal the "reflectance of a suitable gray card" that you would have to have if you want to take reflected light meter readings off a gray card and use them directly ... and have them agree with an incident meter.

Suppose average scene reflectance includes a good chunk of sky in the frame... literally the more sky you assume people include, the higher the average scene reflectance. As you assume more sky you have to recommend a darker gray card to get a meter reading that gives the correct exposure directly.

This is where I start to believe a 12% gray card would be handy for direct readings, even if they are not common.

MattKing · Nov 26, 2016

The grey card's 18% came from the world of lithography, not photography.

The 12% figure comes from statistical analysis of photographs, and the subjects recorded in them.

The instructions for the grey card instruct the user to hold the card at an angle, which has the effect of reducing the light reflecting back to the meter to approximately the same as what would result from a 12% reflectance target viewed straight on.

Bill Burk · Nov 26, 2016

Bill Burk said:
The statistical average scene reflectance comes not from the middle of black to white, but from the typical pictures that people take, and people usually include some things in the shade that they still want to see, and the middle of that range, from something white in the sun to something dark gray in the shade (we don't really need to go as far as capturing something black in the shade)... draws down the statistical average from middle gray 18% to something a bit darker.

I was wrong about the statistical average being darker than 18%... It is the gray card that has to be darker, because the statistical average is a high value such as 18%.

wiltw · Dec 8, 2016

Bill Burk said:
Perhaps you can compare your palm's deviation from incident reading, and deviation from a 12% gray... Because that's where I would expect 1 EV

No, used an 18% grey card, then my palm..so the 1.2EV-1.33EV difference is vs that standard...after all the point is to find an '18% grey card surrogate'.

DREW WILEY · Dec 8, 2016

So if you spend a week at high altitude in high UV conditions, how much melanin is produced using an SFP 30 sunblock lotion versus SPF 50, and what
precise percent does that skew your gray card surrogate? Does it need sunblock too? Cause gray cards do fade.

wiltw · Dec 9, 2016

DREW WILEY said:
So if you spend a week at high altitude in high UV conditions, how much melanin is produced using an SFP 30 sunblock lotion versus SPF 50, and what
precise percent does that skew your gray card surrogate? Does it need sunblock too? Cause gray cards do fade.

The PALM does not tan readily...in fact it is almost the same tone for Caucasions, Asians, Blacks, you name it. The tan is on the BACK of the hand. And that is why three decades ago -- in the infancy of the public use of the internet! --I read the suggestion (regardless of the racial background of the photographer) was to meter the PALM of the hand as a +1EV surrogate to an 18% grey card.

However, in posting on this point over the years, I note that I had written in APUG postings...

In Oct 2010 I posted, "I metered my own palm vs. 18% gray card and measured precisely +1.3EV difference."
In Jan 2012 I posted, "The palm of my hand meters +1.5EV brighter than an 18% gray card. "
in Nov 2104 I posted, "And in Jan 2012, in writing a post about palm metering on APUG, I had metered my own palm with a Minolta F 1-degree spotmeter and found it to be +1.5EV brighter than the gray card! Doing it just now, I find the difference to be only +1.1EV "
in Nov 2015 I posted, "However, my own palm actually meters 1.33EV brighter...Asian"
in Nov 2016 I posted, "I have actually measured +1.3EV brighter."

...so my own palm does exhibit variability (my comments on each occasion above was always with a new grey card reading and a new reading of my own palm, measured by the brightness difference function of my Minolta Spotmeter F). But 0.4EV difference (as noted in 2014) is different than my own tanning...in summer I see a very marked dividing line between the palm vs. back of my hand, whereas right now it is very faintly different...I can look almost as dark as a Hawaiian islander in the summer!

In Jan 2012 Jim Noel posted on APUG,

"No matter the ethnicity of a person, meter their palm, place it on Zone VI and their skin should record correctly. More than 30 years ago two friend and I experimented with this. I am Caucasian, one is African American and the other Hispanic. We tried varying lighting conditions, and several films. The objective was to make it easier to get proper exposure of each individual in a multi-ethnic church congregation regardless of the light. It was successful."

DREW WILEY · Dec 9, 2016

I was just making a joke. I never use a gray card anyway. Very few of them are neutral gray, and even less the reflectance value they claim. I once
measured a whole stack of em in a serious spectrophotometer. They didn't even match in the same brand. The good ones, like the patches on the
MacBeath chart, are the kind of thing I keep tucked away in storage until its needed as a control reference, like making a master printing neg or transparency, so it won't fade or get dirty.

Jim Jones · Dec 9, 2016

I've found the early Weston Master II to be as accurate and reliable as later models. The original Master also seems good, although bulkier. Norwood and GE made good selenium cell meters. The GE had the advantage of a meter movement with vertical orientation of the pivots and thus was less prone to errors from the armature being out of balance. All of these were made when high quality seemed more important than low cost. My first GE DW-68 cost $30, over a week's pay as a lowly seaman in the U. S. Navy in 1952.

wiltw · Dec 9, 2016

trondsi said:
I don't get why that should work. I never used a card, but have used my grey jacket a couple of times. All I do is put it in the sun if the subject is in the sun, or in the shadow if the subject is in the shadow. Then I set the camera half a stop faster, because the jacket is slightly too dark.

Angle does matter, as exemplified by this series of shots all taken with a single setting

DREW WILEY · Dec 9, 2016

Not only the angle of the blasted card, but the degree of its surface sheen! There's nothing more obnoxious than a reflective plastic "grey" card.
Or is it "gray"? Even the spelling isn't standardized.

Bill Burk · Dec 9, 2016

wiltw said:
No, used an 18% grey card, then my palm..so the 1.2EV-1.33EV difference is vs that standard...after all the point is to find an '18% grey card surrogate'.

I wouldn't say the point is to find an '18% grey card surrogate'...

I would say the point is to put together some rules of thumb so you can find your "exposure based on reflected light readings of convenient standard objects."

So far we have these common standard objects and the corresponding (simplified) instructions:

Take a reading from 18% gray card and open up one half stop.

Take a reading from the palm of your hand and open up one stop.

Up until now I believed these two came up with the same result.

You say they never came up with the same result for you.

Very interesting.

Bill Burk · Dec 9, 2016

wiltw said:
Angle does matter, as exemplified by this series of shots all taken with a single setting...

Which angle did you use for your tests which result in 1.2 to 1.33 EV difference from gray card to the palm of your hand? Not being snarky, actually it matters.

frank · Dec 9, 2016

Waiting for a Pentax digital spot meter in the mail. My first spot meter. I'm usually more cavalier about metering than a spot meter would indicate, but I feel the desire to try one.

wiltw · Dec 10, 2016

Bill Burk said:
Which angle did you use for your tests which result in 1.2 to 1.33 EV difference from gray card to the palm of your hand? Not being snarky, actually it matters.

I tried to measure my palm on about the same plane as the plane of the grey card, but I will admit that there is experimental error in trying to replicate the same angle of the two surfaces. I was consistent in my efforts to never read at the peak of surface sheen reflectivity of the grey card surface, however. I'll conduct a series of measurements tomorrow, to see what degree of variability I can measure across multiple measurements on the same day.

[One day later] I ran a series of tests using the 5 degree spot attachment for my Minolta Autometer Vf. I had tried measuring with my Minolta Spotmeter F, but its one degree AOV made palm measurements much too prone to variability simply on precisely what point on the palm I was reading! In measuring with the Autometer Vf 5-degree spot (and its 'averaging' a larger area of my palm), in a variety of lights (about 6 situations) I saw (repeatable results...each situation was repeatable in results in spite of leaving and coming back to make a later observation!) which varied from my palm being +0.3EV to +0.9EV brighter than a grey card...and this was a day with diffuse light and not a specular source in the sky which might really bias the angle dependence of the metering target with any surface sheen of the target.

My conclusion is that even the "Average Palm = 18% grey+1EV" is an urban legend which is not validated by repeatable results in testing.

AgX · Dec 10, 2016

DREW WILEY said:
I was just making a joke. I never use a gray card anyway. Very few of them are neutral gray, and even less the reflectance value they claim. I once
measured a whole stack of em in a serious spectrophotometer. They didn't even match in the same brand. The good ones, like the patches on the
MacBeath chart, are the kind of thing I keep tucked away in storage until its needed as a control reference, like making a master printing neg or transparency, so it won't fade or get dirty.

Have a look at the cards by Fotowand. The guy behind that enterprise is devoted to test cards only. Since 30 years or so.

Bill Burk · Dec 12, 2016

wiltw said:
My conclusion is that even the "Average Palm = 18% grey+1EV" is an urban legend which is not validated by repeatable results in testing.

Palm metamerism?

DREW WILEY · Dec 12, 2016

The nice thing about a true spotmeter is that you can measure the freckles, the age spots, the blisters and dirt, then apply the Zone System to determine what the palm of your hand really is. If the shade of grey is not dark enough, simply soak your skin in amidol developer for awhile.
If it's too dark mix up some sodium hydroxide; the ensuing screaming and shaking will actually help average the meter reading.

Meter recommendations

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