What Gray Card?

mshchem said:

I think I may have a dozen of these filed away. People give me stuff

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Did you see the prices in the Kodak catalogs? $58.91US for one 8x10" and one 4x5" card. You may be sitting on a small fortune.

mshchem said:

I think I may be Moogs! I'm a Marching Moron, endlessly accumulating junk. No hope for me

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(off topic) I was able to find some references to the short story, The Marching Morons, by Cyril Kornbluth. Sounds like my kind of story! However, I have not been able to reference "moog" or "moogs" other than the synthesizer named after its inventor Robert Moog - or possibly an acronym for Members Of the Opposite Gender - neither of which seems to fit.

runswithsizzers said:

(off topic) I was able to find some references to the short story, The Marching Morons, by Cyril Kornbluth. Sounds like my kind of story! However, I have not been able to reference "moog" or "moogs" other than the synthesizer named after its inventor Robert Moog - or possibly an acronym for Members Of the Opposite Gender - neither of which seems to fit.

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The Sci-FI story is a quick read and is on the Guttenberg Ebook project site for free.

I think "Moogs" was a nonsensical word Kornbluth made-up at the time, but I could be wrong.

It is shockingly prescient for today...

Just testing some of the statements folks have made about what they heard about good metering surrogate targets, to see how close or misleading the statement is...

• 18% gray card, reflective meter (averaged) = ISO 200, 1/6 f/8
• Incident meter = ISO 200, 1/10 f/8
• Newsprint, reflective meter (averaged) = ISO 200, 1/15 f/8

Not all grass reflects exactly the same amount of light, so that is an approximation and NOT a assessment of ABSOLUTE accuracy!
I have not trusted green vegetation in a long time. I measured my lawn in Jan 2017: 1/250 f/5.6 (ISO 400),
and other green trees (both deciduous and evergreen) measured within a range or -0.7EV < 1/250 f/5.6 < +1.0EV, hardly a 'reliable' set of readings.

Grey concrete is equally deceiving. In front of my home we had new concrete driveway approach poured by the city, and a new concrete walkway to the front door and driveway to the garage. 1/250 f/5.6 < 1.4EV walkway < +2.5EV driveway approach.
BTW, the incident meter reading, at the time period of the greenery and concrete metering, was 1/250 f/9.5

As to which gray card, in lieu of Kodak card...
I have mutilple gray cards/metering targets, including

• genuine Kodak gray card(s)
• Douglas Gray Card
• EZ Balance target, 18% gray center strip (plus white and black strips flanking)
• not identified source targets

All of them agree.
One simply needs to be careful about technique in the use of ANY gray card, to address the card surface's reflectivity due to surface sheen. Here is a series of shots all taken at same shutter + aperture, of one gray card, using two different orientations of camera position vs. sun.

Shots 1-8 are with sun at my back, shots 9-15 are with the sun at my left. The main point of this series is the illustration of the criticality of the angle of the card, but also that the card angle can HIDE the variation in exposure caused by change of the position of illumination source vs. subject...shot 2 looks quite like shot 12, even though in theory the incident reading for shot 12 is -0.5EV from shot 2. And #5 looks like #11, again in spite of incident reading for shot 11 is -0.5EV from shot 5. If one compares #5 vs. #13, with similar angling of the card to the lens, one can see some of the lower light condition of shot #13 as expected. but the illumination difference is clearly visible in #1 vs. #9.

That's hardly an analytic test, Wilt. One generalization that everyone should agree on at this point is to outright throw away any card that's shiny. And what you think you can get away with under diffuse natural light, like our natural softbox coastal fog conditions, is likely to become seriously off under strong direct lighting. I already posted how I tested em, which was with a $40,000 instrument which plotted the entire spectrum in each case under identical parameters, along with calibrating the precise average reflectance within half a percent. None of the Kodak cards even agreed with one another; the darn things fade and discolor, and the last known distributor stash of them probably came out of the tomb of King Tut's gardener.

Kino said:

The Sci-FI story is a quick read and is on the Guttenberg Ebook project site for free.

The Project Gutenberg eBook of The Marching Morons, by C. M. Kornbluth.

I think "Moogs" was a nonsensical word Kornbluth made-up at the time, but I could be wrong.

It is shockingly prescient for today...

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I thought I was replying to you, but ended up replying to myself. I think I'm ready to be blasted to Venus

DREW WILEY said:

That's hardly an analytic test, Wilt. One generalization that everyone should agree on at this point is to outright throw away any card that's shiny. And what you think you can get away with under diffuse natural light, like our natural softbox coastal fog conditions, is likely to become seriously off under strong direct lighting. I already posted how I tested em, which was with a $40,000 instrument which plotted the entire spectrum in each case under identical parameters, along with calibrating the precise average reflectance within half a percent. None of the Kodak cards even agreed with one another; the darn things fade and discolor, and the last known distributor stash of them probably came out of the tomb of King Tut's gardener.

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The test was not meant to be analytic. It was meant to demonstrate how the apparent brightness of the 18% gray card can change considerably based upon the angle that it is held at. Kodak used to note the angle to hold the card "Aim the surface of the gray card toward a point one third of the compound angle between your camera and the main light."...I was illustrating what a lot of folks do not take into consideration. I commented on the range that readings could fall into, to impress upon minds simple 'be careful about angle you hold the card'.

I've used Kodak grey cards, stand alone pairs and the Kodak Darkroom Data books, as well as a costly (at that time) a large McBeth colour chart and they both are good references and worthwhile for carrying/using, however the 18% reference I best remember was the large hard-built sweep of the Michael Andera Studio, which was painted with quality paint from a Benjamin Moore store, 5 gallon batches, it was a large sweep.

Today's computer colour matching paint mixing computers should be able to match up a good grey card to make a very close, dried down mat surface, which, besides studio sweeps and heavy canvas, be suitable for making your own grey cards, and even a background fabric oval disk, though it might pay to experiment with mat fabric paint, IMO.

Test out small batches of mixed paints, quart sizes seem to be about right, to be sure you are getting what you want and post the final mix formula to twenty different places, so even your unborn grand kids, kids will be finding them and you always know where to find it, ie, I had notes on that, B.M., 18% paint but can no find it, years on.

eli griggs said:

I've used Kodak grey cards, stand alone pairs and the Kodak Darkroom Data books, as well as a costly (at that time) a large McBeth colour chart and they both are good references and worthwhile for carrying/using, however the 18% reference I best remember was the large hard-built sweep of the Michael Andera Studio, which was painted with quality paint from a Benjamin Moore store, 5 gallon batches, it was a large sweep.

Today's computer colour matching paint mixing computers should be able to match up a good grey card to make a very close, dried down mat surface, which, besides studio sweeps and heavy canvas, be suitable for making your own grey cards, and even a background fabric oval disk, though it might pay to experiment with mat fabric paint, IMO.

Test out small batches of mixed paints, quart sizes seem to be about right, to be sure you are getting what you want and post the final mix formula to twenty different places, so even your unborn grand kids, kids will be finding them and you always know where to find it, ie, I had notes on that, B.M., 18% paint but can no find it, years on.

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Why would anyone need an 18% background?

More on darkroom printing to 18% grey milestones.

What range of settings does your enlarger meter or colour analyzer give you for matching your grey card coordinated negitive?

What kit do you use?

Pieter12 said:

Why would anyone need an 18% background?

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He wanted that shade and it worked out as a great background for people shots.

Beyond that, we never discussed the mater, but his clients were well pleased with his work.

eli griggs said:

He wanted that shade and it worked out as a great background for people shots.

Beyond that, we never discussed the mater, but his clients were well pleased with his work.

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OK. I find when shooting black and white in the studio that using a solid white background it is easy and more interesting to control the tone of the background by positioning the subject at a distance and adjusting the amount of light that hits the background. It can go from pure white to sold black that way. But that's me.

It's almost impossible for an ordinary paint store to mix a true 18% gray paint. McBeth probably had it specially factory batched in standard 144 gal lots. There are very precise corrections which can be done in large industrial vats, and using industrial quality monitoring equipment, and special pigment selection, which no retail paint dealer is qualified for. I could have done it in B/M 5-gals lots of premium product with a lot of titanium dioxide in it, but my assistants couldn't have, even though they did color matching all day long. I'd have had them stop slightly short of the endpoint, and then come to me to inspect their progress under the same expensive German color matching tubes that I still use at my retouching station in the darkroom complex.

Sometimes I'd literally dip the sharpened tip of a pencil into a certain pigment and add it, since even a quarter drop through the colorant dispenser nozzle might be too much. Then a check under direct and diffuse daylight too, to minimize the risk of metamerism (one needs to realize there is no such thing as a true black or true white pigment in the paint industry - to get to "neutral" can be quite a complex exercise jockeying back and forth a number of ingredients). We did a lot of matching for muralists, artists, and architects too, so being nitpicky with color just came with the territory.

I used an 18% gray background wall back when I still sometimes did studio portraits. Made the lighting setup go faster. Then I'd drop down the desired backdrop for the shoot itself in front of the gray wall.

And eli - Darkroom "color analyzers" were once in common use for sake of color negative readings, preferably in relation to a standardized gray card on at least one negative in the same series, or on the same roll of film. I do it in an entirely different manner, but still with the paper batch starting point based on a master negative of a precisely controlled shot of a MaBeth Chart on the same type of film. Since there are slight batch variation in paper, and even greater variations between colorheads themselves, it's impossible to give a single answer. Test strips are mandatory. And even then you still need to esthetically tailor the exposure to the specific image. But that generally goes pretty fast IF one has first matched the original chart test target as best as possible, using its master negative. I do it all visually; but one improves with experience.

eli griggs said:

More on darkroom printing to 18% grey milestones.

What range of settings does your enlarger meter or colour analyzer give you for matching your grey card coordinated negitive?

What kit do you use?

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Years ago, I had shot some calibration negatives and slides that included a photo of the Macbeth Colorchecker card, and a gray card, that I would use to obtain color correct reproduction. Across multiple darkroom sessions, and across different batches of color print paper, this allowed me to achieve reproduceable, consistent results. I did my printing with a Beseler Universal head, with color controller. And I used a Beseler color analyzer to sample the gray card area to achieve same printed results from session to session.
The color filter pack of course varied due to using different batches of print paper. My records of two batches of Cibachrome/Ilfochrome paper were 10Y-15Y, and 35M-40M, as the manufacturer recorded difference between batches.

It's interesting to go through my binder of 8x10 MacBeath Chart prints on Ciba first, then RA papers, and now Fujiflex, reminiscent of Ciba, and seeing how much better my own evaluation of the results has become
over time. I'm setting up for another round soon. If you're talking about the Beseler U RGB head, that can be a temperamental brat if there are any voltage surges or EMI activity going on. We've had a lot of utility upgrades in the neighborhood this past year, so I've mainly been defaulting to the traditional CMY Durst subtractive head on one of my 8x10 enlargers for color printing, since it's a lot more immune to those kinds of issues. But having sophisticated feedback circuitry is otherwise a nice amenity.

The trouble with Ciba is that the color balance shifted from greenish to magenta as the paper aged, which was rather quickly, over just a few months. Fuji RA4 papers are a lot more stable, and seem to be fairly consistent not only batch to batch, but even product to product. Of course, RA4 papers print way way faster than Ciba did, so less heat is involved. For RA4, if I didn't already have a record on hand, I might do my first test strip on a conventional subtractive head around Y30 / M 30 / C00, and go from there.

My log books for 35mm, medium format and large format) have an 18% gray card as the back cover. I don't know how accurate it is. But if you need a log book anyway, it's handy.

Pieter12 said:

OK. I find when shooting black and white in the studio that using a solid white background it is easy and more interesting to control the tone of the background by positioning the subject at a distance and adjusting the amount of light that hits the background. It can go from pure white to sold black that way. But that's me.

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What you do can also be accomplished with 18% gray walls, too. It simply requires more light striking it, to get 'white'

Gray walls have the benefit of lower reflectivity, allowing it to be easier for the photographer to control the amount of bounce back of light to the subject. Different strokes for different folks.

wiltw said:

What you do can also be accomplished with 18% gray walls, too. It simply requires more light striking it, to get 'white'

Gray walls have the benefit of lower reflectivity, allowing it to be easier for the photographer to control the amount of bounce back of light to the subject. Different strokes for different folks.

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Similarly, you can flag lights and the the background so the light doesn't bounce back on the subject. Plus, every studio I have ever been in or worked in had white walls and a white sweep. Must be a reason for that.

It’s been pretty well discussed, but I thought I would add a couple of my observations about gray cards. I find them very useful as a reference point in both color and B&W. The exact accuracy of 18% give or take isn’t critical as I am trying to match the actual gray card in my hand to my print. So it serves as a reference point- as long as I use the same card I’m good. I shoot a gray card frame on every color neg film stock and make a corrected print of it with the filtration and exposure noted. That gets me very close on the first try with subsequent negatives under similar lighting conditions.
And yes, the angle of reflectance has considerable influence on the meter reading. I saw that in a class I took, students that were not careful could be off by a full stop or more with their reading if the angle of the card wasn’t right.

Some studio spaces need to double as display rooms with framed sample prints etc. So the wall color might be chosen with that in mind. All kind of backdrops can be temporarily suspended in front of walls, along with diffuser panels. Who wants blinding white walls anyway? It causes an uncomfortable environment. And any kind of off-white used for bounce lighting effect is going to impart its own hue bias.

btaylor said:

And yes, the angle of reflectance has considerable influence on the meter reading. I saw that in a class I took, students that were not careful could be off by a full stop or more with their reading if the angle of the card wasn’t right.

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I assume all the students immediately went out and bought incident meters.

I haven't kept a gray card in any of my camera bags or packs for the past 40 yrs. No need. And "incidentally", I don't use an incident meter either, just spot meters. Not that that distinction is critical. But I would hope that after awhile one would know how to properly read their subject matter by itself - whether color values in nature or skintones, whatever. We have thousands of square miles of "gray card granite" in our mountains, for example, and endless miles of gray card asphalt all across the country. I also know how to read green foliage relative to meter midpoint too. One can't always hop across a canyon and place a gray card temporarily on the other side, or in the mouth of a lion you're photographing at a zoo.

Generating a master test negative from a standardized chart is another matter, and where I want as accurate an 18% gray reference as possible. And that means not only a perfectly calibrated light meter too, but also a good color temp meter to precisely match the lighting itself to the film standard, using cc or light balancing filters if necessary.

Pieter12 said:

Similarly, you can flag lights and the the background so the light doesn't bounce back on the subject. Plus, every studio I have ever been in or worked in had white walls and a white sweep. Must be a reason for that.

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I remembered one additional reason to have gray, not white...if you project gelled light onto the wall, gray yields better color saturation than white.
This link taken from a post I had many years ago...photos originally posted by TMR Design

http://photography-on-the.net/forum/showpost.php?p=3261798&postcount=7

Of course, changing seamless provides far greater flexibility than painted walls.

DREW WILEY said:

It's almost impossible for an ordinary paint store to mix a true 18% gray paint. McBeth probably had it specially factory batched in standard 144 gal lots. There are very precise corrections which can be done in large industrial vats, and using industrial quality monitoring equipment, and special pigment selection, which no retail paint dealer is qualified for. I could have done it in B/M 5-gals lots of premium product with a lot of titanium dioxide in it, but my assistants couldn't have, even though they did color matching all day long. I'd have had them stop slightly short of the endpoint, and then come to me to inspect their progress under the same expensive German color matching tubes that I still use at my retouching station in the darkroom complex.

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Drew, what does the likes of a colour matching paint machine lack that Macbeth was able to obtain? It sounds like it has its "grey" made by a factory. Was this a factory that made paint colours for other purposes? I'd have thought that the likes of Dulux or the U.S. equivalent thereof can match tens of thousands of gallons consistently. If it couldn't then when I buy say a specific shade of magnolia paint in say 1 litre then realise that I need a second litre Dulux to finish the room, it has to be able to be sure that the second litre exactly matches the first

I take it that in your place of work this final matching, in terms of the "coup de grace", could only be done by you but I assume that you are not the only one with this skill i.e. elsewhere there are others who possess that same skill? I presume your assistants were not quite as good as you but I am not sure this is because of lack of experience or lack of ability?

If Macbeth was able to ensure the exact grey for its colour checker then is it not likely that Kodak could do the same for its its grey card i.e. once it has decided how much grey had to be added to the card then all the factory producing the card needed to do was to ensure that the Kodak stipulation was met

In the case of the inside of the breakfast cereal boxes, my cereal box's grey looks the same each time I open the box and if this grey is tested against a "real" Kodak grey card as stated by the poster then if he says it is a match or very close to a match for the Kodak grey then surely that makes it a pretty accurate comparison? I'll be that even the grey plastic submarines I use to get in the boxes in the 50s were very close to a match for any other- the makers of the subs probably dipped them in the same container of grey-blue . The 4 or 5 subs I had did seem to all look alike

If it can't be guaranteed as a match then I'd have thought that given the ability of the human eye to detect even a small difference in shades ( see my Dulux analogy above ) then if we assume that there might be a small difference in eye detection as opposed to an expensive machine detection can I ask how much difference is this likely to make to an exposure reading?

Fascinating subject this

Thanks

pentaxuser

I was one of the guinea pigs in reference to the whole evolution of paint matching machines. The first ones were very expensive continuous spectrum plotting IBM units about 8 ft tall and 8 wide using a rotating neutral density drum and continuous light halogen light bulb. Modern ones use pulsed xenon at particular wavelength settings. The industrial versions read considerable more points than paint store versions, and hence get a more accurate reading due to less interpolation. But X-Rite has developed devices of this nature up to millions of dollars in cost for special applications. The bigger problem is at the operator end. Paint matching machines a like a round of golf - they save labor getting the ball onto the green, but never achieve hole in one. Just try getting an accurate off-white match. A trained pro eye has to actually make the final gentle hits of the ball into the hole. The machines themselves operate on a computerized 4-axis analytic geometry program based on CIE color mapping, just like inkjet printers do.

I dealt in top-end Euro clear and translucent finishes, especiallyh or the marine variety, but not paints. But even in the best brands, no good painter imagines there will be an identical match liter to liter, or even gallon to gallon. They always want enough to cover at least a full wall at a time, so that no discrepancy will be evident.

Auto paint matchers are the best; but we quit hiring them because most of them had many years exposure to nasty solvent fumes like toluene, much like glue-sniffers, and sometimes went berserk right on the job. Now there's a turn to safer automotive acrylics. In terms of architectural paints, you have to hunt down serious paint stores with real pro clientele and high-quality brands like Benjamin Moore, and see if anyone on site has serious matching skills. Some might charge dearly for the service, other reasonably ask you to leave you sample so they can take their time doing it correctly. Even the paint factories and R&D labs have highly trained personnel who do the tweaks and evaluations mostly by eye, and only partially by machine. They make seriously good money too. Whether under those circumstances or in a color darkroom, learning how to look at things, what to compare, is just as important as the physiological aspect of normal color vision. When I trained color matchers, it started with basic art school color theory - basic principles like simultaneous contrast, successive contrast, metamerism, etc. We would have hired Van Gogh in an instant, since he wasn't making any money selling his paintings anyway.

When I did color consulting on the side, I'd charge $100 an hour plus travel expenses; and that was back in the 80's. Now it would be double if I still had time and energy for it. Plus the same architects would hire me to do the 4X5 camera project shoots and make their portfolios, and sometimes buy framed personal prints from me too. So it was a decent gig when I was still young enough to basically juggle three jobs at the same time. At that time there were only two other people in NorCal all providing that service, and I got much of my business from dissatisfied clients one of them. There's an awful lot that goes into it - visiting the site during representative times of the day, evaluating surrounding enviro colors and the psychological and physiological effects of adjacent colors and seasons, how the paint colors will differentially age over time with respect to each other and planned repainting cycles. I once had a famous gourmet chef ask me to match the color of the trim on his restaurant to the color of his wine bottle labels. I was the only one in the whole region who knew how to do it. That kind of thing would fry the brains of any paint match machine. I should know. When I stated I was a guinea pig for the development of those devices, they'd deliberately seek me out to find the flaws in their system. One of them was the head of the International Color Council, who had a seven figure annual income. We understood each other; even though I was only a little flea compared to his pay grade.

Now per Kodak versus MacBeth. Color control was the primary business of McBeth. They offered color matching booths, special matching light tubes, color densitometers, reference charts, etc. Kodak did sell special density reference plaques for calibrating instrumentation; but the difference between those and a printed gray card is like the distinction between a pile of ten buck Kodak branded thermometers laying on a camera store shelf and their certified scientific grade ones costing two or three hundred dollars apiece. The quality control standards are drastically different.

But just like darkroom thermometers, what counts in a gray reference is repeat predictability. If your cereal box cardboard is what you are accustomed to, and know how to tweak exposures in reference to, along with your own particular meter, that's fine. But cardboard isn't inert; and it's certainly not appropriate for analytical work.

And yes, it's a fascinating topic. Glad you are interested in it too.

It seems to be a gray area for some.