18% Neutral Gray Paint?

Discussion in 'Miscellaneous Equipment' started by snikulin, Sep 29, 2015.

  1. snikulin

    snikulin Member

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    I need a really big (say, a wall in a small room) 18% neutral gray "card".
    I wonder how precise are common paint stores like Kelly Moore and paint departments at Home Depot, Ace and Lowe's?
    Will they be able to measure my standard Kodak 8x10 card and produce good enough neutral 18% gray paint mix?
    What to go for, acrylic, oil?

    Thanks!
     
  2. Ken Nadvornick

    Ken Nadvornick Member

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    I've done this before. Took an 18% card to a local hardware store, they put it in the color machine, out came the "recipe", followed by a mixed gallon of paint, and away I went. The paint was acrylic. I chose a flat finish to help with reflections. When I was done I could drop the 18% card onto the painted surface and it (almost) disappeared. Best of all, the meter readings were the same.

    Of course, I can't absolutely guarantee the same results for you. But it worked on the first try for me.

    YMMV...

    Ken
     
  3. Peter Rockstroh01

    Peter Rockstroh01 Subscriber

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    You can match Kodak's 18% gray card with a Pantone Guide and have a paint shop mix up according to. that reference. A little trickier is matching the matte finish of the cardboard, in order to have - what you are looking for - a very large gray card.
     
  4. Sirius Glass

    Sirius Glass Subscriber

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    18% neutral gray [grey] is the normal color of the sky in Rochester New York. It makes Rochester the world's largest natural darkroom, which is the reason why George Eastman founded Kodak in Rochester. Any one that has worked for Kodak in upstate New York knows this.
     
  5. OP
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    snikulin

    snikulin Member

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    Ken, thanks! That's what I need!

    My matching sucks as I am a male and all my color vision encoded into a single puny X chromosome.
    I am a laughing stock of my wife and her thetrachrome girlfriends, all equipped with superhuman opsins encoded and duplicated into two X'es.
    :blink:
     
  6. AgX

    AgX Member

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    Now I wonder why one would need a wall-sized 18%-grey surface.
     
  7. Trask

    Trask Subscriber

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    That's a joke, right? I mean, the sky is really blue on a sunny day, not 18% grey, isn't it? I once went to Syracuse but only saw cloud cover, so couldn't verify if the sky was blue or some shade of grey.

    Does the grey deepen to 24% when one crosses the Canadian border? If so, should I use incident or reflective metering?
     
  8. Nodda Duma

    Nodda Duma Subscriber

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    Assuming you'll be setting up outside, bear in mind weathering will change the reflectance over time if you keep outside indefinitely.
     
  9. bdial

    bdial Subscriber

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    My light meter can't tell the difference between my car and a gray card, I could send you the paint code:smile:.

    You could probably just take a gray card into the store and tell them to match it, you (probably) don't need laboratory precision.
    As for type, plain old water-based latex should do well.
     
  10. RalphLambrecht

    RalphLambrecht Member

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    They should be close enough:smile:
     
  11. RalphLambrecht

    RalphLambrecht Member

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    feel free to use the Northern sky anyplace for this and don'r pay any royalties to Kodak for it!:smile:
     
  12. Old-N-Feeble

    Old-N-Feeble Subscriber

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    How are you going to light a wall that large evenly and even if you could then how are you going to deal with color contamination from light reflected from surrounding surfaces and objects?
     
  13. benjiboy

    benjiboy Subscriber

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    18% grey is the mid point between deep black and pure white, so if you mix equal quantity of each paint together you shouldn't be too far off.
     
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  15. AgX

    AgX Member

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    It is the mid point visually. And that is not linked to paint volumes.
     
  16. BrianShaw

    BrianShaw Member

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    ditto
     
  17. Sirius Glass

    Sirius Glass Subscriber

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    Sadly no. Because of the lake effect Rochester is heavily overcast most of the year.

    On the more positive side Rochester looks better in snow because it covers up the rust and dirt.
     
  18. John Koehrer

    John Koehrer Subscriber

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    Wouldn't oil base have a sheen to it when it dries?
     
  19. Bill Burk

    Bill Burk Subscriber

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    I was wondering, why not 12%?

    It isn't really critical for film tests "what" the percent is, because you end up adjusting by f/stops to "place" whatever it is... at whatever Zone you are testing for.
     
  20. OP
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    snikulin

    snikulin Member

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  21. Bill Burk

    Bill Burk Subscriber

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    Well, 18% is a good mid point between White and Black... So it's a nice reference. But it's not the meter calibration point. The meter calibration point is better approximated with a 12% gray. So if that's what you were thinking, you'd be a sophisticated game player if you made a 12% wall.

    If you were just thinking of a target for Zone System tests, then you have a lot of leeway. Because whatever the wall tone is... is what you meter. Then you stop down several stops and make an exposure. It really doesn't matter if the wall is 75% bright gray and you meter it and stop down four stops... You'll get the same amount of light on the film as if the wall was 10% dark gray and you meter it and stop down four stops... The meter will indicate a longer exposure but in the end you will put the same amount of light on the film. So the grayness of the target is canceled out in tests.

    Where the gray percent really matters is when you put the gray card into the scene of a picture you are about to take, then you remove the gray card and take the picture with those settings. Then a 12% target would get you a meter reading that will be appropriate without requiring an adjustment "just because it's the wrong gray".

    Did you have any of those reasons in mind when thinking of an 18% gray? To use for Zone System tests or to use as a meter stand-in? Or were you looking for the correct neutral spectral reflection for more demanding purposes? Because if you want a real neutral across the spectrum, I don't know the formula.

    But I know a simple one... Get a can of white paint and a jar of black pigment.

    When I made my painted plywood target for Zone System testing - I went to the local hardware store, took a pint of white base paint off the shelf and explained what I was doing, I picked up and paid for a small container and told them to fill it with "black" pigment. It was small enough not to be a big deal, but if they complain you can always tell them to just meter out the amount of pigment that they would put in if you had ordered the paint "black".

    I mixed in black pigment until I got a light gray, painted the plywood. Then after that was fully dry I added a little more black pigment to the paint, painted the other half of plywood and took meter readings until the two halves metered one f/stop different from each other...

    [​IMG]

    Now that's a Minor White Zone System target. It gives you Zone 0 and Zone I in one shot. Or Zone VIII and Zone IX - whatever you shoot it gives you two different Zones.
     
  22. Sirius Glass

    Sirius Glass Subscriber

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    My beard in now 18% neutral gray. Does that help?
     
  23. Ken Nadvornick

    Ken Nadvornick Member

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    Is that before or after the tinting???

    :tongue:

    Ken
     
  24. Sirius Glass

    Sirius Glass Subscriber

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    No tinting, but after eating there is staining sometimes.
     
  25. RobC

    RobC Member

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    I thought the ansi standard was 12.5% but maybe I'm confusing that with Sekonic whose meters are calibrated to 12.5%. And that highlights the point that if you make your wall 12% and calibrate using a sekonic it'll be wrong. And if you calibrate using a Minolta spot which use 14% it'll be wrong so before painting your wall you should actually make sure you know what your meter is calbrated to unless you are sure you want an 18% wall.

    18% is perceptually middle grey. Light meters don't have perceptual vision and nor does film or paper. Green is more relaxing and yellow will impart a nice warmth to your images hanging on your 18% wall. Duh.

    Just shine a bright spot at your images hanging on wall as that will make them poke peoples eyes out. Infact if the wall if for hanging black and whiote images I'd make the wall darker than perceptually middle so the the images have relatively more POP.
     
  26. Bill Burk

    Bill Burk Subscriber

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    I don't think the Calibration Constant, K of 12.5 is a percent.

    I think ANSI avoided the issue and left that out of the definition. So we can only estimating the approximate equivalent to the standard.

    I don't know if we've come to an agreement whether an ideal gray card considering ANSI meter's calibration is 12%, 12.5% or 12.7%

    But it's in that vicinity. Certainly not 18%.

    Meanwhile, what's a refreshing color for a gallery wall? That's a good question that's worth digging into.
     
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