Are grey-cards all the same ?

Discussion in 'Photography Beginners' Forum' started by <error>, Sep 17, 2015.

  1. <error>

    <error> TPF Noob!

    Joined:
    May 24, 2015
    Messages:
    29
    Likes Received:
    1
    Location:
    Paris, France
    Can others edit my Photos:
    Photos OK to edit
    I have a grey-card on my shopping list, but am confused about the differences in their making and their price.

    Apart from the 18% or 12% question, can I just pick any and be good, or is there something I should consider?

    Thanks guys!


     
  2. jaomul

    jaomul Been spending a lot of time on here!

    Joined:
    Feb 4, 2011
    Messages:
    5,714
    Likes Received:
    1,548
    Location:
    Cork Ireland
    Can others edit my Photos:
    Photos OK to edit
    As in everything if something is very cheap it may not be as accurate, but to be fair a sheet of paper can be used in a pinch so i'd say once the card is robust enough for use you should be ok
     
  3. petrochemist

    petrochemist TPF junkie!

    Joined:
    Mar 9, 2014
    Messages:
    1,604
    Likes Received:
    473
    Location:
    North Essex UK
    Can others edit my Photos:
    Photos OK to edit
    They certainly vary in size & robustness. I'm sure any variation in shade will totally irrelevant if you always use the same one - and I think it's only in cases where your combining multiple shots that the difference between them would perhaps be relevant.
     
  4. Alexr25

    Alexr25 No longer a newbie, moving up!

    Joined:
    Aug 31, 2014
    Messages:
    395
    Likes Received:
    84
    Location:
    Australia, near Melbourne
    Can others edit my Photos:
    Photos OK to edit
    It depends on how deep you want to go into the technicalities of the subject but this article covers all aspects of grey cards quite well.
    http://www.betterlight.com/downloads/whitePaper/wp_gray_cards.pdf

    Personally rather than a card I prefer to use on of these as they are more robust and easier to carry around.
    Lastolite EzyBalance Gray Card LL LR1250 B&H Photo Video

    Edit:
    Fixed the first link as it was pointing back to this thread. Now it points to the grey card article I was talking about.
     
    Last edited: Sep 17, 2015
  5. Designer

    Designer Been spending a lot of time on here!

    Joined:
    Apr 13, 2012
    Messages:
    18,306
    Likes Received:
    4,775
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    The percentages refer to the saturation level of the gray, and either one will work, but the most important factor is the color neutrality. A neutral-color gray is neither warm nor cool, and shows no "color" at all, just gray. So be sure to purchase your card from a reputable photography-equipment dealer.

    IMO, you could use anything without a color cast, such as white for instance. Some cheap photographers use a white styrofoam cup or plate.
     
    • Agree Agree x 1
    • Disagree Disagree x 1
  6. snowbear

    snowbear Oh, hai. I iz bear. Supporting Member

    Joined:
    Dec 9, 2006
    Messages:
    15,440
    Likes Received:
    6,762
    Location:
    SoMD
    Can others edit my Photos:
    Photos OK to edit
    The percentage refers to how reflective the card is.
     
    • Agree Agree x 1
  7. runnah

    runnah Moderator Staff Member Supporting Member

    Joined:
    Oct 16, 2012
    Messages:
    14,630
    Likes Received:
    7,533
    Can others edit my Photos:
    Photos OK to edit
    I've heard there are at least 50 variations.
     
  8. Buckster

    Buckster In memoriam

    Joined:
    Sep 14, 2009
    Messages:
    6,399
    Likes Received:
    2,335
    Location:
    Way up North in Michigan
    Can others edit my Photos:
    Photos NOT OK to edit
    I would add to Designer's post that with today's ISO and post processing from RAW capabilities, luminance isn't as much a problem or even a guessing game as color accuracy is, so I agree that the most important factor is the color neutrality.

    And yes, in a pinch, any white thing is better than nothing. Styrofoam cup is popular because a VERY advanced photographer on this forum has actually color tested various common white objects with this in mind, and found that the Styrofoam cup is as accurate as can be. Many things are not. Paper can have a somewhat bluish tint, other objects may have their own tints.

    I myself use one of these, and am quite pleased with the results: Photovision 14" Pocket One Shot Digital Target DT14010 B&H
     
    • Like Like x 2
  9. soufiej

    soufiej No longer a newbie, moving up!

    Joined:
    Jan 3, 2015
    Messages:
    714
    Likes Received:
    113
    Can others edit my Photos:
    Photos NOT OK to edit

    I'd say you'd have to be either VERY professional or VERY OCD to concern yourself with the % value of a grey card. Professionals using studio lighting where color temperature is a concern may be placed in a situation where exacting color reproduction is essential to their final product.

    If you're in that camp, you've probably already invested in decent reference material to reach the point where you are breathing the air of that rarefied camp. Then it's up to the rest of the chain of reproduction to put what you've shot into real life use.

    If you are concerned as a hobbyist with color accuracy, then you really need to look first at all of the other links in the reproduction chain where color accuracy can go wrong. Even, IMO, to the point you are deciding whether you prefer, say, the "Nikon Look" to the "Canon Look" and so on. There are numerous human errors which will affect color accuracy and you'll first need to minimize those potential issues before you get down to selecting a specific grey card. Obviously, color accuracy first depends on the lighting used for your photograph. For most of us, we simply do not have sufficient control over the available lighting to say "this" is how all of our shots will turn out today. Unless you then reference every single shot to a grey card, that's what you need to expect as a result. Unless you are intending to sell your photos, most likely no one will complain about color accuracy any more than most people would complain about an audio recording which ran a bit fast and altered pitch by, say, 1-2%.

    With a card of any type, you are, as a hobbyist, really only ensuring a consistency in your shots, not so much accuracy. If you take your shot of your card into post production you can then make adjustments which are based on your specific grey card against a color standard which exists in your monitor. It may not be completely 100% accurate color by everyone's standards but it will be consistently right or wrong in one direction. Until the world all agrees on a single color standard for all monitors and all printers, that's about all you can expect.

    Monitor Calibration and Profiling | dpBestflow



    Recently, I ordered a superzoom bridge camera for some work with wildlife shots and it came in a package deal with a bag. Looking at the Velcro'd padded dividers which came with the bag, I noticed they were a grey color which could easily work as a substitute for a purchased grey card. I thought this was a neat idea for the average photographer who may not yet have a grey card or for someone who may have grabbed a bag from a choice of several and not managed to pick up the bag that held their grey card. The dividers and the top inner liner of the bag were certainly large enough and consistent enough in color to stand in for a grey card for most hobby based photographers.
     
    • Informative Informative x 1
  10. Alexr25

    Alexr25 No longer a newbie, moving up!

    Joined:
    Aug 31, 2014
    Messages:
    395
    Likes Received:
    84
    Location:
    Australia, near Melbourne
    Can others edit my Photos:
    Photos OK to edit
    I think you meant "reflectance" rather than "luminance", at least I hope you did because the only way you are going to get luminance out of a grey card is by setting fire to it.
    But that minor quibble aside, whether the reflectance is important or not depends on what you intend to do with the grey card. If you are going to use for metering, as grey cards were designed to be used, then its reflectance is very important. If on the other hand you are just using it for white balance then spectral response is the important quality and any white or grey object will do.
     
  11. TCampbell

    TCampbell Been spending a lot of time on here!

    Joined:
    Mar 31, 2012
    Messages:
    3,615
    Likes Received:
    1,555
    Location:
    Dearborn, MI
    Can others edit my Photos:
    Photos OK to edit
    The point of the percent gray has to do with using the gray card as a kind of light meter. Your camera's built-in "reflected" light meter is designed to assume some average level of grey (average reflectance). Ansel Adams says that "middle" gray is 18% reflectance and some cameras were actually calibrated to assume that. Most cameras now assume a bit closer to the 12% value but this can vary by camera.

    The idea of using the grey card as a light meter was that if you made the gray card the prominent thing in the center of your frame and metered it, the meter reading you get would be accurate because the reflectivity of the card (the amount of light reflected) is a known quantity. If you snapped a photo of the gray card and checked your histogram, it would create a spike in the very center of the graph (well... it only lands in the very center of your graph if your camera's notion of average reflectivity happens to exactly matched the reflectivity of the gray card.)

    So while it's technically possible to use a gray card to improve the accuracy of the reflected light meter in the camera (allowing it to have the accuracy of a hand-held "incident" meter), very few people use it that way. It's mostly just used to establish white balance.

    Also... to establish REALLY accurate color, you'd need to be even more elaborate and use a color-checker card (such as an X-Rite ColorChecker Passport). The chart uses a number of colored tiles with known color values. Your camera may be more sensitive to some colors than others. That means your "reds" might be more saturated or less saturated then the actual "red" object you photographed. The color checker allows you to detect that (it includes software). This means that whereas as a normal "gray card" is helping establish neutral white balance, the "color checker" card is helping to establish accurate hue and saturation of each color within the spectrum.

    All of this assumes you have a color-calibrated monitor and, if you do your own prints, a color-calibrated printer (which requires calibrating the combination of paper and inks that you use.)
     
    • Informative Informative x 2
    • Like Like x 1
  12. Buckster

    Buckster In memoriam

    Joined:
    Sep 14, 2009
    Messages:
    6,399
    Likes Received:
    2,335
    Location:
    Way up North in Michigan
    Can others edit my Photos:
    Photos NOT OK to edit


    Good points.

    Which do you use yours for, and which type / brand do you prefer to use, and why?
     

Share This Page