DIY Grey Card

Discussion in 'Photographic Discussions' started by 2ART, Mar 30, 2009.

  1. 2ART

    2ART TPF Noob!

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    Q: If I made a new layer in Gimp, colored it black and adjusted the
    visibility of the layer to 18% and printed it out - would I have a
    18% grey card ?
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I'm not sure if that is how to get %18 grey....and your printer would have to be perfectly calibrated.
    So probably not.
     
  3. 2ART

    2ART TPF Noob!

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    ok..:D 15-20% then ! lol

    thanks mike!

    I'll give it a spin, see what happens!
     
  4. jlykins

    jlykins TPF Noob!

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    Why would you bother? a grey card is only like $5...
     
  5. Dweller

    Dweller Inconspicuous Supporter

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    I tried this as well until I realized how inexpensive they were. When I compared visually to what I had come up with on my own, I do not think I was even close.
     
  6. christopher walrath

    christopher walrath No longer a newbie, moving up!

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    Or try this for a DIY Grey Card. Meter your hand. Light skin is generally considered best rendered on Zone VI. So meter your hand. That is a Zone VI reading. And you can go from there. Anything else matching that reading would fall on Zone VI. Adjust accordingly.
     
  7. Josh66

    Josh66 Been spending a lot of time on here!

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    I've heard that metering off of green grass works good too. Does it?
    (The grass is brown most of the year here.)
     
  8. Tiberius47

    Tiberius47 TPF Noob!

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    That is assuming that the light on your hand is the same as the light on your model. If the model is several feet away, this technique may give you an incorrect exposure.

    The grey card I have is a nifty little thing that is actually three cards. There's the grey card, but also a white card and a black card.

    The idea is that when you take a series of photos, get the model to hold the cards in front of her in the first one. Then for the rest, she doesn't need them. Do this each time the light changes.

    When you get home, open up the first pic in photoshop, with the cards showing. Create a Curves adjustment layer. You'll notice that there are three eyedroppers, a black one, a grey one and a white one. Select the black eye dropper and then click on the black card. Select the grey eyedropper and click on the grey card, and likewise with the white. This sets the brightest and darkest parts of the image, and the grey not only corrects the gamma, but also white balance. Then you can copy this adjustment layers to all the other photos in the same light that you took without the card. I picked mine up for about $20 Australian.
     
  9. Steph

    Steph No longer a newbie, moving up!

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    That works great for me. I often use green grass as a midtone when I meter landscape shots and I get consistenetly good results, even with slides. I live in the UK though, and given the weather here, the grass is always green.;)
     
  10. JerryPH

    JerryPH No longer a newbie, moving up!

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    I agree that this is a neat trick and indeed this is something that I use often... however until you calibrate your hand (lol), it is useless.

    How to calibrate? You need to have shot your hand just once using a WB card. Once you do that, you will know how far off your hand is from 18% grey and can adjust for that. I am what I would call an average white caucasian and my hand is about 1.25 stops off. So, I can go roughly 1 to 1.5 stops off 18% grey and still be very close.

    A black man's hands would be different from mine, as would even someone with a nice tan and this needs to be taken into consideration for the "calibration" aspect.

    To the OP... that said, you could use even a white styrofoam cup to balance against, and it will work consistently too, but the whole point of using a grey card is accuracy, and as has been mentioned, they are very affordable, so why break your head over creating inaccurate ways of doing it? :)
     
  11. Fraggo

    Fraggo TPF Noob!

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    Have you ever used the Threshold method? It has helped me in many of my photo.

    On the bottom of the layers palette there is a symbol the looks kind of like a B&W cookie. (or go to Image< Adjustment < Threshold) This will create a new layer called Threshold 1. You will need the Color Sampler Tool with caps lock on so you can get the cross hairs.

    Move the slider of the threshold all the way to the left and white out the photo. Slowly move it to the right, as soon as you see some black click OK. Zoom in all the way and mark it with your Color Sampler Tool, a cross hair will appear on your photo.

    Next, you will need to click threshold layer on the BW cookie to get your slider back up. Move it all the way to the right this time. If there is already white there, click on that, if not, slide the arrow till you just start to get white. Same thing, click OK and select the white area.

    Now you can turn off your Threshold Layer. Now to set the grey point, you want to have the info window open to where you can watch the numbers of the RGB as you scroll across your photo. When the R hits 128 or as close to it as you can, you can set your grey point the same way you did the B&W points.

    Select Curves via the cookie at the bottom of the layers palette. It will open up another layer named Curves. You select the eye dropper for Black and hover over the cross hair until it disappears, and click on it. Do the same thing with both your white point and grey point.

    Lastly, all you need to do is mess with the RGB in curves and set the following settings for your white, grey and black points.

    Black: 5
    White: 245
    Grey: 128

    I hope this helps and I didn&#8217;t confuse you to much.
     
  12. 2ART

    2ART TPF Noob!

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    Interesting replies - thanks all!
     

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