Richard D Posted February 12, 2009 Share #1 Posted February 12, 2009 Advertisement (gone after registration) Hi, Although I have put manual white balance to good effect by just using a matte-finish white card, I'm a little confused about the purpose of an 18% grey card. I gather it's for proper exposure, not color balance, but even after checking around, I'm not really clear about how it's used. Could someone point me in the right direction? Thanks......:-) Link to post Share on other sites More sharing options...
Advertisement Posted February 12, 2009 Posted February 12, 2009 Hi Richard D, Take a look here Purpose of a Grey Card?. I'm sure you'll find what you were looking for!
miami91 Posted February 12, 2009 Share #2 Posted February 12, 2009 Hi,Although I have put manual white balance to good effect by just using a matte-finish white card, I'm a little confused about the purpose of an 18% grey card. I gather it's for proper exposure, not color balance, but even after checking around, I'm not really clear about how it's used. Could someone point me in the right direction? Thanks......:-) I can't speak for in-camera manual white balance, but I use a grey card (a WhiBal) for white balance in post-processing. What I do is I take a throw-away frame with someone holding the gray card, then do my shooting. Then, when in Aperture, I use the eyedrop tool to set the white balance on all the images from my outing by sampling the gray card in my throwaway image, and then stamping the adjustment onto all the other images taken in the same shoot. The key to this approach, of course, is making sure you take a gray card shot each time the light changes substantially (ie, moving outside to inside, or if outside as the day goes and the nature and temperature of the light changes, etc.). So to answer your question, is an 18% gray card absolutely necessary for this approach, or would a piece of white paper or fabric work just as well? Aside from the fact that not all white objects are spectrally neutral like a gray card, I believe that this is also the standard that photo programs like Aperture, Photoshop, Lightroom are calibrated for, so alternatives may not work as well. Also, I think it's just as easy to carry a proper card as anything else. I bought several WhiBals in several sizes, and have them in all my camera bags as well as frequently have one in my pocket or around my neck on a lanyard. Best, Jeff. Link to post Share on other sites More sharing options...
andit Posted February 12, 2009 Share #3 Posted February 12, 2009 Hi Richard, This is one of those things that no one uses anymore nowadays (I still carry a grey card in my camera bag and still use it from time to time). If you look around you, where ever you are and you take all the light that you see (highlights, shadows, mid tones) in the scene, and mix it together (imaging putting the whole scene in a blender) you will be left with a uniform grey color that is 18% grey. Exposure meters in every single camera and light meter are calibrated to 18% grey. This is the default known value (could be likened to an SI Unit such as Kilogram etc). The camera takes the value that it gets from the light meter, then compares that value to the calibrated norm (18% Grey) and works out the correct exposure accordingly. A camera's light meter is fooled in a couple of situations though - such as taking pictures in snow, by black subjects, strong back lighting or in mixed lighting situations. This is where the grey card comes in handy. Place the grey card in front of the subject you want to take facing the camera. Spot meter the grey card - the value that you get from the grey card will give you the right exposure value for the metered subject. This does not however give you the right color temperature for the white balance. It gives you the correct exposure value for the light intensity metered. Hope this explains it a bit. Andreas Link to post Share on other sites More sharing options...
andit Posted February 12, 2009 Share #4 Posted February 12, 2009 One thing that I must add here, the proper grey card is an extremely accurate and scientific object. They were only manufactured by a couple of companies such as Kodak, Fuji, McBeth etc to extreme tolerances. The one way that one would estimate an exposure without a grey card was to meter off the back of your hand - due to exposure latitudes in film this normally worked out ok. Andreas Link to post Share on other sites More sharing options...
Overgaard Posted February 12, 2009 Share #5 Posted February 12, 2009 Take a loog at this video: http://whibalhost.com/_Tutorials/WhiBal/01 and note how he's saying the WhiBal is NOT for metering (it's not 18% grey) Also, here is my page on WhiBal cards for white balancing: leica.overgaard.dk - Thorsten Overgaard's Leica Pages - WhiteBal greycards for white balancing digital photography and video Link to post Share on other sites More sharing options...
giordano Posted February 12, 2009 Share #6 Posted February 12, 2009 The one way that one would estimate an exposure without a grey card was to meter off the back of your hand - due to exposure latitudes in film this normally worked out ok. Depends what the back of your hand looks like - especially in Africa:D. Link to post Share on other sites More sharing options...
fotografr Posted February 12, 2009 Share #7 Posted February 12, 2009 Advertisement (gone after registration) Proper exposure is as important in digital photography as it is in analog shooting. A grey card can help obtain accurate meter readings. A grey card can also be used to set a custom white balance. In fact, many people prefer to use a grey card to a white card for this purpose. A good 18% grey card should have no color cast. Link to post Share on other sites More sharing options...
Richard D Posted February 12, 2009 Author Share #8 Posted February 12, 2009 Thank you for all the input; I'm learning a lot here. Another question: I've just been looking at the 'whiBal' tutorials. I'm thinking of buying their small card (2-3.5"). Occasionally, I would include it in a test photo, but more often than not, I would want to take a white balance at the camera position. If I do a manual white balance by filling the central outline on the LCD screen of my D-Lux 4, does the image have to be in focus? I would have to go into macro mode to do so. Thanks again. Link to post Share on other sites More sharing options...
Richard D Posted February 12, 2009 Author Share #9 Posted February 12, 2009 Proper exposure is as important in digital photography as it is in analog shooting. A grey card can help obtain accurate meter readings. A grey card can also be used to set a custom white balance. In fact, many people prefer to use a grey card to a white card for this purpose. A good 18% grey card should have no color cast. Interesting. I don't think they mention it on their video, but is the WhiBal card actually an 18% grey card? If not, am I going to also want a real grey card for those occasional situations where it might be useful for proper exposure? Link to post Share on other sites More sharing options...
Richard D Posted February 12, 2009 Author Share #10 Posted February 12, 2009 A grey card can also be used to set a custom white balance. In fact, many people prefer to use a grey card to a white card for this purpose. A good 18% grey card should have no color cast. Also interesting. Would I use it the same way as I would a white card or WhiBal card for a manual white balance setting on my D-Lux 4? I'm sorry, I'm still a little confused about this.....:-( Link to post Share on other sites More sharing options...
Richard D Posted February 12, 2009 Author Share #11 Posted February 12, 2009 A moment ago, I asked if the WhiBal card was actually an 18% grey card. I see now from one of their tutorials that it is actually a lighter grey. So scratch that question......:-D Link to post Share on other sites More sharing options...
KM-25 Posted February 12, 2009 Share #12 Posted February 12, 2009 This is one of those things that no one uses anymore nowadays (I still carry a grey card in my camera bag and still use it from time to time). I still do, because I shoot a lot of slide film. My new Kodachrome Project T-shirts are 18% gray so you can meter off of them: kodachromeproject.com Forums Link to post Share on other sites More sharing options...
Overgaard Posted February 12, 2009 Share #13 Posted February 12, 2009 Just to add some more homework. The first link shows a greycard for exposure metering in a way where one can see how dark 18% is. I usually call them middlegrey because that is what they appear to be. useful accessories COLORRIGHT MAX Link to post Share on other sites More sharing options...
earleygallery Posted February 12, 2009 Share #14 Posted February 12, 2009 Apparently if you don't have a grey card, metering off green grass (yes of course grass is green but sometimes its brown or muddy or dried and straw like !!) or something bright red will also give an accurate exposure. Link to post Share on other sites More sharing options...
Overgaard Posted February 12, 2009 Share #15 Posted February 12, 2009 I've used the spot-meter in Digilux 2, Digilux 1 and other small digital cameras a lot by pointing the spot towards something middlegrey (wood, bricks, paintings, hair, clothing, etc), lock the exposure and then reframe and shoot. Link to post Share on other sites More sharing options...
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