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03-21-2010, 03:12 PM   #1
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The 18% Gray card

Some time ago I've made photos for some real estate agency. On the camera screen it was good, but when i came home i discovered that most images was incorrectly exposed. Snow was gray as mice. So I questioned about buying a gray card.

How many of you people have this card, and do they really so much helpful?


P.S. I understand that practice makes it perfect.

03-21-2010, 04:23 PM   #2
Damn Brit
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If they were underexposed, that would imply that you were metering incorrectly in the first place. Using a gray card and metering the same way you have previously done might just give you the same under exposure.
It would also depend on the amount of underexposure and whether it is with all or some lenses. Most photographers get to know the nuances of their cameras meter and compensate accordingly. Doing some research on exposing to the right (ETTR) might also help you.
If snow was grey in your shots, that could also be to do with your WB settings.
03-21-2010, 04:24 PM   #3
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They are quite a useful tool to have in your kit. Especially when correct colour and white balance are necessary for your final images/client.

To give an example of how extreme some people are about the 18% gray card:

A professor of mine actually painted the wall behind his computer screen in his office 18% gray for accurate colour correction.
I'm not saying you need to do this, I found it incredibly ridiculous when I heard it.
Whatever it takes, I guess.
03-21-2010, 04:57 PM   #4
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The thing with a gray card is that you must take the reading under the same light as your subject. If your subject is lit by heavy sun and you are standing in shadow, your reading will be off if you take the reading from the gray card, while using reflected light from your subject would likely give a properly exposed picture.

I think you should get a decent book on exposure like "Understanding exposure" by (if I remember correctly) Brian Peterson.

03-21-2010, 05:53 PM   #5
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A good thing to do is research the zone system. You'll learn a lot of useful tips like that healthy green grass in sun is 18% gray, and that white snow in the sun should be exposed 2 or 3 stops less than the meter reading.

The only time ive ever used a gray card is when in the studio, where I not only need complete perfection, but also where there isn't really anything else I could meter to get an idea for an accurate exposure.
03-21-2010, 06:28 PM   #6
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The expodisc started life not as a WB tool, but an exposure tool. It now is a WB, exposure, and dust, tool.

ExpoImaging, Inc.
http://www.expoimaging.com/MediaFiles/instructions/EN_17.pdf
Name:  EN_17_11.jpg
Views: 1270
Size:  54.6 KB


If you are looking to a cheap way to try out a grey card, US $6
http://cgi.ebay.com/Canon-18-Gray-Card-Color-Balance-Chart-Guide-Book_W0QQit...item2eabdd9987



I really like these 18% grey micro cloths, US $8
http://cgi.ebay.com/Cleanstar-Micro-Fiber-Lens-Cloth-18-Grey-Photo-Card_W0QQ...item23050a8573




Thank you
Russell

Last edited by Russell-Evans; 03-21-2010 at 06:40 PM.
03-21-2010, 07:22 PM   #7
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QuoteOriginally posted by Damn Brit Quote
If they were underexposed, that would imply that you were metering incorrectly in the first place. Using a gray card and metering the same way you have previously done might just give you the same under exposure.
It would also depend on the amount of underexposure and whether it is with all or some lenses. Most photographers get to know the nuances of their cameras meter and compensate accordingly.
Okay, yeah, but in this case, a gray card is almost certainly the right answer. Or, since we're talking digital, simply dialing in a stop or more of positive exposure compensation and taking some test shots. Bright white snow is the classic case for exposure compensation the metering of any camera that doesn't realize it's dealing with a snowy day is very likely to be confused and make it too dark.

(That's why point & shoot cameras usually have a "snow scene" mode.)

QuoteOriginally posted by Damn Brit Quote
Doing some research on exposing to the right (ETTR) might also help you.
Orrrr, it might confuse you horribly and cause you to make a lot of photographs with blown highlights.

QuoteOriginally posted by Damn Brit Quote
If snow was grey in your shots, that could also be to do with your WB settings.
Really? Bluish, okay, yeah, but neutral gray?
03-21-2010, 08:03 PM   #8
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QuoteOriginally posted by mattdm Quote
Okay, yeah, but in this case, a gray card is almost certainly the right answer. Or, since we're talking digital, simply dialing in a stop or more of positive exposure compensation and taking some test shots. Bright white snow is the classic case for exposure compensation the metering of any camera that doesn't realize it's dealing with a snowy day is very likely to be confused and make it too dark.

(That's why point & shoot cameras usually have a "snow scene" mode.)
Agreed, but in the absence of a gray card, a test shot and a look at the histogram can help.




Orrrr, it might confuse you horribly and cause you to make a lot of photographs with blown highlights.
It's worth learning though.



Really? Bluish, okay, yeah, but neutral gray?
Yeah, maybe ya got me there but underexposure could account for looking more gray than blue.

03-22-2010, 12:34 AM   #9
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Thanks for the answers. So how I understood, the card is no such needed but can be helpful in some situations.
03-22-2010, 12:41 AM   #10
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Just WB and meter off the snow +2EV you will get almost perfect shots everytime. For difficult situations, a piece of white paper helps, so is the spot meter of the camera.
03-22-2010, 01:52 AM   #11
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Yes, but i don't have snow all the time in my place. I heard that people use a asphalt for WB and exposure, never really tried that.
03-22-2010, 03:52 AM   #12
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QuoteOriginally posted by Eugene-S Quote
Yes, but i don't have snow all the time in my place. I heard that people use a asphalt for WB and exposure, never really tried that.
I do so many shots (from my truck) that include the white paint of road markings that I just use those for setting WB in Lightroom. It probably isn't the exact perfect solution, but it is consistent. Seems to give a bit of a warm cast to the photos, but not unnaturally so.
03-22-2010, 03:03 PM   #13
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Grass is Good

Gee, I was taught the "meter for the grass" trick by the PJs in my unit in 1969 and hadn't heard much about it since, probably owing to my absence from photography (for which photography is grateful) and our current 3.75 giga-element exposure systems.

I still meter for the grass. When I can. In Wisconsin.
03-22-2010, 03:35 PM   #14
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QuoteOriginally posted by PeteyJ Quote
A good thing to do is research the zone system. You'll learn a lot of useful tips like that healthy green grass in sun is 18% gray, and that white snow in the sun should be exposed 2 or 3 stops less than the meter reading.
I think you mean we should open up a couple stops for snow, right? Because the meter reads it as something very bright and wants less exposure, averaging out to 18%--or 12% or whatever I've read that camera manufacturers actually use. But we want the snow to look white, so we open up a couple stops (or something like that, depending on the situation--how much snow, how much sun) so the snow will be white rather than grey.

I'm hoping I won't have to think too much about it over the next, say, eight months. Hopefully, the "healthy green grass" will assert itself soon!
03-22-2010, 03:39 PM   #15
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QuoteOriginally posted by glanglois Quote
I still meter for the grass. When I can. In Wisconsin.
Our snow's all gone here, glanglois--unless there's some hiding on the north side of the hills north of Spring Green.

And our rhubarb has just started coming up, too! And soon, the mosquitoes. . . .

Everything's a trade-off, I reckon. . . .
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