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Old Feb 21, 2004, 8:53 PM   #1
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Default where is the middle grey on histogram?Why not in the middle?

Try it: shoot on the wall or ceiling or grey card. The result: the exposition is not in the middle of the histogram. It is 2/3 or 1 value left from it! Why? ops:
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Old Feb 22, 2004, 1:08 AM   #2
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My only thought (don't know if I'm right) is that a grey card is 18% grey, not 50% grey. So it should be shifted towards the light side.

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Old Feb 22, 2004, 7:24 AM   #3
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Default Re: where is the middle grey on histogram?Why not in the mid

Quote:
Originally Posted by digiteye
Try it: shoot on the wall or ceiling or grey card. The result: the exposition is not in the middle of the histogram. It is 2/3 or 1 value left from it! Why? ops:
In theory it should be centered (and you can by adjusting the EV); However, it is better to underexpose than to overexpose -> IMO the manufacturers usually set their cameras to slightly underexpose to protect the photographer from blowing out the details on the highlights: http://www.planetneil.com/nikon/d100-customcurves.html

:P :P :P
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Old Feb 22, 2004, 8:12 AM   #4
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NHL,
Yes, I think this is the case: given that the curve of digital is quite straight, has not any elbow up (unlike film), engeneers try to protect us from burned details. :lol:
thanks for thinking together
best regards
Peter - digiteye
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Old Feb 22, 2004, 6:25 PM   #5
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Default 13.5% gray

Well heres a couple facts that you can do with as you will. The Gray Card is a printer and artists aid which reflects 18% of the light that strikes it. It is in fact a median or 50% gray which is a printers term. Actual median light would be near 13.5% reflective. The Gray card was just used as a standard as it was easy to produce and standardize.
Take your gray card to a camera store, ask the man for his best reflective light meter. Check your gray card with it and you'll see the difference between 13.5% median and an 18% gray card.The truth of the mater is what difference does it make? It is a tool that has become a standard, that is all it is!
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Old Feb 23, 2004, 11:32 AM   #6
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Aside from previous answers; A greycard represents average scene reflected light. Using a card that causes a spot on middle peak in a histogram would be quite useless. Cameras also meters are also set for 18% reflected light being exposed right. Otherwise we would end up with blown-out foliage, portrets (northern people), and other common scene subjects.
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Old Feb 28, 2004, 9:47 PM   #7
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Kodak 18% grey cards do indeed reflect 18% of the light that hits them. I own 3 Canon dSLR's and the 18% grey card is in the center of each histogram. You may be holding your grey card at an angle, which can effect the reflectance. You may also have a camera that needs adjustment. Is your exposure compensation set?
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