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Old Mar 8, 2003, 6:00 PM   #1
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Default trouble focusing on gray cards

Is it just me or do others have diffulty focusing on a gray card. I have a d100 and while playihg with it today, I found it next to impossible to focus on the card. The only way i could manage was to focus on the edge of the card and then bring the lens over. Is this how its done or are there better ways.
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Old Mar 8, 2003, 6:11 PM   #2
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your going to find focusing on any flat featureless surface quite challenging with any AF system.

remember your testing/setting your light metering system not your focusing system with this card.

if you need it to focus just draw a light to medium crosshair on the card in the center and use that as a focus point. it will have no effect on the metering but should quiet down the AF substantially.
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Old Mar 8, 2003, 6:24 PM   #3
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I can't think of any reason the gray card has to be in focus to set exposure.

A gray card is really nice to use for situations like snow covered fields, but I always seem to have left it behind. I've found that getting an exposure reading from the palm of my hand, then opening one stop works well. And I haven't forgoten my hand - yet.
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Old Mar 8, 2003, 7:06 PM   #4
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You'll find that on any plain surface without definition that you won't be able to focus on it...in fact you won't be able to focus on a scene that doesn't have vertical line(s) (at least with most digital cameras). If your interest is setting the white balance, you don't need to worry about that...just follow the instructions for that in your manual.
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Old Mar 8, 2003, 8:33 PM   #5
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Mike- the D100 has AF sensors for both vertical and horizontal lines. it uses the CAM 900 sensor array (5 sensors) for vert/horiz coverage. it isn't the 1300 but works pretty darn good though.
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Old Mar 9, 2003, 4:44 AM   #6
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For exposure setting it's better to have a card defocused anyway. On older cams, any texture sometimes introduced an alias which interfered with the metering. The usual method is zoom in and defocus.
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Old Mar 9, 2003, 7:35 AM   #7
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now thats one i've never heard
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Old Mar 9, 2003, 7:46 AM   #8
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Quote:
Originally Posted by voxmagna
For exposure setting it's better to have a card defocused anyway. On older cams, any texture sometimes introduced an alias which interfered with the metering. The usual method is zoom in and defocus.
that's a good point.......i remember reading that a while back.
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Old Mar 9, 2003, 8:04 AM   #9
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... Well, what's wrong with the histogram function? Some few lucky folks among us even have it in real-time with their EVF cameras! 8)
Aren't we suppose to ween ourself away the film day anyway? :lol: :lol: :lol:

Also one can shoot a picture with the grey card put in a corner, and with the D100 exposure latitude and the magic of Photoshop, one can always work it out the detail in post-processing (especially in raw). Again there's another histogram there (grey card...? Duh!)
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Old Mar 9, 2003, 9:11 AM   #10
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you know all the histogram stuff is great. and yes it does work as long as the metering system is accurate. if the meter is off it shifts the histograms readings too. its always good to have a reference point to guarantee the meter is reading accurately to begin with. i use a Wallace ExpoDisc 18%+/- 1/6 stop and white balance with color accuracy R0.00 G0.01 B0.03 density. sets a pretty mean white balance. it's also easier than dragging a grey card around and it serves 2 purposes at 72mm in dia.

http://www.expodisc.com/

more on histograms:

http://www.luminous-landscape.com/tu...stograms.shtml
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