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18% grey card/spot meter


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#1 Louis

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Posted 02 October 2005 - 06:42 PM

Here's a simple question: when using a spot meter to do readings, how important is it to have an 18% grey card on hand. Using a spot meter requires pre-visualization and inference skills either way (i.e., you have to know how much to open up when shooting a certain skin tone and how much to close down when shooting a different skin tone), so how important is it to actually have an 18% grey card on hand? It seems to me that it's not completely necessary, but I haven't tried this theory out yet.
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#2 Kevin Zanit

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Posted 02 October 2005 - 08:13 PM

If you are going to use a gray card with a spot meter, why not just use an incident meter? It should give you the same result.

I use a spot meter to measure the reflectance of a given subject.


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#3 Louis

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Posted 02 October 2005 - 10:32 PM

I might have some wrong information then. What do people usually use 18% grey cards for?
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#4 Dimitrios Koukas

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Posted 03 October 2005 - 03:16 AM

I might have some wrong information then. What do people usually use 18% grey cards for?


You don't have wrong information at all, it's that the grey cards were used more for still photography,
while in cinema the photodome incident meters seems to have established.
You see it's much more easier to walk around the actor's path with the photo meter on hand than having someone hold u the grey cards that u will measure with the spot meter from cameras point of view.
This doesn't mean that u can't use the gray card for any reason, it's just more practical this way i guess.
A spot meter is good when u have your subject on a distance, or different areas that reflect different amount of light to your film's frame, that you want to check them for exposure reasons.
For example if you have a window somewhere on your frame and you want to see if the compensation lighting you are using for it is enough or you need some more, or gel the window with ND filters.
18% of a gray card simulates white skin.
The same does the 18% photodome on an incident light meter.
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#5 Stephen Williams

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Posted 03 October 2005 - 04:26 AM

18% of a gray card simulates white skin.
The same does the 18% photodome on an incident light meter.
DImitrios Koukas



Hi,

Normally I would say average Caucasian skin colour is 1 stop over mid grey.

Stephen
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#6 Robert Hughes

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Posted 05 October 2005 - 11:47 PM

The grey card comes in handy at telecine time, allowing the telecine operator to determine a neutral grey tone as a baseline for color and video level adjustments.
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#7 Nate Yolles

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Posted 06 October 2005 - 12:29 AM

The same does the 18% photodome on an incident light meter.
DImitrios Koukas


Actually your light meter is not calibrated to 18% grey.
http://www.bythom.com/graycards.htm
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#8 Dimitrios Koukas

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Posted 06 October 2005 - 04:21 AM

Actually your light meter is not calibrated to 18% grey.
http://www.bythom.com/graycards.htm


Nate,
Very interesting, thank you.I can't totally agree, it's too sophisticated for me, I was satisfied all this years (18yrs) believing that it's similar to 18%, and it didn't affect my work either.
I guess that's why we all happy to overxpose a bit?
Dimitrios Koukas

Hi,

Normally I would say average Caucasian skin colour is 1 stop over mid grey.

Stephen


Yes,
I have to agree here, and thank you for the remark.
Dimitrios Koukas
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#9 Andy Sparaco SOC

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Posted 06 October 2005 - 07:21 AM

Ansel Adams Zone system manual -"the Negative" covers a lot of the info in this discussion.
Visualization in 10 steps of grey Bright to Dark give you a way of evaluating any scene no matter how complex. Valuable in Digital video also.
The Grey Card gives you a standard reference across scenes. A 4X5 Grey card is easy to carry and eliminates guesswork
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Gamma Ray Digital Inc

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