what is the IRE equivalent for a 18% gray card?

[odedbinnun]

Hi there,
I would like to calibrate my light meter to be in correlation with the camera's spot meter.
for doing that I am going to direct the spot meter of the camera on a 18% grey card, and then change the f-stop until the "right" IRE . but what is the right ire for a 18% grey card? is it half of 108?

is the spot meter of the camera represents the raw footage or only the conversion of it?

also, in false color mode, why is there a difference between the 18% and the skin-tone? I always thought that 18% is the right exposure for an average skin tone

and if I may, just another thing, regarding the zebra, one would expect that the best way to use it would be to put it on 108 and then you know exactly how to avoid white clip and still use all the dynamic range. so why or when would I want to put it on 90?


thank you very much,
Oded binnun
www.odedbinnun.com

 

[bobbystone]

Skin tone

Skin tone

The 18% Gray card is the the standard which light meters recognize. Average Skin tone is considered to read 1 stop brighter than an 18% Gray Card (with an reflected reading) If you were to take a reading on an "average" face with a spot meter and got an f 5.6, you would then open the lens by one stop to an f4 for a proper exposure.

 

[Anders Yarbrough]

just send your meter into quality light metric, 323-467-2265. It's a small fee for a accurate meter.

Oh, and fyi....the one stop whiter than 18% grey is average Caucasian skin tone.

 

[odedbinnun]

thanks a lot for the info regarding the right exposure for skin-tone, but what about the IRE? can you please tell me what should be the right IRE when measuring an 18% gray card with the camera's spot meter?

Now that I think of it , I can probably use the "false-color" view and see that the grey card shows green.... Hmmmm maybe that shall do it, except that the green area is not as accurate as the IRE

 

[donatello b]

based on observations ... i've seen persons with film background set 18% grey card mostly around 42-44ire .. while video background persons i've seen set between 46-48 ire ...
AND i've seen my 2k film scans come in around 34-36 ire ....

for all builds up to 15 i have used a light meter and do use the Red spot IRE meter to check blacks & highlights - haven't used it to check a grey card ...
not sure the method i'll use with build 16 ?