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Quick Question About 1/3 Overexpousre


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#1 anthony derose

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Posted 10 September 2007 - 03:20 PM

So I'm shooting some test, just to play around. I want to overexpose the stock by a 1/3, I'm working with 250D and 200T.

Just to make sure, when I shoot the grey card do I expose at the regular ASA (250) and then overexpose the following shots? And when giving the lab my stock do I tell them to print down?

Thanks
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#2 Jonathan Bowerbank

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Posted 10 September 2007 - 03:41 PM

You shoot the grey card exactly like you'll be shooting the rest of the roll. So you'll want to overexpose the grey card 1/3 and shoot the rest of the roll at the same overexposure level.

This way, you don't have to tell the lab to print down, the colorist will do it automatically after seeing your grey card is overexposed.
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#3 K Borowski

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Posted 13 September 2007 - 02:11 PM

YOu're rating the film at 320D and 250T EIs, respectively, so that entails basically metering at the box speed and then opening the F/stop up 1/3 stop from the meter's reading (i.e, you'd open from F/8 to F 5.6 2/3 which is I think a 7.2 or 6.8 or something). Or you can meter the card at 320 and 250 and then set the F/stop to what the meter tells you. Either way will work, but the method of just manually opening another third stop always has the potential for accidentally underexposing a third, which is a 2/3 stop shift. So just meter using your EIs of 320 and 250 off of the card and then treat the film as if it is the speed you're rating it at.

Regards,

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#4 Jonathan Bowerbank

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Posted 14 September 2007 - 01:08 AM

YOu're rating the film at 320D and 250T EIs, respectively, so that entails basically metering at the box speed and then opening the F/stop up 1/3 stop from the meter's reading (i.e, you'd open from F/8 to F 5.6 2/3 which is I think a 7.2 or 6.8 or something). Or you can meter the card at 320 and 250 and then set the F/stop to what the meter tells you. Either way will work, but the method of just manually opening another third stop always has the potential for accidentally underexposing a third, which is a 2/3 stop shift. So just meter using your EIs of 320 and 250 off of the card and then treat the film as if it is the speed you're rating it at.


I think you're thinking in the wrong direction Karl. Using the ASA's you said, he would actually be underexposing. To overexpose, he would actually rate his exposure at a lower ASA. For the 250D he would rate at 200, and the 200T at 160 ASA.

The purpose of setting your ASA is so you don't have to think about making that extra 1/3 adjustment. If you're shooting with 200T film, rated at 160 ASA, and your meter reads f/4, then you set your lens for f/4 and you're automatically shooting at 1/3 overexposure.
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#5 K Borowski

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Posted 14 September 2007 - 07:25 PM

Sorry Jonathan, I'm thinking bass-ackwards with the EI. *OVER*exposing a third would entail EIs of 200 and 160, respectively.

The EIs were a third in the underexposed direction, but the advice on the F/stop correction is correct.

So see, following my own advice, just set the light meter to the correct settings, 200 and 160, and you won't go a third the wrong way in your head, as I have effectively just demonstrated :blink:

~KB
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#6 Jonathan Bowerbank

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Posted 14 September 2007 - 08:19 PM

No worries, it happens to the best of us

:)
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