# Lighting for mixed 500t and 200t ?

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### #1 Jay Young

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Posted 24 November 2015 - 02:42 PM

So the details: I have 7219, rating at asa 320.

I'm lighting to the meter @ asa 320 for a key stop of f8.

I'm shooting through some wonky lenses that loose at least 2/3 a stop (let's say 1 to be safe). That means light hitting the film is around f5.6.

But the film is actually 500t that I'm overexposing, so what's hitting the film is actually 500t @ f4.5? Or so?

I can't find anymore 500t (thanks walking dead), but people have loads of 200T - If I light for 200t @ f8, then loose a stop the math then works out as follows:

asa 320 = f8 on the meter (loose a stop due to lens = f5.6) asa 500 would = f4.5 as we gain the loss from the lens back plus the stock sensitivity. Really, were only talking 2/3's over exposure here.

asa 200 would = 2/3's underexposed meaning I would then need to shoot at f...3.2? to gain the loss back?

I want to intentionally over expose the 500t by 2/3 stop. I want to match this footage with the 200t, but I don't want to relight the scene!

I don't really need to over expose the 200t if I can get away with opening up the lens from f5.6 to f4 or so.

Thoughts? Math is hard.

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### #2 David Mullen ASC

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Posted 24 November 2015 - 04:26 PM

I'm confused just reading the post...

It would simpler to just think of your 500T stock as 320 ASA if that's the average level of density you are aiming for. So if your lens loses a stop of light, you'd open up a stop to compensate, then you are maintaining your 320 ASA rating. So if you meter at f/8 and shoot at f/5.6 to compensate for light loss (though I can't think of a lens that is one stop off in terms of transmission) then are still exposing correctly for 320 ASA.

If you switched the rating back to 500 ASA, you'd stop down by 2/3's of a stop to compensate.

If you switched from a stock rated at 320 ASA to one rated at 200 ASA, you'd have to open up by 2/3's of a stop in the same lighting set-up. So if you were shooting at an f/5.6 at 320 ASA, you'd have to shoot at f/4 and 1/3 for 200 ASA.
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### #3 Jay Young

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Posted 24 November 2015 - 05:14 PM

Thanks David,

I think I was thinking about it too hard.  Sorry for the confusing post!

Yes, all I have to do is think of the stock that's in the camera as 320, and not worry about what it says on the tin.

That's the ticket, 320 and 200 are not that far off, but I'll have to print a test to see if the 200t can be printed at a matching density.

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### #4 Gregg MacPherson

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Posted 24 November 2015 - 07:55 PM

Hey Jay,

Aside from that...these thoughts...

- Small errors can compond to become significant errors.  Just meaning they add up.

- Chase down some data on the T vs f stop for your lenses.  Search the archives.  Pop the question on that...feel lucky.

- Exposure (the light meters) refer to T stops.  Depth of field calculatoions use f stops. (get a Kelly Wheel)

- Rate these T500 vs 200 separately.  Change your meter ASA if you change stock.

- Light meters, at least the old ones, used 1/3 stop increments.  Whatever tool you have,  get used to those increments.

- Be very clear on the common language. David's f/4 and 1/3 should mean 4.3 as some meters may give it,  (1/3 stop closed) or "1/3 down on 4" in old speak.

Cheers,

Gregg.

Edited by Gregg MacPherson, 24 November 2015 - 07:56 PM.

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### #5 David Mullen ASC

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Posted 25 November 2015 - 10:30 AM

The thing is that 500T rated at 320 ASA won't be the same density as 200T rated at 200 ASA, obviously the first will be denser than the second.  But the idea is that by overexposing the 500T, the grain will be tighter and match 200T rated normally better.  If you were making a print, you'd probably notice that the 500T printed down would have a little more snap with deeper blacks because of the high printer light values, but for a video transfer / D.I. you can match black level and contrast.

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