500T Question

[Ryan Ball]

I'm shooting some Vision 2 500T with a camera notched for 250 ASA. How much do I stop down while using the intenal meter? I'll be running and gunning and won't be able to meter each shot externally.

[Michael Lehnert]

If your camera reads the inserted ISO 500 cartridge as ISO 250, then the compensation would be exactly one f-stop.

 

You see: every doubling or halfing of a given ISO or rather EI value corresponds to one f-stop plus or minus: 500 - 250 - 125 = 2 f-stops difference. Or: 400 - 200 - 100 - 50 = 3 f-stops difference. Or 160 - 100 = 2/3 f-stop difference.

 

-Michael

[Jim Carlile]

Well, it depends upon how the film is cartridged and notched.

 

If it's Kodak's 500T negative, they speed-notch it at 400T/250D (?-- forgot the specific daylight of that speed indice-- it's about 2/3 stop below ASA 400.) And they supply it in a notchless cartridge.

 

So, if your camera will read up to ASA 250, it will think the film is ASA 250, not 400 or 500. But-- and this is important-- the notchless cartridge will set the meter to the 'low' ASA of that speed indice-- which is ASA 160.

 

Every speed-indice has two ASAs associated with it- a high and a low, or a tungsten and a daylight, 2/3 of a stop apart (the same as the factor for an 85 conversion filter.)

 

So this ASA 500 film will be read at ASA 160-- which is about 1 2/3 stops overexposed. Too much.

 

Kodak's intent is to speed notch the film at ASA 400, and then use the daylight notchless cartridge to kick it down to about ASA 250-- one whole stop, the way they like it. But that only works for cameras that will read the ASA 400T speed-indice. Everything else will be way off.

 

Solution? Either manually meter, or cut a notch for the filter pin. Then the daylight film-speed triggering will be disabled, and the film will be read at ASA 250T. You can then even use the internal 85 filter if you want to, for this tungsten film.

 

Not sure how other companies notch their negative stocks.....

[Art Leal]

Not sure how other companies notch their negative stocks.....

 

 

Here are a few from Pro8mm

 

Fuji 500T and the Fuji 500D

[Jim Carlile]

Well, the 500D is in a notchless cartridge, and the 500T is notched, so in SMPTE-compliant cameras they will be read different from each other.

 

I can't tell the speed-notch indice-- I suspect it's 400T-- the max for most cameras, and not 640, which as far as I know can only be read on the Nizo sound cameras. So that means the 500T will be read at the straight ASA 400 in cameras that go that far, while the 500D will be read at the low ASA of the 400T speed-notch size, which is ASA 250.

 

But--- for the ASA 250-max camera-- which only reads to ASA 250T, the 500T will be read at ASA 250, the 500D at ASA 160-- it thinks it's ASA 250T, then knocks it down 2/3 stop with that notchless cartridge, to the daylight ASA of the 250 speed-indice, which is 160.

 

Which means-- if you want exact ASA 250, you're better off with 500T. 500D will read at ASA 160-- which is only 2/3 stop overexposed.

 

BTW, even if those films are notched for ASA 640, a camera that only goes as high as ASA 250T will still read them at ASA 250T.

 

Here's the notch-size specs:

 

http://www.kodak.com/global/en/service/faqs/faq2107.shtml

[Jim Carlile]

P.S.

 

BTW, that Kodak chart is great for the notch sizes, but lousy for correct info on VISION 200T notching and ASA speed reading-- it's inaccurate.

 

VISION 200T is speed-notched for ASA 160-- like it says-- but it is supplied in a notchless cartridge, which means it is read at the low ASA of the 160 speed-notch size, which is ASA 100. That's not just 1/3 stop overexposed, it's one-full stop.

 

Kodak likes it that way-- but their info here is wrong.