Angenieux 9.5-95 Rx c-mount

[Kurt Collins]

I have a c-mount 9.5-95 zoom and it has 2 sets of stops that differ. One set is in red one set is in white. 
 

what do I need to set the lens to after I meter. I always split the difference because I’m not sure which is correct. 
 

Like right know I’m metering 200 film stock at 24 fps and 144 angle and getting a 3.6. So I’m setting the red numbers to 4 and the white numbers read a little past 2.8 (see photos) 

I’ve shot a million times with it and have never had an issue splitting the difference. I just want to know what the 2 sets of numbers are for.

for reference: the white number have stops— 2.2, 2.8, 4, 5.6, 8, 11, 16, 22

 

red numbers have stops—

3, 4, 5.6, 8, 11, 16, 22

My thought is the red numbers are if you’re using it on a  non-reflex camera?? Idk? Help. lol. 

 

 

 

[Brian Drysdale]

The red numbers are transmission stops. On the 9.5 to 95 zoom you really need them because at f2.2 the transmission stop is T2.8 on a reflex camera, if you've got T3 I assume that's to cover the built in reflex viewfinder that attached to the lens.

[Kurt Collins]

It’s an RX lens on an RX bolex. Theres no viewfinder on the lens. 

[Dom Jaeger]

The white numbers are f stops - geometric aperture - which you would use to estimate depth of field.

The red numbers are T stops - transmission stops - which are a measure of the actual amount of light getting through the lens. Use these for exposure. 

T stops help you expose more accurately, because every lens loses light internally through reflections and scattering, a zoom even more so because it has more elements. Your zoom loses almost a full stop of light, so at f/2.2 the transmitted light is the equivalent of f/3. 
 

The T stops on the zoom are not compensating for the light lost to the reflex prism, so you need to open up another 1/3 stop to compensate for that, or use the “adapted” exposure times listed in the manual. 

[Kurt Collins]

I set my meter to 144 degrees instead of 180 which is effectively compensating that 1/3 yeah?  

[Kurt Collins]

Also thanks for the info. Very good to know for sure now where to put the lens. 

[Dom Jaeger]

9 hours ago, Kurt Collins said:

I set my meter to 144 degrees instead of 180 which is effectively compensating that 1/3 yeah?  

Well that’s only compensating for the shutter angle, not the prism. 

You can meter a couple of ways - either use the adapted exposure times listed in the manual (1/80 sec at 24fps) or if using a meter that goes off frame rate and assumes a 180 degree shutter angle then you need to compensate 1/3 stop for the difference in shutter angle (144 instead of 180) and another 1/3 stop for the prism light loss.