[Konvas] foton zoom ....

[colcam at aim.com]

 Okay, don't feel lost-- I had five of them on a test fixture and T4.8 at 4800k became T4.3 at 2800k

I redid the test a couple of times and then did some other lenses and did it again before I swallowed the test results. 

And I guess the effect was the same way that an 85 filter lowers the light coming through by blocking some of the spectrum, but at that time I just wanted measured T-stops because I'm a fanatic and was paranoid about matching variable focal length lenses with primes for delivered exposure.

The Angeneiux 20-120 f2.8 (t3.4) I tested was the joker in the deck.  It measured out as t2.7 to t2.9 during the tests, depending on focal length. 

It was in Arri B, and I was going to have it converted to PL for the BL3, but the tech called me and said he had someone who really wanted it as-is, and named an amount I could not refuse.  Ten years later and I've yet to see another one for sale.

 


 

 

-----Original Message-----
From: Adam Frey <thefirstrule at chainsawlinux.com> 


colcam at aim.com wrote: 
> and is actually a higher T stop under 2800k and lower temp lighting 
> than under 4800-5600k. 
 
Could this be because of the warmer aspect of the lens? At 2800k, would the warmth of the lens virtually darken a portion of the light spectrum, seemingly making the T stop greater? Like shooting B&W with a red filter - clouds become bolder and more menacing, but the clear part of the sky remains the same (assuming you've adjusted exposure for the light loss of the filter). 
 
Hmmm, I know what I'm trying to say, but it's not coming out quite right... 
 
Cheers, 
 
Adam Frey