OK.. sorry for delay.. heres my cooke 25-250 v zeiss zf test

[Antoine Fabi]

Hi,

Cooke measure & mark each lens individually T4 is really T4.

Hi Stephen,

...then, if so, based on this test, Zeiss are conservative
...ie indicated T4 = real T3.8 or something

In this test, the Zeiss definitively lets more light go in.

Antoine

 

[Zakaree Sandberg]

In my findings.. the cooke just has better black representation...
the blacks are rich.

The lenses were all def set at t4..

 

[Antoine Fabi]

Yep, the blacks are richer, but also... the midtones and highlights are brighter with the Zeiss

Antoine

 

[Stephen Williams]

Hi Stephen,

...then, if so, based on this test, Zeiss are conservative
...ie indicated T4 = real T3.8 or something

In this test, the Zeiss definitively lets more light go in.

Antoine

You would need to test the lens in question, guessing won't help however I suspect the focal length of the lens in question may be off by upto 8% (quite possible) from what is written on the barrel. That in itself would cause an error of about what we are seeing.
Using standard scales for focus (8 I believe for Zeiss) is less accurate than testing the actual lens in question & adding marks.

The Zeiss lenses may be more telecentric than the Cooke, thats more important for digital but not an issue for film

Interestingly the field of view is always different, that can be accounted for by the front nodel point of the Cooke is probably 10 inches in front of the Zeiss, moving the camera backwards 10 inches would fix the problem & the DOF would then be close (F/Tstops difference), in every shot the DOF is more with the prime lens however the image size is always smaller.

 

[Federico Rizzo]

Cooke 20-100 T 3.1 and Zeiss zf 100 T 2

Cooke 20-100 T 3.1 and Zeiss zf 100 T 2

Could you compare Cooke 20-100 T 3.1 and Zeiss zf 100mm T2 ? Which is the sharpest?

 

[Zakaree Sandberg]

off the bat zeiss...

the old cooke zooms are not known for their sharpness.. but rather color, low contrast, and creamy cooke look.