BackFocus, different for the Master-Primes ?

[Arthur Reinhart]

Cześć
I just did a visual test on three sets of lenses Master-primes, Ultra-primes and S4s. We had, to change the back-focus for the Master-primes a tiny bit, to get the best performance compared to the Ultra-primes and S4s. It was the same on two different cameras. My question is, do the Master-primes in reality require a bit different back-focus or was the Master-prime set we had a bit off (However the rental company confirmed twice that the lenses where checked and are dead on, and all the wider lenses in the sets performed the same way). Can anybody confirm or comment on this phenomenon, please.

 

[Jacek Zakowicz]

27 and 40mm master primes

27 and 40mm master primes

Cześć
I just did a visual test on three sets of lenses Master-primes, Ultra-primes and S4s. We had, to change the back-focus for the Master-primes a tiny bit, to get the best performance compared to the Ultra-primes and S4s. It was the same on two different cameras. My question is, do the Master-primes in reality require a bit different back-focus or was the Master-prime set we had a bit off (However the rental company confirmed twice that the lenses where checked and are dead on, and all the wider lenses in the sets performed the same way). Can anybody confirm or comment on this phenomenon, please.

Czesc,(nie mam polskich liter)
I'm aware of issues with focusing the 27mm and 40(?)mm MPs.
Have you looked at R3Ds or just visually on monitor?

 

[Arthur Reinhart]

I'm aware of issues with focusing the 27mm and 40(?)mm MPs.
Have you looked at R3Ds or just visually on monitor?

The difference was easily visible on the HD-Monitor. It was off by ca. 40cm on the 3-meter mark on the widest MP lenses.

 

[David (dudi) Namir]

How this can be?
You can't change back focus on a film camera. So what do you do then?
Could it be another optical parameter that these specific lenses have and noticeable with a digital camera?
I also heard the MP have many calibration problems due to their weight.
I prefer Cooke S4, Leica Van Diemen, Angenieux Optimo 17-80 and the new RPP on my Reds.
They all work like a dream.

David Namir

 

[Ernesto Lomeli]

it is a known issue, i know a few rental houses
that either shim the master primes only for RED use.
or they recommend you keep it a master
prime only shoot .

if you are shooting or sharing a set of master primes
with a camera other than the RED your gonna need to make
a hard choice.

some rentals houses need to be told if
you are shooting on the RED to shim the primes
accordingly.

i was told Arri knows of this but,
but not from arri.

 

[Tøt]

different? NO, Just a little more critical

And its no problem to change back focus on a film camera, (shim and 52.. same thing, different name)

 

[Pawel Achtel]

Cześć :001_tongue:

It is a myth.

My master primes came calibrated from Munich and tripple checked here in Australia by Arri. I further confirmed on the MTF machine and they are all within 5 microns. On Red One they are all spot on: measured with (Leica Disto to 3mm accuracy from image plane). The Red Prime 300mm was out by 14 microns on the MTF machine and slightly out on the Red camera.

Yes, they are sharp and fast and therefore most of the time out of focus rrr:

 

[Arthur Reinhart]

Thanks,
I will do more testing next week at Panavision it is confusing me way this is happening on the MPs.
Best

 

[Peter Repich]

Cześć
I just did a visual test on three sets of lenses Master-primes, Ultra-primes and S4s. We had, to change the back-focus for the Master-primes a tiny bit, to get the best performance compared to the Ultra-primes and S4s. It was the same on two different cameras. My question is, do the Master-primes in reality require a bit different back-focus or was the Master-prime set we had a bit off (However the rental company confirmed twice that the lenses where checked and are dead on, and all the wider lenses in the sets performed the same way). Can anybody confirm or comment on this phenomenon, please.

Arthur,

as you may already know, Master Primes are very sharp lense and when set with an appropriate lens collimator, will be dead on. Zeiss factory sets these lenses within 0.00005" without exception. I have checked back focus on several new and used Master Primes and never saw otherwise. If you test the back focus with anything other than a profetional collimator such as Gecko or Chroziel, you are only estimating an approximate BF. The Richter Collimators require an occular adjustment that at best gives you a subjective image. Gecko and Chrosziel are capable of measuring up to 0.000001" if you need to.

I hope this helps.