On Set and Need Help Calibrating Brevis

A

Avenger007

Well-known member
Hello all,

I am between setups on location and trying to calibrate this Brevis but it seems either the unit simply won't adjust to what I need or I am not properly setting it up. This is the 2nd shoot I have received a Brevis and I am still not happy with the results from the last one. I can't access instructions (other than a few simple videos from google) because non-owners don't have passwords to the site.

The corners are soft and the focus just isn't tack sharp. Also the lens barrel markings are off still.

Is there a more efficient way to adjust collimation and GG focus?

Here was my process -

Entire system already cleaned part by part. Fully Charged
Brevis fully slipped onto Macro and Aligned using 90% guides in camera.
Did best to tighten 4 screws in order of aligning the GG frame in center.
Attached my Prime and stopped down fully to see GG. Set HVX to F2.4
Focused to GG (or at least what appeared to be sharp overall). Settings were Z73 and F09.
Is the focus enhance good for this application or does it affect results?

Then I measured 1 foot from what I guessed was the location of the GG to a text chart in front of camera.
Loosened 4 front screws on Brevis and adjusted lens mount until chart appeared in focus at 1 foot on the Lens barrel.

I still can't tell if I can truly trust the barrel markings. What is the actual location of the ground glass as well. Is it exactly in the center of the Brevis?
And what is optimal F-stop to set the HVX? I have mainly stayed at 2.4/2.8

Here is the complete setup:
HVX, Brevis (non-flip), Zeiss Planar Primes, Marshall HD monitor

btw does anyone have a PDF or tiff of a resolution chart? I can get to a Kinkos by call time and get it blown up. That would be major help. Thanks for any tips.
 
I like to keep my camera in the f/4.8-5.6 range if possible.

To set the back focus of the 35mm lenses I set it to infinity and then point it out a window and adjust the mount until it is tack sharp. Be careful because it is easy for the mount to become not perfectly perpendicular to the GG and a good part of your image might be slightly soft.
 
According to cinevate, the GG is 33.6 mm back from the front edge of the Brevis (not the lens mount flange). PM me your email and I'll send you some resolution charts
 
I can send charts also but you need to post an email address.


William is right about the back focus though you really should focus on something very far away 300 yards if you can. The moon might be good.
Using a 1' mark sounds very very dicey.

When you get the resolution charts go to Kinkos - blow up to 3 or 4 ' wide and tape or clip to a piece of foam core.

Focus enhance is OK but you really should use a decent monitor and focus so that you get your corners good also, just at the far end of your good center focus. Video camera should be wide open when setting focus on GG.
35mm lens should be wide open when setting Nikon lens back- focus.
Do you have the flip - that seems very flat corner to corner.

2.4 - 2.8 is good but I have shot at wide open many times.



Lenny Levy
 
Av, set yourself up at our forum using your real name and pm me here. We can have you set up in about 10 seconds. Alternatively call us at 647 723 2664 during the day.
 
Thanks all for the input and Dennis thanks for the information. I will send you my info when I get back home. We are getting some great footage with my zeiss primes and I look forward to seeing the brevis in its truest form. It has become a regular around here alongside our numerous M2 adapters.
 
You must log in or register to reply here.
Back
Top