Doubts on swapping mounts... [related to Birger's mount]

[Emanuel A.]

Same than RED method? Or is it a different one?

Is it possible to get it on production field? On set?

How long does it take?

Does it require collimation? After changing mounts in order to return back to PL mount?

 

[Stephen Williams]

Hi Emanuel,

The Berger mount will have to be accurately collimated if you use a zoom lens. (the lens will also need to be collimated). For eye focus only with primes you can 'get away' with small errors assuming you can reach infinity.

Stephen

 

[Gordon Prince]

One-time operation?

 

[Mr. Paul White]

One-time operation?

Interesting doubt..

 

[Mr. Paul White]

Someone has asked something more:

Sorry if this has already been asked, but how easy is the swap between the birger lens mount and pl mount and how long does it typcially take to do?

http://www.reduser.net/forum/showthread.php?p=64904#post64904

 

[Shawn Nelson]

What does 'collimated' mean and how do you do it?

 

[Poi Boy]

The mount changing questions have been around for many threads; unfortunately the red team has not given us any information and we will have to wait and see. Big bummer.
-A

 

[Stephen Williams]

What does 'collimated' mean and how do you do it?

Hi Shawn,

With a film camera it's fairly simply as only a depth gauge & a flat piece of steel are required to collimate the mount. Just slightly adjusting the tightness of the screws can be enough to correct small errors.
With Red an autocollimator will tell you if its approximately correct, what it won't tell you is that the mount is out by say 5 microns at the top 8 microns right/left & 12 microns at the bottom. There will be lots of trial and error for people without the correct tools.

Instructions to build an autocollimator http://www.geocities.com/leafshooter/collimator.htm

Stephen

 

[Mr. Paul White]

How much can it cost? Where can I find one?

Easy operation?

 

[PaulClements]

I find the whole mount changing problem mind boggling. Why some kind of locking mechanism can't be produced that is exact and precise is very very odd. We can make a sensor the size of the tip of your finger that has 10 million pixels on it but we can't make something that is easily swappable without the need for collimation, weird.

 

[Stephen Williams]

I find the whole mount changing problem mind boggling. Why some kind of locking mechanism can't be produced that is exact and precise is very very odd. We can make a sensor the size of the tip of your finger that has 10 million pixels on it but we can't make something that is easily swappable without the need for collimation, weird.

Hi Paul,

Not really, just depends how you define 'exact & precise'. The lens mount has to be parallel with the sensor, so you already have 2 variables to start with.If the widest lens people used was a 25mm @ f 5.6 you would not have to worry so much.

Stephen

 

[Don King]

How much can it cost? Where can I find one?

Easy operation?

Here are good questions asking your answer Mr. Williams.

 

[chuck colburn]

Hi Paul,

Not really, just depends how you define 'exact & precise'. The lens mount has to be parallel with the sensor, so you already have 2 variables to start with.If the widest lens people used was a 25mm @ f 5.6 you would not have to worry so much.

Stephen

Hello Stephen,

You can check for parallelism by having an optical flat (window) that sits in the lens seat portion of the lens mount. When the parallel rays of the auto collimator bounce back to the eyepiece of the collimator the two images of the sensor and the optical flat should over lay each other. This is a very sensitive and revealing test as even a small error in parallelism shows of very quickly.

Chuck

 

[Stephen Williams]

Here are good questions asking your answer Mr. Williams.

Hi Don,

This website was not working earlier today so I could not answer
http://www.chamblesscineequip.com/catalog/richter_kollimator.htm

A guy used to make a pocket one that he sold on Ebay for $175, he retired before I managed to by one.

I would recommend asking the tech at your local rental house to change the mounts for you, it should be a 15 minute job so should not be expensive, if you plan to rent PL mounted lenses then they will probably do it free.

If you are using still camera lenses they will also need to be collimated, this will probably take 30-60 minutes (per lens) the first time as the mount may need to be ground down, adding shims is quicker! (15 minutes) Lenses should be checked on a regular basis, (30 seconds to check) usually they will only need adjusting after dropping or rough use.

Stephen

 

[Emanuel A.]

Thanks once again for your help, Stephen. BTW, can we handle the task by ourselves after an initial learning?

Is it easy to get it alone later?

Take care,
Emanuel

 

[Stephen Williams]

Thanks once again for your help, Stephen. BTW, can we handle the task by ourselves after an initial learning?

Is it easy to get it alone later?

Take care,
Emanuel

Hi Emanuel,

Testing is easy, adjusting more complex but possible. Not worth learning if you live near a friendly tech!

Stephen

 

[Emanuel & Co]

Hello Mr. Williams,


I believe Emanuel has in mind to buy one of these devices. Is it necessary any further accessory beyond the autocollimator?


Why auto? Any advantage?


Cris

 

[Shawn Nelson]

Stephen, that's a good description of how to do it, but what is it (what problem are you fixing?) and why do you need to do it?

 

[Stephen Williams]

Stephen, that's a good description of how to do it, but what is it (what problem are you fixing?) and why do you need to do it?

Hi Shawn,

PL lenses focus the image @52.00mm from the PL Mount (Flange Focal Distance), unlike swapable video lenses there is no back focus adjustment. It is therefore vital that:-
1) The mount is exactly 52.00mm (film cameras may set to 51.975 +/- 0.005 so that the focus falls inside the film. Each manufacture will quote a FFD for a specific camera) The exact distance for Red is at this time not known.
2) The lens must focus at @ 52.00mm when set to infinity.

When cameras & lenses are so adjusted any camera & any lens combination can be used. Therefore you can rent a lens and be sure that the focus points marked on the lens will be correct when used with your camera.

Stephen

 

[Martin Drew]

This issue has been discussed loads in the past, both here and before on dvxuser. It should be noted the no one from Red has chimed in on any of these discussions, that usually means that they are not ready to talk about it... Interesting. With that in mind at this stage I think it might be better to wait for the LART results rather than guess what is required when swapping mounts on the RedOne.

M