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Slight crisis developing... my 2-perf Cameflex will not focus.


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#1 Zachary Vex

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Posted 21 November 2008 - 01:57 AM

Mind if I scream?

We did a test using a couple of Nikon primes and a zoom, and everything seemed a bit soft. The film was scanned on an Arriscan and I wasn't sure if it was operator error, so I went back to the studio and started studying through the eyepiece. What I noticed is that using the Nikon mount and a 14mm lens, objects 1 foot away had to be adjusted to .5 meters in order to appear in focus. As a second test, I stuck a piece of vellum over the gate and taped it tight, observing the focus at the gate using a 12X loupe, and sure ehough, exactly the same problem. The camera simply won't focus properly on anything distant, and objects nearby require a much more distant setting than should be required. I have a spare Cameflex body I've scavenged for parts and I tried the turret from that one (quite an ordeal to remove the original and replace it, but I did it, and I had exactly the same results, even though the other body worked great with its own turret, rolling easily through focus on far to near objects.

I know that George at Optical Electro House works on Cameflex cameras, but I'm wondering if anyone can point me to someone who specializes in solving problems of this kind? I'm really under the gun, unfortunately.
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#2 Chris Keth

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Posted 21 November 2008 - 02:32 AM

Your flange focal depth is off. It's a pretty simple adjustment for someone who has the proper tools: a depth gauge and whatever your camera takes to adjust the mount.
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#3 Zachary Vex

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Posted 21 November 2008 - 05:08 AM

With these symptoms, will the mount likely need to be moved away from or toward the film?
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#4 Tim Carroll

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Posted 21 November 2008 - 07:14 AM

Zachary,

Yeah, sounds like your Nikon mount is not in the right plane. I am not familiar with the Cameflex cameras. You mention a Nikon mount, and then a turret (which is usually two or three mounts). Has your camera been modified for the Nikon mount? If so, and the image in the viewfinder is off, and the image you projected in the gate (with the velum) is off, then the Nikon mount sounds like it is in the wrong plane.

It is two separate issues, your Flange Focal Distance is off, and your ground glass is off. Using a 14mm lens would make the issue much more noticeable, as the depth of focus for wide angle lenses is pretty shallow. Definitely need to have a camera tech look at it and set in back to spec. Just make sure the tech does the FFD and the ground glass both.

You can see a short description of FFD and Ground Glass at the link below.

Service Issues on Arriflex Cameras

Best,
-Tim
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#5 Adam Frisch FSF

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Posted 21 November 2008 - 08:09 AM

Your mount needs to get shimmed forward.
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#6 Stephen Williams

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Posted 21 November 2008 - 08:39 AM

Your mount needs to get shimmed forward.


Hi Adam,

As he can't get distance in focus is would seem to be too far forward already.

Stephen
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#7 Tim Carroll

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Posted 21 November 2008 - 09:35 AM

I agree with Stephen. If you can't reach infinity, the FFD is too long. If it reaches infinity and then goes past it, the FFD is too short.

Think of it this way. If the lens is properly collimated, which for this discussion I will assume that it is, and it is set to infinity, then the lens has reached infinity and is projecting a "sharp infinity image" toward the film plane. Our goal is to make sure that "sharp infinity image" falls right on the film plane. Take your lens and focus from the close end of the range out to infinity. As you watch the image on the film plane, if you never get a "sharp infinity image" as you focus the lens to infinity, then the "sharp infinity image" is falling somewhere in front of the film plane and the FFD is too long.

If, on the other hand, as you are focusing this same collimated lens from close to infinity, and the "sharp infinity image" comes in clear and sharp on the film plane before the lens has reached it's infinity setting, and when the lens reaches infinity the image on the film plane is soft, then the "sharp infinity image" has passed through the film plane and is falling somewhere behind the film plane and the FFD is too short.

Best,
-Tim
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#8 Paul Bruening

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Posted 21 November 2008 - 11:24 AM

http://www.visualpro...UsPersonnel.asp

I tend to talk to Paul. But, that's because I often have insane-in-the-membrane, modification questions. All these guys know their stuff, though. Measuring tools are good for setting FFD, but getting the whole system collimated is better

I guess the first thing we should ask is where are you located?

Another issue that I've had with my Nikon board is focal keystoning. When I bought the camera, the board was shimmed with a piece of wratten gel some guy had cut to fit. Pretty sloppy. Depending on how many screws you have holding the board to the body you can end up with a flange plane out of square with the film plane. Just another thing to throw in to make it more worry. Sorry.
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#9 Zachary Vex

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Posted 21 November 2008 - 04:12 PM

I'm in Minneapolis.
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#10 Evan Pierre

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Posted 22 November 2008 - 03:43 AM

Using a 14mm lens would make the issue much more noticeable, as the depth of focus for wide angle lenses is pretty shallow.


Sorry if this is off topic, but I thought that the wider the lens the deeper the DOF?
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#11 Tim Carroll

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Posted 22 November 2008 - 08:01 AM

Sorry if this is off topic, but I thought that the wider the lens the deeper the DOF?


The wider the lens the greater the depth of field, the shallower the depth of focus.

Best,
-Tim
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#12 Adam Frisch FSF

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Posted 22 November 2008 - 11:20 AM

Yes, I misread. It should be moved backwards if it can't reach infinity.

Basically the rule is - if nothing is focusable, the mount sits too far back. If stuff is focusable, but you can't reach infinity then it sits too far forward.
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#13 Zachary Vex

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Posted 23 November 2008 - 05:27 AM

I contacted Visual Products, and Paul is headed out on vacation for the next week, so now the camera is headed to George at Optical Electro House.
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#14 Dan Goulder

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Posted 23 November 2008 - 09:49 AM

Mind if I scream?

We did a test using a couple of Nikon primes and a zoom, and everything seemed a bit soft. The film was scanned on an Arriscan and I wasn't sure if it was operator error, so I went back to the studio and started studying through the eyepiece.

Advice for the future: Make sure the footage is master quality before springing for an Arriscan.
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#15 Zachary Vex

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Posted 23 November 2008 - 12:54 PM

Advice for the future: Make sure the footage is master quality before springing for an Arriscan.


You make a lot of assumptions. 8^)
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#16 Stephen Williams

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Posted 23 November 2008 - 01:12 PM

You make a lot of assumptions. 8^)


Hi,

No, he just read your first post.

Stephen
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#17 Zachary Vex

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Posted 23 November 2008 - 03:02 PM

Hi,

No, he just read your first post.

Stephen


Like I said, he made assumptions. He assumed that I didn't examine the film before the arriscan. I did, under a 100 power microscope, and the camera operator, director and myself could not decide whether the focus was soft or not, based on the 35mm lens test. After we did the scan, it was apparent that the focus was not quite even across the frame. I then went back and started looking through the camera with shorter lenses (although we did not intend to use shorter lenses on the project) and discovered the more serious focus problems I posted about.

The reason the scan was done was to determine if the transfer facility could do standard transfers of 2-perf for dailies and the scan test came up when we began to question what was going on with the focus. The whole thing was a test. There was no "master quality" negative involved... there was nothing but footage to be examined for a work-flow test. The test had many purposes... to determine if the camera was working properly, the magazines were working properly, the dailies could be generated at a reasonable cost, and if we could keep track of frame numbers in a manageable way.

It's insulting to suggest that anyone is "springing" for something without being responsible. I've never suggested any such thing in any post. That was another assumption on his part. I find this forum to have a number of posters who are quick to confrontation, usually as a result of bad assumptions. As a result, I generally avoid it. I posted about this issue because it was rapidly becoming an emergency, and I thank those that helped me out.
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#18 Christian Appelt

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Posted 23 November 2008 - 03:23 PM

Another suggestion:
Shoot a few feet of simple test patterns (Siemens stars will do), take your 2-perf negative, make up a short loop and watch in in a movie theatre. Much better to spot back focus or pressure plate problems on a huge screen, 4-perf will work fine because you are not concerned with motion but only with your test pattern. That's what I do when I use vintage equipment for commercial jobs.
Just my $0.02... ;)
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#19 Zachary Vex

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Posted 23 November 2008 - 04:08 PM

I'll do that with my next test. Perfect use for my 35mm projector. Some of the problems with using a microscope are that you can't see the whole frame at once and you can't see what happens frame-to-frame.

Edited by Zachary Vex, 23 November 2008 - 04:09 PM.

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#20 Zachary Vex

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Posted 24 November 2008 - 11:49 PM

Update on this Cameflex issue:

Ack! Some of you may remember when I snagged that Techniscope camera from eBay a couple of years ago. I received more than one PM requesting to purchase it if it was for sale again. It turns out my worst fear is true... the turret was damaged, bent, so that two of the three mounts are out of spec. That's probably why the seller was so anxious to get rid of it. It appears that the turret was open when the camera was dropped onto a very hard surface. I have a spare turret from another Cameflex, but it has focus problems too because it's set for a different depth (they were all hand-made, and like snowflakes, are all different.)

Sigh. So now Bob at Optical Electro House is getting an estimate for having it machined back into tolerance. What a bummer!

Looks like we're shooting on a Red instead. Trying to scare one up (someone who owns one owes the producer a favor.)

Drat. I really wanted to shoot this on 2-perf.

We built a circular set (not yet complete) for 360 degree shooting using an old 50's crane from Paramount Pictures. We're going to wallpaper the set and hang pictures with green screen inserts for later animation, and rotate the talent 360 degrees while he's sitting on that chair (it will be dyed to a subdued color), probably for a total of 6 full rotations during the song. Grips will run behind where he's just been and update the set so the next time around it looks different... things will also drift into frame from the ceiling (falling leaves, snow) and there's a window in one spot around the circle that will have different things appear behind it (fireflies, moonbeams) until the talent eventually exits out the window and enters a live performance segment. The whole circular room shot will have no edits.

There's a counterweight at the back of the crane that balances the whole thing perfectly. It will ultimately have about 750 pounds of lead and fine-tuning 20 lb shot bags in it to balance two people (camera operator and talent) plus the chair, table, 32" HD monitor and lights at the other end. The crane can effortlessly be lifted up and down about 8 feet (we'll only be moving around 4) in addition to spinning endlessly on its axis. It's a magnificent old machine that's been obviated by modern jibs with x-y controllers, but you can't fly talent on a jib arm!

Posted Image

The operator can turn that crank on the left side of his seat to rotate the talent (and himself) around the camera risers, which are fixed to the crane. This way he can change the perspective and look straight out the window as he passes it. A wheeled couch will carry the rest of the band along, dragged by the crane next to the singer for a portion of the video.

Posted Image
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