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Pulling focus on a Panasonic DVX-100...

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#1 Frederic Chamberland

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Posted 03 October 2004 - 06:17 PM


Looked around for something on the subject but could not relate to my last night's experience. First time I was flying the DVX 100 (in the weight cage) with my Scorpio attached to it and a dented wheel attached to the rubber focus ring on the DV.
If you have worked with the DVX, you know the focus wheel is infinite and focus is digitally transmitted to the camera when turning the knob.
We attached the motor and calibrated the motor manually to both ends (infinite and minimum). We then took a measuring tape and eye focused to give the assistant a couple of references (2 ft, 3,4,5,6,8,10) .
Then hell begun for him, Every time we would do anything to the camera (change batterie, putting on VCR mode for playback, going too fast on the focus,even zooming in or out...), the "digital" knob was resetting itself in another space dimension.
The motor was not skipping the gears , everything remained the same on the Scorpio, the in and outs were fine, but the digital scale of the focus (speed and precision) was always shifting . We tried different formulas to get by this but abandonned and rechecked every freaking mark before every take .

Did anyone encounter such a hassle? Focus was critical at some points in the shot and putting it on AUTO focus was not an option.

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#2 Kelsey W. Smith

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Posted 03 October 2004 - 07:25 PM

Hey Seadifred

I am assuming from your post you were using a focus ring attachment on your DVX-100. There are 2 available that I know of, one from Abel Cine $350USD and one from Cadvision (BC) for $100USD. No question that the one from Abel Cine is a nicer metal gear but it's not worth the extra $$. I bought one from Cadvision, it's plastic, but it works great! I have the DVX-100A so I petty sure that it's the same as the 100. Once you set the in and out points on the lens and engage the motor, it should stay even if you power off or change batteries on the camera. On a couple of occasions the lens didn't correspond with the transmitter but it was an easy fix. All we had to do was set the lens to infinity and then set the transmitter to infinity, engage and all was good. It might have been a problem with the camera, seems a little strange to me.

I see a lot of people are using cages for DV cams. I went and bought a 4"X12" (approx. 12lbs) steel plate, drilled the appropriate holes, attach DVCAM..........works like a charm!

Any who, hope all is well is Montreal!

Kelsey W.
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#3 RobVanGelder


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Posted 03 October 2004 - 07:48 PM

One thing to check for sure is the backfocus from the lens. Not all (if any?) consumer lenses are made with such precision that you can zoom in, focus and zoom out while staying in focus the whole time.
Normally the autofocus would handle that, is what the manufacturer beliefs.
I think that the Canon XL-1 with the 16x zoomlens has this problem too.

But as you discribed it, it sounds like a reset everytime in which case it is not really solvable.

Just thought about something, which is why I edit this post:

BECAUSE the focus ring is infinite in its movement, towards infinity as well as close-focus, it might be very tricky to determine the exact point where the focus-movement of the real lens stops. You can easily pass that moment by turning the ring a bit further and thereby expanding the scale of the follow focus. This would be different every setup, but imagine you get it right, you might try to focus to infinity before doing anything to the camera and see if that position is saved when powering up again.
Having said that, I remember that my minolta camera always parked around 5 ft before switching off, so it could be just any point that the manufacturer has decided.
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#4 Lawrence Karman

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Posted 03 October 2004 - 09:13 PM

Check this web site for a chart on converting the numbers on the screen to actual footage distance. While I have never used this camera this chart may make it easier to set your motor.

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#5 Mitch Gross

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Posted 04 October 2004 - 12:22 AM

That chart is a great aide and I know many people laminate it for reference. Btw, it's CAVISION, not cadvision. The nicer gear ring available from Abel is made by Century Precision Optics and it has the advantage of also having a white ring to allow for visible marks on the lens. Not that they'll remain accurate, but there's a lever which allows you to disengage the ring and reset the position relative to the gear so that the marks are again accurate.

The trick is simply not to shut off the camera or even let it drop out of standby mode. Somewhere in the menus there's a setting for disabling the auto shutoff in standby, which otherwise usually kills the power after 5 minutes. Should the camera need to be shutoff (or put into VTR mode or whatever), simply set the lens to infinity (99 on the viewfinder focus scale) and reset the focus gear to this position.
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#6 Larry McConkey

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Posted 04 October 2004 - 06:00 AM

I bought the Century version sold by Abel and found that it limited the travel of my DVX 100A to about 5 feet on the close side, whereas the actual lens travels to less than 2 feet (if memory serves me correctly). The lever mentioned causes a pin to drop into a machined slot in the gear thereby limiting the lens travel. I just machined the slot longer and now get the entire lens focus travel. I have not found that memory of focus position is lost when powering down, but I'm not sure about battery changes and mine isn't here. Maybe there is a difference in the A model?

BTW, I also got the Chroziel Mattebox system and external focus knob which I calibrated. The marks are still exactly accurate almost one year later so there is absolute repeatability. I only remember having to sync up the Century lockout ring a few times, so again, either you were just slightly exceeding the electronic travel of the lens occasionally, or maybe there is a problem with the 100 which was fixed in the 100A??

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#7 Charles Papert

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Posted 04 October 2004 - 09:36 AM

Somewhat off-topic, but if anyone is planning a Mini35 shoot with their DVX-100's, I own the Mini35 setup for that camera and do rent it to trustworthy individuals (you supply the PL lenses though). Fantastic looking images.
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