Eli Aronoff

I actually do keep the clip on matte box as loose as possible, like you said, but still having this problem. I'll see if I can replace the lenses that I have trouble with and maybe have some luck with that.

It's actually several lenses (35mm, 40mm, 100mm). I'm using the super strong DM1X motor so I shoulnd't have any problems. My 50mm is good, although I do agree that 50mm's are usually the stiffer lenses.. My lenses aren't that stiff, thats one of the qualities I look for in a lens at the camera check out. Also the lenses are calabrating just fine. the freezing happens in the middle of the shot when the focus is static for 5-10 seconds. Then when I have to adjust it freezes. This doesn't happen every time but enough that it's a problem. Preston says that it's the safety feature in the MDR that stops the motor if it draws a certain amount of amps to move a stiff lens. This is to prevent the motor from burning out. The only thing is that my Preston has worked just fine with these same lenses for months even in the bitter cold weather, and all of the sudden now I am experiencing this problem on a regular basis even in a warm studio. I'm not doing anything out of the ordinary. Preston is going to adjust the limit on that safety feature a little bit to give me a little more leeway. Maybe that'll do the trick.

it actually happens with a dm1x!! I'm able to calebrate fine but in the middle of the shot when the focus doesn't have to move for about 10 seconds it freezes sometimes on some of the lenses.

I've been going through the same thing with my Preston. What kind of lenses have you been using? I've been using Panavision Primo lenses with a clip on matte box (which stiffens the lens a little bit). The cold adds even more stiffness. I've used my Preston before in these conditions in the past succesfully. It is much slower/sluggish and I had to assist the calabration process by twisting the focus along with the motor. But at least it worked! But now even when I'm not in the cold some of my lenses make the motor jam up. And I'm using the very powerful DM1x. The MDR firmware has a safety feature that is meant to protect the motor from burning out. In doing so, it shuts down your MDR and Motor if the motor needs to use too much power to move a particularly stiff lens. I'm in the process of altering the tolarence of that safety feature to give me more leeway for moving these stiffer lenses without it shutting down or freezing up. I'll find out next week.

I've had my Preston remote focus system for over a year. It's been getting a lot of use on the TV show that I am a focus puller on. I use Panavision Primo lenses. I use a "clip on" matte box for steadicam and hand held shots (because it's lighter); and a "studio" matte box when the camera is on a dolly or remote head. This is common practice for most AC's. For the past couple of months the Preston motor began to "feeze" or "jam up" at randem times when I am using the "clip on" matte box. The clip on matte box adds more stiffness to the lens. I've spoken to almost every engineer at Preston and we've finally decided that it is freezing because the MDR's firmware has a safety limit of power allowed to the motor which shuts it down if the motor needs to draw too much power to move a particularly stiff lens. This is to prevent the motor from burning out. From my experience, I don't feel that these lenses are particularly stiff but maybe thats what it is. Has anyone else experienced this problem?

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