Wireless focus in cold weather

[Rogerhaugen]

Hi!

 

Working on a feature these days, not steadicam, but using a preston wireless system.

We have been having some problems working with it outside in minus degrees. The motor have been slow and not able to

drive the lens. I have also experienced this in cold situations with my own bartech, Heden motor unit.

This time we could just use the regular arri follow focus, bit If I had been there with steadicam we would not have been able to shoot. (Its been - 10 to -20 celsius by the way)

Any comments on this issue?

 

Roger

[Nikolay Kerezov]

It happens to me few days ago.What I think about this is,that the lens stiffens but not the motor.If you take the lens and try to turn it by hand you'll se that is also hard to do it by hand.

I get out of this by changing the motor(FMG I've used for first and last time) with my beloved Heden M32p,but sometimes this is not enough.If it's for one shot only you can simply warm up the lens till the smoothest moment you can get(depends how much time you have)

Good look!

[max volokh]

I can't recommend you to warm up your lens, in low temperature the result will be a condensate or you can get the ice inside of it. BFD is very good with M-One motor, but eating about 4 Amp at 12 Volt. I use NiCa batteries with my BFD at temperature lower then -10C. According to the ActionProducts U-Lex, I just begin testing it in Russian winters. Still no temperature problems, but I think if it down the -20 I'll change the power from 12 to 24-30 Volt. They make this mode for heavy conditions. I don't now if the Preston could work from 24V but if it can use NiCa batteries.

Good lack

[Sean Jensen]

Hi Roger

 

I often shoot in -20C conditions. Years ago I was on a show where we were shooting in -40C and the lens froze almost solid. Couldn't even turn it by hand. We pointed a 2K at the camera from about a foot away and also wrapped the lens and camera with a plug in car battery warmer between takes. Did the trick but by the end of the shot we had to heat it all up again. What lenses are you using? I've never had this problem with Cooke S4s or Primos but older lenses, yes.

 

I'll agree with heating up the lens. We did not have any condensation problems. Probably because it was so cold we only heated the grease in the lens. If you can, try "Hot Shots" taped to the lens. They sometimes work and give a constant heat source for a couple of hours, don't weigh much and don't get in the way too much.

 

Good luck and stay warm.

 

Sean

[Rogerhaugen]

Hi Roger

 

I often shoot in -20C conditions. Years ago I was on a show where we were shooting in -40C and the lens froze almost solid. Couldn't even turn it by hand. We pointed a 2K at the camera from about a foot away and also wrapped the lens and camera with a plug in car battery warmer between takes. Did the trick but by the end of the shot we had to heat it all up again. What lenses are you using? I've never had this problem with Cooke S4s or Primos but older lenses, yes.

 

I'll agree with heating up the lens. We did not have any condensation problems. Probably because it was so cold we only heated the grease in the lens. If you can, try "Hot Shots" taped to the lens. They sometimes work and give a constant heat source for a couple of hours, don't weigh much and don't get in the way too much.

 

Good luck and stay warm.

 

Sean

 

 

Hi Sean!

 

We are using a set of cooke panchro. Today it was -6 C and we didn´t have any problems.

 

But we are shooting two cameras SI 2K with cables. And we have had so many problems with this setup in the cold. Working with computers outside in snow, cameras suddenly not working, then starts working again without knowing why.

Not to be recommended.

 

Max: Is that Optica Elite you are using on the Red? How do you like them? Hard to find a good review on those lenses.

 

Roger

[max volokh]

Yes It's "Optica Elit" Not bad for that money, but the open iris is useless. It's useable at 2.8 and soft at 2.0. Mechanically you need to be very attentive with it. Some of them are disassemble in hands, some time the distance marks is wrong. If you wont to purchase it new you have to get long time warrantee. Any way, they are chip, but for me second hand Distagons, or Cooke, or ... is better. We use it, because it next door made. And according to my experience the service are not so friendly 8-(

Edited February 10, 2010 by max volokh

[Rogerhaugen]

Yes It's "Optica Elit" Not bad for that money, but the open iris is useless. It's useable at 2.8 and soft at 2.0. Mechanically you need to be very attentive with it. Some of them are disassemble in hands, some time the distance marks is wrong. If you wont to purchase it new you have to get long time warrantee. Any way, they are chip, but for me second hand Distagons, or Cooke, or ... is better. We use it, because it next door made. And according to my experience the service are not so friendly 8-(

 

 

Thanks! Good to know!

 

Roger

[Eli Aronoff]

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.