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Eugene Verenyov

Distance measure tools.

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At first I want to apologize for my English.


I'd like to ask you about distance measure equipment.

There are two kind of range finder on the market: ultrasonic(CineFlow, ARRI UDM, etc) and laser(cfinder iii). It's have very different specification.



+ wider angle of measure


-short distance of measuring

-low accuracy




+measuring range

+speed of measurement


-low angle of measure (probable <1°)


What is the better kind of range finder in your opinion? I mean a practical use on set. Most part of time you make deal with less then 15 meters (50 foot) set and ultrasonic equipment can work with it. From my point of view laser range finder is worse because it have a low angle of measuring beam, and for this reason if you want to use auto focus function you may meet with a problem like beam doesn't hit an actor.


What do you think about it?

What kind of distance measure equipment do you prefer?



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I've only used the laser rangefinder. It works OK, although I use it for longer distances. I'd like to try the ultrasonic someday. The laser can be pinpointed to whatever object you want, so isolating an actor or object is not an issue.

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I've used the Cinetape (ultrasonic), ARRI UDM (ultrasonic), Ward Sniper (laser), and Preston Light Ranger 2 (laser).


I was brought up on the Cinetape so I know it best and knows how it behaves and figure out what it is reading. So I may be a bit biased.


I personally think the Cinetape, although an older technology, is fine for most circumstances. If you are pulling focus, usually the hardest moments are within 10 feet (3.6 meters). In those cases, usually both laser and ultrasonic based system work quite well. I mean, at the end of the day, you still need to understand what the device is measuring (the front of the actor's hat vs his face).


What I do find the ultrasonic systems is better at is error margin. If your device isn't aimed 100% correctly, because the ultrasonic beam is relatively wide, usually it will still read the actor.


But because the beam is wide, sometimes it can end up reading a foreground actor (in an over the shoulder situation), or even the boom mic when it is low enough. I also find ultrasonic systems slower in terms of refresh rate.


Laser based system needs to be aimed more accurately but they are more accurate when they do work and they refresh faster. They also work over a longer distance. But fog/atmosphere does interfere with the device. But it can work through windows. And because the laser based systems require such precise aiming, some assistants have even mounted them on motors (so they can pan the laser). See here: https://cleanscamerasupport.com/product/rangefinder-bracket/


The only exception is the Light Ranger 2. Which I find very accurate, very fast, and really pushes the boundary of what focus pulls can be done. The only downside is you need a monitor and you have to get used to the amount of information that is presented on the screen.

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It appears that most of the additional mounting brackets only allow for tilt adjustment, and not for panning.


I would imagine that the pan is more valuable.


Any thoughts?

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The link I provided is a bracket for pan adjustment. You use a motor to pan the sensor left or right.


I've used it personally myself (the rig was owned by someone else though). The way I've seen it used is a Preston motor is plugged into the MDR-3's AUX motor port and attached to the bracket. On the HU3 handset, you assign the AUX to your handset's slider. So now as you use the slider, you are panning the sensor.


Ignore the pictures on that website that shows the Light Ranger 2. Reason being that you'd never really want to pan the Light Ranger 2. You'll only want to tilt it (hence the pictures show it mounted in a tilting position). Panning will actually mess up what it is reading.

Edited by Alex Leung

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