Using a laser measuring tape for focus distance

[Matt Pacini]

I saw one of these in OSH when I was buying mortar, and a light bulb went off over my head, as I fantasized about not having to have someone whipping out a tape measure to get proper focus when Im' using prime lenses, but just pointing one of these things to where I'm shooting.

 

Has anyone here used one of these for this?

can you think of any down-side? (other than the obvious; not shining the laser in your actors eyes!)

Seems like it would speed things up considerably, eh?

 

Matt Pacini

[Cris Moris]

Matt,

 

I'm not an AC but I have used these before mainly to get footprints of buildings and that kind of technical meausurment.

THE DOWNSIDE to these is that the lens of the device has to be parallel to the object/wall you are measuring. So you could try to do set it next to the camera and aim at the subject/actor's shirt or something.

The laser is not visible like those of pointers so it may be hard to get it right where you want it. However its a plus becasue you wont get the actor in the eyes.

I would test one out and see how you like it, compare it to a tradiotional tape.

 

Maybe some AC's have used these and have different opinions.

 

I'd like to see what other people think.

[Max Jacoby]

I have worked with focus pullers who own Leiko Distos. They are good for getting distance readings on actors/objects that you can't get to physically. They were especially useful when we shot in Venice with boats.

 

They are very precise and they have a trigonometry function as well, so you can calculate the height of a wall for instance.

 

The limitation is that on dark, non reflective surfaces it can be hard to get a reading and obviously you can't point them into actor's faces either.

[Carlos M. Icaza]

Interesting. I am amazed at what one learns everyday.

 

I was also just thinking about this from a post I made in the off topic section not long ago.

 

here is the link to the Distos.

 

http://www.lasermeters.com/

 

I think one of them will be on my x-mas wish list.

 

Thanks,

 

C.-

[Greg Gross]

Tape Focus:

Distance is measured from the film plane(mark on camera housing)to plane

of critical focus.Near and far points that need to be in focus can be measured

too. Considering that depth of field is adequate,calculate split focus distance

and set focus.Sometimes more accurate with wide angle lenses then eye focus.

Warning!, Lens should be collimated for the focusing scale.

 

SPLIT FOCUS DISTANCE=(2X NEAREST DISTANCE X FARTHEST DISTANCE)

DIVIDED BY

(NEAREST DISTANCE+FARTHEST DISTANCE)

Zoom Lens Focusing- Depth of field is minimized at the longest focal length.

Focus by zooming in(all the way)set focus and then zoom

to focal length you wish.

Watch out for depth of field charts, you may be off by 15 to 20%.

[Laurent Andrieux]

I know a very famous AC who tried all the possible systems you can find.. He has dropped out, and went back to his tape measure, for sure.

[Matt Pacini]

I know a very famous AC who tried all the possible systems you can find.. He has dropped out, and went back to his tape measure, for sure.

Do you happen to know exactly why he went back to the tape measure?

 

Matt Pacini

[Laurent Andrieux]

He said that fiability compared to hassle in setting up, using etc... was no use to bother anymore

[che broadnax]

Do you happen to know exactly why he went back to the tape measure?

 

Matt Pacini

I'll tell you why I prefer using a 2nd AC with tape over my laser. When I use the laser, I have an actor or an item in space, with a red dot on it. I get an accurate reading, and it's fast to get. When I use a 2nd AC with a tape measure, I get to see the true distance, I watch them walk out to the actor, I see the tape measure itself. It takes longer, but I get a sense not only of that one point in space but of a continuum. I don't only know that the actor is 7' 8" from the film plane, but I also have a sense of what 5' from the film plane is, and can extrapolate 10'. Now, obviously any good AC is good at guessing/gauging distances, but I find that on shoots where I don't get to break out a tape measure, my eyeball's natural calibration starts to drift. That tape measure is like a recalibration every time it comes out.

 

That said, my hard tape is only 16' and my soft tape is 50' My laser is accurate up to at least 150' -- beyond that the natural shake of my hand makes it difficult to keep the laser steady. For crazy pulls, when somebody runs from 80' right up to the camera, the laser is very useful. Unless of course we're in a daylight exterior, where the red dot can be very challenging to actually see. Sometimes on microbudget projects I don't get a 2nd AC, or we don't have stand-ins or don't get to see rehearsals, so all I can do is get architectural marks with the laser. That works, too. Though not ideal.

 

The sonar range finders are generally only accurate up to maybe 40' and they have a wide cone instead of a narrow beam, so you might not always be measuring what you think you are. If you're doing an OTS shot, you might be measuring the back of somebody's head instead of the front of somebody's face.

 

To be fair, I've never used the cinetape system, but I'd like to. Though I worry that watching the numbers might become an unhealthy crutch.

[Keith Walters]

I saw one of these in OSH when I was buying mortar, and a light bulb went off over my head, as I fantasized about not having to have someone whipping out a tape measure to get proper focus when Im' using prime lenses, but just pointing one of these things to where I'm shooting.

 

Has anyone here used one of these for this?

can you think of any down-side? (other than the obvious; not shining the laser in your actors eyes!)

Seems like it would speed things up considerably, eh?

 

Matt Pacini

Most rental companies already offer gadgets similar to what has already been described. They have their uses, but the bottom line always is that most of the time, a sub $10-Dime Store tape measure will work just as well, and you can be pretty damn sure that if it says "8ft 9in" the distance actually is 8ft 9in! And you don't need to worry about batteries, and actors don't generally freak out if you bring a "tape" tape measure near them :-)

Electronic measuring tapes are useful for measuring distances to inaccessible objects or from cameras mounted on cranes and so on but most of the time an old-fashioned "dumb" tape will be more than good enough. There's nothing to stop you carrying both types of course.

 

Edited to add: Erk - I only just noticed that this thread is over 7 years old!

[Tom Jensen]

I tried them and hated them. My rule of thumb is to tape everything 35mm and below at close distances. Eyeball and tape 50-100 at close distances up to about 20 feet. Eye focus everything longer and distances beyond that beyond that.. It's efficient and it works.I've had very few focus issues in my career. Actors move and often don't hit their marks so you have to be flexible. I always looked at 3 things, the actors face, his feet or mark and the lens barrel. I rarely used focus discs and mostly used a stabilo pencil right on the lens. Keep it simple. When I stopped assisting, the Pana Tape was relatively new and never got the chance to use it. So I can't really comment on the use of it or the Leikos Distos but I know that eye focusing on long lenses works better than just about anything.

[Frank Glencairn]

I might get some Flak for this, but we switched over to focus peaking on the monitor quite a while ago and it works just like tape, but with out the tape.

 

I have a TVLogic monitor n the camera for my focus puller, that has a very finetunable focus peaking.

He sets the marks on the FF disk by checking distances with the peaking function of the monitor and is very flexible (and mostly spot on) when the actor decides to ignore his marks, changes his timing ore something else happens.

Really like that constant realtime feedback, that peaking (or focus in red) gives you.

 

Maybe not for everyone, but for us it works just fine.

 

Frank

Edited February 29, 2012 by Frank Glencairn