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Clever ways to keep things in focus


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#1 Jason Anderson

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Posted 26 May 2008 - 07:14 AM

I recently bought a laser pointer for my AC kit not really knowing how I would make use of it. The first AC borrowed it and rigged it up in a gobo arm that extended off the dolly and pointed the beam at the floor. He used it to get a better idea of how short or far the actors were while the dolly kept pace.

So i'm wondering about the setups where things were not so cut and dried, you could not just pull out your tape or laser measure, throw down a couple or a few marks for the actors and then roll?

Have you ever done a setup that required someone else to verbally help you out with focus?

When have you been stumped on how to pull focus for a shot, and had to come up with a plan on the spot?

If you miss your focus mark who should you inform, the camera operator, the DP, the AD or just make an exasperated exhale that everyone on set can hear :rolleyes: ?

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#2 Frank Gardner

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Posted 26 May 2008 - 10:55 AM

Hi Jason

The first thing all good AC,s should learn is honesty and Trust. If Your operator has not noticed that you "missed your marks" then it is up to you to inform him/her of this. There might be sufficient depth of field that you may still hold focus or he /she will make the call if you have to reshoot the take.
A laser pointer is great for quick reference and I mount mine onto the camera with a Monfroto mount which allows you to adjust the angle of the laser.

The best way...often safest ...is to still pull tape or refer to your Depth of field charts.

Remember bad focus cannot be corrected so get it right on your shoot day..... this may mean a little embarrasment but will save your butt later.

Regards

Frank (1st AC South Africa)
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#3 Allen Achterberg

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Posted 28 May 2008 - 04:01 PM

knowing your DOF is very important. It will help a lot. Laser Pointers are good for some, not so practical for other shots. When you mention having some one verbally helping you with focus do you mean that if it's soft someone is telling you this? Or, are you describing Ron Dexter's radio focus pulling technique?

http://rondexter.com...cus_pulling.htm

best
Allen
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#4 Jason Anderson

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Posted 28 August 2008 - 02:52 PM

The ron dexter thing is a good example of what I was thinking about. Thanks for the link.

How would you approach this shot: Camera is set up looking towards the entrance to an elevator, an is actor coming down in a cage elevator, the dolly moves towards the actor as the elevator approaches. Focus becomes more and more critical as the dolly approaches, because of the longer focal length lens. The actor does not get off the elevator however, because they continues past the entrance heading down past the level the camera is setup on. We are still dollying forward and see the actor descending through the open cage style elevator.
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#5 Alex Worster

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Posted 28 August 2008 - 04:31 PM

If the shot you set up was really so critical that you couldn't hold the elevator fence and the actor as he/she goes by then you'd need to rely on a decent dolly grip hitting his/her marks during the take. If I were faced with this shot I would stick the actor to a specific spot in the elevator with a mark then dolly the camera to the frame which the DP and director like for the actor crossing through the shot. I'd take my measurements and set a floor mark for me so I know when to go from the elevator fence to the actor and also make sure the dolly grip has a good mark so he/she knows that's the spot to be when the actor is passing the camera. Then dolly back and set some incremental marks to hit so i can hold the elevator fence while we dolly in, same for after the actor passes through the shot. Rehearse to make sure everybody is comfy, especially the dolly grip because that shot is probably harder for him/her than you, then go for it.

The message in all this is many times carrying good focus relies on a calm minute of thought and mental walk through, good easy to follow marks, a couple rehearsals, and a good dolly grip. Get to love your dolly grip, buy them a beer, they play a big part in not making you look bad.
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#6 Allen Achterberg

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Posted 28 August 2008 - 05:55 PM

Those sort of shots are not easy, but like Alex says your mental state will make a good difference. Theres so many things to learn when it comes to the art of focus pulling. Read the Zen Focus Book, Science and Optics by fritz. may have the title wrong, I've got it lying around somewhere. These things come with experience. Learn to understand the relationship between your stop, lens length and how big your subject is in screen. Learn to match object growth from the monitor and your pulling speeds. a few visual marks for yourself are good.

there's two ways to do these things, one way is with trust on everybody to be on que (which often requires multiple takes or rehearsals) the other where you learn to basically Be the focus. Learn to pull focus without tape and marks, judge subject size compare it to lens length, you can understand distance that way without a measure. Learn to know what your DOF IS and how it grows and shrinks, Learn to visualize it, spend time with a lens or Lenses so that you can get a very intimate feel of the barrel rotation and how that particular lens effects distance. Practice with long lenses on a video camera (2/3") or redrock M2 at home, or from a still camera. Practice Practice and Practice! Practice guessing Distances! Do all if this Wide Open on Lenses.

this is one of those jobs that require dedication! very few are naturally good at this stuff. It takes practice.

Since you are asking HOW to approach pulling focus on these sort of things I know your experience level is low and therefore I recommend some alone time with a long lens, and a medium lens.

The above is described in a perfect world, its ideal that everyone hits their marks. And if everyone hits their marks, or are close to hitting their marks on time, and you miss....? Learn to be ahead of the game!!!
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#7 Jonathan Bowerbank

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Posted 28 August 2008 - 10:25 PM

1. So i'm wondering about the setups where things were not so cut and dried, you could not just pull out your tape or laser measure, throw down a couple or a few marks for the actors and then roll?

2. Have you ever done a setup that required someone else to verbally help you out with focus?

3. When have you been stumped on how to pull focus for a shot, and had to come up with a plan on the spot?

4. If you miss your focus mark who should you inform, the camera operator, the DP, the AD or just make an exasperated exhale that everyone on set can hear



1. Firstly, you gotta be EXTRA vocal about getting some focus marks, no matter how much of a hurry production is in, they have to know that it's all for not if it's out of focus. Then again, prod. should rarely have to "wait on camera", so be sure to get in there and get your marks quick. Having a lasertape will help loads since you won't be scrambling around, but you can at least get your marks as they're blocking out the scene.

2. I worked a 2 camera shoot, and whenever B camera was not being used, the other 1st AC was thoughtful enough to camp by the monitor with a walkie to squawk in my ear and let me know. He didn't have to call me out at all, but it gave me some extra confidence when he would say "Kudos on the focus, Jon" at the end of each take.

3. I think this is when experience is your biggest asset. When you've developed the talent for eyeballing distances and zenning focus. Otherwise, it's especially nice, if you're shooting video/HD, to have an onboard monitor for shots such as this.

4. The DP is the head of your department, and your umbrella from other production issues. Tell him/her.

Edited by Jonathan Bowerbank, 28 August 2008 - 10:26 PM.

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#8 Dan Diaconu M

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Posted 29 August 2008 - 01:15 AM

All good advice so far and I'll just add what I think was missed: dolly's speed/position should match the position of the elevator (with talent on the mark of course). At the risk of playing "much ado about nothing"...any encoders to "read" the elevator/dolly and CTRL a focus motor might be another option (like a motion CTRL "thing")
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#9 adam ward

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Posted 06 November 2008 - 01:33 PM

All good advice so far and I'll just add what I think was missed: dolly's speed/position should match the position of the elevator (with talent on the mark of course). At the risk of playing "much ado about nothing"...any encoders to "read" the elevator/dolly and CTRL a focus motor might be another option (like a motion CTRL "thing")



you might try a Sniper, the MArk II is fast enough to match pushins on the dolly..enough so that one has only to mach the display with the barrel. (unconventional I know)
adam ward
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#10 Rob Vogt

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Posted 20 November 2008 - 09:07 AM

Not sure if u have the cinematographers bible too but it has a pretty in depth chart for DOF at certain F-Stops and w/ different focal lengths for 16, S16 and 35 (maybe more too but that's all ive used it for and id have to look at it)

http://www.amazon.co...a...9807&sr=8-1
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#11 Dan Goulder

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Posted 20 November 2008 - 10:10 AM

The ron dexter thing is a good example of what I was thinking about. Thanks for the link.

How would you approach this shot: Camera is set up looking towards the entrance to an elevator, an is actor coming down in a cage elevator, the dolly moves towards the actor as the elevator approaches. Focus becomes more and more critical as the dolly approaches, because of the longer focal length lens. The actor does not get off the elevator however, because they continues past the entrance heading down past the level the camera is setup on. We are still dollying forward and see the actor descending through the open cage style elevator.

I understand your desire to shoot the takes with a long lens. However, just for sake of assuring you've nailed the shot, I'd also try some takes with a wide lens lit to T2.8 or higher. That will be easier to pull off, and will only increase your chances of getting a good, usable take. It never hurts to keep from getting inflexibly locked in on your focal lengths where real world locations come into play. (Who knows? You might even prefer the results.)
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