Procedure for measuring out focus with a tape measurer and pulling focus?

[Jackson Miller]

Hi all. I kinda know the basics of focusing on a professional set or at least I think I do. I know that actors have blocking marks that are measured out with a tape measurer so that the focus puller knows exactly what marks to hit. But how exactly do they calculate how many feet away the camera is focusing? For example, my dvx lcd has a focusing indicator that goes from 00 to 99. That is not feet though. And not meters... so how does this process work exactly? Could someone write it out in a brief step by step list maybe? I am talking about the follow focus and marking it also. Thanks a lot guys.

 

[Huy Vu]

You can change the focus display to feet or meters on the camera, but without knowing what the film plane is (where the focus starts) you can't really measure distance anyway. Shooting on a bare camera it is rarely necessary to measure focus in this way because the DOF is already so deep.

On a 35mm adapter focus is measured from the film plane which should be clearly indicated on the adapter. However it is necessary to adjust the flange distance (backfocus) of the mount and the GG such that the marking on the lens correspond to actual distance. Once this has been correctly set, simply measure from the marked film plane to the focus point and adjust the lens marking to that value.

 

[Cassius]

The original DVX only had the percentage numbers, not feet. However, somewhere in the Internets is a chart that approximates how those numbers translate to measurable distance. I'm not going to find it right now, but I know I saw one long ago.

 

[Sad Max]

The basic sequence:

Measure from focal plane (marked on the camera or adapter, as Huy Vu notes above) to your subject.

Open your Cinematographer's Handbook to the appropriate chart (for your focal length and format) and check it for your aperture setting and distance to subject.

Set your focus accordingly.

 

[RyanT]

The basic sequence:

Measure from focal plane (marked on the camera or adapter, as Huy Vu notes above) to your subject.

Open your Cinematographer's Handbook to the appropriate chart (for your focal length and format) and check it for your aperture setting and distance to subject.

Set your focus accordingly.

I would just make that chart up in excel or something, laminate it, put velcro to the back and then stick it on your mattebox. I'm sure you can pretty easily figure out where the focal plane is with some tests.

Honestly though, doing this is sort of useless...the distances don't help you unless you can actively look at them and change your focus. Having an intermediary step of having to think about the focus numbers and then think about that in relation to the distance makes all of your pulling a few seconds too late. I know a bunch of AC's don't even like using a cinetape, because it's just distracting, even if it does tell you how far away they are.

What I would say is either on the follow focus or the lens, make marks on that what your close focus is and what infinite is, then do a bunch of marks inbetween, doing more as you get closer to the focal plane. The thing that sucks though is that a lot of these digital cameras don't have a hard stop for close focus and infinite, they just keep turning, so one wrong move and all your marks could turn inaccurate. Just look into ways to fix this...maybe you just tape a little thing to the focus dial and then another thing to the body of the camera that stops it before it spins too far.

Just don't let people tell you that it's unnecssary to pull focus on these cameras, because man...it is. I've watched too many soft hvx films to know that they needed a good focus puller on their side. It may not be the most difficult focus pulling, but you do need it.