Focus on subject, whilst in motion

Mj882

Mj882

Well-known member
With my last production, I used the Letus35 Elite for the first time with my Panasonic HPX170.

One of the issues that I encountered was maintaining focus on a subject whilst the camera is in motion (tracking etc). Below is the film, you'll notice in the last quarter of the film, the focus kept going on and off of the actress whilst I was tracking her.

http://www.vimeo.com/5191655

How do I make sure the focus remains on a subject whilst the camera and the subject is in motion?

http://www.vimeo.com/5191655
 
Get a good 1st ac. Or, go out to a busy park and practice. There's no simple solution, holding focus isn't easy.
 
Even the slightest movement seems to cause it to lose focus though. Is it really supposed to be that hard to lose focus?
 
stop down the still lens which will reduce your DOF, that should help out a little bit.
 
Stopping down the lens INCREASES dof fyi. Depth of field refers to the distance which is "acceptably" sharp. Stop down, more, open up less.

Here endeth the lesson.
 
IanD said:
Stopping down the lens INCREASES dof fyi. Depth of field refers to the distance which is "acceptably" sharp. Stop down, more, open up less.

Here endeth the lesson.
Click to expand...

Stopping down decreases depth of field because you're going down to a larger f stop. (e.g Stopping down from f/1.2 to f/2.8) Less light is picked up thus less depth of field.

So I guess that's one of the things I'll do whilst tracking.
 
Mj882 said:
Stopping down decreases depth of field because you're going down to a larger f stop. (e.g Stopping down from f/1.2 to f/2.8) Less light is picked up thus less depth of field.

So I guess that's one of the things I'll do whilst tracking.
Click to expand...

Wrong. IanD is right. Stopping down INCREASES the DEPTH of field. Increasing dof = more things in focus.
 
I'm not too technical when it comes to lenses and DOF, but I usally have that problem with my 50mm. if I can't hit my marks with the Follow Focus (which can be a pain in the ass sometimes) I just switch to the 28mm and run with that.
 
Mj882 said:
Use marks of the camera movement in my plan? What's an AC?
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Yes, marks....pieces of tape or objects on the ground which directly relate to where a character is going through space, often with time constraints, in a scene. These marks are to be directly related to marks you make on the lens(different focus setting on your lens). These marks are then used by the AC(Assistant Cameraman).

By doing these things you can have precise camera moves that display something or another in focus in a repeatable pattern. By having the AC you are free to make sure you get the shot.

A follow focus would be a very good tool for your AC, but not always necessary. I've done the job lots of time without one.

One other option as well is just taking off the adapter, stopping the lens down as much as possible on the camera, and getting the shot.....then just try to match the footage in post.
 
Voytech said:
Wrong. IanD is right. Stopping down INCREASES the DEPTH of field. Increasing dof = more things in focus.
Click to expand...

When you stop down, aren't you going to a larger number/smaller aperture thus less light? And less light = less depth of field?

And the opposite being 'Opening Up', which increases the depth of field because you're going to a smaller number/larger aperture...which takes in more light thus more depth of field?
 
No matter what the terminology:

1. When you close the iris more stuff comes into focus
2. When you open the iris less stuff is in focus

I hope that clears that up.

This is an age old horror, as it means that if you have more subject matter depth wise you need to have a iris that is more closed, and thus the scene becomes darker, and thus the need for giant insane pieces of lighting equipment......like it, love it, but whatever you do, the larger your film plane(or sensor, or Ground Glass) becomes the more you'll have to grin and bear it.
 
Ok sorry, I meant stopping... forget it. Opening up your lens say 2.8 would give you a much shallower DOF than say 5.6 or greater
 
Mj882 said:
When you stop down, aren't you going to a larger number/smaller aperture thus less light? And less light = less depth of field?

And the opposite being 'Opening Up', which increases the depth of field because you're going to a smaller number/larger aperture...which takes in more light thus more depth of field?
Click to expand...

Stopping down = smaller aperture opening = bigger number = less light = MORE depth of field (DEEPER depth of field, more "range" in focus)

Opening up = larger aperture opening = smaller number = more light = LESS depth of field (SHALLOWER depth of field, less "range" in focus)


Example of stopping down, f/4 to f/5.6.

Example of opening up, f/2.8 to f/1.8.
 
well u have the stopping down and up the lens thing in reverse. But that term can be confusing...as the others have said...open up the iris= less DOF, closing the iris= more DOF (more things in focus). What u can do is close the iris a bit so u dont have a rzor thin plane of focus and also keep the distance between you and the subject constant so u prolly wont even need to touch the focus ring at all. Keeping the same distance trying to track a moving subject i imagine is easier than setting marks....i duno...never used one :) ... But the principles of photography remain.
 
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