View Full Version : Focus pulling on DV?
03 March 2005, 09:53 PM
I've been making some short films on DV, and am constantly fighting to get a better picture. I'm getting up to speed with moving the camera properly around, to create nice, dynamic cinematography.
But with a moving camera, focus becomes a real bitch, and my last project was almost constantly out of focus (and no, autofocus is not the way to fly).
So.... what I need is some kind of focus pulling. But having a guy running beside the camera operator camera, turning the focus ring is not really an option, particularly with lightweight DV cameras that are not mounted firmly on heavy dollies.
So, there ought to be some kind of focus pulling mechanism, preferably a remote control...
Does anyone know anything about this? What do you folks do?
03 March 2005, 11:57 PM
they do make them, but usually only for high end DV cameras like the CanonXL or Sony HDV cams.
but since most DV cameras have electronic controlled focus, it's delayed and not a 1 to 1 ratio. meaning that you may have to turn the ring a few rotations to get the focus to change. that's useless as it takes to long. also since it's electronicly delayed, you won't be able to mark on the camera any settings so that you know when you are here, you need this number and when you turn this way, you need this number.
are you try to get DOF effects? where the forground is in focus and the background is out of focus? if so, then you are probably SOL, because you are hitting on the phsyical limit of what a small cameras lens can do.. the lense are so close together and small that there is not enough space to cause this to happen. the only way to get DOF is to get far away with the camera and zoom in and then you might get DOF effect, but then you can't move the camera without a dolly cause you are zooming.
I'm not saying give up like some of us have. most of us, at least I know I do, are doing DOF digitally in POST. you can matte out your forground pretty easy and blur out the back. no lost footage because it's all out of focus.
now others are trying to get it done in camera by using a real prime lens, those lenses you have on a 35mm camera. you can buy or build you own device that connect to a 35mm lens you can either buy a new one or get a used on. it does degrade the picture slighty but if you look here you can see the focus shifting is amazing.
and to, I think you will most likely always have to have a guy next to the camera because anything electronic will always be to slow and to late to keep up with the action. I think even the big boys in Hollywood still have to do it that way.
just my 2 cents and half a bean
03 March 2005, 12:36 AM
Hey, thanks for the reply!
No, I'm not trying to get a DOF effect, on the contrary, I just want my action to be IN focus.
(but actually, in other cases I might be interested in the DOF effect, so thanks for those tips too! :) )
03 March 2005, 04:40 AM
ok well two things then
1. why are you not using auto focus? if you are using a newer camera, the auto focus is pretty quick, but it helps if you keep the camera pulled out to it's widest and make sure you have plenty of light. keep the background far enough away and the action centered and that will help keep the auto focus
2. get a piece of string. break your action scenes into controllabe shots. then setup string or tape on the ground for the camera man to follow. now do the same for your actors, keeping them with in a range of the cameras focus. then set the auto focus to get the distance and focus the camera, then turn it off then just stay close within those marks you made and it should stay in focus. remember the more you are zoomed in the more the focus will shift, keep the camera zoom pulled back but then move physically closer to the action.
on your extreme shots, try putting the camera in infinity focus. you can't get to close to an object, but stuff at a distance will be fine and everything will be in focus. then you could zoom in a bit in POST.
since there is no real way of manual or electronic auto focus off the camera, distance control will be the key. so you may have to tie string from the camera operator to the actor, if it's a medium shot where you don't see the string, to keep them at a distance from the camera. but keeping the distance is the key, especially if you auto focus is goofy. I had an older camera where it was goofy and if someone moved just an inch it would loose focus and go in and out, especially if it was dark. then the only other option is to get a new camera.
03 March 2005, 09:24 AM
Thank you very much, those distance tips are very useful!
I guess I'll have to use the autofocus when I want to pull back and push in. I just have baaaaaaaad experiences with autofocus! But that was a while ago.
03 March 2005, 05:45 AM
There are two ways I know of doing it.
1. With a telephoto lens on your camera, the distance between lenses will increase, and so will the DOF. This if you want extra DOF and not having to spend a few hundred dollars on the mini 35 systems.
2. Some prosumer cameras have some buttons for which you can assign focus presets. If your actors move to a different marker, you can simply press your second preset and have everything you want back in focus. hence, you won't be having a juggling autofocus, nor will you be needing to guess how much to move the focus ring on your cam.
Hope this info helps!
03 March 2005, 05:45 AM
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