How to focus well with slow zoom?

[rw5653]

Greetings,


I'd like to buy a DVX-100B but I have a few autofocus questions first. I'll be shooting low budget training scenes (using a tripod) which may need slow zoom ins or outs vs stopping the talent to do cuts.


After reading some posts, it appears that using autofocus when in 24p and doing even a slow zoom with good lighting will not give great results. True?


When doing a slow zoom in 60i, will the autofocus provide great results? I've seen pretty good results even from a $1,000 consumer camcorder.


Yes, I'm new to professional technique but here goes – what is the professional technique to keep good focus when using a slow zoom? Do you actually use both the zoom control and focus manually at the same time while not shaking the camcorder?


Feel free to laugh!


:dankk2:

 

[235 Studios]

Feel free to laugh!

Ok then I will. rogar-BigGrin(DBG) :grin: :grin: :2vrolijk_08: :grin: :laugh: :laugh: :laugh: :laugh:


Now with that out of the way- what you want to do is pull critical focus. Using manual focus zoom all the way in on your subject and pull focus, then zoom back out and frame accordingly. If you zoom the camera your image will remain in focus so long as your camera, or subject does not move. If there is some movement, your image may go a little out of focus, but it should not be too noticable. The further you zoom in the shallower your depth of field will become, making what is in focus and what is not infocus more noticable.

Hope that helps- oh, and one last thing- stay away from autofocus- it will keep readjusting, throwing your image out of focus form time to time.

 

[ryan brown]

Exactly what 235 said, but let me try and explain so it's a little easier...

Your focal point will stay in the exact same place, even as you zoom in and out. So, like 235 said, you want to zoom all the way in on your subject, and manually make sure he/she is in focus. Now when you zoom back out, your focal point is still right on your subject. Zoom in and out as much as you want, and your focal point will stay right where you want it.

 

[rw5653]

Focus, zoom, and pan with Varizoom?

Focus, zoom, and pan with Varizoom?

Thanks 235 studios,

I'll give the critical focus a try when I buy the camera - it's a bit challenging to understand the concept at this point. My concern is that the talent will move and there won't be an opportunity to stop and apply critical focus. The talent are not professional actors and may be speaking and demonstrating from memory and interrupting them to refocus etc. may be disastrous.

It appears like folks who zoom, manual focus, and pan simultaneously (especially when their talent moves) use a gadget like a Varizoom product so all of the controls are near each other on the tripod head pan arm. Is this another accepted way to accomplish the simultaneous focus and zoom?

Thanks again,

Roger

Ok then I will. rogar-BigGrin(DBG) :grin: :grin: :2vrolijk_08: :grin: :laugh: :laugh: :laugh: :laugh:


Now with that out of the way- what you want to do is pull critical focus. Using manual focus zoom all the way in on your subject and pull focus, then zoom back out and frame accordingly. If you zoom the camera your image will remain in focus so long as your camera, or subject does not move. If there is some movement, your image may go a little out of focus, but it should not be too noticable. The further you zoom in the shallower your depth of field will become, making what is in focus and what is not infocus more noticable.

Hope that helps- oh, and one last thing- stay away from autofocus- it will keep readjusting, throwing your image out of focus form time to time.

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[rw5653]

rcbrown 23,

Thanks for the summary - I think I'm getting it. I'll have to try it out hands on.

Roger

Exactly what 235 said, but let me try and explain so it's a little easier...

Your focal point will stay in the exact same place, even as you zoom in and out. So, like 235 said, you want to zoom all the way in on your subject, and manually make sure he/she is in focus. Now when you zoom back out, your focal point is still right on your subject. Zoom in and out as much as you want, and your focal point will stay right where you want it.

 

[235 Studios]

It appears like folks who zoom, manual focus, and pan simultaneously (especially when their talent moves) use a gadget like a Varizoom product so all of the controls are near each other on the tripod head pan arm. Is this another accepted way to accomplish the simultaneous focus and zoom?

Yep that works as well.

If you are concerned about being in exact focus with your talent moving around, stop down (the F-Stop increases in number say from f2.8 to f5.6) the lens to increase your focal plane (The area infront and behind of your subject that remains in focus). The more closed your lens is the greater the depth of field is, and the more room your subject can move while still staying in proper focus. The further you stop down your lens, the more light you will need to compensate for the light loss. Try keeping your lens somewhere inbetween f5.6 & f8, that should give your talent planty of room to move. As with any new endeavor, practice with your camera before it comes time to film. That way you'll be prepared, and feel comfortable when the pressure is on.

Check out this description on depth of focus: http://en.wikipedia.org/wiki/Depth_of_focus