Dolly shots and focus

B

Bobonli

Well-known member
I'm considering getting a tabletop dolly/rods-mounted slider system like the Cinevate Pegasus. I'll be shooting with a 35mm adapter most of the time. My question pertains to maintaining focus.

The promo ads I've seen for these rigs often show the user moving the dolly toward and away from the scene. I don't ever see anyone adjusting focus! I'm a newbie at dollying but don't you need to rack focus during this type of move (since the camera to subject distance is changing), don't you?

It seems to me that the only time you can move the camera on a system like this and not worry about focus is when the distance to the subject remains static, perhaps a short left to right or top to bottom move. Is that correct?

Maybe I'm paying too close attention to the ad !
 
Depends on a number of factors (subject to camera distance, aperture, length of the move), but in general, yes, you need to focus.
 
Indoors or in low light, a lens adapter will typically take an inherently long DOF camera (like an HVX200 or other 1/3" CCD cam) almost completely the other way, so yes, focus will be very critical, and an FF unit will be a great deal of help. Outdoors in daylight the adapter will be much easier to manage since you'll have things like ND filters to give you some f-stop/DOF options.

But with something like an HVX *without* a lens adapter, if you've got enough light to be stopped down to f5.6 or so, many dolly moves can be done with little or no refocusing. This is where the otherwise (and often annoyingly) deep DOF in these cams suddenly becomes your best friend. Even more so with a steadicam...
 
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98% of the time, even without an adapter, you should have someone right there at the follow focus. So yes yes yes yes yes.
 
Perhaps what you are seeing, is the use of a wireless FF system?

If the dolly cannot support or fit the 1st ac, (as such it would be on steadicams and jib arms) the 1st can go 'mobile' with a remote FF and will most likely be standing at a 90* to the line between camera and subject. I find judging distance is easier looking from a profile.

But as the others before me have said.... yes! When the camera to subject distance changes, and you wish the same subject to remain in focus, the lens must change. If the subject is moving away as the camera moves towards (at the same speed) that would obviously negate my last statement.
 
there should always be someone manning focus or you will most likely pay for it later. On dolly moves it is typical to put tape marks on the floor with distances written on them and corresponding marks on a follow focus marking disk and precisely lining up the timing. Doesn't matter if it's a Preston or a man with a whip the ideas are all the same.
 
I found that I still need to focus even on wide angles, which was my main issue with most pedestal dollies that would make me hunch over the track and legs while I tried to run the camera...only to kick the pedestal and ruin the shot.

I like to zoom in a bit and open the iris up to get some soft backgrounds, especially with talking heads, so focusing/framing while pushing the dolly is critical for me.
 
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YES.

you absolutely need to pull focus with a DOF 35 mm adapter, whether it's a letus, brevis, redrock m2, pro35 etc. And remember, this is a focus puller on the 35 mm lenses not the cam, since you have the adapter mounted.

This is especially true of HD work, especially if you are down to the focus assist quality level on your shot as far as how zoomed in (CU, MCU etc) you are.

If you are doing a tracking (Straight or curved) shot of medium wide or wide subject, if you are a uniform distance from subject and moving horizontally (with a steady hand on the fluid head for any pans) then, as long as the focal plane isn't changed you are cool.

But if you are moving camera and changing distance to/from subject, you need to pull focus- unless the effect is to come out of focus and in etc.

NEWBIE TIP: remember it's critical in HD 1080 to use that focus assist button, if available (and it should be) or, prep your shot: zoom in as tight as you can on eyes or most important part of shot, focus, then zoom out for the shot. You'll be crisp (even in zooms) as long as you don't move camera/lens in and out.
 
still lens zooms

still lens zooms

back focus collimation and lens quality/design all need to be perfect for the lenses to be able to zoom in all the way for "absolute focus" and zoom out. Some still lenses are just not designed to work this way.
 
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