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style="margin-bottom: 0">Focus Exercise

Published : 7th August 2003


Hi All,

I shoot wildlife with a long zoom (Canon 150-600, Arri SR2). focus is something that I'm constantly wrestling with. When my subject moves while I'm filming stopped down, I have a hard time keeping in focus without opening the iris, finding critical focus, then stopping down again to shoot. this obviously, can screw up a sequence.

1st question :

>Would finding a lighter viewfinder help me? (I use an Arri viewfinder with an extender and I was told once that an Aaton eyepiece could be mounted on an SR2 that allows much more light in)

2nd question :

Can anyone recommend a good practice for sharpening follow focus skills?

I have found that as I often have my face glued to the viewfinder for long periods that my eyes get quite messed up, even when I keep both eyes open. this means that I’m better at following something in focus when I first put my face to the camera but less accurate with more time in the viewfinder. can one exercise the eyes and/or filming stamina???

Does anyone on this list wear an eyepiece (eye-cover) when shooting?

Thanks for your ideas,

James Christian
Boston, ma
wildlife cinematography
http://www.james-christian.com



>When my subject moves while I’m filming stopped down, I have a hard >time keeping in focus without opening the iris, finding critical focus...

A brighter, faster VF certainly helps, as does a large eyepiece. Also, use efficient lenses that have as little disparity between f/stop and t-stop as possible. Older zooms are not as good as the newer ones.

I'm also one of the few people that does not like using chamois, and get my eye right in there so I can see the edge focus really well too. Also make sure the mirror-shutter's clean and scratch free and aligned/collimated.

You can have a perfectly collimated lens/gate, but the mirrors out-of-wack and giving you a softer image in the eyepiece. Unlikely culprit, but something to check to be safe, but the first thing you should try is NOT stopping down, and shooting wide open - or only a stop down from max aperture. It helps you see focus. And don't worry - its a docu and since you don't have a scornful Focus Puller next to you - you can only blame yourself.

When you close down too much, the ground glass appears really grainy, and seeing focus becomes that much more difficult. What's more is that you don't see the focus fall off as distinctly due to the bigger DOF, but just when you think you're safe, you may get a soft shot, or end up racking through the focus more than needed.

Another thing you can do is, before you start a sequence, try to grab the focus knob or barrel in a way where you can feel your thumb (or index) is at a certain position - say at 3 o'clock or hitting against the rods or zoom motor, or tai chi position in space, whatever - then you're at about minimum/maximum of what's likely to happen, or at a certain focus point for which you've already prepared.

Just be sure to grab the lens in the same way each take (thumb at 3 ft, index at 15 ft., something like that). But its a good guide, and you get a better feel for when something's coming at you, and you know, "when that person hits the sidewalk, and starts crossing the street towards me, thumb's gotta be here on the lens".

It helps you anticipate the accelerated focus speed of a logarithmic scale.

I also like the Panavision viewfinder where you can gently flip-in the magnifier (not hand-turn it) and quickly snap in and out to check critical focus, even during a take (but on some eyepieces this changes the diopter setting a little !).

Though, I'm lucky to work with excellent Focus Pullers that I never need to worry. But first, try shooting pretty much wide open. You'll be amazed how
much it can do to improve focus. Did I actually say that ?

Mark Doering-Powell
LA based DP



Using an eye patch does relieve eye strain. You may want to consider loosing the eyepiece extension. Someone once told me it automatically puts you at a 4 stop.

They can be out of adjustment and they just add more glass. And as a general rule of thumb: If it's out of focus you have probably pulled it too close. Try focusing back towards infinity first. Unless it's a charging cheetah running at for the food you have stored in your shirt pocket.

Tom Jensen
Lens Tech LA



>Can one exercise the eyes and/or filming stamina???

I met an operator who would look through the viewfinder with one eye before lunch and the other eye after lunch. That way he "worked" his eyes but didn't overextend them.

I think the eye patch suggestion is a good one. I haven't done it yet but I might. The eye that is closed ends up looking worse than the eye you've been using all day. Better to keep it open.

Art Adams, DP
Mountain View, California - "Silicon Valley"
http://www.artadams.net/



Hi,

> Here's a wild idea!! Perhaps have a focus puller!!!

Here's a wilder idea! You sell the concept to the money people!

I have never turned down a focus puller (and I shoot video.) Oddly enough, I've never had the chance to turn one down, because I've never been offered one.

Phil Rhodes
Video camera, edit, focus, zoom, and stop puller,
London



> Here's a wild idea!! Perhaps have a focus puller!!!

I have yet to see a separate focus puller assistant on a wildlife documentary, which is what I believe the original poster shoots?

Perhaps on Imax documentaries they use focus pullers?

Steven Bradford
Seattle



> Perhaps on Imax documentaries they use focus pullers?

The ones I worked on all had 1st Assistant/Camera assistants, but their prime objective was rarely pulling focus...and we ALL had to carry things...heavy things.

A lot of Imax shots do not have focus pulls in them...Watching the "other part" of the frame going out of focus on that big a screen from not that far away is a truly uncomfortable experience...remember that until relatively recently, "common wisdom" was that a close-up in Imax was a head-to-toe shot such that the head was generally somewhere between 1/2 way up the frame and 1/3 of the way up the frame.

Mark Weingartner
LA based



>Here's a wild idea!! Perhaps have a focus puller!!!

And to think I wonder why business is slow, it seems that as we move in to more electronic image creation there is this idea that things like a camera assistant are no longer needed.

Here's a wild idea. focus pullers don't work in wildlife . Can you figure out why? I hope so.
ps. Super 16 ain’t electronic bro.

To everyone else that responded to my post thanks for your ideas.

Steven - the one good eye, one bad is exactly what I have been concerned with. very scary.

Art - an operator with ambidextrous eyes is unbelievable and I don't think I could possibly ever pull it off.

Mark - thanks for the cleaning shutter idea and the shooting open suggestion. the only reason I might be shooting closedown is because I’m forced to. I suppose I could use ND’s but that would constrain me when the subject moved into an area of lower light. its also a pain to deal with a mattebox and filters when you have to carry the stuff for miles.

Tom - I heard that the extension took light away too but I wasn't sure how much. did you say four stops???

many thanks,

James Christian
Wildlife Cinematography
http://www.james-christian.com



Arri SR2. Focus is something that I’m constantly wrestling with.

I don't know if you use your own camera. Because the older SRII camera's have a filter slot for gel filters. This would solve your problem as well. Just put a ND 9 gel filter in (or more) and things will brighten up. If you rent a camera maybe you can get one of these.

The Jon Fauer 16 SR book has a chapter about it. I always try to go for the highlights (eyes,etc.)if there are any.

Herman Verschuur, cameraman
Amsterdam, Netherlands


Steven Gladstone wrote:

>Remember you have MORE depth of field behind the focus distance >than in front of (at least that is the way I learned).

Generally, it follows the 1/3 - 2/3 rule -- you have 2/3 of your DOF behind the point of focus, and 1/3 in front of it. Not scientifically accurate, but useful nonetheless.

Jeff "doesn't have 2/3 behind himself yet" Kreines



James Christian wrote:

>Tom - I heard that the extension took light away too but I wasn't sure >how much. did you say four stops???

I'm not Tom, but it isn't 4 stops. I think what Tom was referring to is that an extension eyepiece gives the image your eye is seeing an artificial f stop of about f-4. So therefore, in the viewfinder you have more depth of field than the image being formed on film. Even when shooting wide open. Making it harder to set focus by eye.

By the way, most of the out of focus stuff I see has the focus shifted back (Although not sure about wildlife, I'm more used to Narrative).

Remember you have MORE depth of field behind the focus distance than in front of (at least that is the way I learned).

Is your 150-600 a complete conversion, or only Bayo/Pl mounted?

Steven Gladstone
Cinematographer - Gladstone Films
Cinematography Mailing List - East Coast List Administrator
Better off Broadcast (B.O.B.)
New York, U.S.A.



Steven Gladstone wrote:


>Is your 150-600 a complete conversion, or only Bayo/Pl mounted?

My 150-600 is a complete century. Lt weight conversion. Thanks for your ideas. sounds like the convenience of of my extender may not be worth it.

Cheers,

James Christian
Wildlife Cinematography


>I have yet to see a separate focus puller assistant on a wildlife >documentary, which is what I believe the original poster shoots?


Understood, as well as on most sports shooting. I didn't understand that was what was referred to here, my bad.

Bret Lanius


>I have never turned down a focus puller (and I shoot video.) Oddly >enough, I've never had the chance to turn one down, because I've never >been offered one.


I don't mean to imply that most operators/shooters would want to work without an assistant. My point is more that the money folks seem to want you to do it, and there seems to be a certain amount of acceptance of this.

Bret Lanius


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> ...an extension eyepiece gives... an artificial f stop of about f-4. So >therefore, in the viewfinder you have more depth of field...

I thought the issue with the extension eyepiece is more the darkness & slightly degraded image & accompanying eye strain. Its not like the "f/4" extension eyepiece is letting you see "f/4" DOF when the taking lens is actually set at f/1.4.

Its just that its darker and harder to see. Remember, the sharpness & focus of the image has already manifest itself on the ground glass, which is what you're viewing with that extension eyepiece.

If anything, the eyepiece might have the f/4 rating to deliver a sharper image with less aberrations, albeit darker.

Its a camera with a ground glass, not a telescope.

Mark Doering-Powell
LA based DP