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Relying on Monitors When Pulling Focus


Forrest Kos
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Hi all,
 
Photographer turned Videographer here. and I had a few questions about pulling focus that i was hoping some of you could give your input on.
 
I have been using a Tilta Nucleus on Canon c200 setup for about 3 years now. We have done a few jobs with this setup but I haven't been around a big film crew where I would have seen a real pro pull focus. So everything is DIY and pretty self explanatory. 
 
However, we did hire someone to pull focus and they did a few things that after some research has still left me a bit puzzled. We were using Cinema Zeiss Lenses and they firstly matched the Tilta focus ring on the remote to match the lens foot by foot. 
 
But what really puzzled me was throughout the day he would measure his focus from camera to subject depending on the shot, the camera stayed relatively still in Z space for our shots. After researching why this was, I am finding it isn't good to "rely on your monitor for focus" because you can "lose your focus in the space of the 2D image. Can any focus pullers out there explain to me why you don't rely on the monitor when in todays age it seems like you see everything for what it is?
 
-Any other tips are appreciated
 
Thanks!
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Hi Forrest, 

As long as you have taped out your lenses to confirm the witness marks for all distances match up with real world objects,   (Which typically is done at a prep the day before with a focus chart) then measuring distance repeatedly, and having a sense of all distances among stationary objects, and as they relate to talent, is usually the most reliable method. We often use ultrasonic distance measures on camera with readout on the hand unit as an additional tool, but when ACing, I would still use a laser distance measure, as well as physical measuring tape, or literally just my best guess in various situations, and basically repeatedly cycle through a couple tools at my disposal for critical shots. Certain situations such as extremely long lens closeups are better suited for monitor work because of extremely thin depth of field, and additionally there are overlay displays which create a visual representation of the depth of field over the image on a monitor and / or on the wireless focus unit. Still, I find that for most normal and wide lenses, I can best anticipate an actor’s direction and distance by watching their feet. It’s not until reaching into longer lenses or very large apertures that this method fails to keep up with the alotted depth of field. A huge part of this whole process is a knowledgeable DP who knows the right amount of depth of field to use to various scenarios, and the “likelihood of success” curve as you vary your depth of field via focal length, Iris, and distance to subject for a given shot. 

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I was once on a show where they were focusing only by the monitor for the first week of shooting. Panavision Alexa package, all top tier stuff. 50% of the footage was out of focus. We in the post team hypothesized that the monitor was so small (or was not full HD) such that the scaled down image looked in focus when it actually was just ever so out of focus (and not salvageable by post tools). After repeated warnings from us production finally started using laser rangefinders measuring from the image plane to talent, and lo and behold suddenly everything was in focus.

On camera monitors lie, or at least are not suitable for interpreting the final image short of a calibrated high rez monitor in a dark tent at video village.

Get your marks, measure your focus with a tape measure or a laser finder, or ideally get a cinetape or similar if spending the extra 15-30 seconds to measure your marks is too great an inconvenience. Doing any less is potentially throwing money into a shredder, and leading to heartbreak, disappointment, and scrambling in post to save the picture.

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Depending on the monitor and how they set it up with focus assist and peaking that those can be deceiving. Even with things like Light Rangers and Cinetapes, they're tools but not always 100% accurate. If the lens is calibrated and you know distance, you can pull on digital or film and not need a monitor. 

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22 hours ago, Robin Phillips said:

I was once on a show where they were focusing only by the monitor for the first week of shooting. Panavision Alexa package, all top tier stuff. 50% of the footage was out of focus. We in the post team hypothesized that the monitor was so small (or was not full HD) such that the scaled down image looked in focus when it actually was just ever so out of focus (and not salvageable by post tools). After repeated warnings from us production finally started using laser rangefinders measuring from the image plane to talent, and lo and behold suddenly everything was in focus.

On camera monitors lie, or at least are not suitable for interpreting the final image short of a calibrated high rez monitor in a dark tent at video village.

Get your marks, measure your focus with a tape measure or a laser finder, or ideally get a cinetape or similar if spending the extra 15-30 seconds to measure your marks is too great an inconvenience. Doing any less is potentially throwing money into a shredder, and leading to heartbreak, disappointment, and scrambling in post to save the picture.

Every AC works different. Not every high end AC uses a focus assist tool and those tools are only aids anyways ...some do like working off monitors. most veteran AC's have a 9 or 13' 1080 display these days. 

 

 

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Monitor focus pulling is a different skill set from traditional focus pulling that requires patience and practice to master. For me, after over 3 decades of film focus pulling, I successfully have made that transition. It offers me many more opportunities to help tell the story via focus. Focus pulling is no longer a technical process but now a creative one. I love that. 
 

I sit quietly in my chair, away from set, with my Small HD 1303 monitor in front of me, my Preston handset mounted to the monitor stand and a Comtek in my ear so I can hear the dialogue. This allows me to “watch” the movie and make story telling decisions in real time on how and where to play the focus so it maximizes the effectiveness of the shot. It’s almost like a video game! The point is, I can see focus opportunities that I wouldn’t see if I was standing next to the camera pulling in the traditional way. Finally, since I can see my work as it happens, I don’t worry about if I got the shot in focus or not. I can guarantee my work with confidence right then and there. 
 

G

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14 hours ago, Gregory Irwin said:

Monitor focus pulling is a different skill set from traditional focus pulling that requires patience and practice to master. For me, after over 3 decades of film focus pulling, I successfully have made that transition. It offers me many more opportunities to help tell the story via focus. Focus pulling is no longer a technical process but now a creative one. I love that. 

Do the more traditional "film" sets, even with HD taps, have a similar method or are they all using the old school non-monitor method? 

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14 hours ago, Tyler Purcell said:

Do the more traditional "film" sets, even with HD taps, have a similar method or are they all using the old school non-monitor method? 

I would say the old school non monitor method Tyler. The quality of the film HD taps are not good enough to pull critically off of a monitor. They really never materialized as we had hoped. 
 

G

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6 hours ago, Gregory Irwin said:

I would say the old school non monitor method Tyler. The quality of the film HD taps are not good enough to pull critically off of a monitor. They really never materialized as we had hoped. 
 

G

Got ya, figured as much. Thanks, hope you are well. 

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On 8/31/2022 at 11:03 PM, Tyler Purcell said:
13 hours ago, Tyler Purcell said:

Got ya, figured as much. Thanks, hope you are well. 

 

All good Tyler! Thank you! I’ll be in LA soon to start my next movie. It’ll be hard to be away from my family yet again! Hope you’re doing well too!

G

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In 2011 I was doing unit stills on a UK BBC drama and was amazed to see the focus puller alongside the steadicam op on a walking shot pulling focus without a monitor. I asked him how he did that and he very politely said "it's my job to know what 10 feet is". In 2021 I bumped into him again on His Dark Materials and he was pulling off a monitor next to a camera on a dolly. When I reminded him about 2011 he said: "I wish I still had those eyes!"

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  • 3 weeks later...

A well-rounded focus puller nowadays should be good at both the old measuring/guessing distances method and pulling from a monitor. There are situations that favour both.

Additionally, they should be learning how best to use the various types of autofocus that are appearing in non-cinema cameras like the A7S3, FS6 and various Canon cameras - this will filter up to the cinema cameras eventually. Using autofocus properly and in combination with manual methods is a real skill, and it can do things that are pretty much impossible with solely manual methods.

As resolutions increase, focus is is going to get more and more critical.

Edited by Mei Lewis
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3 hours ago, Mei Lewis said:

Additionally, they should be learning how best to use the various types of autofocus that are appearing in non-cinema cameras like the A7S3, FS6 and various Canon cameras - this will filter up to the cinema cameras eventually. Using autofocus properly and in combination with manual methods is a real skill, and it can do things that are pretty much impossible with solely manual methods.

This comes up on this blog a decent amount and while it’s not untrue it’s also a bit myopic, the reason those cameras are able to have such advanced AF systems is because the camera is using a dedicated AF lens with motors inside, cinematographers have for years been using mostly pl or pv mount cinema lenses that can not integrate such tech because frankly they would be huge. It’s possible with external motors but it would have to exist within the ecosystem of something like a preston with a light ranger or like smallhd’s rangefinder af integration which is nowhere near as accurate because it can’t detect faces or contrast and would still need to be operated by a first AC making dedicated focus decisions. I agree that the best firsts can and do rely on a bit of both (although only very relatively recently) but it’s important not to minimize how different these systems’ implementations are in the real world. 

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