How should focus control be implemented in LUMIX S?

Here is a design that I would like to propose to Panasonic. A manual focus control system that is simple, effective, and make sense to professionals. It is also highly doable if Panasonic really wants to make it.

There are four main components to this system:

  1. Wireless focus controller that directly talks to the internal lens motor
  2. Hybrid lenses optimized for video shooting
  3. An accurate focal distance scale
  4. Accurate flange depth

1. Wireless focus controller:

There is already an AF motor inside each native lens. Why don't we make a wireless controller to take advantage of it?

The focus controller should have a large hand wheel, just like those professional wireless follow focus. The hand wheel should have hard stops on both ends.

It should also control aperture, zoom, and start/stop of the recording.

A thumb wheel version can be created for single operator shooting. The thumb wheel does not need to have hard stops. But it should work in tandem with the wireless hand controller, so that a camera operator and focus puller can work together during shooting.

Wireless focus controllers, like this model from Arri, can be used to remotely and precisely pull focus. Panasonic could make one that takes advantage of the AF motor inside each native lens.

2. Hybrid lenses optimized for video shooting:

With the success of hybrid camera designed for photo & video shooting, don't you think we need hybrid lenses too?

Traditionally, professional focus pulling requires the use of cinema lenses, which are manufactured to a much higher price bracket. I believe the gap between cinema and photo lenses can be closed if Panasonic’s engineers are willing to think outside the box.

A side note to our Panasonic marketing department. Here is a real marketing opportunity. A pro series of well-designed hybrid lenses optimized for video shooting will give us great reasons to buy your lenses. Users who invest a lot of money in your lenses become loyal users.

Hybrid lenses for cinema should have the following features:

The internal lens motor must be smooth and quiet during focus pulls. We don't want the focus pull to move in steps, and we like to keep our sound guy happy. Same for aperture.

Each lens should come with an internal data table/curve that helps the camera translate lens motor position into actual focal distance. (Ideally, the table should be customizable so that the user can compensate for any inaccuracy, just like how a camera assistant sometimes need to redo the marks on a lens that is out of calibration.)

I created a custom curve for each lens I use with the Blackmagic Micro Cinema Camera. These curves are the key to distance-accurate focus pulling. They work surprisingly well. (More info about this setup below)

Parfocal zooms. The optical design of traditional motion-picture zooms are parfocal (i.e. no focus shift during zoom), but they are large and expensive. I propose that an internal data table can be used to electronically compensate for the focus shift of a non-parfocal optical design to mimic the behavior of a real parfocal lens. If this can be done, all of a sudden, non-parfocal optical designs that are compact and affordable can now be used for motion-picture. This is big!

Minimal amount of breathing. Real cinema lenses have some breathing too. I don't need absolute zero breathing, but it shouldn't be distracting like the Sigma 50-100mm F1.8.

Linear focus ring action with hard stops. The dual-mode focus ring design in the newly announced LUMIX S lenses is a great step in the right direction. It can be set to have hard stops and linear, repeatable response. No more fiddling with fly-by-wire focus ring that never behaves predictably. Great applause to Panasonic!

Focus and zoom rings in cine direction. Both rings must operate in the same direction as professional cinema lenses. Current LUMIX lenses for m4/3 have zoom rings that work in the wrong direction. This tells me one thing: Panasonic hasn't been very serious in optimizing their m4/3 lenses for video. Hopefully Panasonic will try harder now with Lumix S.

A side note to our Panasonic marketing department. Here is a real marketing opportunity. A pro series of well-designed hybrid lenses optimized for video shooting will give us great reasons to buy your lenses.

Motorized zooms. Ideally, a zoom lens should be controllable in two ways: 1) Speed mode: zooming speed is controlled by a force sensitive button (rocker switch), just like a LANC controller or the Microforce lens control system, and 2) Position mode: camera operator can grab on the zoom ring and quickly rack the zoom to a specific position, and it should be repeatable. Both modes are useful to professional filmmakers depending on the situations. e.g. An emotional close-up of a sad face would call for slow creeping motorized zoom, while a fight scene usually calls for snappy, confident zooms by hand. Motorized zooming is also useful when the camera is mounted on a crane.

3. Display of an accurate focal distance scale:

A good sense of focal distance is central to the craft of a focus puller, who spent years training his/her ability to judge distance by naked eyes. A clear display of the focal distance scale is an essential requirement for focus pullers to do their job.

The remote focus controller should have a screen that displays the distance scale.

The camera LCD, EVF, and video output should have the option to display the distance scale, and it should be clearly marked down to feet and inches.

The distance scale display should have minimal delay.

The focus ring on the lens should have the distance scale accurately engraved down to feet and inches.

4. Accurate flange depth:

This very important detail is rarely talked about. All the above features designed for good focus pulling is in vain if the flange depth of each camera body is inconsistent.

Flange depth is the distance from the mounting flange to the sensor plane. It is a fact that every individual camera body has a slight variance in flange depth due to manufacturing tolerance. Autofocus cameras are allowed to have more tolerance in flange depth than MF cameras because the AF motor can compensate for it. The on-sensor AF detection of mirrorless cameras makes such compensation even easier to perform. However, the MF system I propose requires a data table in each lens to work with all LUMIX S camera bodies. Variance in the flange depth between camera bodies will throw off the accuracy of the lens data table and render it useless.

A good sense of focal distance is central to the craft of a focus puller, who spent years training his/her ability to judge distance by naked eyes. A clear display of the focal distance scale is an essential requirement for focus pullers to do their job.

Real cinema cameras like the Alexa have interchangeable shims behind the lens mount to ensure perfect flange depth, especially when there is a big change in environmental temperature. The same shimmable design is useful for the LUMIX S, but it may be too costly to manufacture.

Another possible solution is to design an automated algorithm to measure the variance of each camera-lens combination. When a lens is mounted on a given camera for the first time, the camera would ask the user to point the camera towards a far-away object. The camera would figure out the flange depth of this combination, compensate for any discrepancy, identify the lens, and store the information for future use.

The DJI X7 camera system is a good example with such flange depth compensation algorithm.

It will be the ultimate compact camera system

Camera reviews like to compare the size of camera bodies. But I think it makes more practical sense to consider the size of a whole camera setup in its operational state.

You may be surprised how such a MF control system can shrink down a whole camera setup in a meaningful way.

Here is a visual comparison:

At minimum, a mirrorless camera setup that supports accurate wireless focus pulling looks like this today:

With the focus control system I propose, the same setup can turn into this:

A cinema lens is no longer required for distance-accurate focus pulling. When the cinema lens is replaced by a native lens, mattebox and large filters can be replaced by lens hood and small screw-on filters

It has been done before

Unlike today’s AF technology, which is still far from useful for professional filmmaking, the technology to design a good MF control system is readily available.

In fact, such MF control systems have been successfully created in the past. They take advantage of the internal motor of photo lenses, and they are accurate enough for professional focus pullers. Many filmmakers, myself included, who have direct experience with them are generally quite happy with these systems. I am sure Panasonic can do even better if they want to.

Example 1: EF Mount for RED One by Birger Engineering + Viewfactor wireless controller:

Back in 2007, a small American firm, Birger Engineering, created a smart EF mount with wireless capability. It allows precise, repeatable focus pulling with Canon EF lenses. But it is not perfect. Users need to make their own distance marking disc for each lens, and the marks can be off when you switch camera bodies, or if you use another copy of the same lens.

Example 2: Blackmagic Micro Cinema Camera with Fresky RC Controller via SBUS:

It took me two months of research and experiments to come up with a setup that is quite practical and reliable. I am able to perform repeatable focus pulling that is accurate down to feet and inches.
This setup requires a lot more DIY to work. It took me two months of research and experiments to come up with a setup that is quite practical and reliable. I am able to perform repeatable focus pulling that is accurate down to feet and inches.

The RC controller even allows me to remotely control aperture, shutter angle, ISO, white balance, zoom, frame rate, start/stop, and even audio level.

I wrote a dedicated post about this setup.

Other good-to-have video features

While we are at it, here are some good-to-have features that I'd like to see if there is a future video-centric LUMIX S model in the making.

  • GH5-style flip-out screen. Lots of video people don't like the 3-axial screen on the S1/S1R. Even the Alexa Mini has a flip-out screen design. Why change it?
  • High-bright screen. Make it extra bright. Make it viewable under sunlight. I know it eats battery and heats up quick. But it really is super useful outdoor. Just make it smart enough to dim down automatically when the light gets dark.
  • Internal ND filter
  • 4K 10-bit V-Log 60fps
  • Highly integrated long-range video transmitter. Either build it inside the camera or make an add-on module that is highly integrated with the camera. Monitoring thru Wi-Fi isn't reliable enough. (I know I am getting greedy…)
  • Sturdy, positive-locking lens mount. For the time when we do use a cinema lens. (Just like the mount upgrade option on the Canon C300 MK2)
  • Special stabilization mode for organic handheld movement. 5-axis stabilization works very well for stills, but sometimes it looks too flowy and unnatural in video. More stabilization isn’t always better for video. Sometimes all we need is a moderate amount of stabilization that makes handheld shooting with a 2-lb camera look like it is done with a 20-lb camera on a shoulder. The key is natural and organic movement.
  • Ergonomics. For the video-centric pro model, please, don't make it too large, otherwise the whole talk about small cameras getting good focus control becomes moot. At least give us one video-centric model with DSLR-like form factor. And please, for god's sake, don’t make it shaped like the Canon C100 / C300. They have the worst ergonomics.