Follow Focus battle – part 2

This is a follow up to an article I wrote about difficulty in finding a reliable follow focus that also doesn’t break your bank – in an essence – it doesn’t exits. Follow focus to work needs to be of very high quality which in turn makes it expensive.

One needs to ask what it takes to get a good focus. The answer obviously doesn’t start with the follow focus units but the lens. Distance focus ring has to travel from close to infinity is crucial. In most cases most modern lenses (especially zoom lenses) “suffer” from this distance being extremely short – often as short as 1/4 of the lens barrel revolution thus your subject moving from distance of, say, 4 to 6 feel will only need a tiny focus barrel move – difference often not significant enough for reliable focus pull. Here old lenses, prime lenses and cine lenses shine as those often require significant barrel move to focus from our example of 4 to 6 feet thus any error in mechanism of your FF unit (such as gear play) or error of the focus puller will be much less noticeable.

The question of the kind of lens gears attached to the lens is crucial too. There are many proposed solutions but it seems only the ones that have a constant diameter work. The flexible gears seem to change the pitch of the gears when flexed thus are not recommended as this introduces yet another possibility of error.

Assuming that we take care of the above – we find a good lens with good optics that has long traveling distance from close to infinity and we equip that lens with a good lens gear we can look at various FF units.

Here is how each column of the chart below represents FF’s behavior:
gear play – how much it takes from the marking wheel to move before the gear engaging the lens gear moves – obviously the lesser the better as with the gears not perfectly mashing against each other we start introducing errors that can have unforeseen effect on the sharpness of the footage

marking wheel size – originally the assumption was that the larger the marking wheel the more exact the markings are but this alone is not so. The reduction gears (if the FF unit has those) inside the gear box allow for the marking wheel to travel larger distances to achieve the focus – look at the marking wheel from Cinevate, Zacuto and Shoot 35, the Cinevate shows much smaller distance traveled on the wheel as opposed to Zacuto and shoot35. This can have both positive and negative implications, smaller distance might be a blessing on prime lenses while disadvantage on zoom lenses, while longer distance might have opposition effect. Moreover introduction of reduction gear might add unwanted gear play.

rods mount – or how sophisticated the mount is. In other words how many screws are necessary to make adjustments – for instance with Genus it takes 3 screws to make adjustment while in case of say Redrock it only takes 1. Some units were failed in this category because of plastic construction of the mount.

“sticks”category – when FF is mounted on the rods, then slid close to the lens, then tightened it tends to “stick” to the lens which in turn might add unforeseen forces to the lens that will influence ease of the focus pull. This category is a bit problematic as it’s really hard to measure properly.

movable maker – for all those out of ordinary focus pulls where marker in other then standard position is necessary.

small gear box – how much of a hustle the size of the gear box will be (especially while working with small prime lenses).

verdict column – this category is based on experience of shooting for living and seeing all the necessities that one might need in general set situations – in other words the final verdict is: does it do what it’s suppose to.
(click chart for larger version)

general notes:
Dfocus, Indifocus – it is what it is – some plastic parts put together that might teach you about the workings of a FF unit – don’t expect too much as the units don’t seem to have reduction gears, the gear play is quite large. Useless unless you are a student. Save your money and get a better unit that will last longer and actually work

Cavision, Redrick – those units actually kinda work if your don’t worry about having to repeat unsuccessful focus pull a few times – but if you are working where FF performance is essential (for instance working with actors) then there is too much error being introduced with gear play for rigors required from working set.

Genus – move your focus wheel then watch it slipping back by a millimeter or so… this unit only feels good in your hands and would probably make for a cool decorative piece but just doesn’t work (in class with Dfocus and Indifocus when it comes to its working quality)

Shoot35 – very impressed with the performance, based on the test I’m ordering one myself

Cinevate – near zero gear play (actually closer to NONE) but at the price of doing away with reduction gears. Large gear box is an issue but over all I’m happy owner of this unit.

Zacuto – work very well but surprisingly feels very cheap in your hands.

Arri – very good

Chrosiel – no opinion as I didn’t play with it long enough to form an opinion.

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Things that were not looked at even though might influence your purchase (based on suggestions of other cameramen):
– can gear pitch be easily changed (are other gears available)?
– can gear be mounted on the other side of the FF arm? If so how easy is the transition?
– durability
– does it have ball bearings? what grease is used? (cheap one will freeze in cold)
– is marking wheel permanently attached and if not is there a notch on it to prevent it from sliding?
– is marking wheel easy to mark?