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Monday, December 31, 2012

••◊ Zeiss ZF.2 lenses for filmmaking/video

The Zeiss ZF.2 lenses have become popular for low budget filmmakers for a couple reasons.
  1. You can adapt the Nikon F-mount to Canon EOS, Sony E-mount, or even PL-mount.
  2. They are much lower cost than CP.2's, but based on the exact same glass.
  3. High quality precision optics
  4. Great flare control at wide apertures. Much better than most pro-sumer lenses.
  5. The aperture ring can be de-clicked for cinema style smooth aperture control.
  6. It's easy enough to add a lens gear (mostly).
What I'm going to discuss here is my personal experiences with trying to use these lenses as a film making tool. Let's start with the lens used in a matte box. As you can see below the stock Zeiss lenses all come with a beautiful silver anodized front ring. This is completely benign when used as a still lens, but behind an ND filter it becomes troublesome. While I was out shooting plates at a local park in mid day sun I noticed some flare problems even though I had the matte box flags closed down to control side spill. The silver front ring was likely reflecting back onto the ND filter. The easiest way to fix this is to add a cheap filter step up adapter that's matte black; in this case to 77mm (second photo below). My circular polarizer has a 77mm thread mount, so that was the logical choice. Also the Zeiss ZF.2 lenses are inconsistent in front ring size, so it's good to standardize this filter thread size for the economics of having a common screw on filter size. As an added bonus the step up adapter conveniently grabs onto the matte box bellows, which means you don't have to mess around with the bellows being caught in a telescoping lens barrel!

So, speaking of telescoping lens barrels...this example is from my 50mm macro lens. Notice how is almost doubles in height when focusing from infinity to macro? You need to take this mechanical displacement into account when mounting the lens in back of the matte box filters so you don't accidentally crash into them! This is definitely an issue that true cinema lenses don't face. They tend to have the same front diameter, the same length, and the same placement of lens gears in order to ease the headache of on-set lens changes. That's one of the reasons why people choose the Zeiss CP.2's instead of the ZF.2's. If your talent is costing $1k/hour then it better not take more than 5 minutes to change a lens and reconfigure the camera!

The last point I'm going to discuss is the necessary modifications needed to make the lens ready for film making. Typically these lenses need a focus gear and de-clicking of the aperture ring. For those not daring enough to do it themselves, service shops like Duclos in Los Angeles offer it as a turn-key solution. Video Gear sells the Novoflex adapters to convert the lens to whatever mount you need and the filter adapters area incredibly cheap online. So all you really need is the gear and de-clicking.

Now you may ask why I didn't use a el-cheapo zip gear? ...and there lies one of the first problems I had to solve. The 50mm Zeiss ZF.2 has a 349-degree focus barrel rotation! There's no room to put the zip tie or screw attachment points! The 35mm Zeiss on the other hand has about a 1/3rd turn focus barrel rotation, so it could potentially be used with a cheap off the shelf zip gear. If you use a rigid mount gear on one lens and a zip gear on another you'll have the same lens changing issue. If you have the budget I recommend making your lenses as mechanically interchangeable as possible.

What I also took note of is that the Zeiss 35mm lens is an incredibly heavy beast. It weighs more than my 24-70mm L-series Canon zoom lens and that thing is a beast to lug around! At least is doesn't telescope.

When purchasing the 100mm macro lens the telescoping becomes an even greater factor. Both the focus barrel and front ring translate! So you can use an extra wide lens gear, but even with that I'm not sure you'll be able to use a follow focus over the entire focus range - I haven't tried it myself. That lens is really meant for extreme macro detail shots anyway, so it's probably not a big deal to not be able to use a follow focus - in most cases.

Other than the ergonomics of trying to make a low cost SLR lens work for cinema, these really area excellent precision made lenses. They do breathe while racking focus, just like any other SLR lens, but the CP2.s do that as well. It's only when you step up to the big budget lenses that those problems go away and in that case it makes more sense to rent.

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