Parfocal vs. varifocal

DDK

DDK

In learning about photography in order to understand my camera, I'm starting to think about lenses for filming vs. photography. I've been informed that parfocal lenses are generally better for film work but as I understand it, require special mounts and types of cameras to work.

So I was hoping for some insight into the issue from people who actually use things like the 600D or GH2 for film as opposed to photographs, as to what they use and whether or not I should be investing in varifocal lenses now or saving for parfocal lenses later on when I get something more suitable for video, like say a BMPCC.
 
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DDK said:
In learning about photography in order to understand my camera, I'm starting to think about lenses for filming vs. photography. I've been informed that parfocal lenses are generally better for film work but as I understand it, require special mounts and types of cameras to work.

So I was hoping for some insight into the issue from people who actually use things like the 600D or GH2 for film as opposed to photographs, as to what they use and whether or not I should be investing in varifocal lenses now or saving for parfocal lenses later on when I get something more suitable for video, like say a BMPCC.
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All that means is that the focus will stay sharp (parfocal) when you're changing the focal length (zooming). Unless you plan to do a lot of zooming in and out, it's not a big deal. Varifocals do just that, the the focus point moves as the focal length changes, so you need to refocus afterwards.

Before focus peaking and digital zooms, it helped as you could zoom in, focus tight, then zoom out to frame. With most cameras now though you can zoom in digitally while focusing, so it's not much of an issue.

Personally, I wouldn't turn down a parfocal lens, but I sure wouldn't spend more money on one just over the par/vari focal issue.

For mounts, it's not so much a special mount, as special adjustments. You need to carefully set the focus exactly, which sometimes requires adjusting the focal flange distance; between the back of the lens and the capture surface. Some fancier lenses have a separate focus for this, sometimes you can adjust the distance of the film plane, sometimes you adjust the lens itself. I've seen a parfocal working fine on a GH2, but they had to adjust the lens via some set screws on it before it focused properly.

CraigL
 
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DDK said:
In learning about photography in order to understand my camera, I'm starting to think about lenses for filming vs. photography. I've been informed that parfocal lenses are generally better for film work but as I understand it, require special mounts and types of cameras to work.

So I was hoping for some insight into the issue from people who actually use things like the 600D or GH2 for film as opposed to photographs, as to what they use and whether or not I should be investing in varifocal lenses now or saving for parfocal lenses later on when I get something more suitable for video, like say a BMPCC.
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Everything CraigL said is spot on. I'd just add that the lenses that tend to be parfocal are broadcast zoom lenses, or Cine lenses. Both are expensive, they are also expensive to adapt to a GH2 with the adapter running upwards of $300. I was able to purchase a broadcast zoom with a huge zoom range, but found out the adapter was 100x what I paid for the zoom. In most cases its not worth it. Most broadcast zooms with a lower end below 20mm will vignette on the four/thirds sensor.
 
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