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Nikkor Lenses Shift With Follow Focus


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#1 Jeremy Drake

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Posted 05 October 2009 - 10:27 AM

I have a set of Nikkor lenses (24, 35, 50, 85) that I use with a red rock follow focus on a red.

Whenever I switch directions with the focus.. say someone is walking away and then towards me.. the lenses shift slightly causing a little bump in the frame. Its especially noticeable when I use my focus assist.

I'm worried that the follow focus may be putting too much pressure on the lens or damaging them. I try to use the threads so the tips do not touch but I still see a slight shift.

Anybody else had this problem?
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#2 Paul Bruening

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Posted 05 October 2009 - 11:20 AM

Yes. The still lens problem with FF. If you are sure there is no play in the focus rings then the bump you encounter is likely in the FF unit. FF units have some cross directional play in the gears known as "lash". If it's a geared unit then it will always have some amount of lash. Lash isn't as noticeable in cine lenses since they were designed to allow for this and other issues by having a greater ratio of ring-to-element movement. Still lenses have such a short "throw" that gear lash seems huge. If you can fine tweak the distance between the lens gear and the FF drive gear (at least on your cross pull shots) you might reduce the lash there. I think that toothed belt FF systems will have to replace gear types as more still lenses come into use. Though, I hear gripes about the pressure they put on the barrel. If you find a solution, please, share it with the forum.
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#3 Noah Yuan-Vogel

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Posted 07 October 2009 - 06:54 PM

Yes, This is definitely a problem with some older AI and AIS Nikkors. I think Paul is talking about something else, since im not sure how FF gear lash would contribute to this issue. It certainly seems like optical elements shift back and forth quite a bit in these lenses when you change focus direction. My take on this was always that these 30year old still photo lenses either are prone to internal elements becoming loose or maybe they have just always been like that since such an effect would never be noticeable when operating the lenses for still photography. Either way, this is why I am very very skeptical of the use of such old still photo lenses for motion picture applications. I've always been a little surprised I hadnt heard more about this since I often hear people raving about the quality of old nikon still lenses and cant seem to agree.
I have a few zeiss contax still photo lenses I like to use and certainly have better mechanics than nikons about the same age and have some dampening and no sign of loose bits, but even these lenses I find have a weird issue with the aperture blades closing into an odd pattern, creating some odd bokeh when shooting with the aperture 1-4 stops down from open (imagine a polygon with sharp spikes sticking out of it). Moral of the story is probably that still photo lenses made over 20years cant be relied upon. Next time I try to use still lenses for cinematography, I plan to test them very very carefully.

Edited by Noah Yuan-Vogel, 07 October 2009 - 06:55 PM.

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