Prime lenses, rack focus...alert

My Zeiss ZF's (not ZF.2's) don't do it either. There's breathing and a shift due to the mount, but not this other thing that's being described.
 
Love to see footage to know what's going on - since there are two possibilities.
 
Shooter said:
This effect is not "breathing".

It is an image shift in the direction of the focus rack. Rack counter clockwise and it shifts left ( and vice versa).

I have not observed it shift up or down but believe that I could induce that. ( Will test)

It is absolutely the "slack" and "wear" in a lens that is not usually observed in movement of the focus ring. eg.a still photo is taken after the focus is made.

The operator and the AC need to be aware of it.

It is subtle but enough to ruin a shot.
Click to expand...



Sounds like gear back-lash.

When you change direction on the focus gear, the gears smash and the image jumps/ jolts a little.
 
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If the image is shifting off its center axis, not just changing size as in breathing, it has to be mechanical play in the lens or mount or lens elements that have shifted out of concentric alignment due to wear or damage. Shouldn't happen due to a follow focus unless it is pushing the lens barrel off axis, which means play in the mount or the lens mechanics anyway.
 
Will be posting up a Vimeo link to a test we shot today shortly.

Stand by your beds folks!

also...Spoke to my lens techo. He is confident he can alleviate the issue to a certain degree.


In the next 24 hrs...will also be posting up screen grabs of the rest of the testing we did today. Scene files, gammas, knees... a very interesting and productive day.
 
This is a common issue in many of the Nikon AI/S lenses I've used. My understanding is that it is related to wearing of the helical focusing gear in older lenses. I've used lenses that exhibit this issue on Red One and 35mm adapter systems. The issue is especially noticeable when adjusting focus while looking at a magnified image. When pulling focus, sometimes it unfortunately becomes a question of whether to even follow for small adjustments since it can be better to have a chance of going soft than definitely having that weird image shift every time the focus ring changes directions.

I only own one Nikon lens, a 50 f1.2 AI'd and I was lucky enough to get one that doesnt have any image shift problem as far as I can tell. This lens should be older than most of the MF Nikons I've used, but maybe it hasn't taken as much wear on its focus ring over the years as those ones with the issue.
 
Test.

Chris and I tested a number of my Nikkor AI - MF lenses to see how the "image shift" issue displayed.

Here are just 2 of them. A 50mm and a 35mm. Other lenses displayed varying degrees of the issue.

The focus pull was being done as one would in actuality. Subtle movement without mechanically loading the lens or adapter mount.

I overlayed the grid as a reference.

http://vimeo.com/19021498

Point of this thread ...is a caution ... and to encourage the use of cine style lenses and discourage over enthusiasm ( that may eventually dissapoint) in the use of still lenses for cine work.

Be careful out here folks!


Can anyone report on RP Lens Cinevised Nikkor lenses please. Tests would be good.
 
^
Yup, that's the image shift thing. IF you actually look at the front of the lens, as you rack focus, you can see the lens element physically shifting as you change focus direction. Again not all vintage still lenses do this. I haven't seen an FD L series lens or a Contax zeiss lens do this.. and I've only had a few regular fd do this. That's why I like buying lenses at KEH, 14 day return policy.
 
supertakumars dont do that either. I was all set on getting a nikkor prime set soon. what is the prob exactly and how can it be avoided when buying an older nikkor?

edit: k kholi said loose barrel. hmm..hope i dont get duds when i buy my set.
 
...what is the prob exactly and how can it be avoided when buying an older nikkor?
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I have now posted a vimeo link that shows the prob in the first post of the thread .

Answer to your second question is probably...you need to do a test of any lens you may buy.

I am sending one or two of my problem lenses to a lens technician. I will report back after he does what he does.
 
I know what you're talking and yes, it's an issue with some lenses. Just for the sake of someone else reading this, you must first be sure that your camera, any lens mount and follow focus are REALLY locked down tight because the turning of the gear on the follow focus can also physically push the lens right and left a millimeter or two.
 
Kindredmachine said:
I know what you're talking and yes, it's an issue with some lenses. Just for the sake of someone else reading this, you must first be sure that your camera, any lens mount and follow focus are REALLY locked down tight because the turning of the gear on the follow focus can also physically push the lens right and left a millimeter or two.
Click to expand...

I have confirmed that it is the lens and not the mount or the follow focus.

The tests shown actually were hand racked and also tested some with rings and F/F.

All lenses we tested exhibited different and repeatable "effect" at different points in the focus range and they all differed from each other.
 
wbrock001 said:
Do the duclos cine mods for nikon glass exhibit this?
Click to expand...

I have asked Peter at RP Lens to advise how their cine modded lenses work in regard to the issue.

I posted them the link.

Hope fully Duclos wil resopnd to someone as well.

Not sure if anyone here has actually done a test on their own cine modded lenses. If they have..they arent telling.
 
They don't take the lenses apart to the point that cinemodding them would cause what you're experiencing. Declicking involves the most taking apart of the lens and all that is is removing the mount and the aperture ring is right there. The inside of the lens doesn't get exposed and the glass is never touched or altered in any way... unless you specifically ask them to clean the lens or check the inside of the lens of course.
 
I have an old Nikon 50mm f 1:4 that I really love the look albeit it is not super sharp wide open, but it has backlash as well with my Redrock follow focus. I spoke with a guy in the Orlando area who rebuilds and re dampens lenses and I was gonna give him a shot at trying to fix this since I am so fond of this old lens.
 
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