Focus Does Not Match Markings On Lens

[Brian Mills]

Hi All:

So I got a set of Rokinon Cine DS primes that I am generally happy with, but when I screwed in that tape measure holder into my FS7 and checked the focus on a focus chart with a tape measure, I found the markings on the lens barrel were WAY off.

Has anyone else experienced this? Would it be a problem with my camera or my lenses?

[Doug Jensen]

Are you actually planning to use those witness marks to set focus instead of looking through the viewfinder? If not, then just ignore the discrepancy. I personally wouldn't even care if a lens had markings on it all because I would never use them.

[Gary Huff]

Originally Posted by Brian Mills

when I screwed in that tape measure holder into my FS7 and checked the focus on a focus chart with a tape measure, I found the markings on the lens barrel were WAY off.

The Rokinon Cine lens markings are for show, not for use. That requires the purchase of real cinema glass.

[Brian Mills]

Originally Posted by Doug Jensen

Are you actually planning to use those witness marks to set focus instead of looking through the viewfinder? If not, then just ignore the discrepancy. I personally wouldn't even care if a lens had markings on it all because I would never use them.

It's not that I would EVER only set focus with a tape measure (although that is how I was trained back in the days of film school), it's just that I was concerned that because the markings were so inconsistent, that perhaps I had a backfocus issue or had a bad set of lenses (I just got these and have not shot with them other than tests).

Plus on the rare occasion I have the luxury of an AC, it would be nice if the witness marks on the lenses were accurate to help him/her judge a focus pull (yes I put down marks, I'm talking the speed of the pull).

But I guess the consensus is that the markings are just not accurate and I should not use them or worry that they do not work.

The lenses do appear to work fine when focused by eye, and are pretty sharp stopped down to a F4 or so.

I was just wondering if anyone else had observed something similar...

[Olof Ekbergh]

You could mark the back of a tape measure to match the markings on the lens and use that for the "traditional film school way" to focus.

Just a thought...

I would also make sure infinity is close to right, or have it adjusted. A lot of lenses focus the end just past infinity, so that in extreme temps you can still hit infinity.

[Brian Mills]

I guess I was just wrong to expect $500 Rokinon lenses to accurately display what they are focused to on their markings.

Apparently, I need to pay $2500 for that:

Hands-On Review: Rokinon XEEN, True Cinema Lenses for Full-Frame Production | explora

I'm happy enough with these lenses to pay $500 for them, not so much for $2500 (yes these new ones are better built, but how much better are they optically?).

I suppose I'll just rent lenses for the bigger budget stuff...

[Brian Drysdale]

It's not that unusual for a 1st AC to make their own distance marks on a lens using a sharpie to put the focus marking onto a white tape around the lens barrel .

The new lenses use the same glass, so I wouldn't expect much difference optically. The cost of cine lenses is the mechanics and the accuracy of the focus markings. How accurate those are on cine Rokinons will depend on how they're going about it. With the expensive high end lenses they calibrate each lens individually.

[Brian Mills]

I did not realize that having the witness marks not align was such a common thing for lower end lenses.

I was concerned maybe I had a bad set, but I guess its common.

I really do like the lenses generally, especially for the price!