Thread: Soft Focus at Infinity with Epic and Tokina 11-16 f/2.8 II - Any Solution?

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  1. #21  
    Quote Originally Posted by Frank Glencairn View Post
    It also doesn't look that bad if I bolt the 11-16 on a DSLR - I run out of ideas. Think I give it back.
    Maybe the Nikon mount version with an adapter?
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  2. #22  
    Senior Member Blair S. Paulsen's Avatar
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    Just be aware that if you are dialing in the FFD (flange:focal depth) by eye with a regular taking lens you are dependent on the lens and its markings being spot on. I can remember doing a prep at Clairmont Camera where they pulled out a hero lens that never left the building to do final confirmation as they knew it to be spot on.

    Unless you are out on a gig and need a quick fix I strongly suggest you use proper tools to set your FFD. I'm not saying you can't get it right by using charts/targets and good monitoring but why take the risk that a slightly out of collimation lens or poor witness mark alignment could create error?

    RED even offers a tool for this task: http://www.red.com/store/products/red-focus that should fix you right up. Of course it's two grand with tax and shipping so that's a pretty big disincentive from a budgetary standpoint unless you run a rental house. Perhaps RED could offer a rental program where you pay shipping plus $50 to use it for a day? Just a thought.

    BTW, if you've read this far be aware that the IR/OLPF in front of the sensor can fool some collimation tools so double check with the most reliable lens at hand.

    Cheers - #19
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  3. #23  
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    I'm not sure if the RED focus will help – it's PL and the tolerances on still lenses are pretty high.
    Rather set the flange distance by using the widest angle on the Tokina, measuring a fixed distance and adjust to it, then check several times at different zoom positions if it stays in focus.
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    Uli

    My Red is called Vertov after a Russian avantgarde filmmaker, a pioneer in modern cinematography, a true revolutionary who later suffered under Stalin's bureaucracy.
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  4. #24  
    Quote Originally Posted by Matt Ryan View Post
    flange depth is backfocus haha. backfocus is the incorrect term though. Flange depth is distance between sensor to rear element of lens. So adjust your camera flange distance as a test first. If thats not off it's the lens.

    http://en.wikipedia.org/wiki/Flange_focal_distance
    If all your other canon lenses focus correctly then it's not time to adjust the flange distance / back focus. Then it's very likely that the lens need service. in other words the lens needs to be collimated. And basically it need to be adjusted so it gets closer to the sensor. I do not know how it's adjusted on the lens in question. Some lenses use shims that can be removed and others have a lock screw and then a threaded ring that is used for adjustment. Best is probably to hand in the lens to a "lens doctor" if you do not feel like digging in to it yourself. As it is such a wide lens it should be quite possible to see when it's right by adjusting it so it's perfectly sharp at infinite then the rest of the marks should line up as well.
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  5. #25  
    Senior Member Peter Moretti's Avatar
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    Quote Originally Posted by Andy Maser View Post
    ...

    I'll try it on my Scarlet tomorrow and see if I have the same problem.
    That seems to make the most sense to me. Before messing around with anything, test the lens on another body.
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