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June 21st, 2010, 01:56 PM
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#1 |
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Regular Crew
Join Date: Oct 2004
Location: Cambridge, UK
Posts: 57
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New Canon lens, daft question...
Does anybody know/care to guess whether the lens will be parfocal? Since I started using my EX1, I can't imagine ever going back to a lens that isn't.
Regards, Oliver. |
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June 21st, 2010, 02:18 PM
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#2 |
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Inner Circle
Join Date: Apr 2006
Location: Wales
Posts: 2,130
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I'm sure it will be. It looks like the lens is going to be one of the big selling points (as you'd expect from Canon).
Steve |
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June 21st, 2010, 11:04 PM
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#3 |
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Trustee
Join Date: Oct 2008
Location: Byron Bay, Australia
Posts: 1,155
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Most camcorder lenses are parfocal. I've never used a camcorder that didn't have a parfocal lens. Most people who've got into videogpraphy recently (in the past 15 years) wouldn't even know about or be concerned with the differences between parfocal and varifocal lenses if it wasn't for the whole DSLR video movement.
Sony has had big problems recently with their lenses in some of their cameras and it seems as though every prosusmer camera they release lately is having back focus problems. The extensiveness and severity of this problem shows just how disastrous the effect of not having a parfocal lens is on even a professional videographers image - so many people were caught out by the faulty cameras (which were, due to the problems, behaving similar to varifocal lenses) and ended up with unnacceptable footage becuase they expect and assume that all video lenses are parfocal. I can only image the storm that would've ensued if they'd taken their faulty cameras back to Sony and they'd replied "There's nothing wrong with it, it just isn't a parfocal lens. Did we forget to mention that?" Instead they have honoured the warranty in most cases and adjusted the lenses so they work as they are designed to - as proper parfocal lenses (in fact they fixed my 2-year old, out of warranty FX7 free because they were well aware of the problem) |
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June 30th, 2010, 04:08 PM
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#4 |
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Regular Crew
Join Date: Oct 2004
Location: Cambridge, UK
Posts: 57
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Servo zoom only?!?!?!
Having downloaded the manual (page 77), it seems that even though the focus has end stops, the zoom is still a servo controlled one either in ring or rocker mode. Please tell me I'm wrong! If you're going to make a decent manual focus lens, at least give us proper manul zoom too!
Oliver. |
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June 30th, 2010, 04:53 PM
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#5 |
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Major Player
Join Date: Jul 2004
Location: Burbank, CA 91502
Posts: 949
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Oliver-
It is either a manual or servo.......in other words, you turn it on to manual with hard stops and read outs or turn it off and its a servo with no stops or read outs......kinda cool how the read out appears and disappears.... Jim Martin FilmTools.com |
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July 1st, 2010, 11:42 AM
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#6 |
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Regular Crew
Join Date: Oct 2004
Location: Cambridge, UK
Posts: 57
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Thanks Jim. Just to clarify, the ZOOM has hard stops as well as the focus?
I'm so used to flicking my EX1 zoom to max, focusing and zooming back out that I can't imagine having to power zoom every time I want to focus! Regards, Oliver. |
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July 1st, 2010, 12:38 PM
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#7 |
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Major Player
Join Date: Jul 2004
Location: Burbank, CA 91502
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You are correct sir.....
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July 2nd, 2010, 01:04 PM
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#8 |
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Major Player
Join Date: Apr 2008
Location: Chicago, Illinois USA
Posts: 692
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OK, I'm stumped and know a bunch of film/video/photo terms, but what the heck is parfocal???
(Or maybe I just forgot) |
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July 2nd, 2010, 02:12 PM
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#9 |
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Inner Circle
Join Date: Sep 2007
Location: Cambridge UK
Posts: 2,853
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Parfocal
__________________
Andy K Wilkinson - https://www.shootingimage.co.uk Cambridge (UK) Corporate Video Production |
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July 3rd, 2010, 12:16 AM
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#10 |
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Major Player
Join Date: Apr 2008
Location: Chicago, Illinois USA
Posts: 692
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Thanks Andy.
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July 5th, 2010, 05:45 AM
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#11 |
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Trustee
Join Date: Oct 2008
Location: Byron Bay, Australia
Posts: 1,155
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For the benifit of those who are too lazy to follow the link to wikipedia:
A parfocal lens is one which holds focus throughout the entire zoom range. With these lenses you can attain proper focus by zooming in as far as possible, focusing on your subject, then zooming back out to the desired framing. Pretty much all video lenses are parfocal and some still lenses are too. The opposite of parfocal is varifocal. These lenses will have a shift in focus when you zoom, so any change in zoom means you need to re-adjust your focus as well. |
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July 6th, 2010, 01:19 PM
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#12 |
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Major Player
Join Date: Apr 2008
Location: Chicago, Illinois USA
Posts: 692
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John,
I wasn't even aware that anyone even made anything other than a "parfocal" lenses. On old super 8 and 16mm cameras, the focus was always done at full zoom, then reframed to desired zoom for best focus. Even with my still camera zooms I tend to always full zoom, focus, re-frame. Jonathan |
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July 6th, 2010, 02:30 PM
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#13 |
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Inner Circle
Join Date: Apr 2006
Location: Wales
Posts: 2,130
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It's stills lenses that tend not to be parfocal. Often the depth of field can hide focus shifts as of course it gets massively bigger the wider you go. I'd be quite surprised if ANY stills lens holds focus even close to perfectly. This why companies like Century have in the past rebuilt lenses with entirely new bodies (ie the Canon 150-600) to enable them to hold focus for movie use.
Steve |
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