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Author Topic: Lens quality for HD video on 5d ii  (Read 7423 times)
ChrisS
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« on: March 13, 2010, 02:15:58 PM »
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Is lens quality on the 5d ii as crucial for HD video as it is for still photographs?
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bill t.
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« Reply #1 on: March 16, 2010, 01:28:27 PM »
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I would venture that things like good contrast and resistance to flare are very important, and things like excellent edge sharpness and low chromatic aberration are less important.  Lenses with the first two will usually be OK with the second two, so maybe you just need an overall decent lens.

Even so still camera zooms are way behind their best-quality cinematic cousins (I said cinematic, not Video!) so if you want to run with the big movie dogs you might best stick with primes.
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Chris Sanderson
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« Reply #2 on: March 16, 2010, 03:47:59 PM »
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I agree with bill t.

I would simply add that you are recording only to 1920 x 1080 pixels; so video, even at HD dimensions, appears a lot less critical than most stills.

However there is a reason that Cine lenses are built to extremely high standards (Arri, Cooke, Panavision et al.): a superbly engineered lens will always produce a better looking picture than an average or poorly massed-produced lens - no matter what the resolution of the recording medium.
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Christopher Sanderson
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« Reply #3 on: March 17, 2010, 01:11:35 AM »
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Quote from: ChrisS
Is lens quality on the 5d ii as crucial for HD video as it is for still photographs?

Please forgive me as I have the 5D mk1, with no video  

That said, I've used all the major motion picture lenses and many higher end video lenses.  I will say that the optical quality of good Canon lenses will be more than adequate for motion capture on a 5d II.  Many movies have used Canon and Nikon long lenses converted to motion picture camera mounts.  Even Panavision offers these.

The real issue here is keeping moving action in focus with very, very shallow depth of focus.  Auto focus lenses are not designed for this and you might just find yourself tearing out some (or all) of your hair  

The big advantage of motion picture lenses is that they are manual focus, have accurate distance scales, and a long rotation to place enough space between the footage marks.  As you may, or may not know, motion picture focus is usually done by a specialist who's job it is too estimate the distance to the moving subjects and adjust the lens accordingly.

I think I've heard that Zeiss is planning to build a special version of their manual focus primes with a long rotation for use shooting motion on the 5dII or 7d.  If this is true, then these may very well be the best choice of lens to use with a 5d.  Short of that, perhaps some old manual focus nikon or pentax lenses and an adapter will be helpful, but the lens rotation is short and that will be a challenge.

There is no real way to view critical focus yet while shooting with the 5dII in movie mode, so focusing by distance with moving subjects is really important.
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Bruce Alan Greene
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ChrisS
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« Reply #4 on: March 17, 2010, 03:55:44 AM »
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Thanks for your really helpful replies, everyone. Wow - where else could you ask such a newbie question and get such accomplished people answering?!

For me, I think it's going to have to be a 'suck it and see' process. I plan to film surfers on waves, so image quality toward the centre is more important than toward the edges of the screen. I have a Canon 70-300IS lens, which doesn't really have the reach I need with the FF sensor (it's fine on my 40D), so I was thinking to try adding a 1.4 teleconverter. I know (from what I've read) the 70-300 isn't perfect for stills, but it does a good job for my needs and looks fine for video work. Paying a lot for a prime isn't really an option at the moment, so I think I'll have a shot at the TC. Or, as you say Bruce, some old manual focus lenses and an adapter.
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Chris Sanderson
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« Reply #5 on: March 17, 2010, 06:18:43 AM »
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Quote from: ChrisS
I plan to film surfers on waves, so image quality toward the centre is more important than toward the edges of the screen. I have a Canon 70-300IS lens, which doesn't really have the reach I need with the FF sensor (it's fine on my 40D), so I was thinking to try adding a 1.4 teleconverter. I know (from what I've read) the 70-300 isn't perfect for stills, but it does a good job for my needs and looks fine for video work. Paying a lot for a prime isn't really an option at the moment, so I think I'll have a shot at the TC. Or, as you say Bruce, some old manual focus lenses and an adapter.
Surfers with up to a 400mm lens equivalent is going to be really, really hard to focus. I think you will definitely be bald very quickly  
Let us know how you fare. I think if I was faced with that challenge, I would preset a focus area and hope the subject passed through it... I would also practice a focus pull on a non-critical subject - remember the focus action on that lens is not that smooth and was never really designed with focus pull in mind.
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Christopher Sanderson
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ChrisS
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« Reply #6 on: March 17, 2010, 11:24:49 AM »
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Quote from: Chris Sanderson
Surfers with up to a 400mm lens equivalent is going to be really, really hard to focus. I think you will definitely be bald very quickly  
Let us know how you fare. I think if I was faced with that challenge, I would preset a focus area and hope the subject passed through it... I would also practice a focus pull on a non-critical subject - remember the focus action on that lens is not that smooth and was never really designed with focus pull in mind.

I've obviously got a lot to learn. I think I'll work more at the 300mm end of the lens I have before spending money and going for more reach. The surfers tend to be about 100 - 150 yards away (this can vary a lot, though), and I was hoping to use a small aperture allowing greater depth of field. The movement tends to be more across the shot than toward the camera, though the latter clearly does happen. Next time there's some swell, I'll post a link so you can see what I managed. Thanks again.
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bill t.
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« Reply #7 on: March 17, 2010, 03:06:10 PM »
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Quote from: ChrisS
The surfers tend to be about 100 - 150 yards away (this can vary a lot, though),

You describe a situation where contrast is supremely important.  You will lose a lot of contrast to atmosphere and water haze, and even worse the bright sky and overall high-key scene will produce lots and lots of flare inside the lens.  You can't afford to lose an ounce more of contrast to a poor lens or to the typically poor anti-flare baffling inside a low cost lens or zoom.  For absolute sure you need some sort of matte box scheme to keep light from just outside the image from entering the lens.  Yes you can crank up the contrast in post processing, but that also cranks up the noise and degrades the image...the less you have to crank the better.

And I think you are talking about 500mm+ here.
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ChrisS
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« Reply #8 on: March 18, 2010, 03:12:14 PM »
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I'm not sure if this adds anything, but I shot the following this morning (completely unedited!) as a test:

http://vimeo.com/10264767

It was set at about f10, 1/60th second 100 ISO from a distance of about 100 yards. The guy on the board is coming straight in, which wouldn't be the case in a proper ride, but maybe it allows us to see the effect of change of distance on focus?  I set focus before he came in, and I think the NSP on the bottom of the board looks OK when viewed full screen as he steps out of the water at the end. I used the standard lens hood for this lens.

I reckon I need about 1/3 more magnification for the shot to be OK for my needs - will the increase in focal length (which I would get from the 1.4 converter) really mess up focus?

ps I'm also not sure I've got the hang of uploading to Vimeo, so maybe the image quality is too poor to judge.
« Last Edit: March 18, 2010, 03:18:15 PM by ChrisS » Logged
bill t.
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« Reply #9 on: March 18, 2010, 10:48:10 PM »
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Hey nicely done and it looks as good quality wise as any other Vimeo piece.

But you gotta be a LOT tighter to really engage a viewer.  If that's 300mm, start thinking about 1200mm!

There are some clever things you can do with focus that would let you use a cheap manual focus lens.  Attach a protruding stick to the focus ring, as with pipe strap from Home Depot.  The stick should be strong enough to easily move the focus ring.  Attach two "limit" bumpers under the lens so you will be at your farthest anticipated focus the stick is up against one bumper, and up against the other bumper for closest anticipated focus.  For shots like your Vimeo piece there wouldn't be a lot of difference in those positions.  By feeling the relative stick position between the two limits you can pretty well nail focus through guesstimation in most circumstances, or at least you wont get lost and do wild focus swings.  And come to think of it, you also wouldn't have the wild focus swings you can  get from an autofocus lens.  Just like the good old days.  I heard about this from a guy who got very rich shooting surf movies in the early 70's.


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ChrisS
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« Reply #10 on: March 19, 2010, 01:23:08 PM »
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Thanks, Bill. I'm going to have to work on that focus trick - I can only imagine it gets much more difficult as the lens gets longer. Point taken about getting in closer, too. That said, I'm completely new to this and find it hard enough finding/ following people with 300 mm...

There was more swell today, so I went back and tried for some better shots. I edited this one, and I'm pleased with the footage (though some of the edits are clumsy) for a first real go. The sound's awful, but that's for another thread!

http://vimeo.com/10286707

I know it's hard to see on the link, but watched at full size from my hard drive, there doesn't seem to be any significant loss of focus in these - as I said before, most of the change of position is across rather than toward the camera. The IQ from the hard drive seems fine to me - I just wonder how much this would reduce with a 1.4 x or even 2 x TC. Or maybe it's going to have to be an FD prime - I believe they used to say 600 mm was the optimum length for surf photography.
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Chris Sanderson
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« Reply #11 on: March 19, 2010, 03:40:48 PM »
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Looking good - although still rather wide...

Check out Sam Morgan Moore's focus rig
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Christopher Sanderson
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ChrisS
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« Reply #12 on: March 26, 2010, 03:49:48 PM »
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I'm still trying to figure out the issue of lens quality for 5dii video. I just read this on http://nofilmschool.com, concerning old manual focus lenses:

'whereas many of these older manual lenses may not be up to the task of resolving 21 megapixels with aplomb, they donít need to; in video mode, 1080p amounts to just shy of 2 megapixels, and any decent SLR lens outstrips this resolution'

Given this, is the need for high quality lenses on the 5d ii less for video than for stills? Sorry if I'm just repeating the original question here, but reading that was news to me.


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