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Difference between Video Lenses and SLR Lenses?

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Tim Ward
Difference between Video Lenses and SLR Lenses?
on Jul 25, 2008 at 10:24:43 pm

I posted this yesterday in the Broadcast Video forum, but thought maybe the Cinematography guys would be more familiar with it.

What's the difference between the quality of video lenses versus still lenses? Broadcast video lenses (and Professionals, to an extent) cost so much more than SLRs, why is that? I understand that video lenses need to operate differently with respect to zoom and focus, as well as use high-quality servo controllers. Is the SLR glass of better quality than Broadcast video lens glass? More elements in video lenses? Coatings? Breathing?

And, a step further, the difference between SLR primes and video/film primes?

This is just my ponder for the week.

Thanks,
tim


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Todd Terry
Re: Difference between Video Lenses and SLR Lenses?
on Jul 25, 2008 at 10:50:41 pm

[Tim Ward] "the difference between SLR primes and video/film primes?"

The difference can be very little, or can be a lot.

In fact, many SLR primes are being used as cine primes, especially with depth-of-field converters. Often, the glass itself is more or less the same... and sometimes you see SLR lenses that have a couple of additional things done to them to "turn them into" cine lenses... including gearing, remounting, or rehousing.

With gearing, it's the simple addition of a focus gear ring to the lens allowing the use of a follow focus rig.

With remounting, the SLR lens is remounted so that it now fits a cine mount... for example, a Nikon mount may be changed to a professional PL cine mount.

Full rehousing is the most drastic of the changes. When a lens is rehoused they pretty much save only the guts of it and the glass, and put everything in a new housing. This new old lens will now have proper gearing, a real cine mount, will be collimated, and now the focus mechanism will now operate like a cine lens.... that is, going from nearest focus to infinity will now take almost a full barrel turn of the focus ring, not just the tiny amount (usually 1/5th barrel turn) that it did when it was an SLR lens.

Manufacturing toleraces are much tighter with production for cine or SLR lenses than they typically are with video lenses. Video lenses must only "resolve" the picture at the resolution of the camera to which it is attached... i.e., 1080 lines for an HD camera, or about half that for an SD camera. Many do resolve greater than that, but they don't have to, so there's no guarantee that they will. Cine lenses and SLR lenses, on the other hand, must resolve images at much much higher resolution than video lenses... so their manufacturers must adhere to much tighter tolerances and specs than if they were producing video-only lenses.


T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com






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Tim Ward
Re: Difference between Video Lenses and SLR Lenses?
on Jul 25, 2008 at 11:46:21 pm

Thanks for that, Todd. Very informative. That's pretty much what I thought, with regard to quality. We have an XL2 that I want to get the EF lens adapter for to be able use our Canon SLR lenses for certain situations, especially telephoto.

All this being said then, why does a Canon HJ11x4.7 cost ~10 times more than a Canon EF 28-300 (with same zoom factor), and why do my video lenses cost a lot more than my photographer's lenses? I can see where the fact that video zooms can have much larger zoom factors might be a cause, but "wow"!

Thanks for indulging me! *grin*

tim


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Jeffrey Buras
Re: Difference between Video Lenses and SLR Lenses?
on Jul 27, 2008 at 7:14:44 am

[Tim Ward] "All this being said then, why does a Canon HJ11x4.7 cost ~10 times more than a Canon EF 28-300 (with same zoom factor), and why do my video lenses cost a lot more than my photographer's lenses? I can see where the fact that video zooms can have much larger zoom factors might be a cause, but "wow"! "

The zoom factor is the same, but focal lengths are still different. A 4.7mm high-resolution lens is very hard to make, so it's very expensive. But video cameras require such short focal lengths because their sensors are so small. To get a standard wide-angle shot, you need a very very short focal length. If you were to find a 4.7mm SLR lens it would be pretty darn expensive.

Another factor is that SLR lenses benefit from economies of scale. Canon produces a lot more SLR lenses, cutting down on manufacturing costs. Video lenses are more of a specialty item, making them more expensive.



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Tim Ward
Re: Difference between Video Lenses and SLR Lenses?
on Jul 27, 2008 at 6:59:32 pm

[Jeffrey Buras] "The zoom factor is the same, but focal lengths are still different. A 4.7mm high-resolution lens is very hard to make, so it's very expensive. But video cameras require such short focal lengths because their sensors are so small. To get a standard wide-angle shot, you need a very very short focal length. If you were to find a 4.7mm SLR lens it would be pretty darn expensive.

Another factor is that SLR lenses benefit from economies of scale. Canon produces a lot more SLR lenses, cutting down on manufacturing costs. Video lenses are more of a specialty item, making them more expensive."


I can see where that could make sense. But just to play devil's advocate here: you can also get a 10mm SLR for under $1000. A 10mm Professional (not Broadcast) video lens is 10-times that, with inferior glass. I don't see where supply-and-demand would have that much of an effect, but I'm not in the lens business either. :)

tim


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Todd Terry
Re: Difference between Video Lenses and SLR Lenses?
on Jul 27, 2008 at 8:20:34 pm

And on top of all the valid and real reasons that have been mentioned (economies of scale, supply and demand, different quality requirements)... there is to a degree the same reason that a great deal of filmmaking equipment costs so much...

Question: "Why do they charge so much for that?"

Answer: "Because they can."


T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com






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Jeffrey Buras
Re: Difference between Video Lenses and SLR Lenses?
on Jul 29, 2008 at 6:23:19 pm

[Todd Terry]"Question: "Why do they charge so much for that?"

Answer: "Because they can."
"

And because we're still willing to pay for them.

Unlike every other piece of equipment drifting more to prosumers and the prosumer price-range, lenses are still used by professionals.



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Asmund Voll Tesdal
Re: Difference between Video Lenses and SLR Lenses?
on Jul 30, 2008 at 8:12:56 pm

Since the thread over at the broadcast video forum pretty much died, I'll quote my own post here so you guys can tear it apart :-)

(and after reading the thread here in this forum, I'd guess that constant focus while zooming is one of bigger factors. How does the pricing on film zoom lenses compare? I've always had the impression that they're a lot more pricey than video lenses.)


My original post:

Interesting ponder. I don't really have much clue when it comes to SLR lenses, but if I were to take a wild guess, I'd agree that servos and more lens elements is a big part of the equation. For one, video lenses have a set of elements in them to maintain focus while zooming, most have built-in extenders, and my impression is they generally have greater zoom ranges (starting around 15-20x) and smaller f-numbers (larger apertures). And since every moving part needs to be remote-controllable, I'd guess that comes with a price in servos, too.

But again, I'm really just making a qualified guess here, since I don't know much about the "features" of SLR lenses. Feel free to educate me, though :-)



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