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Why do digital cinema cameras, e.g., BlackMagic, Canon C series, etc. focus on using prime lenses over zoom lenses? Bear in mind that by "zoom lenses" I am referring to lenses with variable focal lengths, not telephoto lenses.

A range of prime lenses that cover the most common range of focal lengths would cost you tens of thousands of dollars at least (for good ones anyway), meanwhile, a single zoom lens that covers the same range of focal lengths would cost under $1,000.

So, why are prime lenses so prevalent in digital cinema?

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You seem to have a serious misunderstanding of cinema lenses. Primes are almost always cheaper to cover the same range than zoom lenses. Comparing prime lenses that cost thousands of dollars a piece to a $1000 zoom lens is not a valid comparison.

I have a $2400 Canon 24-70 f/2.8 II. It is the single best zoom lens Canon has ever made for under $50,000, yet it is only comparable in sharpness to the $300 - $400 f/1.4 lenses and barely exceeds the sharpness of the $100 f/1.8 primes.

Additionally, sharpness is only one factor to consider, you also have speed. Long exposures aren't an option with video, so if you want good low light performance, you need a fast lens. Prime lenses are much, much faster than zooms and thus provide much better low light performance while keeping shutter speeds quick enough to avoid too much motion blur.

Finally, even high end photography lenses are not parafocal, meaning that as you change the focal length, the focus shifts as well, making them undesirable for any kind of push or pull shot (though you can work around it by following focus carefully.)

The cinema lenses help with this problem (though they don't solve it entirely), however, the Canon prime lenses are $20,000 a piece while the zoom lenses are $55,000 a piece the last time I looked at their pricing.

So in short, primes are the cheaper and higher quality option on a budget. You only really want zoom lenses when you need the flexibility on the fly or need to execute a pull or push shot. Given the difficultly of pulling off a good pull or push with photography lenses, it isn't that common to bother with them unless the camera is also used for photography.

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For one, prime lenses aren't encumbered by all of the physical mechanisms required to make a zoom lens work. They're simpler, and the loss of that bulk translates into a wider maximum aperture. Less glass makes them more transmissive. But also, each lens can be much more carefully crafted for a specific focal length, since it only covers one. Zoom lenses, on the other hand, may have "sweet spots" where the lens performs best through a given focal range, but doesn't perform optimally throughout its entire range. Since most seasoned cinematographers don't zoom during a shot, they often opt for quality over versatility. But for an aspiring filmmaker on a budget, a zoom lens is often a good place to start.

As an additional note, certain lenses contain a manual iris control. These are often called "cine" lenses, and are crucial for smooth exposure adjustment when shooting with certain cameras, including DSLRs and the Black Magic Cinema Camera. Since still photographers do not require this functionality, the lenses are tailored to a much smaller audience, and are therefore more expensive.

  • Downvoted because a zoom lens is not a good place to start on a budget. Primes work better on a budget. – AJ Henderson Feb 20 '15 at 23:28
  • @AJHenderson for an "aspiring filmmaker on a budget," a Canon EF 28-105mm f/3.5-4.5 is under $200. This is an entry lens. It's enough to learn about framing and composition at various focal lengths. Sure it's not sharp. Sure it's slow. Sure it's construction is cheap, but show me a set of primes that covers the same range for that price. The closest I saw on B&H was 6K, and that's only 21-85mm. bhphotovideo.com/c/product/818396-REG/… – Jason Conrad Feb 21 '15 at 4:23
  • The nifty 50 is under $100. The 35mm is $125. Both are substantially better options for getting started. You could round it out with an 85mm which runs a bit more at around $400, but you are looking at around $650 to have 3 prime lenses vs substantially more for anything even remotely approaching the level of quality in a zoom. I suppose if you only care about framing and don't give a crap about quality, then you could go with a dirt cheap zoom, but at that point you are better off selling the DSLR and getting a camcorder for half the price. – AJ Henderson Feb 21 '15 at 6:33
  • Um. I rest my case. – Jason Conrad Feb 21 '15 at 7:43
  • If that is all you are trying to say, I do agree but your phrasing seems confusing to someone who is obviously very confused already about the value of zoom lenses. Perhaps just clarify the point a bit that dollar for dollar and pound for pound primes are a much better value unless you can't even afford that basic level. I still would argue that having a zoom isnt the best place to start, as learning to use depth of field is probably more significant than zooming, but it would be more opinion difference then rather than confusing the op on something they are already confused about. – AJ Henderson Feb 21 '15 at 11:50

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