Today I was reading a camera discussion forum in which someone asked how to build a lens collection on a budget. He was looking for Nikon lenses to use on a Sony NEX-FS100 camera. I could relate -- I was in his position in 2006 when I started to look for Nikon glass to be used on video cameras with a Letus, on the Red One, and so on. I hadn't purchased a lens since my senior year in high school (for my venerable Pentax K-1000), and I knew only the most basic things to look for. Since then I've built up a nice collection of Nikon lenses, which now work on a host of cameras. I love my Nikons and have no regrets!
So what follows are some very basic tips I've learned on how to build a lens collection. I make a few allusions to Nikons vis-a-vis the NEX-FS100 below, but my advice could just as easily be interpolated for someone buying Canon lenses for the Red Epic or a Panasonic AF-100.
1) Determine your needs. Obviously, you need to think about what kind of coverage you want. Even if you primarily shoot wide angle footage, you probably also want a normal and a telephoto lens in your bag. But only you know your tastes. Likewise, only you know your budget. You're going to be keeping this in mind as you build a list and prioritize your needs.
But beyond these things, there are other considerations:
What cameras now and in the future, might you use these lenses on? Do your lenses need to be full-frame to be future-proof? Must they have aperture rings? I prefer having aperture rings on my lenses because I sometimes have to use "dumb" adapters (i.e., those that can't control aperture).
Since I was working with a very limited budget, for me, the most important question when I began building my collection was whether to go for primes or zooms. I primarily would be using these lenses to shoot narrative work so I opted for primes; if I was shooting a documentary, I'd want a good zoom lens (if I was shooting with the NEX-FS100, would actually just get the Sony kit lens since autofocus is nice to have in a pinch).
The thing to remember about zooms intended for still lenses is that they are often not parfocal, which means that they don't hold focus across the zoom. (Some are. You have to test to find out.) To me, a non-parfocal zoom negates at least part of the purpose of having a zoom, so that's another reason I went with primes.
2) Familiarize yourself with the lenses that are out there. Researching Nikons, I visited sites like Photozone and those by Bjorn Rorslett (go to the LENSES page and then dig deep into his reviews, especially the "Best of" page) or Ken Rockwell. Different people trust different reviewers (some people HATE Ken Rockwell, for example). But the point is this: When all the websites praise a lens, that's a pretty good sign of a winner.
I'm obsessive, so I prefer to make lists and tables of all the lenses I'm considering. It helps me keep track of what I've looked at, the (dis)advantages of each, and the price.
3) Read reviews, but with a grain of salt. Remember that if you're only going to use lenses for video, you don't have to fret about their resolving power nearly as much. A lens intended for full frame negative film or a 16MP digital camera must resolve far more detail than you'll ever get out of HD or even 4K video. For example, many lens testers worry about blurring in the corners; you don't have to worry about this quite as much since using a full frame lens on a Super35 sensor means you're using the sweetest spot of the lens.
Having said all of this, I do think you should buy the best lenses you can afford. Like microphones, and unlike video cameras, they tend to hold their value for much longer. In 20 years we may be shooting with cameras that capture 8K footage… and it's possible I could still be using my Nikons.
4) Test. Try out the lenses you're considering, especially if they're pricey. Assuming you don't have a friend who happens to have all the Nikons ever made, your two best options for testing are a) visit a fantastic photo store in your area and try out the lenses or, if you don't have a great photo store (I don't), b) rent the lenses. I've saved a lot of money by spending a few bucks to rent a bunch of lenses and then buying the one that I actually like. (I have happily used and endorse LensRentals.com. I have received no promotional consideration for that endorsement.)
5) Buy used (if possible) and buy smartly (always).
Start by finding out the going price for a used lenses by visiting KEH and the going rate for a new version on B+H or Adorama.
If KEH has the lens, and you have the money, buy a lens from them -- they grade their lenses very fairly and have a great return policy. (Again, I've received nothing from them for this endorsement.)
If they don't have it, or it's too pricey, go for one on buy on Ebay, keeping the KEH prices in mind. If you're going for AI-S lenses you can get GREAT bargains on Ebay since many photographers, needing autofocus, consider these obsolete lenses. When buying on Ebay all the usual cautions apply. Make sure the seller has fantastic ratings and that the photos clearly show the quality of the lens. Only bid on the lenses that look pristine.
Whatever you do, don't overpay! If a lens on Ebay starts approaching anything close to its price on KEH, just get it on KEH and be done with it. The return policy will be far better than the risks you take with an Ebay seller. Or wait for another auction.
6) Watch for warning signs and, if necessary, seek help. I say this jokingly, but building a lens collection can be addictive fun -- and can distract you from the real purpose of building a collection, which is to go out and film! Don't say you weren't warned.
If you have other tips or disagree with any of the above, share in the comments below.