In this video, I’m going to cover the second most crucial part of your camera system, your lenses. If your camera body is the heart of your system, then I consider the lens to be the soul, as the lens choices you make have a direct impact on the look and feel of your images.
Lenses are measured in focal length. The length of a lens is the measurement, or to be more precise a calculation of the distance from the lens to the point where the light rays converge at the sensor. This measurement is given in millimeters. Because this is an actual measurement, it is key to point out that the focal length of a lens never changes. It is fixed. Even if you change sensor sizes- the focal length remains the same. A 50mm lens, is a 50mm lens regardless of if you use it on a camera that has a full frame sensor, or a micro four thirds sensor. What happens when you change sensor sizes is that you are cropping what the camera can see from that lens. So you are changing the field of view- or you are seeing less of the image that the lens is projecting. But I get into that more in the video on sensor sizes and crop factors. For now, what is key to remember is that the focal length of a lens, never changes, it is what it is regardless of the camera’s sensor.
Not only is the focal length of a lens a measurement, …
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Hi Ryan, Would you recommend a modified lens–from photography lens to cinema lens–for feature film work and renting it, like G.L Optics 18-35mm. They converted Sigma zoom lens f1.8 in to cinema housing. I am thinking of buying one. Please share your thoughts; it could be used as variable prime.
I think rehoused photo lenses are a great choice for more budget friendly lenses. They can be rehoused to work well in a feature film workflow. In fact, there have been many times over the years where a production will have a photo lens rehoused for a film specifically because the cine version either doesn’t exist, or the cine version is too big / heavy / whatever for their particular needs. (For example the film The Bourne Ultimatum rehoused two Nikon Lenses (28-70mm & 80-200mm).) So it’s done all the time at all levels of production.
In regards to a specific recommendation, I have not personally used rehoused lenses from G.L. Optics so I cannot speak from personal experience. The specs on the web site look good and it seems like they would be well done (aluminum bodies, steel mounts, etc.). But only real world use will be able to tell if the specs live up to the experience. I have used rehoused lenses from Duclos Lenses, and I know they do quality work. I’ve never had a bad experience. So what I would recommend is contacting G.L. Optics if that is who you want to buy from, and see if you can rent a lens or two from them. Then I would play with that lens to see if you like it and feel it meets your needs. Then you can buy it.
Other alternative “rehoused” lenses are the CP.2‘s from Zeiss and the CN-E’s from Canon.
A couple drawbacks to most rehoused photo lenses is that: 1) they breath more (image changes when focused) than cinema lenses, and 2) they change in length, weight, and diameter more than a set of cinema lenses (which can slow you down if you are having to rebalance your camera, move accessories around, etc. with each lens change). Just something to keep in mind. 🙂
Schneider has come out with a set of affordable cine lenses (Xenon Full Frame Primes) that looks interesting. (I haven’t used them.) Instead of taking photo lenses and rehousing them like Zeiss and Canon did, they came at it from the other direction and took their knowledge from their cinema lenses and made a more affordable version. So they have similar weights, sizes, diameters, and length.