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Choosing a Lens 101


If you’ve never used a detachable-lens camera like a DSLR or mirrorless camera before, the prospect of choosing lenses can be a bit intimidating.  There are some alright guides online for still shooters, but we felt we needed to write something specifically for people shooting video.  Here’s the quick-and-dirty overview of what you need to know before you pick a lens or set of lenses, whether it’s to rent, borrow, or buy.

Lens Mounts

The camera and the lens need to make a physical connection and an optical one.  If you use a lens and a camera that share the same mount, this is usually pretty easy.  The three most common categories of lens mounts in the video world are EF (Canon), F (Nikon) and PL (cinema cameras), but you’ll see others like Sony’s Alpha/NEX/E-mount, micro 4/3 (MFT) mounts, and more, too.  Frequently, you can use an adapter to connect one type of mount to another, but it can be kludgy and often you’ll lose any electronic features built into the lens, like autofocus or vignette correction.  And often, adapters will only work in one direction.  This is because of the imaging area of the lens.

Each lens creates a circle of the image it is capturing inside the camera.  Some lenses have a very large image circle.  These are usually more expensive and heavier.  They can be adapted more easily to almost any mount.  Some lenses have a smaller imaging area.  These are usually more affordable and lightweight, but can’t be used on a larger image sensor.  This is the reason EF lenses (approx. 43mm imaging area diameter) can be used on crop-factor cameras like the T5i (approx. 30mm sensor diagonal), but EF-S lenses can’t be used on fullframe cameras like the Canon 5D mark III.  This holds true for Nikon lenses (called DX) and some other third-party lens manufacturers, too.

If all your cameras have the same imaging area, it’s a non-issue.  If you have different sensor sizes, it may make sense to buy for the biggest sensor, since you may be able to adapt your lenses to fit the smaller sensor.  Or buy a separate set of lenses for each of your different camera mounts, if you don’t mind carrying around all that extra glass.  For beginners, definitely start with a mount that matches your camera.  You’ll have plenty of time to experiment with odd mountings later in your career!

vintage-lens-ad

Not all vintage lenses are great lenses. This Tamron would be pretty slow by today’s standards.

Lens Length

Wide lens.  Long lens.  Normal lens.  Telephoto lens.  These all have meanings, and they all depend not just on the lens itself, but on the camera and imaging sensor they are designed to be paired with.  A “normal” lens is one that gives a field-of-view similar to what we see with our eyes.  We measure lens focal length in millimeters.  What tends to look normal is a focal length approximately the same as the diameter of the imaging area (the diagonal measurement of the camera sensor).  Fullframe cameras like the Canon 5D and 6D are often paired with a 50mm lens when the shooter wants a natural sense of depth and dimension.  Crop factor cameras have a smaller sensor, so the measurement of “normal” will be smaller, too.  On a APS-C sized sensor as found in lots of DSLRs (T2i, T3i, T4i, T5i, T6s, 7D, just to name a few) a 35mm lens will look about normal in most cases.

Normal lenses, because they are doing “normal” things with light, tend to be the easiest to engineer.  This is why the $300 50mm Canon f/1.4 lens can look amazing, but nobody makes a 300mm f/1.4 at any price.

Usually a photographer’s first lens is a zoom lens, this means it has variable focal length.  A lens that does not zoom is called a prime lens.  Prime lenses are easier to engineer than zoom lenses, so they tend to be less expensive, smaller, lighter, and of significantly higher image quality.  If you have time to switch lenses, or a team of people to help you, you’ll almost always want primes.  If you need to compose your shots on-the-fly, and don’t have time to dig through a set of 5 different lenses for the right one, a zoom might be the best choice.  Historically, zooms have been favored for 35mm photo and television, while primes have been used more for motion pictures and large-format photography.

A wide lens is a lens that has a smaller focal length than whatever “normal” is, depending on the camera.  So on my Canon 6D, a 35mm lens is a wide lens, but on my Canon T5i, it’s a normal lens.  A wide lens tends to exaggerate space and perspective.

A long lens (also called telephoto lens) has a focal length greater than normal.  Some lenses go much beyond normal, and are called super-telephoto lenses.  A long lens tends to compress space and minimize distance.

A perfect bag of lenses would have all your focal lengths covered.  When I shoot with the Canon 5DmkII, I usually have a 20mm, 28mm, 35mm, 50mm, 85mm, and 105mm in my bag.  That way I know I can get just about any shot I want.  I usually only shoot with a zoom lens if I know I need to cover a lot of different kinds of action at the same time.

Lens Speed

If you don’t know the difference between stops and f-stops, take a moment to read our guide.  Once you have an understanding of how f-stops work, you can start to compare lenses.

As far as we’re concerned, any lens with a maximum aperture of about f/2.0 or faster is a fast lens.  f/2.8 is right in the middle.  Anything slower is a pretty slow lens.  All other things being equal, faster is better.  But there are plenty of times when we’re shooting with an f/4 lens, too.  It’s just a question of what lens is right for the job.

If you’re shooting outside during the day, you won’t need a fast lens.  Fast lenses really pay off at night, or in interiors.  They are also great for interviews, and any time we want that “background-out-of-focus” look we call shallow depth of field.  I find I can usually shoot people by streetlight with a f/1.4 lens on a fullframe camera.  Even campfire shots are a possibility.

Lens speed is one of the places where prime and zoom lenses really start to diverge.  As an example, Canon’s 24-105mm f/4L zoom lens is top-of-the-line, and costs about $1000.  But Canon’s 50mm f/1.4 prime lens is less than half the price, and three stops faster!  If you’re shooting indoors, that extra light can be a huge help.

Image Stabilization

Image stabilization is an option on some lenses made for DSLRs.  It tends to be used by people shooting in the style of television as opposed to the style of film, since video cameras have supported some kind of image stabilization for more than a decade.  Canon’s lenses that support it are marked IS, Nikon’s are marked VR (for Vibration Reduction), and others are marked VC (for Vibration Compensation).  As a video shooter, you’ll only want to turn it on if you’re shooting handheld or shoulder-mounted.  Almost all image-stabilizing lenses are zoom lenses, with notable exception.  There are different kinds of image stabilization, and some very high-end lenses will support two or more different IS modes.

If you do a lot of run-and-gun shooting, a zoom lens with image stabilization might be a good choice for you.  But if you tend to do most of your work on a tripod, you’re better off taking something with extra speed or other features you might need.

These are the four easy-to-compare differences between lenses.  Of course, we haven’t even touched on image quality, build quality, close-focus ability, or other important factors.   We also didn’t mention autofocus at all, but that’s because for video shooters on DSLRs, manual focus is pretty much the only way to shoot, for now.  How do you choose a lens?  Let us know in the comments below.

Posted by Jon Kline


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