All about lenses

Focal length - by the numbers

There is no shortage of videos explaining focal length, but most are either confusing, over-technical, or expose the hazy understanding of the presenter. We’ve scoured the lot to pick out a video we think strikes the best balance between clarity, simplicity and brevity. And the award goes to: Dave McKeegan.

Source: Dave McKeegan

Focal length - what it looks like

Mike Browne offers a very practical, visual demonstration of the effect of changing focal lengths on picture quality and the importance of “dollying” the camera rather than zooming.

Source: Mike Browne

Shutter speed

Shutter speed is pretty self-explanatory: the faster the speed, the shorter time the camera shutter stays open. But if you’re new to the concept, it’s worth watching this three and a half minute video explaining the shutter mechanism and the implications of different shutter speeds.

Source: Apalapse


Understanding how your camera aperture affects the picture unlocks a wide range of creative choices. Here’s a great, concise explanation of what an aperture is and how to set it for the kind of effect your shot needs.

Source: Apalapse

Depth of field

Chris Bray uses his Aussie charm to explain how aperture works, but more importantly how it changes the depth of field of an image.


Ah, F-numbers. D.P.’s love to talk about them like they’re as common as inches or centimeters. The rest of the crew just smiles and nods with that far-away look of incomprehension. Well, fear not, Dylan Bennet is here to sort it all out for you—Khan Academy style. For the Math phobic we feel compelled to tell you that he does mention the square root of 2, but only briefly. If you made it through elementary school math, you’ll survive. At the end of the day, F numbers are mathematical so wrestle through and you’ll be grateful you did.

Right at 11 minutes in he presents a nice way to remember the F-stop sequence (spoiler: just remember 1 and 1.4 and it’s all doubling from there .

Source: Dylan Bennett


ISO is one of those weird terms carried over from analog photography that probably shouldn’t have been (“gain” would have been a better term in the age of digital sensors), but helped traditional photographers and cinematographers make the jump to digital.

Here’s a nice overall explanation of what ISO is and how it affects your final image. Discover the mystery of a camera’s base ISO, along with why different cameras can have different ISO bases and ranges.

Source: Apalapse

Bringing it all together

One thing that rarely gets explained well is the interaction between aperture size, shutter speed and ISO. Tony Northrup gives a great, non-technical explanation of this very thing. He gently plugs his book on the way through but, hey, you’re getting a free training video here.

Source: Michromatic

Zoom versus Prime

The most important point to get here: prime lenses have a fixed focal length, zooms can “zoom” between different focal lengths. If you want a more detailed treatment as to which is better, check out Matt Granger’s in-depth analysis of the debate.

Source: Matt Granger

Cine lens versus still photography lens

DSLR lenses look amazing and they’re cheap. Well, cheap in comparison to cinema lenses, or “cine lenses.” So why spend all that extra money on a cine lens? Find out in this video from LensProToGo.

Source: LensProToGo

Lens distortion

Lens distortion is a reality for every lens. Modern lenses are optimized to reduce it, but many cinematographers love the “feel” of older lenses with heavy lens distortion. In this video, Matt Granger does a great job of explaining the concept of lens distortion and the introduces the concept of a rectilinear lens and why you might want to spend your hard-earned cash on them.

Source: Matt Granger

Anamorphic lenses

If you’re wondering what the big deal is with anamorphic lenses, look no further than Tom Antos’ excellent explanation of the history and practical application of anamorphic lensing.

Source: Tom Antos

Chromatic aberration

What is chromatic aberration and how do you fix it? Check out Laura Shoe’s explanation and how to fix it in Adobe Lightroom. It’s short so watch to the end where Laura shows high contrast fringing as well.

Source: Laura Shoe

Airy disk diffusion

For the nuclear physicists in the crowd, this next video gives a breakdown of the math behind an Airy Disk (the reason even the best lenses have some softness to their focus). The rest of us can just be content in our ignorance.

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