June 21, 2014


There are so many lenses out there, but which features are the most important? And, how can we use these lenses most effectively, for cinematic results? Find out in this week’s video.

 

Check out the video right here:

CHOOSING A LENS TO BUY:

Ask your self this question:
How much money am I going to spend?

That’s always going to be the limiting factor when it comes to lenses – the price.
After price, here are the features I look for in a lens (in order of importance)

  1. Focal Length – How ‘zoomed-in’ or out the lens is. Having a range of focal lengths is very important (A good starting point would be lenses to cover 24mm to 200mm Super35 equivalent)
  2. Maximum Aperture – Aperture controls both exposure and depth of field. For lowlight shooting with a blurry background, f/2.8 lenses are very nice! Primes lenses offer even larger apertures of f/1.4 f/1.8 etc!
  3. Physical things – Focus throw (see the video for an explanation), build quality, size + weight
  4. Optics – including sharpness, chromatic aberration, distortion, flaring.
  5. Image Stabilisation – Helps to reduce camera shake in handheld shooting. Doesn’t make all footage silky-smooth, but does make a bit of a difference.

Now if you want to have all of these features, the lenses are going to be very expensive, so you have to weigh it up and decide which are your priorities. If you shoot in lowlight a lot, then a fast aperture might be your priority. If you film events, then having a telephoto lens will probably be very important. If you are working with a gimbal stabiliser, you’ll need to keep the weight down, and might choose a wider focal length.

The good thing is that most of these features are included in the title of the lens!

Eg1:  Canon EF-S 18-55mm (Mid-range variable zoom) f/3.5-5.6 (Aperture that stops down as you zoom in, not the best for low-light) IS (with image stabilisation).

Eg2:  Canon EF 50mm (Mid-range prime lens) f/1.4 (Fast aperture for shallow depth of field / low light)  (No image stabilisation)

Eg3:  Tamron SP 70-200mm (Telephoto variable zoom)F/2.8 (Fairly fast aperture, constant across zoom range) Di VC (with image stabilisation) USD

As for Optics and Physical features, checkout http://www.dpreview.com and http://www.the-digital-picture.com/ for full specs including size and weight, focus throw, filter size, and optics testing!

So there we go, no need for any comments or emails asking me what I think of lenses, right..? I’m only joking of course, email away!

 

CHOOSING THE RIGHT LENS FOR THE JOB:

I’d like to outline two ideas that should help you to be more intentional with your which lens you choose, and how you use that lens. It’s just two simple changes of perspective that could go a long way!

PART 1: Aperture

Opening and closing those aperture blades not only changes the amount of light that hits the sensor, it also changes the depth of field. And I think depth of field is far more important than low light capabilities. Let me explain.

aperture demo

Here we have two shots which demonstrate the difference that aperture makes, in terms of depth of field. The shot on the left was shot at f/2.8, so the background is very blurry, and in the other shot I stopped down to f/7 which I think gives a nicer result on this occasion. You’ll notice that the both the ISO and shutter speed do not change between the shots, and I could only do this because I increased the intensity of the lights.

So when we have control over the lighting, we don’t have to use our aperture to set our exposure, we can choose the aperture that gives the desired depth of field. I think that’s the best situation to be in.

aperture demo2

The same principle applies when we don’t have control over the lighting. If it’s too bright, we have to stop down our aperture to get a good exposure. In this case, I wanted to shoot at f/4, but it was so bright I had to stop down to f/11.3. That’s where the ND filter came in. The ND makes the image darker, so that we can have control over our aperture even in bright conditions.

If it’s too dark for the desired aperture, bring in some more lights, or up the ISO. 

If it’s too bright for the design aperture, use an ND filter!

Part 2: Focal Length

Similarly to aperture, focal length has two functions. The first thing is to increase the field of view, so that we can get a close up even though we are 20ft away. Or a wide shot even though we are in a small room. But, there is a very important ‘side effect’ of zooming in or out. Compression.

Lets look at some more examples.

zoom demo3

For this comparison, I have darkened the background, so that we can clearly see that the field of view is the same. The teddies in the foreground are pretty much the same size, even though we are using completely different lenses. The difference is that with the wide angle shot, I was very close, and then I moved the camera far away for the telephoto shot.

zoom demo2

Now if we look at the flowers in the background, we can see a clear difference. The wide angle shot makes the flowers look further away, and includes a lot more of the background. The telephoto shows the flowers as much closer, and crops the background a lot. The difference is in the compression – how far away the background seems.

So what’s the lesson here? 

Often we choose our focal length based on field of view alone. If you can’t move the camera (in a small room, or at the back of a wedding) then we have to zoom to ‘get closer’ to the action. There’s nothing wrong with that, but we should be aware of the effects that zooming have in terms of compression. That way, when we do have space to move, we can choose what sort of compression we want, based on the shot.

Backing up and zooming in, or getting closer and zooming out, changes the image hugely. Let’s try to use it intentionally, not just our of necessity.

Same goes for the relationship between aperture and depth of field.

 

USEFUL LINKS:

DSLRguide Lens Recommendations: https://www.youtube.com/watch?v=DzVmhrgNmNI

Lens Review Website: http://www.dpreview.com

Lens Comparison Website: http://www.the-digital-picture.com/Reviews/ISO-12…

Simon Cade

Filmmaker, and host of DSLRguide. Since I was making my first film age 11, I have always been fascinated by the way films are produced, and the effect it can have on the audience.