What focal length should I use and why?

Here’s a quick, hopefully informative snippet as to why you might choose one focal length over another, and why.

The idea for this blog came about when I was asked recently “Why don’t you just zoom-out to get the person in the frame?”. This is a very good question and I felt it needed a mini demonstration to really help answer it. All one needs to conduct this experiment is the following:

• A willing volunteer – I had a Marc
• A zoom lens of any kind – In my case, the XF18-135mm lens
• Oh, and a camera!

The experiment is simple; frame your subject (Marc) the same each time and take a picture at different focal lengths. I chose four focal lengths along the barrel of the lens to best demonstrate. With this, we had the ever-helpful Terry to hand with a camera to capture the experiment from the third person perspective.

Hopefully what you will notice is that the wider the angle, (18mm) the more clutter there is in the image whereas at the 135mm setting, pretty much all clutter has ‘disappeared’.

Why does this happen?

Without going into huge mathematical detail (that I don’t even fully understand) it is because wide angle shots will achieve a larger angle of view and long zooms won’t. This is how much ‘fits’ into the shot – peripheral vision if you like.

As a rule of thumb, wider angle lenses work great for landscape photography and indoors (where you don’t have a lot of room to manoeuvre) as they can fit more in. Wider angles, however, are not great for portrait shots as they will pull the centre of the frame forwards creating distortion in perspective – example image below.

Longer zooms on the other hand work great for de-cluttering a frame to create stunning portraits. This is because the angle of view is smaller, and more importantly, they have a compressing effect. In essence, a long zoom pulls the background closer to the foreground and can give a more natural, slim looking head shape whilst also helping aid the bokeh effect – increasing the focal length of a lens decreases the depth of field.

Here are two example shots I took that hopefully help demonstrate the difference:

The image on the left (135mm) shows Marc’s head in proper perspective. However, the right shot (18mm) shows the nose being ‘pulled’ forward towards the lens and his head being turned into a rugby ball! You will also notice there is more of Marc’s surroundings in the wider angle shot – this diverts some attention away from his face, which, in a portrait shot we don’t want to do.

I hope this post gets you thinking more about which focal length to use rather than just zooming in and out for convenience.

Having a zoom lens is incredibly helpful at times, but it would best to think of your zoom lens as a series of prime lenses. Most photographers, if not all, use specific focal lengths for specific purposes; this is due to the individual optical effects each focal length provides. It really does make a difference to the end result – as (hopefully) shown above 😉

If you can, please go and try this yourself to get a real feel for it. It will help with your own understanding as to what focal length you might want to use, and for which subjects