Understanding Focal Length and Its Effect On Composition
The focal length you use to take a photo will significantly affect the photo you create. It will determine what is in a photo, what is not in a photo, how small or large the elements of the photo are, and how the elements in your photo relate to each other. The focal length you use will also determine the depth of field, or as I like to call it, depth of sharpness, that there is in a photo.
The focal length you use will significantly impact the photo you get. Let's find out all about this.
And that was the answery bit.
How utterly splendid.
Hi, and a very warm welcome to Episode 203 of the Photography Explained podcast. I'm your host, Rick. In each episode, I will try to explain one photographic thing to you in plain English in less than 27 minutes (ish) without the irrelevant details. Yes, really.
I'm a professionally qualified photographer based in England with a lifetime of photographic experience, which I share with you in my splendid podcast.
And no rules this week, which has to be a good thing.
What is the focal length in photography?
Let’s start by looking at focal length and its meaning.
The focal length of a lens is the physical dimension between the lens and the camera sensor. Which bit of the lens are we measuring? It is the bit within the lens where the light rays are travelling without changing direction. I will stop there as to say any more would take me into the realms of irrelevant detail—knowing any more would not help me.
There is a significant thing here, though – in general terms, the larger the focal length value, the larger the lens. That makes perfect sense, doesn’t it?
I need to go through some stuff quickly here. I want to talk more about composition than the technical stuff, so I am going to go through the technical stuff very quickly. Check out episode 189—Camera Lenses Explained—My Beginner's Guide for more.
Focal lengths explained quickly.
OK—to explain focal lengths so we normal people can understand, let's start with a standard lens. A standard lens has a focal length of 50mm on a full-frame camera.
Yes, sorry, but we get into a complications straight away. A full frame camera has a sensor that is 36mm wide by 24mm high.
There are cropped sensor cameras and micro four-thirds cameras, which have crop factors, which makes this even more complicated. I will return to crop factors, but let me first go through this for full-frame cameras.
A 50mm focal length on a full-frame camera gives a horizontal field of view, of about 40 degrees. That is similar to how humans see the world. I prefer the angle of view to the field of view. Do we have to be in a field? But that is not important here. Sorry. Move on, Rick.
A wide-angle lens has a focal length smaller than 50. The smaller the number, the smaller the focal length, the wider the field of view, the larger the depth of field, and the further away and smaller things in a photo look.
A telephoto lens has a focal length larger than 50. The larger the number, the larger the focal length, the narrower the field of view, the shallower the depth of field, and the larger things look in a photo.
Crop factors explained quickly.
A micro four-thirds camera has a crop factor of 2x. A cropped sensor camera has a crop factor of 1.5 – 1.6x, depending on the actual sensor size. Yes, these vary with different manufacturers and, indeed, different camera models.
The reason is that cropped sensor cameras have sensors smaller than those in full-frame cameras, and micro-four-thirds cameras have sensors smaller than those in cropped sensor cameras.
But what does this mean?
A 50mm focal length on a cropped sensor camera gives an effective focal length of 50 x 1.5 or 1.6 ish, which is 75-80mm.
A 50mm focal length on a micro four-thirds camera gives an effective focal length of 50 x 2, which is 100mm.
I know it's more complicated than we would like.
And that is the nuts and bolts of how focal length affects the composition.
As I said earlier, I am not going into the technical side here. I want to stick to the compositional side.
Composition and focal length
Composition is what you include in a photo and how the things in your composition relate to each other. Your focal length will determine what you include and do not include in a photo.
The horizontal angle of view is about 84 degrees with a 20 mm focal length and about 10 degrees with a 200 mm focal length.
I hope you can picture these.
I think we can quickly relate what we see, about 40 degrees, to an angle of view of 84 degrees. It is a massive difference. A 20mm focal length gives us an angle of view that is more than double what we see. A 200mm focal length gives us the middle quarter of what we see.
A 50mm focal length replicates what we see and how we see things relative to each other.
The wider the focal length, the further apart things appear in a photo.
The longer the focal length, the closer things appear to each other in a photo.
Again, the focal length is relative to what we see at 50mm.
One problem with wide-angle lenses is that the subject matter can get lost in a photo if you are not close enough to it. But if you are shooting a wide vista, that is fine.
But with a telephoto lens, you can fill the frame with the subject matter and exclude everything else, which can be a good or bad thing.
So, if you want photos that look natural and familiar, a 50mm focal length seems like a good idea, right? There are many views on this, but ultimately, this is up to you, dear listener.
And this is the point—there are so many variables, but the best focal length depends on what you photograph and how you want to convey it. Yes, this is down to you, dear listener, and this is the beauty of photography. As the photographer, you take all these variables and use them to take the best photos you can.
The other factor – where you are
Where you place yourself will have a huge impact on a photo. Rather than zooming in, you can always get closer to the subject matter or go further away. Where you are relative to what you are photographing affects the composition and influences how the focal length works with the composition.
Depth of field or depth of sharpness? I can’t help myself.
Aperture and focal length both influence the depth of sharpness in a photo.
- Small aperture – large number – more depth of field.
- Large aperture – small number, less depth of field.
- Long focal length – less depth of field.
- Wide focal length – more depth of field.
Perspective
- Long focal length – things appear closer together.
- Wide focal length – things appear further apart.
The focal length will determine the perspective and how close things are to each other.
But if you take a photo of something very close up using a wide-angle focal length, this will change how everything looks.
And with a long telephoto lens, things can look compressed, closer together.
A quick word on sharpness.
The longer the focal length, the more magnified the image is, so the less forgiving the camera is to blur in photos caused by camera shake. No, the camera is not shaking, but that is the term we have ended up with for any movement when taking a photo that causes a blurry photo. Camera shake, Don’t start me on that one.
This is why if you are shooting handheld, your shutter speed should be faster than the reciprocal of the focal length. In English, this means that if you are taking a photo handheld with a 200mm focal length, your shutter speed should be faster than 1/200th second—unless you have image stabilisation.
And this little lot might explain why there are so many lenses and so many different focal lengths.
OK that is that – that is all I want to say here.
What focal length should I use?
Do you know what? I am going to apply this little lot to my photography, including photos of buildings, landscapes, and travel photography. I think that an episode on each of these will finish this series of episodes on composition nicely.
How utterly splendid.
Right - here are some things that you can do
Work out what 20mm, 50mm and 200mm look like with your eyes.
Take a photo of something using the widest, standard, and longest focal lengths you have and compare the differences.
And if you are feeling adventurous, do the same with the maximum and minimum apertures.
And have a look at what you get.
Learning from your own photos taken with your own gear is much more effective.
Once you have done these things, let me know how you got on.
What if I use a phone to take photos?
Well, focal length is a bit of an issue. You just need to forget that it is not physical, but the effect is the same. On my iPhone 15 Pro, the 1x setting is the default. When I touch the 1x bit, the focal length of 24mm appears. 2x is 48mm. 3x is 77mm. I know, 24 x 3 does not equal 77.
Using one of my apps, the 1x lens gives a field of view of 71 degrees, while 24mm on a full-frame camera gives a field of view of 73 degrees.
Similar but not the same.
I quite like the iPhone 1x, 2x, etc. It removes the numbers and leaves us with what we can see, which I like.
So, using a phone, you have focal length just like you do with a camera, if the numbers are a bit different. But with similar results.
What do I do?
I have a Canon 17-40mm lens. The 17mm bit gives me a whopping 93-degree field of view.
I have an Olympus 12-40mm lens, but the 12mm gives me a paltry 71 degrees because of the crop factor. I need an 8.5 mm focal length lens on my micro four-thirds camera to get the same field of view as my Canon. Yes, 2 x 8.5 = 17. See, crop factor isn’t that bad.
And I use 17mm for most of the photos that I take.
That is what I do.
Some thoughts from the last episode
Did you check out the rule of thirds? How did you get on with it? Let me know; it would be lovely to hear from you.
Next episode
10 Landscape Photography Composition Tips That Will Instantly Improve Your Shots. Yes really. It's time to put all this composition stuff to practical use. Excited to do this.
A quick plug for me and what I do.
Well, why not? If I can't plug myself on my podcast, where can I?
You have found this podcast, so why not check out the podcast website photographyexplainedpodcast.com? I have another photography website, rickmcevoyphotography.com, where I write blog posts about my photographs of buildings and other good stuff. On my courses page, you will find my course, How To Become A Real Estate Photographer. You can also find me on YouTube talking about my podcast and my blog - type my name in, and you will soon find me.
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That's enough of the self-promotion.
Ask me a question
If you have a question you would like me to answer or you just want to say hi, email me at sales@rickmcevoyphotography.co.uk, visit the podcast website, or text me from the podcast feed.
It is always lovely to hear from you, dear listeners.
This episode was brought to you by a cheese and pickle sandwich and a bag of salt and vinegar crisps. Yes, I consumed it before settling in my homemade, acoustically cushioned recording emporium.
I've been Rick McEvoy. Thanks again for listening to my small but perfectly formed podcast (it says here) and for giving me 27 minutes of your valuable time. I reckon this episode will be about 15 minutes long after I have edited out the mistakes and other bad stuff.
Thanks for listening
Take care and stay safe.
Cheers from me, Rick
