One of the most important reasons why you buy a lens is down to the focal length. This little piece of information lets you know how close you need to be in relation to the subject you are capturing.
A longer focal length is necessary for objects further away. A smaller focal length captures more of the scene in front of you. To understand focal length in four, easy steps, read on.
Why You Should Know What Focal Length Means
Knowing what the focal length of a lens means in relation to your camera, is very important when it comes to buying lenses. Read this post to find out what different lenses are used for, which ones are right for you, how to use them creatively, and all the technical speak you’ll need.
Lenses are divided into two categories based on whether they can zoom. There are the ones that have a fixed focal length (prime lenses) and those that have a variable focal length (zoom lenses). In general, prime lenses are sharper and often have a wider aperture, great for low light conditions.
Zoom lenses allow you to use one lens to cover a range of different photography fields. One lens means less time spent searching for and changing lenses. There are advantages and drawbacks to both types of lenses, so having a mixture of them gives you versatility and power.
We can use the human eye as an example. Its focal length varies between roughly 17mm and 25mm, depends on who you ask and who’s eye you examine.
We have an approximate field of view of over 180°. This is different from the 90° angle of view from a lens, which is down to the fact that we have two eyes.
The area that we actively perceive is smaller, similar to a 40-50mm lens. That’s why the 50mm is called the ‘standard’ focal length.
On PetaPixel, you can find a great article explaining the human eye in-depth.
For more information on the two different types of lenses, read our Prime Vs. Zoom lens article here.
Section 1 – What Does It Mean?
The focal length of the lens determines how ‘zoomed in’ your photos are. The higher the number, the more zoomed your lens will be.
It is often misunderstood that the focal length is measured from the front or rear of the lens when, in reality, it’s the distance between the point of convergence in your lens to the sensor or film in your camera.
Take a look at the diagram below that explains this:
Section 2 – Different Focal Ranges and What They’re Used For
Ultra Wide Angle and Fisheye 14-24 mm
These lenses are often considered speciality items and not often included as part of a kit lens. They create such a wide angle of view that they can appear distorted. this is down to the lens having to fit more of the scene into film or sensor.
Ultra wide-angle lenses are often used in event and architectural photography. They help to get a lot into a photo when shooting in a confined space. Wide and ultra-wide lenses are about putting yourself in the middle of it all, rather than fitting in the whole of a scene.
These lenses are not suitable for portraits as they enhance the perspective so much that facial features can look unnatural.
Rectilinear wide angles project an image in which the straight lines remain straight. Fisheye lenses distort the scene into a spherical shape.
Wide Angle 24-35 mm
This is where you’ll find most kit lenses for full-frame cameras start. 24 mm is the point at which the distortion that appears to stretch the side of an image stops appearing unnatural.
They are used by photojournalists for documenting situations. This is because they are wide enough to include a lot of the context, whilst still looking realistic.
Standard 35mm-70 mm
It’s in this range (at about 45-50 mm) that the lens will reproduce what our eyes see (excluding peripheral vision). I like to use this range when shooting on the street or with friends in a closed setting. Examples would be at the dinner table or the pub.
A standard lens such as a 50 mm f/1.8 is an excellent, inexpensive addition for a camera. It will provide excellent results. Prime lenses will always provide better results than your kit lens, as it is built with a single purpose. It does one job well.
Mild Telephoto 70-105mm
This range is often where kit lenses stop. Here, you’ll start to get into the range of telephoto lenses and portrait primes (around 85mm). This is a good range for portraits as the natural perspective of the lens will separate the face from the background.
It does this without isolating it.
Telephoto 105-300mm
Lenses in this range are often used for distant scenes such as buildings or mountains. They’re not suitable for landscape photography because of the way they flatten the perspective of a scene. Lenses in a range higher than this are used for sport and animal photography.
Section 3 – How Does Focal Length Affect the Perspective of A Photo?
I tackled most of this in the previous section. To give you a better idea of how the focal length affects the perspective of a photo, I took four photos of the same subject at different focal lengths and compared them below.
The subjects (three soup cans) remained in the same position (about 10 inches apart from one another) in every photo. It’s worth noting that these photos are shot with a crop sensor. This means the actual focal length will be higher than listed – something I explain in Section 4.
To say it’s the focal length that changes the perspective is, however, quite misleading. You see, it’s the distance from the subject.
The focal length of a lens is an indicator of the distance from the subject: the images are all framed the same. Differences arise because the focal length is getting longer (zooming in) as the camera moves further away from the subject.
Remember, the distance from the subject is changing the perspective. The focal length is just used to compensate for this.
Section 4 – What About My Crop Sensor?
Shooting on a crop sensor has what’s known as the ‘crop factor’. What you’re doing is zooming in on an image, and avoiding the widest parts of the scene. The diagrams below show the way this works.
Even lenses built for crop cameras such as the EF-S range and DX range will still have this effect. This is because lenses are listed by their physical focal length rather than their field of view or equivalent focal length.
However, these lenses will not work on a full-frame body without heavy vignetting. This is because the image will not project onto the whole of the sensor.
That’s it!
Here are two focal length examples that were taken at very different focal lengths of the lens.


Before you go, check out this cool video we found.
Hey there, first of all, thanks; no one ever explained it so well before. Im so happy to have found this website 🙂 I do have to mention, though, a wonderful website like this loses credibility with such spelling mistakes as “How does the focal length ‘effect’ the perspective of a photo?” Effect and Affect are two different words. The focal length AFFECTS the perspective, therefore it gives you a different EFFECT on the picture. Believe me, this comment goes with the best intentions, I truly love the site.
Cheers
Thanks JMM, I got a few posts in before that started to dawn on me and as it’s in a heading, it must have slipped through the net. I did have a really good editor, but she’s away at the moment. I’ll get her back on it when she’s back!
Josh
Extremely useful article! Thanks.
Josh, thanks so much for the info. Like the saying goes…. “A picture is worth a thousand words”!! It’s so nice to have somethings explained to where the “average” person, like me, can understand it!! I appreciate it!!
Thanks, I spent a lot of time on this tutorial. Please share it with your friends to help get the word out there, It was written a few months ago when the site was a lot less popular. – Josh
Awesome tutorial, Josh! Thanks so much for sharing with us.
very good site josh,also easy to understand i’m new to photography,and its hard to understand a lot of the terminology,if you know nothing about it,i see you sign your photographs.how is this done i use a mac with’ i photo’ only so far . thanks
You can do it in Aperture
Hi Josh,
The conversations do reflect your expertise in photography.
From your responses to various queries I am quite sure you can answer mine. I tried taking some moon pics with my canon rebel xti with quantaray 70 – 300 mm lens. for some reason, the pic always seems to be very small (smaller than the ones I have seen on the net – not that thse have been taken with high end lens). Request your guidance and thanks in advance. Cheers… Sanjay.
Do you mean the actual moon looks really small? It’s funny you should mention it because my friend came over last night with a photo of a moon on his camera taken with his brand new 70-300 at it was also small. The moon is far too far away to capture at a good size, even at 300mm. Professionals will likely have used longer focal lengths and 2X entenders which double the focal length. What I recommend you do is work on your exposure so that you can see detail on the moon and wait for a night where the moon is particularly large. Then shoot at your maximum resolution and crop the image around the moon for the best effect. Hope this helps – Josh
Wow! Blown away here! Fantastic how you put this article together.
I have to ask, how does the “submit a photo” thing work, maybe an article on THIS?
I don’t know how I found this site but I’m glad I did. For sure, I will return often.
I’ve added this to my INFAMOUS Pearl Tree. You sir are now a rock star.
Keep up the good work and Psss.. “You’re a Pro” You can’t fool me.
Thanks so much, submit a photo is in the header underneath the photos.
Hi Josh
Liked your article very much.
I live in Sunny, hot, stinking humid Florida but orignally from London where I was born and Hastings where I lived till I emigtated here.
Carry on the good work.
You make it simple!!and thats all i need. Thanks, hsve paid people before to explain this and still didn’ quite get it..
great read pictures which i need to understand thank you
Great article, Josh! I have been struggling with this subject for a while. You cleared it up in a few paragraphs. Wonderful talent, that!
I’m a little slow, I guess (well, I know, but I like to hide it some), but I miss the correlation between the last example photos. I was hoping to see a comparison of the two extremes on the same subject, so I may be missing the point entirely.
Perhaps they’re not great examples, but if you look at the trees in the first one, they’re far apart and you can see the details between them, where as the plants in the second one are much more pushed together, so that you can’t really get a sense of depth. I might consider changing them at some point, thanks, Josh
Josh, I did not mean to knock the examples, but just to indicate that I missed the point of comparison. Trust me, I am far too ignorant of photography to believe that I could critique anything! Just trying to learn.
Thanks for the clarification!
No, I see your point and agree with it, I’ll try and find something to replace it with.
Message to JMM of May 24, 2011 at 9:09 pm – You have grammatical errors in your post. Ironic.
I wonder this article with so stupid mistakes is widely reposted. I wonder all photographers didn’t learn optics in school and cann’t just read wiki. At first, focal lenth is not the distance to the sensor (but to the image of infinitely distant object). Just try to unplug your lens – FL wouldn’t become several meters. At second, the lins at the picture looks like having focus inside it, named “the point of convergence”. Beginner will hardly understand the reality.
Could you say that again in English, please? If you’re going to be rude and patronising, you could at least be clear about it, love!
Hello and Merry Christmas
Thanks for the article; looking around and noticing the quality of your posts it becomes clear that I will spend a lot of time on your site.
I do have a questions though. I’m a beginner and putting together an equipment list. As far as the camera is concerned I decided on Nikon D5300. It is still unclear to me what to pick as prime lens for this camera body. I was thinking to get the AF-S NIKKOR 50mm f/1.8G. My confusion is in regards to the focal length. Since this camera has a 1.5 crop sensor, should I get the AF-S DX NIKKOR 35mm f/1.8G instead?
Thank you
I’d personally go for the 35mm!
This is in correct, at least in part. I put a 35mm Takumar lens (FX, m42-mount) onto a K&F m42-m4/3 glass-less adapter (no lenses inside, just a metal tube) and this onto my Olympus E-M5 MarkII micro-four-thirds camera, and the field of view was not the same as when using a native 17mm* lens on that camera (no adapter needed). The field of view with the 35mm FX lens was the same as a native, m4/3 35mm lens (I used my kit lens zoomed to 35mm).
APS cameras have a 1.5X crop factor; m4/3 cameras have a 2X crop factor.
How is that possible for a lens to completely change the appearance like that? My mind is aboggled.
Thanks a lot for this article it is explicit, simple and to the point easy to understand. I was having problems with the cropping and the focus thanks this was very helpful keep posting articles like this I will be your follower. thanks
This was such an amazing explanation. Thank you so much. I had been struggling with what this means