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Free Photography Class #3: All about Focal Length

Camera Focal Length Explained and Comparison

We are going to explain the world of camera focal length for you in an easy to follow way. We are going to discuss the benefits of types of lenses, how to apply those benefits, and the settings you need to learn. Then, at the bottom, I will provide examples so you can see the real difference in each topic. Today is lens focal length, so let’s dive in!

There is all kinds of confusing jargon and abbreviations lens manufacturers use. Just a few numbers or letters somehow make one lens worth $200 and another worth $2300.  We will first look at Focal Length, so we can understand the whole purpose of a lens and then move to each feature, preparing you for your next lens purchase!

What is a Focal Length?

Put simply, it’s how far can the camera see (we will get into the numbers in a minute).  There are two types of lenses, Prime lenses and Zoom lenses. Prime lenses do not adjust or “zoom” in and out, they are a fixed focal length. So whatever focal length you purchase, that is where the lens will always be. You can adjust the focus (clearness of an image) with a ring that spins on the lens or your autofocus (the lens automatically focuses on the subject) but it will not zoom in and out like a pair of binoculars. 

Zoom Lenses

Now zoom lenses have a zoom range, so if you see on the advertisement something like “70mm-200mm” that means that when you look through this lens, you can adjust how far you can zoom anywhere from 70mm to 200mm.  You probably wonder, well why would I ever want a prime lens if I can get one zoom lens to cover multiple distances?  Well, a quality zoom lens will be far higher priced and much heavier. 

Prime lenses

Prime lenses are also notorious for a very high-quality image (think bang for your buck) because they have so few moving parts.  Plus, some beginners really love that you are removing one big variable from your shooting.  With all the settings to consider, and we will learn later, focal length won’t be one of them. You just move closer or further to your subject to zoom (zoom with your feet so to speak).  Well Jon, why wouldn’t I just spend less money on quality lenses and get all primes? 

Which is best for you?

First off, you can spend a lot of money on one really quality zoom lens that could be the only lens you have to take with you, or you might have multiple prime lenses that you have to switch out every time you need to “zoom in” but can’t walk closer.  Many professional portrait photographers exclusively use prime lenses, and these are great for them since they are often in a studio and know what lens they need for different distances; but if you are a wildlife photographer, it could get pretty old swapping out lenses when you can’t move from your spot because you would spook the wildlife.

As far a focal length goes, they say the human eye can see at a focal length of about 25mm, some go as high as 50mm.  But that does give you a rough idea… so a 14mm lens is going to give you a very wide angle and short focal length (excellent for big wide-open landscapes) but a 600mm lens would let you look at a small bird in a tall, tall tree like he was right next to you.

What is Minimum Focal Distance?

Sometimes you will have to hunt for this number in the description of a lens you want to buy, but minimum focal distance is just as it sounds.  If you have a min. focal distance of 6 feet, that means no matter what the zoom is on the lens, you can’t focus on anything less than 6 feet away.  However, with a min. focal distance of 12 inches, you could literally be right next to the subject and take pictures. 

If you are a wildlife photographer or landscape photographer, this isn’t as big of a deal since your subject is typically more than 6 feet away.  But if you like to do macro photography, a lens with a min. focal distance of 6ft is almost useless to get up close and grab the amazing details in tiny critters. So not something to keep you up at night, but definitely something to consider and be aware of on your new lens.

I heard that the type of camera I use can change the focal length?

Well, you heard right, kind of. It is the sensor (the small screen on the inside of the camera that is visible when you remove the lens) that can directly affect your focal length. There are two types of sensors, Full Frame and APS-C.  Full frame just means that the sensor inside your camera body is bigger, has more surface area and therefore, does not “change” the focal length of the lens.  So, a 200mm lens will see the same distance on any full frame camera. 

Focal length on aps-c sensor cameras

Most of the market uses APS-C sensors since they are less expensive (in most cases).  These sensors are much smaller, and you have to break out your calculator to figure out the true focal length of a lens.  I am a Canon guy, so for all Canon APS-C cameras, you simply take the focal length and multiply it by 1.6.  So, if you were using a 50mm prime lens on an APS-C camera, the focal length would be closer to an 80mm prime lens on a full frame camera.  So, if you wanted a true 50mm lens for an APS-C camera, you would need to make sure your lens is set to around 32mm. 

Kind of confusing I know, but there is a wide array of lenses that have a wide zoom focal length.  So if you are just getting into photography and thinking about dabbling in many different genres, just get a zoom lens that covers a wide focal range and you will be covered until you start really figuring out which focal length you use the most.  That goes for other companies also, although the number to multiply by may be different.  Many other manufacturers have slightly larger sensors so you would only multiple by 1.5. But you would have to check your camera or drop me a comment and I will let you know!

Dude, what? I gotta do math? 

Now, if you are like me, you learn by seeing, right?  I mean, we are photographers after all!  So below, I have a chart of the different lens categories there are and the focal lengths for each.  Also, if you were wise enough to go with a Canon camera body, I have a conversion table for you so you can make sure you are in the right category without using your handy abacus.  Below that, are some examples of me staying in the same place and taking pictures at different focal lengths.  That should really bring it home for you!

Focal lengths and drawbacks

Should I get a manual or auto-focus camera?

If you disagree with what I say here, drop me a friendly comment below, I would love to hear your thoughts. But in almost every case I can think of, I would say get a lens with auto-focus. These focus systems are so advanced today that a manual focus is a huge constraint on your photography. All auto-focus should have a way to place the lens in manual focus mode, which I use often, but most auto-focuses are so quick and precise it is almost impossible for you to compete focusing manually.

I have used manual mode and saw that my pictures were slightly off and i couldn’t tell from the small screen or through the viewfinder. The only way an auto-focus will be off is if you are focusing on the wrong subject. These things are dead accurate and have features to recognize eyes, moving targets, etc. I wouldn’t waste your money on a manual focus, go with auto; you always have the option at that point to focus auto or manual.

I bought a kit that came with a lens that has the word “macro” on it. What does that mean? 

Well, it depends. Most of the “kit” lenses that have macro on them are not true macro lenses, so you are probably just fine shooting with it just like you would any other lens in that focal length. You might even get a little sharper image from it, although perhaps a little darker (which we will learn later how to combat.) A “true” macro lens is an image ratio of 1:1. What you talkin’ bout Willis? It simply means that when you are at your minimum focal distance, whatever you are taking a picture of is life size.  This comes in handy with very small objects like bugs and flowers. 

minimum focal length

So, if you are at your minimum focal distance (say 18 inches) and that bug is say… 1 inch tall, it is going to appear bigger on your sensor than non-macro lenses. It’s a 1 to 1 ratio, so if your sensor is 1 inch and the bug is 1 inch, then the bug is going to take up the whole picture at that distance.  That does not mean that you can’t use a macro lens for other purposes, say portraits. In fact, there are several benefits to using such a lens.  Macro lenses are made to see the finest details in objects, so when you step back and use a macro lens to do a headshot, you are going to see amazing details you just wouldn’t see in a similar non-macro lens. 

However, they always seem to run a little darker, so non-macro lenses are always going to be the route to go if you care less about sharpness and more about having beautifully blurred backgrounds (called: bokeh).  We will get more into that in the aperture discussion.  So, if all you have is a macro prime or zoom lens, it’s not the end of the world. You can focus closer than other lenses and get crisper images, you just sacrifice auto-focus speed, bokeh and a few other things that really aren’t too important to the beginner, like lens breathing.

need examples?

So as promised, below are a few images at different focal lengths so you can see how this small change completely changes the picture. If you have a zoom lens already, give this little example a try! Go outside and focus on something and without moving, take pictures at different focal lengths. Then look at your photos after and see the differences. How did focal length change the quality, the brightness, sharpness, etc. Get to know your lens so when you are on a shoot, you know exactly what to expect.

Up next, we are going to talk about the aperture of a lens, the setting that really provides the most options for creativity! I can’t wait!

Studio Examples

All examples were taken in studio with artificial lighting at 8 feet away from the “subject” (old homerun baseball) on a tripod. Final image is an example of a Macro lens from 12 inches away. Check the captions below each picture for the focal length.

Ultra Wide Angle

Wide Angle

Standard

Telephoto

Super Telephoto

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Photography and writing by Jon Frederick also check out our Instagram!