What do the numbers on a camera lens mean?

One of the most important factors in property photography is using a high-quality wide-angle lens, as it allows you to fit more into the shot and gives a better overall impression of each room. But what do the numbers on a camera lens mean?

When you’re faced with them all at once, they can be a little overwhelming. But, they’re actually not as complicated as you might think.

If you’re not new around here, you’ll know that the Sigma 10-20mm EX DC HSM 3.5 wide-angle lens is our top choice for property photography, so this is the lens that we’ll be using as an example.

What does 10-20mm mean?

These are the most important numbers when considering a lens for property photography.

These numbers refer to the focal length of the lens. While millimeters (mm) are used as a basic description of the lens, this is not a measurement of any dimensions of the lens itself.

The numbers are actually a calculation of an optical distance of converging light rays and… I’m gonna stop here as it gets very technical and it really doesn’t matter.

Just know that the lower the number – in this case, 10mm – the more you can fit in the shot. For property photography, we want a nice low number so we can fit lots of detail in the shot.

With the lens fully zoomed out at a 10mm focal length, you can fit loads of the room in the frame, perfect for showing off your vendors home like a pro.

To help complete this picture for you, let’s look at the other end of the spectrum. Imagine you’re on holiday in the Serengeti with a camera trying to photograph a pride of lions, from far away (obviously).

You’re gonna need a camera that you can zoom in from a long way away. For this, you’d need a high focal length e.g. 600mm.

Back to the 10-20mm lens though, 10mm is on the low end of the scale. For reference – you’re typical iPhone X shoots at a 28mm focal length (remember, higher number so fits less of the room in shot).

What focal length is best for property photography?

Below, you can see an example of why images look much more professional when shooting with a DSLR and wide-angle lens with a 10mm focal length vs a phone with a 28mm focal length.

Generally, the lower the focal length number – the better as you’ll fit more of the room in shot. The 10mm focal length on a crop sensor DSLR is perfect. However, if the focal length is too low, then things look a bit fishy (fish-eye lens pun, anyone?).

If your lens just has one number on it, such as 85mm, it means you’ve got a fixed lens (aka a prime lens).

You don’t really want a prime lens for your main camera for property photography as you’re gonna want more control over zooming in and out (slightly) to perfectly compose your shot, for that you need a zoom lens.

This Sigma model is a zoom lens, offering a range from 10 to 20mm, which can be adjusted by twisting the zoom collar.

To recap and summarise; the lower the focal length number, the more you can fit in the photo. Perfect, moving on…

What does 1:3.5 mean?

This indicates the maximum aperture of your lens, this is the size of the hole that light it lets in. The lower the number, the more light is allowed in. The ratio looks confusing, but this is simply how apertures are measured; just pay attention to the number after the colon!

A useful analogy for aperture is thinking of a water pipe. A wide pipe lets through a lot of water quickly, a thin pipe lets water through more slowly.

Some lenses have a range of aperture, for example 1:3.5-5.6. This means that the more you zoom in, the narrower the aperture will become, and the less light is let in.

For property and real estate photography, we advise keeping things simple. Allow the aperture to be set automatically by using Auto-flash off mode. This way you don’t have to worry about controlling the light levels hitting the sensor yourself for each shot.

Want to learn more about how to take property photos? Download our Ultimate Guide to Property Photography for FREE!

What does AF / M mean?

AF lets you know that the camera has built-in auto-focus, whereas M (or MF) refers to manual focus.

This means that you can either let the lens adjust itself to provide the best focus for the subject, or override this by switching to manual focus to create the desired shot.

Autofocus is perfect for property photography, as it helps you to save time fiddling with manual controls. It also makes your property shoot more efficient.

If you’re finding your shots are always a little blurry, you could have your lens set to M, flip this to AF and you’re good to go!

What does EX mean?

This indicates that it is a pro lens, and therefore higher quality than its non-pro counterparts.

Lens manufacturers make many different lenses to suit various budgets and usage requirements. We’d always recommend investing money in the lens rather than the body of the camera if you have budget constraints. Pro lenses are just the ticket for property photography.

What does DG / DC mean?

This refers to whether the Sigma lens uses a full frame (DG) or cropped frame (DC) sensor. Other camera manufacturers use different letters for this. For example, Canon uses EF and EF-S, whereas Nikon uses FX and DX.

What does HSM mean?

This tells you that the lens uses a silent wave motor. Again, other companies use different letters for this, but if you see initials ending in “SM”, it’s probably referring to a silent wave motor.

Three great advantages of this are 1. A much faster focus than standard lenses. 2. Near-silent adjustment of the lens 3. Less or no movement of the end of the lens when focusing.

Now you’re a camera lens expert…

…take that newfound knowledge and apply it to the next property in your portfolio, instead of spending thousands of pounds a year to hire a professional photographer.

However, no matter how well you know your camera kit, you’re bound to need a few edits here and there, and that’s where Elements Property’s Image Enhancement service comes in.

Register today and use code BLOG50 to receive your first three orders absolutely free!