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Posted June 24, 2015 by Gavin Hoey in Articles
 
 

How Focal Length Affects Your Background

There are many reasons for choosing one lens over another and which one you shoot with can have a massive impact on the final photo. Like many photographers I love the flexibility of zoom lenses and often have to make the choice of shooting with a wide angle and short telephoto lens. At first glance the choice of lens is pretty obvious… if I want to go close I shoot with a telephoto focal length and if I want to see more I zoom out with a wide angle focal length.

Look around on the internet or ask your photography peers and you’ll find that the general consensus is that wide angle lenses increase perspective distortion and telephoto lenses compress background. It’s common knowledge but sadly, it’s also not true… although I completely understand why so many photographer think it is.









In the video above I explain and show how changing focal length alone doesn’t affect compression or distortion but moving your feet does

Google focal length compression and you’ll see photos like the one below and as you can clearly see the more I zoom in the more the background appears to grow in relation to the model. We call it background compression and it’s a really handy trick to learn.
Compression-ALL

But in order to keep my model (The amazing model Fern Meave ) the same size I had to increase my shooting distance as I zoomed in and it’s that increase in distance that causes the background to compress. Let me say that again…
Increasing your focal length does NOT compress your shot, increasing your distance from the subject does. Unless you want your subject to be small, once backed up you have to zoom in to maintain the composition and that’s why so many photographers will tell you telephone lenses compress your shot.

To prove the point. Take a look at the photos below. For the one on the right I used a 200mm lens, the one on the left is a from a shot taken with my 24mm lens and the middle image is a tight crop from the centre.

lens-compress-debunk

The distance from myself and the model was the same in each shot, only the focal length changed. Spot the difference?  Ignore the the depth of field difference between the two shots, that’s a side effect of the different focal lengths and I’ll save that for a future blog post. There really is no difference in compression and perspective distortion when you change lens focal length.

So if background compression isn’t caused simply by zooming in, do wide angle lenses increase perspective distortion? No they don’t (excluding exotic lenses such as fisheye’s). With a wide angle lens you often go close to fill the frame and that increases the distortion. In theory you could take a wide angle shot using a 200mm lens, you’d just need to take lots and lots of images and join them together like a jigsaw puzzle. Search Google for Gigapans to see this in action.

Still not convinced? Here’s a simple test to try, no camera required… next time you’re in front of the bathroom mirror, get your head really, REALLY close. Close one eye and look around at your refection. Your nose will look huge, your ears will look small and all because you’re close to the mirror. Step back and your face will appear as normal as it was before.


Gavin Hoey

 


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