Focal Length – A Simple Explanation

Jed with camera -1I am constantly surprised by the number of photographer’s who come to me for private lessons who don’t really know the focal length of their lens.  Knowing the importance of different focal lengths and the impact they have of their images is really important.

Some lenses magnify the image you’re taking, while others make the image smaller  (but in doing so allow you to get more in the picture).  So typically, if you like to shoot lots of landscape photos with rolling mountains and beautiful lakes in the forground, you’ll want a focal length that gives you a very wide viewpoint (Field of View).

If you’re into wildlife, you’ll want a very different type of lens – a telephoto, one that makes the bird or animal look closer.  The field of view in this case will be quite small.  Try taking a photo of rolling mountains with a telephoto lens and you’ll probably only see a small part of the mountain.  The mountain will be magnified in much the ame way as using a telelscope.

Linda with long lens

The 400mm focal length on this lens is perfect for shooting sports and wildlife

One of the most common areas of confusion is between telephotos and zooms, with a sizeable majority mixing the terms up, believing they are one and the same thing.

In pure techno-speak, focal length is the distance between the point of convergence and where the lens focuses, which in digital cameras is the sensor.  Back in the old days it would have been where the film was.  That kind of detail is less important than the understanding that different focal focal lengths affect your photos in different ways.

However, in this video (which I made back in May 2018) I try to explain in simple terms, what focal lengths are.

All the assumptions in the video are based on a 35mm film camera or a full-frame digital camera being used.  Once you put any lens on a crop-frame camera body, things get slightly more complicated.

For more information about the difference between full-frame and crop-frame, you should watch this video: CLICK HERE

If you’d like to know more, drop me an email at

Learn Photography

If you’re looking for photography workshops, photography courses or photography lessons, check out our website at Hampshire School of Photography or call Tuesday – Friday 01252 643143

Kevin Ahronson

Kevin is a full-time professional photographer and has been teaching photography since 2009. He founded the Hampshire School of Photography where he runs photography workshops and gives one to one mentoring to photographers at all levels, from complete beginners through to those who want to turn professional

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