A Photo a Week Challenge: Depth of Field

If you read Nancy’s post you will find the factors involved in limiting depth of field explained. The f-stop description is as Nancy says – counter intuitive. The key to understanding is that f-stops are a ratio with smaller numbers indicating a wider opening to let light in. One of the best ways of understanding this is to view the number as being the number of holes of that size that would fit on your film so 2.8 is, by definition, a much bigger hole than the hole that would fit onto your film 16 times. f-stops have been around a long time and the direct correlation to film / sensor size no longer exists. Nancy mentioned that focal length also plays a part in the depth of field – it’s worth adding that cropped sensors affect your lens focal length compared to full frame sensors and therefore also have an effect on the depth of field in your final image. I hope my additional thoughts help.

Limiting depth of field is a technique used in sports photography to isolate the action from the background. Thus, you will find many sports photographers shooting using aperture priority to keep the depth of field small whilst adjusting the ISO setting to maintain a suitable shutter speed. Some photographers will shoot with the lens wide open – I tend to try and use somewhere between f4 and f5 because sometimes I find that f2.8 is a bit too tight for my subject matter. Of course when it gets dark and I’m photographing under the poor quality floodlights at a non-league football match then I have to resort to shutter priority and adjust the ISO to get reasonable exposures at the widest aperture – such is the life of a football photographer šŸ˜‰ Here’s a couple of shots from a recent match at Leatherhead – one of action and one of a couple of stewards…


  1. I appreciate your explanation, Martin. Your football photos are always so clear and you capture the action with a very professional outcome. I was very interested in hearing some of your technical methods. I might want to practice a bit!

    1. Thanks Debra. One key thing to remember is that I’m right next to the pitch. Replicating this type of shot from the stand at an American Football match would be very difficult. However, the technique should work well at a skateboard park or if you can get seats near the front at a Basketball game.

  2. Interesting that you get good results at that f-stop. I find I tend to like my results starting at about f6 and above if I want some but not all the details in the background. I know photographers like to go on and on about a “best” result, but that’s a bit of a waste in my opinion. If we were all the same, the resulting photography would be a bit boring. Anyway, thanks for sharing your settings. Very nice results, as always.

    1. Thanks Amy šŸ™‚ The light often dictates what settings I can use in the middle of winter. I’m usually aiming for acceptable results that the club can then use for the match programme and the players can download to share with family. The lens for these shots is the Canon EF 70-200mm f/2.8L IS II USM. The softness is a result of using the 5D mkiii at ISO16000 to combat failing light and poor floodlights. If I was using the 7D mkii the max ISO I’d use would be 10000 and the results would appear superficially sharper but also much noisier.

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