The Relationship Between Shutter Speed and Focal Length

Gerry van der Walt All Authors Leave a Comment

Friday is tutorial day on Wild Eye and if you’ve been following along on the Photo Chat videos you will know that this means anything from a Lightoom tutorial to a step by step blog post.


After running two introductory photography course the last two weekends I thought that today I’d have a basic look at the relationship between shutter speed and focal length as it is a nice way for new photographers to start paying attention to one of the important things to focus on in digital photography.


You see, as you grow as a photographer there are a number of moments when things fall into place.


It is these moments when a concept or little bit of theory suddenly clicks into place and you understand how, and why, it will make a difference in your photography.


One of the most common problems new photographers have when starting out is, once they take the plunge and move away from shooting in Auto mode, to create sharp images.  Images that are not blurred.


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There are a lot of factors that influence the sharpness of images but one of the main ones you should always keep in mind is your shutter speed.


In a nutshell, shutter speed refers to how long, or short, your camera’s shutter remains open.  It that sound you hear when you take a picture and you can very clearly hear the difference between a fast shutter speed, such as 1/1000 and s low shutter speed of 1 second.


If you look around on the net you will more than likely find two general guidelines as to how fast your shutter speed should be.  


The first is that you should, in a very general manner of speaking, be able to handhold a camera and get sharp images at a shutter speed of anythign above 1/30.  The second is that your shutter speed should always be at least 1/focal length.


Now each of those does make sense but they do contradict each other a bit.  For example – if I was shooting with a 600mm lens in low light conditions the chances of me getting sharp images at 1/30 pretty slim.  Not impossible, just quite improbable.  The idea of your always keeping your shutter speed above 1/focal length does however hold some merit.


Basically what it means is that if you are shooting with a focal length of 300mm your shutter speed should be at least 1/300.  Yes, it is a very broad guideline but one that does hold some weight. 


One of the other factors you need to consider is your subject, how fast they are moving and the amount of light available.  Here are a few examples.

 

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This image of a fish eagle in flight was shot at a shutter speed of 1/125 with a focal length of 400mm.  


It is quite evident that the shutter speed was not fast enough to freeze the action in this image.  If I were to have shot this at a shutter speed of 1/400 the image would more than likely have been a but sharper but it would not have been 100% crisp as the subject was moving quite fast.  

 

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In this image the lions face is just not as sharp as it could have been.  


The image was shot at a shutter speed of 1/160 and a focal length of 200mm.  Very close, and if you were to brace the camera or use some or other kind of support you would get it more crisp and create a much stronger image but in in this case the image falls flat.


If I had shot this image at a shutter speed of 1/250, or above, I would have stood a much better chance of creating a nice, sharp image.


But how do you do that?  Change the shutter speed?


If you are on Auto you have no hope.  The camera will decide everything for you and you just have to nod and smile when you see the results.


If you are shooting in shutter speed mode it is as simple as dialing in a shutter speed that exceeds 1/focal length.  If you are shooting in a very low light situation you might also need to push your ISO up to increase the sensitivity of your camera’s censor which will give you the ability to achieve fatser shutter speeds.


If you are shooting in Aperture Priority mode you have two choices.  You can open up your aperture as much as you can, to allow more light into the camera, or you can push your ISO up.


Remember that the above all of course assumes that you are shooting handheld without any kind of support.  If you were to use a beanbag or tripod you could get away with shutter speeds that are slower than 1/focal length but the resulting sharp images will also rely a lot on your subjects and fast they are moving.

 

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This image was taken with a focal length of 240mm and a shutter speed of 1/800. 


It is quite evident that the subject was standing very still and combined with a fast enough shutter speed, in relation to my focal length, makes for a nice and sharp image.

 

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Compare this image to the previous one of a fish eagle in flight.


The birds moved at very similar speeds but in this example my shutter speed was fast enough to freeze the motion.  Since I knew what I was going to photograph – a fast moving subject – I set my camera to Shutter Speed Priority and dialed in a shutter speed of 1/2,500.  I had to push the ISO just a bit to get there but in the end the result speaks for itself.


As with anythign in photogrpahy the shutter speed – focal length relaitonship is purely a guideline.  Some people say that you should always use a shutter speed of double your focal length while I have also heard a number 1.5 x thrown around.  The important thisn is, and that is the point of this post, that you should be aware of the relationship.  And know how it works.


Once you understand how the shutter speed – focal length relationship works you can, as with the rule of thirds, start breaking the ‘rule’.

 

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At a focal length of 140mm and a shutter speed of 1/30 I purposefully created this motion blur of a group of zebra on the move. 


Panning and motion blur image are awesome to play with as it gives you a whole new world of shooting opportunities when the light starts fading out in the bush.  The catch is however that you have to toss everything I just wrote in this post out the window.  But we’ll look at all of that in a future post.


If you have anything to add or have any questions – comments are open.


Until next time.


Gerry van der Walt


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Comments 0

  1. Guy Dekelver

    Hi Gerry, that zebra panning shot is just perfect with one of them, exactly the right one, being sharp! Cropped more tightly this would make for a great FaceBook or website banner

  2. Jdkimaging

    Nice info, I personally enjoy the Satara area for Leopard sightings, the s100, s41 s90 as a sircular route and been sucessfull. Still busy area but usually less that lower down..

  3. Villiers

    You’re right – that’s a little golden triangle of its own up near Satara! What makes the S100 special is the fact that you can see both leopard AND cheetah on the same road. I just spoke to a good friend of mine that saw two cheetahs on it this morning.

  4. Marcelle

    Its been such a long time since I visited south of the park. We generally stay from Satara and upwards. Sounds like the south gets real busy. Ive seen many leopard there on that particular stretch of road. None have been great sightings but I recall them all being very exciting! There are so many little pieces of KNP that are special for some or other reason. Thats why we always stay further North…the road from Orpen Gate to Satara and back is a gem for almost any species including regular sightings of wild dog.

  5. Jdkimaging

    I try to visit different sections whenever I go, but Satara, Balule, Tampoti Stayes my faviourites, the Leopard Population seems to do very good at the moment in KNP, Lions taking a nock, but that why it stayes great as there is still continuous changes 🙂

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