Focus Blur: Something Fun to Play With

Gerry van der Walt All Authors, Gerry Leave a Comment

During last year’s Tuli Nature Photography Workshop, we did quite a bit of star photography – always fun!

One of the fun things we explored a bit was focus blur.  This is a technique where you start with the subject – in our case stars – sharp and in focus and then, during the long exposure, turn the focus ring to throw the focus off and create a soft, almost ethereal look to the image.

This was one of the images I shot of the sky earlier on in the evening when we where still just getting warmed up for a great night of star photography.


Nikon D800, 18mm, f/2.8, 20 sec, ISO 3,200

The theory is pretty simple.

Or let me rather say, here is a simple explanation of the theory.

When you lock focus on a subject – in this case the stars – the camera renders the lines and points in the frame sharp.   If you were to shoot a frame with an out-of-focus lens, you will see all the detail in the image as soft and, well, out of focus.

All you do to create an image like the one above is to start with a sharp and focused image and then, during the long exposure, turn your focus ring.  Looking at the image you will see soft blobs of light, which is the out of focus bright stars, and in the middle or next to each of these blobs you will see the star as it was rendered when the focus was still sharp.

Remember that to create an image like this you need to turn your focus ring during the exposure and not the zoom ring which will give you an image that creates this kind of effect.


Nikon D800, 14mm, 20 sec, f/2.8, ISO 3,200

In this case, you can see that the stars have not turned into blobs of out of focus light, but are rendered as sharp lines of light as the lens elements move while you zoom.

So, let me try and make this really simple for you.

  • Soft blobs of light = turn the focus ring on your lens during a long exposure
  • Star Wars effect = turn the zoom ring on your lens during a long exposure
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The options are endless and the best part about this is that the more you play with these techniques, the more amazing images you are likely to create.

This is just one of the images that I was quite taken by from the Tuli trip, but you can be sure that when I head up to Kenya in a few weeks time we will be trying more of these kinds things with our camera’s pointed to the skies above Kilimanjaro!

Play around and see what you come up with.  You might just surprise yourself.

I’m glad to finally be back on the blog so make sure to check back for more posts coming soon.

Oh, and apologies for using terms like ‘blobs’ and ‘Star Wars’ in this post.

Until next time.

Gerry van der Walt

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