Focus Stacking


A passion for motorbikes and photography fused together in the creation of this picture.
At first glance it’s just another trendy close up of a bikes fuel tank but if you look more closely you will note that the picture is in focus all the way through its depth, that is to say both the nearest and furthest handlebars are in focus at the same which apparently defies the physics of normal photography which insists that there is a single plane of focus in a picture and that the scene gets fuzzier the further away elements of the picture are from it .

By increasing the depth of field (DoF) to include everything within the frame a much smoother and more pleasing image is created, details that would normally be out of focus are brought to life and the whole becomes clearer thus enhancing the viewing experience. There are times when the opposite effect is desirable, ie, a fuzzy background highlighting the main subject but in this case the clarity throughout is what makes the picture.

The two methods of overcoming depth of field issues are, a) use a camera with a smaller format/sensor or b) reduce the aperture (increase the f number) to as small as is practicable. Both of these routes can result in a reduction of image quality or problems with insufficient light so here is a third way forward and it is known as focus stacking.

Focus stacking is a made possible by digital cameras and requires a programme designed to undertake the task. The later versions of Photoshop have the facility or there are proprietary items like Helicon or Zerene which cost around the €200 mark and come with excellent reviews. However, if you just want to try the method out before spending too much there is a free download called CombineZP which is what I used here.

So what’s the process?  It’s really quite straightforward. You will need a dSLR and tripod and in this case a macro lens. First choose the subject, sounds obvious but it’s best to try one where DoF can cause problems, that way you will see the greatest benefits, and then choose the angle at which you want to shoot it. A close up across the handlebars like this would normally suffer all sorts of DoF problems so it was a good test.

The idea behind focus stacking is to take a series of shots or sections of the scene, moving the plane of focus through the image as you do so. These are then loaded into the programme which collates them into a single image.

The way I did it here was to find the focal mid point of the scene, that is the focus point half way through its depth. I then focused on the closest point I wanted to appear sharp in the final image. Using the indents on the focus ring of the lens as a marker I then took a series of shots, moving the focus further into the shot each time by turning the focus ring by one indent at a time. Having reached the midway point I then took the same number of shots, focusing beyond it by the same amount each time.

Having downloaded the images on the PC I then loaded them into Combine ZP which worked its magic and produced this finished item. You will need to trim the ‘output’ image with a crop tool before its finished but once produced it can be manipulated like any other JPEG.

That’s the story behind this picture anyway, I’ve skipped some of the detail and the more technically minded might point to flaws in the methodology, but if you are familiar with the the concepts of camera function then it could be a rewarding diversion from ‘normal’ photography. The method worked well on the bike yet I am still struggling with smaller subjects such as a lichen covered twig and I am grateful to members of the Luminous Landscape Forum for helping me get this far with the technique.


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