Focus Stacking; Jumping Spider
As part of my Jumping Spider; Jumping through the edits series I am covering the steps that were carried out in editing the image which was processed using Helicon Focus. Because of the lens combination and the significant magnification (e.g. > 2:1) the Depth of Field (DOF) was very shallow and which required the image to be focus stacked.
Whilst A full description of depth of field, and focus stacking is outside of the scope of this post, I will provide a brief summary:
Imagine that your lens is pointing towards the image you are photographing and there is an imaginary line moving in the same direction as the lens, this is called the Plane of Focus. Depth of field refers to how much of this imaginary line is acceptably sharp or in focus, a large depth of field means more of the image will be in focus along this line, whilst a smaller depth of field means that the amount that will be in focus in smaller.
To increase the depth of field, usually you would use a higher f.stop (also known as a narrower aperture) however, with some lens combinations there is a limit to how high the aperture can be increased, and the depth of field may still be fairly narrow. This is especially true of macro photography, and micro photography.
In the image below of the jumping spider, only the head (circled green) is in focus, but as you move across the body of the spider (e.g. the plane of focus) moving towards the back, the spider is no longer in focus.
Given the limitations are often optical, to increase the depth of field sometimes there is a need to conduct what is called focus stacking with something like Helicon Focus. This is a process where multiple images are captured with a slightly different focus point. Specialised software is then used to take the various “Sharp” components of each of the different images and combine them into one overall image. There are a number of limitation to this process, but the greatest is that the subject needs to be still, also typically the greater number of photos the better the stack will be (some limits).
In the case of the Jumping Spider image, I needed to stack a total of five (5) images to create the final focus stacked image, ideally I would have stacked more images however, as the spider was moving (and was not harmed) I was only able to capture five (5) images in quick sucession before it moved.
To create the stack, I used a tool called Helicon Focus which has an add-on for Lightroom. Helicon Focus took the five images above, and using a specific algorithm (In this case I used Mode B) it combined the images into one focus stacked image (below).
To achieve this, Helicon has looked at which parts of each image is sharp, and it has extracted that into a new image which contains the sharp peices from each of the individual images. I hope this has been a bit useful, in this case there would be no way I would be able to get a sharp image without using a focus stacking piece of software like Helicon Focus.
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