BY DAVID OSBORN
Having spent a great deal of his working life in aviation, firstly as an air traffic controller and then as an airport manager, David Osborn FRPS is now a UK based professional wildlife photographer. He joins us to share his experiences of in-camera Focus Stacking with Olympus kit.
Although I owned an Olympus camera, I’m not too sure what convinced me to try using it for focus stacking. I was very happy with the results from my DSLR equipment, even though the process was very slow and time consuming and required manual focusing throughout. I guess I didn’t really believe that focus stacking could be done so quickly and efficiently in-camera. But try I did and what an absolute revelation it proved to be! Images I’d never thought possible in the field were now achievable. The Olympus system is so quick, it achieves accurate AF throughout and the whole process is speedy and efficient.
Focus stacking has only really been possible since the digital era and technology now gives us the ability to stack images together, to increase the range and depth of focus. For me, in practise it allows me to use the best lens aperture to achieve the best possible image quality. It avoids the use of high F-stops (therefore eliminating any possible lens diffraction issues) and by using wider apertures it generally avoids the need to use higher ISOs, which minimises noise whilst blurring any potentially distracting backgrounds. And, of course, it ensures focus throughout your subject. So it’s quite something! To have the option as a built-in camera feature is simply amazing.
I currently use the OM-D E-M1 Mark III with the M.Zuiko Digital ED 30mm & 60mm Macro lenses and under Shooting Menu 2 > Bracketing, the camera offers two options for stacking images; Focus Stacking and Focus Bracketing.
Focus stacking is all done in camera, with the camera producing a final, slightly cropped ‘stacked’ jpeg ready to use.
Focus bracketing is a much more flexible option and the camera can take up to 999 raw images all automatically focused, but the final stack must be done using separate software on a PC or similar later.
There are some excellent Facebook video tutorials produced by Olympus UK on specific camera settings relating to macro imaging, which I would highly recommend viewing.
Whilst learning the system I initially opted to use the focus stacking option – it’s a good place to start and gives great results, but I quickly realised that I needed greater control in order to be more accurate and precise, and that the focus bracketing option would be best.
I have focus bracketing set as a Custom Function which makes it immediately accessible and it’s also set as a backup on ‘My Menu’. I always manually focus and use focus peaking to ensure accurate focus, focusing on the closest point of the subject to the camera.
Accessing the menu, I select an appropriate number of images and focus differential to ensure focus throughout. It’s difficult to say exactly what works as every circumstance will be different, but a good starting point is 15 images at a differential of 4, and an aperture of F5.6. As you get closer to a smaller subject you’ll need more images and a lower focus differential, as you get further away you’ll need less images and a higher focus differential. This will also change when you change aperture. I often use F4 to achieve a softer background and the change of aperture then requires more images to achieve the required depth of field (for example, on small flowers using F4 I normally take 25 images at a differential of 2 or 3, if I used F8 then I would only need 12 images at a differential of 4). Experience, along with trial and error, helps immensely, but you’ll quickly develop a feel for what’s needed.
Once I’ve taken the set of images I always preview. I check the first and last shots of the sequence for focus accuracy and make amendments as required. I also always take more images than needed, as there’s nothing more frustrating than getting home, processing a focus stack and finding that you’re a couple of images short and of course it’s then far too late to make amends.
My current workflow
- Tripod mounted, IS off.
- Select aperture, shutter speed and ISO (basics pre-set on Custom Function setting).
- Based on the subject and aperture, select the number of images required and focus differential.
- Manually focus using focus peaking.
- Shoot and always use a shutter release – you’ll always ‘jerk’ the first image if you use the shutter button and if the images don’t align they won’t stack.
- Preview the first and last image to confirm that you’ve achieved correct focus. Amend as necessary.
- If, for whatever reason, the subject moves during the process then you’ll need to start again.