John & Maria's Photography Pages

 Focus stacking and bracketing

One reason I chose an Olympus EM1 MkI for my first foray into the M43 world was it's ability to do both focus bracketing and stacking in camera.  I was familiar with bracketing from my Canon days, using either a focusing rail or manual selection of different focusing points to generate a series of images where the plane of sharp focus was progressively moved forward within the same framing.  Those images could then be stacked using external software - I currently use photoshop - to generate a composite image with far greater depth of field than any single image in the stack.

It worked, but it was clumsy.  It took too long to set up and generate the necessary images and, because the camera and lens had to be handled during the exposure, risked introducing movement between the frames and consequent misalignment during the stacking process.

The EM-1 Mk I was a revelation.  For the first time I had a camera that would handle the bracketing automatically and, as an added bonus, perform the necessary stacking in camera.  Stick the camera on a stable tripod, frame the shot selecting a focus point for the beginning of the bracket, switch focus bracketing on in the menu and fire the shutter.  The camera then uses the autofocus motor of the lens to move the focal plane progressively forward to generate a set of bracketed images that could either be stacked on the computer or, if set up for stacking, in camera.  I was getting some excellent results.

With the EM5 MkII and now the EM1 MkII this capability has been enhanced and I find I use focus stacking more and more. Take this shot of Salvia 'Amethyst Lips':

Taken in my garden, it's a composite of 8 shots, using the 60mm macro lens at f3.5, stacked in camera to generate a final JPG, with good front to back sharpness of the subject.  It's not perfect - I have better shots available for licensing on Alamy - but it illustrates the ability of bracketing / stacking to vastly improve the depth of field within the subject while also retaining the diffuse background generated by the wide f3.5 aperture of the lens.

Or consider this shot of a forest of meadow cranesbill, Geranium pratense.  Another 8 shot in camera stack with the 12-40mm Pro at f3.5, 35mm focal length.

The image is sharp, front to back, through the whole frame.  As with the top shot, which did make a magazine front cover, it's suitable for print uses which need that level of detail across the whole image.

Of course, there are disadvantages to the in camera stacking on the EM1 MkII.  For a start the stack depth is limited to eight shots.  That might not be enough, particularly for static macro shots. The final image is a JPG, with all the lack of post processing manipulation leeway.  Subject movement can cause the in camera stack to fail to process.  Finally, the camera is frozen while the stacking takes place.

None of these are deal breakers.  Apart from the generated stacked JPG, the individual frames are saved as both JPG and Olympus RAW formats so they can be post processed individually and then stacked on the computer.  Particularly with non macro shots even eight frames might be too many.  Easy then to discard the unwanted and then do the stacking,  Because that can take awhile - my current computer is way underpowered - I've got into the habit of using the in camera stacking and then examinng the final JPGs from a number of tries to determine which one(s) to select and post process the RAW files before putting those through the stacking procedure in Photoshop.  And, of course, if the stack fails due to movement between frames (wind is your mortal enemy) you still have the individual frames.  There might well be a good shot amongst them.