Focus Stacking with the Fuji X-T3
(you can also see my follow up to this: Focus Stacking: Helicon Focus vs Photoshop).
One of the things I’ve been wanting to experiment with for a while is focus stacking. Focus stacking is a way to create an image that is sharp across a wider area than the hardware camera/lens combination’s depth of field would otherwise allow. I first learned about focus stacking when I sat in on a lecture by George Lepp, a photographer I’ve long appreciated and whose images I found very difficult to emulate. It turned out, after having a chance to talk to him, was because he shoots a lot of stitched panoramas and focus-stacked images, so you can’t take the kind of images he shoots with a single image out of a camera.
A focus-stacked image is more or less the same thing as a stitched panorama, except that you’re moving along the focus plane as opposed to the horizon. If you ever see macro images of something like a flower with a deep depth of field, or a landscape of a large flower field where the entire field is sharp and crisp, there’s a good chance those images were focus-stacked.
Here is an image I took the other night of a flower. It is the first in a sequence of images I took that I later stacked together. This was shot with my 60mm macro at F/11, and you can see clearly that only part of the image is sharp and the sharpness falls off severely away from the front part of the central part of the flower were I set the focus for this. Even shooting at F/22, maximizing the depth of field for that lens, didn’t allow me to make the entire central part of the flower to be sharp.
Fuji’s X-T3 has a feature called focus bracketing, where you can set up the camera that manages many of the mechanics of doing the image shoots: you set up the distance you want between images and the number of images you want to shoot, and optionally, a delay between images into the camera. You then set the focus so that it is sharp at the location nearest to the camera that you want to be in focus, press the shutter, and the camera will take the sequence with no more work on your part.
In my case for this test image, I set the number of images to 45 and the distance offset to 10 (Fuji allows this value to be 1-10, but it’s not at all clear what any specific value means in terms of distance; in practice, I expect mine will always be 10). I used manual focus with peaking to set the starting location and pressed the shutter, and the camera started snapping away, shifting the focus deeper into the image a bit with each image.
It should be noted a process like this needs the camera to be rock solid and stable, so a tripod is a necessity. You also want to use manual exposure so it won’t change from image to image or you risk light/dark banding problems, and practically speaking, you have the same problems a stitched panorama has, where wind might cause blurring and movement of things within the image can cause ghosting, so if you do this outside, you need to catch a break from the wind, and a technique like this won’t work well with people or animals or vehicles in the image. I know some photographers who use this in portraits to extend depth of field but you need a model who can keep still throughout the sequence.
In the end, I had 45 RAW images I imported into Lightroom. If you want to do post processing it makes sense to do it to one of the images and then sync the processing across all of the images. After that, you need to shift the images to photoshop to do the rest. To do that, select all of the images within Lightroom, and then use the Photos->Edit in->Edit as layers in Photoshop, which will copy each image as a layer within a Photoshop document.
Once it’s in Photoshop, you need to select all of the layers, and then you can run Edit->Auto-Align errors followed by Edit->Auto-Blend layers on them. Then go grab a coffee, because these are computationally expensive operations. On my iMac, a modern unit (but not an iMac Pro), it took about 30 minutes and 45 minutes for these two operations, taking up all CPU and memory while they’re running.
The overall time for this image was about 2 hours with setup, taking images and the Lightroom and Photoshop work. The end result has a high level of detail with crisp focus across the flower. I could have extended it further with more images — up to 200.
Dan Bailey has a good tutorial on this that I used as the basis for setting up my own tests.
The deep depth of field look may not be to everyone’s taste, but I think at times it can really change how we react to an image. It’s not something I expect to use every day or every shoot, but it’s nice to have this tool in the toolbox, and I think for macro work, it’s going to become a regular technique for me.
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