Fuji’s Focus Bracketing Explained

Update – Aug 2020:  I’m happy to note that Fuji has significantly improved their focus stacking option by providing “automatic” focus stacking in their most recent cameras.  You select a starting point, ending point using manual focus, hit start and the camera will collect the right number of images for your lens and focal length.  Really cool.

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Happy New Year.  Hope your holiday season was fabulous.

This post is specific to Fuji users, so everyone else can have a break.  We’ll see you in a couple weeks.

In mid-2018, Fuji provided an upgrade to the firmware of it’s X-series of cameras.  Known for adding new features and functions, Fuji users were delighted to see the addition of new menu options and one particular update:  the addition of in-camera focus “bracketing”.

Unfortunately, there was a series of missteps with the upgrade and it was initially retracted, then re-released, which is a surprise for a company that prides itself on its quality options for photographers.

Even though it was corrected, Fuji made another mistake in not providing useful information to help us get the most of the upgrade.  This post is specifically about focus bracketing.

Bracketing is a well-known concept.  It provides the option for collecting a series of exposures where typically the lighting can’t be properly addressed in one image.  The shadows are too dark and the highlights are too bright to allow for single image recording without blown-out results.

So, you find the bracketing options, select a progression of exposure values (1/3 EV to up to 3 EV with each subsequent shot) and select the number of shots to be taken.  With one shutter press, the camera collects the full sequence, and these can be combined either in-camera or in post-processing to provide a properly exposed single image.

When the problem is light, you can bracket either for ISO or for aperture.

But now manufacturers are offering bracketing for other purposes, including depth of field.  Known commonly as focus-stacking, photographers until recently could either manually or through third-party software collect a series of images and “stack” them in post-processing to achieve desired depth of field, regardless of the lens or aperture.  This was done with both close-focus scenes (macro work) and distant-focus scenes (landscapes).

Now many cameras have a feature available in-camera for dealing with depth of field.  Fuji calls it “focus bracketing”.

As we all know, depth of field is dependent on the focal length of the lens, the aperture selected and the distance of the subject to the lens.

Longer focal length lenses generally have shorter depths of field than standard or wide-angle lenses.

Wide open apertures generally result in shorter depths of field than closed-down apertures.

All other things being equal, depth of field increases as the subject to lens distance increases (setting aside the discussion of hyperfocal distances – I’ll let you find out about that on your own).

So how can anyone provide a bracketing option that covers all of the above?  Surprisingly, I think Fuji got it right.

When you select the focus bracketing option in the bracketing menu, you see three simple settings (in the Fuji X-T2):

Frames – a number from 1-999, indicating the number of shots to be taken for the stack

Step– a number from 1-10, with 1 indicating slices close together and 10 indicating slices further apart; the actual spacing is relative and dependent on lens, aperture and focus point

Interval – how much time should elapse between each shot

That’s it.

The user guide is no help.  It simply advises you to make the right choices with no help on how to do so.  Instead, Fuji has decided to rely on trial and error by its photographers to find the right settings for their needs in any specific situation.

Surprisingly, I think that actually was a brilliant decision.  Here’s why:

1. Those who are likely to use the focus bracketing feature are most likely those who already do some form of focus stacking.  For the subjects they shoot and the situations they are in, they already know how many shots are typically required to get a good stack.  They also know whether the “slices” to be taken for each shot should be close together or further apart, depending on the detail in each subject.  For example, I have used and continue to use a 100mm macro lens for the botanical macro subjects I shoot with my Canon DSLR, and I’ve never used more than 30 frames.  I do typically require narrow slices in order to get everything in focus.  So, when working with my Fuji close-up, I start with 30 frames, slices set at 2 or 3 and 1-2 second delay to account for vibration between shots.  Then I shoot and adjust.
2. The camera automatically adjusts the positioning of each slice depending on the focal length of the lens, the aperture and the subject distance.  Fuji could have provided charts and graphs with different focal lengths, apertures and subject distances so that we could pick the perfect values, but instead divides up the tasks so that the photographer adjusts for the look desired and the camera adjusts for the mechanics.  It’s a perfect blend.
3. Even if the first result doesn’t meet the need, it’s easy to readjust and try again.  Once the perfect settings are obtained, they are the perfect settings anytime in the future for the same situation.  Fuji doesn’t need to give us huge amounts of material for lenses and situations we won’t encounter.  Instead, we can easily create our own reference materials.

Yes, it would have been nice if Fuji had explained that to us on release.  At least the basic premise of why the feature was built this way would have been helpful.  But most manuals are written by engineers, not users, so it’s not surprising.

If you are really interested in some charts and graphs, Jim Kasson, a former electrical engineer, tested in detail the focus bracketing feature of the Fuji GFX line of cameras.  He explains specifically how lens focal length, aperture and subject distance affect the results, especially of the step selections.  There are lots of charts too.