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Author Topic: Fuji Focus Bracketing  (Read 4778 times)

Chris Kern

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Fuji Focus Bracketing
« on: July 23, 2018, 03:40:59 pm »

I finally got around to trying out the new focus-bracketing feature introduced by the version 4 firmware for my Fuji X-T2 and I must say I'm favorably impressed.  I don't have much experience with macro photography in general or focus-stacking in particular, but being able to automate the captures without having to move the camera brings the technique into the range of my limited skill level.

One question: has anybody figured out the semantics of the step value in the focus-bracketing menu, and how or whether it relates to the focal length of the lens or the distance between the lens and the subject?  The explanation in the manual (see below) is not very useful.

armand

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Re: Fuji Focus Bracketing
« Reply #1 on: July 23, 2018, 08:39:02 pm »

Some discussions here: http://forum.luminous-landscape.com/index.php?topic=124652.20

No, I didn't figure it out exactly the numbers but I think they depend at some extent on the focal length. I don't think there will be a clear answer out there.

Chris Kern

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Re: Fuji Focus Bracketing
« Reply #2 on: July 23, 2018, 08:57:53 pm »

Some discussions here: http://forum.luminous-landscape.com/index.php?topic=124652.20

Thanks.  I'd forgotten about that thread—even though I contributed to it!  Senior moment, I guess.

Quote
No, I didn't figure it out exactly the numbers but I think they depend at some extent on the focal length. I don't think there will be a clear answer out there.

This is the kind of inadequately-documented feature I find very frustrating.  I'm sure there is an engineering document somewhere in the Fuji bureaucracy that explains how the step function works.  It should be possible to remove any proprietary information, clean up the prose, and provide some guidance that would help users exploit the capability optimally.

I'll try contacting Fuji-USA customer service to see if they can provide any useful information, but I'm not particularly optimistic.

Having said that, I'm not discouraged by my trial-and-error results.

rdonson

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Re: Fuji Focus Bracketing
« Reply #3 on: July 24, 2018, 07:01:04 pm »

One question: has anybody figured out the semantics of the step value in the focus-bracketing menu, and how or whether it relates to the focal length of the lens or the distance between the lens and the subject?  The explanation in the manual (see below) is not very useful.

Nope.  I'm still experimenting and erring on the side of too many shots but the results have been good. 
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Ron

Chris Kern

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Re: Fuji Focus Bracketing
« Reply #4 on: July 24, 2018, 07:31:31 pm »

I'm still experimenting and erring on the side of too many shots

That's what I did, as well, in my tests.  To make the sunflower pictures I attached to the first post in this thread, I used Photoshop to stack 30 raw files captured at bracket step-level 3 (whatever that means) after importing them from Lightroom.  I suspect the composite would have been just as good with 20 captures if I had known how optimally to set the step value in the camera.

With 30 images, the processing bottleneck seemed to be the time it took for Photoshop to collect the raw files and render them as layers.  Aligning the layers and creating the masks to perform the focus-stacking was surprisingly fast.  (Using a 6-core 2013 Mac Pro with 64GB of primary memory, in case that's relevant.)

Chris Kern

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Re: Fuji Focus Bracketing
« Reply #5 on: July 31, 2018, 08:37:14 pm »

Another focus-bracketing experiment.

My wife bought some "Japanese yams" at a local Asian supermarket, but we never cooked them and they sprouted.  Before discarding them today, I took them outside, sat them on our glass patio table, and shot a focus-bracketed sequence with my X-T2.

Once again, 30 frames at bracketing step 3 (whatever that means).  These were made with the Fuji 55-200mm zoom at 86mm and f/7.1; the metadata don't include the distance to the subject, but I think it was roughly 5 feet/1.5 meters.  The subject was quite complex, with features occupying and occluding each other in several different planes.  I stacked the captures with Helicon Focus, Method C: I downloaded the trial version of the Helicon product after my attempt to process the stack with Photoshop produced some out-of-focus areas.

I'm still hoping to find a Fuji customer service rep who can explain the semantics of the focus-bracketing parameters.  In the meantime, I'm flying blind when I position and configure the camera.  This picture turned out fairly well, but I'm afraid I have to attribute that to dumb luck.

rdonson

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Re: Fuji Focus Bracketing
« Reply #6 on: August 01, 2018, 07:57:27 pm »

Nicely done, Chris. 

With a start at the nearest focusing point you choose in your camera, 3 seems like a good choice.  As the meager instructions say, the shot count stops when focus gets to infinity regardless of the number of frames chosen.  So if you've set up for 30 and it only takes 10.  That's a sign of how to approach a similar scene in the future.  I see no downside though to configuring for 20 or 30 shots and not needing them. 

All we can do at this point is to actually judge by how many of the shots were taken vs what we set it up for. 
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Ron

Chris Kern

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Re: Fuji Focus Bracketing
« Reply #7 on: August 01, 2018, 09:29:51 pm »

Nicely done, Chris.

Thanks, Ron.  Although as I said in my earlier post, getting the parameters right for that shot was just dumb luck.

I've been told to keep an eye out for an article on focus-bracketing that will be posted to the Fujjifilm X GFX website.  Hopefully it will include some information on how to estimate the optimal number of frames and step value for a particular subject based on the focal length, aperture, and subject distance — or some combination thereof.

Stay tuned. . . .

kirkt

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Re: Fuji Focus Bracketing
« Reply #8 on: August 03, 2018, 04:53:10 pm »

I've used it a few times and it works well with the X-H1.

It may be useful to do a few experiments with the camera locked down on a tripod and tilted slightly down, say aiming at the front edge of a table top.  Lay a yardstick (or a meter stick if that's how you roll) on the table top receding away from the camera and focus at a fixed point on the yard stick (say, maybe 3 or 4 inches from the leading edge of the stick).  Then shoot a fixed number of shots (15 maybe) at a few different step choices (1, 5, 10) for a few different lenses or focal lengths and see if you can extract some sort of relationship between focal length and step size in terms of the movement of the focus plane as shown on the ruler.  Crude, but maybe useful?

Kirk
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Chris Kern

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Re: Fuji Focus Bracketing
« Reply #9 on: August 03, 2018, 08:20:41 pm »

Lay a yardstick (or a meter stick if that's how you roll) on the table top receding away from the camera and focus at a fixed point on the yard stick (say, maybe 3 or 4 inches from the leading edge of the stick).  Then shoot a fixed number of shots (15 maybe) at a few different step choices (1, 5, 10) for a few different lenses or focal lengths and see if you can extract some sort of relationship between focal length and step size in terms of the movement of the focus plane as shown on the ruler.  Crude, but maybe useful?

Yes, I think it might be possible to make an initial stab at reverse-engineering the Fuji focus-bracketing step algorithm with a protocol along these lines.  It probably also would be necessary to vary the aperture and distance-to-subject in order to identify and capture the variation among all the possible parameters, wouldn't it?

But I don't know whether this type of experimental approach, even if carried out fastidiously, would be sufficiently comprehensive to yield enough information to eliminate guesswork when actually shooting photographs.

It would be a lot easier if Fuji would (1) tell us precisely what parameters the camera firmware uses to calculate the focus-shift for a given step value and how the algorithm uses them or—if the company considers that proprietary intellectual property—(2) at least provide sufficient guidance to turn an uneducated guess about which step value to choose in a given situation into an educated guess.

I've made this request to the Fujifilm employee who is writing the article on focus-bracketing that I mentioned in an earlier post.  No response yet, but I'm hopeful: my impression is that Fuji has been considerably more open with its customers than some other manufacturers.
« Last Edit: August 03, 2018, 11:54:02 pm by Chris Kern »
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TommyWeir

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Re: Fuji Focus Bracketing
« Reply #10 on: August 04, 2018, 04:04:56 am »

" It probably also would be necessary to vary the aperture and distance-to-subject in order to identify and capture the variation among all the possible parameters, wouldn't it?"

My thoughts too.   A yard or meter stick would be good considering macro or close work... but a landscape is another thing.  Could be more a matter of field testing rather than guidelines. 

Impressed generally on a quick test, had objects as close as a 18" and as far as a distant shore all crisp in the same shot after processing. Lots of detail along the way.  Shot with the 10-24 at 24mm and at f4.  Put in for 30 shots, step of 5, 1 second apart.   The camera shot 19 frames before stopping, assembled in PS, I tried Affinity auto stacking while I was at it, but didn't do as good a job as PS.

I think I'll do a proper test with the 35 1.4 and the 50-140, the lenses I usually use.

kirkt

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Re: Fuji Focus Bracketing
« Reply #11 on: August 07, 2018, 06:12:49 pm »

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rdonson

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Re: Fuji Focus Bracketing
« Reply #12 on: August 09, 2018, 06:52:15 am »

Thanks, Kirk !!!!
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Regards,
Ron

Chris Kern

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Re: Fuji Focus Bracketing
« Reply #13 on: August 09, 2018, 11:18:36 am »

For the GFX, but some insight:

https://blog.kasson.com/gfx-50s/gfx-fw-3-0-focus-bracketing-with-the-120-4-macro/

Quite an impressive analysis, but even so, as he points out in a follow-up post, "it's hard to figure out where the camera is going to focus at the end of one of these runs."

armand

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Re: Fuji Focus Bracketing
« Reply #14 on: August 09, 2018, 12:21:00 pm »

The best way would be to set the start and stop points, aperture and let the camera figure it out how many steps are needed.

Chris Kern

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Re: Fuji Focus Bracketing
« Reply #15 on: August 09, 2018, 12:29:02 pm »

The best way would be to set the start and stop points, aperture and let the camera figure it out how many steps are needed.

Yes, unquestionably.  And even if that required a lot of processing cycles, it's not a real-time operation, like autofocus, so presumably it ought to be practical for Fuji to implement with current hardware.

BAB

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Re: Fuji Focus Bracketing
« Reply #17 on: August 17, 2018, 01:32:57 pm »

Regardless of the option chosen frames end when lens reaches infinity.This is great for landscapes where the infinity is visible but for your example of tabletop you cant see infinity and Fuji provides a stacking system that has no xyz points pre configured. I would say its best use is to automate bracketing from the 1ST or front focus point in your choice of steps. The issue will be when the steps are going around a curve and the angle is variable... meaning the focus steps must be smaller to catch the curve in perfect focus as the fall off becomes greater.
I would not use any lens but a macro which has a flat field. I would not use stacking in PS it has never worked well. I would use Zerene Stacker https://zerenesystems.com/cms/home or Helicon Focus https://www.heliconsoft.com/store/.
You also need a way to provide a time between shots for camera vibration to settle if not you have a fair amount of work to eliminate the shake blur.Of course goes without saying Shoot at the smallest F-Stop you can without getting diffraction...and never never allow the F Stop to change during the course of capture.
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SrMi

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Re: Fuji Focus Bracketing
« Reply #18 on: August 19, 2018, 06:36:14 pm »

I've noticed that on Fuji X-H1 the amount of focus movement depends on the selected aperture: all other parameters being equal, the focus moves slower with wide open aperture.
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Jonathan Cross

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Re: Fuji Focus Bracketing
« Reply #19 on: August 27, 2018, 06:45:10 am »

Re comment by BAB about camera vibration.  Using the electronic shutter, I have not experienced any sign of this using zero time between shots.

Best wishes,

Jonathan
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