Focus bracketing and focus peaking

Focus peaking can be used to visualize areas of a photograph that are acceptably in focus. This can be especially helpful when creating focus stacked composite images.

I recorded two videos that show simulated focus bracketing using my NiSi NM-200 manual focus rail. Notice how the focus peaking band moved across the subject from back-to-front as the carriage moved along the lead screw of the focus rail. The videos aren’t rock steady because I was turning the larger adjustment knob as I was recording the HDMI output from two of my Fujifilm X Series digital cameras.

The subject in both videos is a quarter, that is, a 25-cent coin in U.S. currency. President Theodore Roosevelt is shown on one side of the coin.

The diameter of a quarter is 24.257 mm (0.955 inches). The APS-C sensor used in Fujifilm X Series digital cameras is 23.5 mm x 15.7 mm. A good indicator of the magnification is how much of the quarter is visible in the photo frame.

Fujiffilm X-T3 camera plus Laowa 25mm Ultra Macro lens

The following YouTube video shows a simulation of focus bracketing using a Fujiffilm X-T3 digital camera plus Laowa 25mm Ultra Macro lens. Focus peaking (shown in red) helps to highlight areas of the image that are acceptably in focus.

Video of Roosevelt quarter at 2.5x magnification using an aperture of f/4.

Fujiffilm X-T5 camera plus Fujinon 80mm macro lens

The next YouTube video shows a simulation of focus bracketing using a Fujiffilm X-T5 digital camera plus Fujinon 80mm macro lens. Focus peaking (shown in red) helps to highlight areas of the image that are acceptably in focus, same as in the preceding video. Although it’s not an apples-to-apples comparison, I set the lens aperture to f/4, like the X-T3/Laowa macro rig.

Video of Roosevelt quarter at 1x magnification using an aperture of f/4.

Safe step size and focus banding

After watching the preceding videos, I think it should be clear why macro photographers use focus bracketing to create focus stacked composite images that show more depth of field than is possible from a single photo.

Focus peaking helps to highlight areas of an image that are acceptably in focus. Focus banding occurs when there isn’t enough overlap between the areas that are in focus from one image to the next. This is why it’s critically important to calculate the safe step size BEFORE you begin a focus stacking project.

Tech Tips

The following YouTube video shows how to set my Fujifilm X Series cameras for “clean HDMI” video output. Sometimes it’s helpful to turn “ON” the info display, for example, when creating “how to” videos like this one. You can see my camera settings at the beginning and end of the video.

Video of Menu settings for “clean HDMI.”

A micro-HDMI cable was used to connect my cameras to a MacBook Air (13″, M1, 2020) laptop computer via an inexpensive HDMI Video Capture adapter (HDMI to USB). I used Apple QuickTime Player (free) to record the HDMI video output from my cameras.

Open Apple QuickTime Player. File / New Movie Recording. Click the down arrow disclosure button located to the right of the red Record button and make the following settings.

• Camera = USB Video [= HDMI adapter]
• Microphone = MacBook Air Microphone [for narration, voice over]
• Quality = Maximum [1920 x 1080p, 25 fps]

Movies are recorded as .mov files.

Related Resources

• BEST Fujifilm Manual Focus Setting! by pal2tech (6:01) – FOCUS PEAK HIGHLIGHT plus Fujifilm film simulations (“Acros” Black and White)
• Understanding Fujifilm Video Recording, by pal2tech (5:11)
• Fujifilm X-T3: Focus Peak Highlight – A blog post by Walter Sanford related to, well, focus peaking.
• What is it? – A blog post by Walter Sanford related to the HDMI Video Capture adapter used to create the videos featured in this post.

Copyright © 2023 Walter Sanford. All rights reserved.

 

Please stay tuned …

I’m working on a blog post that isn’t ready for publication. It should be finished sometime within the next day-or-so, so as the title says, please stay tuned.

Walter

How to measure magnification, revisited

The magnification of any macro photography rig can be determined by using the rig to photograph a metric ruler such as the one shown below.

Plastic 15 cm (6″) ruler from the Natl. Science Teachers Assn. (NSTA).

The following photograph was taken using a Laowa 25mm Ultra Macro lens mounted on my Fujifilm X-T3 digital camera. The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens. Notice that only a small part of the ruler is shown in this “full frame” (uncropped) macro photo.

Segment of an NSTA metric ruler.

The formula for magnification is as follows.

length of camera sensor, in mm / #mm visible in photo frame

Both measurements must be expressed in the same units in order for the units to cancel during division.

The APS-C digital sensor featured in the Fujifilm X-T3 is 23.5 mm long. The annotated image shows ~9.0 mm of the small plastic ruler is visible in the photo frame.

23.5 mm / ~9.0 mm = ~2.6x

Is the actual magnification of the Laowa 25mm Ultra Macro lens slightly greater than 2.5x? I don’t know, but my calculation confirms the minimum magnification setting for the lens is in the neighborhood of 2.5x and that’s good enough for government work.

Photo Credit: Venus Optics.

What are the take-aways?

As a result of photographing the ruler, subject selection should be easier. Now I know ~9 mm is the size limit for subjects to fit entirely within the photo frame when the lens is set for 2.5x magnification. That’s actionable intel.

Related Resources

• How to Calculate Your Camera’s Magnification in Macro Photography, by Stewart Wood (12:02).
• How to measure magnification – a blog post by Walter Sanford that features instructions for using either Adobe Photoshop or Photopea to make measurements of photos.

Copyright © 2023 Walter Sanford. All rights reserved.

Zerene Stacker DOF Calculator

The DOF Calculator featured in Zerene Stacker is by far the best tool for determining depth of field and the safe step size for focus bracketing. Rik Littlefield, creator of Zerene Stacker, recently released an online interactive version of DoF Calculator. Sincere thanks to Rik for sharing his expertise!

How to use the calculator

There are several ways to use the DOF Calculator, as shown in the following screen capture. I used two methods to calculate the “safe step size” (with 20% overlap) for focus bracketing with all of my basic macro photography rigs.

Choose Option 1 for the best quality focus stacked composite images. Set the aperture for your camera lens to its “sweet spot.”

Screen capture used with permission from Rik Littlefield.

Choose Option 4 if you are using a microscope objective for a macro lens.

As you can see in following examples, it isn’t necessary to input values for every field in the calculator.

AmScope / Reakway 4x microscope objective

Determining depth of field – safe step size for a 4x microscope objective is the simplest calculation of all my macro photography rigs. All you need to input is the “NA” (numerical aperture) that’s labeled on the side of the microscope objective. In this case, the NA equals 0.10.

Photo Credit: AliExpress / Reakway.

It’s recommended that you use a 20% overlap between steps. Input a value of 0.2 in the field for “Step overlap.”

Screen capture used with permission from Rik Littlefield.

DoF: 0.054862 mm (54.862 microns)
Step size (suggested) at 20% overlap: 0.04389 mm (43.89 microns)

Let’s apply the output from the DOF Calculator (shown above) to my relatively new NiSi Macro [manual] Focusing Rail NM-200. The larger adjustment knob is shown below. One full rotation of the knob moves the carriage one millimeter, or 1,000 micrometers (microns). The knob is marked in 100 increments, so each increment on the knob is 10 microns. Every numbered increment is 100 microns.

For my 4x microscope objective, I would turn the adjustment knob four (4) increments between shots or 40 microns (rounded down from 43.89 microns). It’s OK to use a smaller step size than the DOF Calculator recommends.

Photo Credit: B&H Photo.

Laowa 25mm Ultra Macro (at 2.5x, f/4) plus Fujifilm X-T3

The Laowa 25mm Ultra Macro lens can be set for magnifications ranging from 2.5x to 5x. The following example shows the lens set for 2.5x. Input a magnification of 2.5, and a lens F-number of 4 (an aperture of f/4 is the “sweet spot” for this lens).

Screen capture used with permission from Rik Littlefield.

DoF: 0.068854 mm (68.854 microns)
Step size (suggested) at 20% overlap: 0.055083 mm (58.038 microns)

For the Laowa 25mm Ultra Macro lens, I would turn the adjustment knob on my NiSi NM-200 five increments between shots or 50 microns (rounded down from 58.038 microns).

Fujinon 80mm macro (1x, f/8) plus Fujifilm X-T3

The Fujinon 80mm macro lens is one of the sharper lenses I own. Maximum magnification is 1:1 (life size).

Screen capture used with permission from Rik Littlefield.

DoF: 0.56306 mm (~563 microns) ← remember 1 mm = 1,000 microns
Step size (suggested) at 20% overlap: 0.45045 mm (~45 microns)

Each increment on the NiSi NM-200 manual focus rail is equal to 10 microns. For my Fujinon 80mm macro lens, I would turn the adjustment knob four numbered increments between shots — equal to a distance of 40 microns (rounded down from ~45 microns).

Canon 100mm macro (1x, f/11) plus Canon EOS 5D Mark II

The Canon 100mm macro is another one of the sharper lenses I own. Maximum magnification is 1:1 (life size).

Screen capture used with permission from Rik Littlefield.

DoF: 1.0647 mm (1064.7 microns) ← remember 1 mm = 1,000 microns
Step size (suggested) at 20% overlap: 0.85176 mm (851.76 microns)

Each numbered increment on the NiSi NM-200 manual focus rail is equal to 100 microns. For my Canon 100mm macro lens, I would turn the adjustment knob eight numbered increments between shots — equal to a distance of 800 microns (rounded down from 851.76 microns).

Canon MP-E 65mm macro lens (1-5x) plus Canon 5D Mark II

The Canon MP-E 65mm macro lens can be set for magnifications ranging from 1x to 5x. The following example shows the lens set for 3x.

Screen capture used with permission from Rik Littlefield.

DoF: 0.12251 mm (122.51 microns)
Step size (suggested) at 20% overlap: 0.098008 mm (~98 microns)

Remember, each increment on the NiSi NM-200 manual focus rail is equal to 10 microns. For my Canon MP-E 65mm macro lens set for 3x magnification, I would turn the adjustment knob nine increments between shots — equal to a distance of 90 microns (rounded down from ~98 microns).

Related Resource

What if you don’t know the magnification of the macro rig you’re using? Or maybe you add an extension tube and/or close-up filter to a 1x macro lens — how does that change the magnification of the lens?

How to measure magnification provides photo-illustrated step-by-step directions, including sample math calculations.

The Backstory

I have been working behind the scenes trying to figure out how to determine focus bracketing step size for a variety of macro photography gear that I own. I have tested many depth of field – step size calculators and all of them are fatally flawed in one or more ways except for the one in Zerene Stacker.

See How to calculate step size for a long thread of posts related to my search for the answer to what turned out to a more complex process than I imagined. Thanks to the many members of photomacrography.net, especially Rik Littlefield, who kindly and patiently answered all of my questions.

Copyright © 2023 Walter Sanford. All rights reserved.

TJ short stack

Just in time for President’s Day on 20 February 2023, I cooked up a “short stack” composite image of part of a nickel, that is, a five-cent coin in U.S. currency.

The face/head of Thomas Jefferson appears on one side of the nickel. Jefferson was the third president of the United States of America.

Part of a nickel (five-cent coin in U.S. currency).

There are many noticeable scratches on the coin.

The metal nickel has a hardness of 4.0 on Mohs Hardness Scale.

A mineral’s hardness is a measure of its relative resistance to scratching, … Source Credit: Mohs Hardness Scale, National Park Service.

Many minerals/common objects are harder than nickel, such as quartz, glass, and steel, to name a few, and can scratch the coin easily.

Tech Tips

The preceding composite image …

• was created using four photos shot with my Fujifilm X-T3 camera and Laowa 25mm Ultra Macro lens. The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens. A single external flash unit was used to light the photos.
• is focus-stacked for greater depth of field. At a magnification of 2.5x the depth of field is extremely shallow. 0.0896 mm (89.6 microns), to be exact.
• is “full frame” (6240 × 4160 pixels), meaning it is uncropped.
• was created using four unedited JPG files, straight out of the camera, that were focus stacked using Adobe Photoshop.

Related Resources

• GW revisited [George Washington, first president of the United States of America.]
• Trust [Abraham Lincoln, 16th president of the United States of America.]
• One thin dime [Dwight D. Eisenhower, 34th president of the United States of America.]

Copyright © 2023 Walter Sanford. All rights reserved.

One thin dime

As you can see in the following test shot, a dime is thicker than the old expression would lead you to believe.

Part of a dime (10-cent coin in U.S. currency).

The face/head of Dwight D. Eisenhower appears on one side of the coin. Eisenhower was the 34th president of the United States of America.

Tech Tips

The preceding photo …

• was shot using my Fujifilm X-T3 camera and Laowa 25mm Ultra Macro lens. The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens. A single external flash unit was used to light the photo.
• is a “one-off,” meaning the photo isn’t focus-stacked. At a magnification of 2.5x the depth of field is extremely shallow. The net result is not all of the photo appears to be acceptably in focus.
• is “full frame” (6240 × 4160 pixels), meaning it is uncropped.
• is an unedited JPG file, straight out of the camera.

Copyright © 2023 Walter Sanford. All rights reserved.

Trust

The following test shot shows part of a penny, that is, a one-cent coin in U.S. currency.

Part of a penny (one-cent coin in U.S. currency).

The face/head of Abraham Lincoln appears on one side of the coin. Abraham Lincoln was the 16th president of the United States of America.

Tech Tips

The preceding photo …

• was shot using my Fujifilm X-T3 camera and Laowa 25mm Ultra Macro lens. The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens. A single external flash unit was used to light the photo.
• is a “one-off,” meaning the photo isn’t focus-stacked. At a magnification of 2.5x the depth of field is extremely shallow. The net result is not all of the photo appears to be acceptably in focus.
• is “full frame” (6240 × 4160 pixels), meaning it is uncropped.
• is an unedited JPG file, straight out of the camera.

Editor’s Commentary

I have been working behind the scenes trying to figure out how to determine focus bracketing step size using a variety of macro photography gear.

Let’s just say it turns out to be far more complex than I ever imagined — every time I feel I’ve made a breakthrough in understanding, I experience some sort of setback and I’m back where I started.

Those who know me well know I won’t give up until I figure it out. In the meantime, I thought you might like to know what’s going on. I’m hoping to share a “Eureka!” discovery soon.

Copyright © 2023 Walter Sanford. All rights reserved.

GW revisited

The following test shot shows part of a quarter, that is, a 25-cent coin in U.S. currency. I took the shot when I was testing my new NiSi NM-200 manual focus rail.

Part of a quarter (25-cent coin in U.S. currency).

The face/head of George Washington appears on one side of the coin. George Washington was the first president of the United States of America.

Tech Tips

The preceding photo …

• was shot using my Fujifilm X-T3 camera and Laowa 25mm Ultra Macro lens. (I bought the Canon version of the Laowa lens. It’s mounted on my X-T3 using the X-mount adapter available from Laowa.) The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens. A single external flash unit was used to light the photo.
• is a “one-off,” meaning the photo isn’t focus-stacked. At a magnification of 2.5x the depth of field is extremely shallow. The net result is not all of the photo appears to be acceptably in focus.
• is “full frame” (6240 × 4160 pixels), meaning it is uncropped.
• is an unedited JPG file, straight out of the camera.

Copyright © 2023 Walter Sanford. All rights reserved.

Proof of concept: NiSi NM-200 manual focus rail (plus Post Update)

The following focus stacked composite image was created using a Fujifilm X-T3 mirrorless digital camera and Laowa 25mm Ultra Macro lens mounted on a NiSi NM-200 manual focus rail.

Toy dinosaur at 2.5x magnification.

The Laowa lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for that lens.

The subject is a small toy dinosaur, viewed from above the anterior end of the dino. The toy is approximately 3.2 cm long (~32 mm).

The carriage of the focus rail was moved 200 µm (micrometers, also known as microns) per step, equal to 20 increments on the NiSi NM-200. A total of 28 photos were taken. A little back of the envelope math shows the carriage moved a total of 5.6 mm from beginning to end.

200 microns x 28 = 5,600 microns

5,600 microns x 1 mm/1,000 microns = 5.6 mm

The camera was set to record JPG plus RAF files. For simplicity the composite image was focus stacked in Adobe Photoshop using the JPG files straight out of the camera. The final output was slightly cropped and sharpened.

Look closely at the full size version of the composite image. I don’t see any glaring “focus banding” so the 200 micron step size seems to have worked. [See Post Update, at the end of this blog post.] As always, a sample size of one proves nothing. That said, I feel confident the NiSi NM-200 works as expected and will be a useful aid for creating macro focus stacked composite images.

Tech Tips

i used a step size of 200 microns — much larger than the 10 micron precision limit of the NiSi NM-200. My goal was to choose the largest step size that wouldn’t show “focus banding.” I’m not sure what the maximum “safe step size” is, given the settings for my photo gear, but it appears 200 microns doesn’t exceed that value.

Related Resource: “Toy dinosaur” includes a photo (shown below) that shows the entire toy. 2.5x magnification is more than it seems!

08 DEC 2020 |  BoG Photo Studio | toy dinosaur

Post Update

In the preceding post I wrote “Look closely at the full size version of the composite image. I don’t see any glaring “focus banding” so the 200 micron step size seems to have worked.”

Well, someone with more experience than me in creating focus stacked composite images actually looked closely at my image, and here’s what he saw.

Annotated image used with permission from Rik Littlefield.

Rik Littlefield, creator of Zerene Stacker, noticed there is in fact a problem with focus banding in my composite image. Rik highlighted the focus bands with a series of black dots.

My decision to use a “safe step size” of 200 microns was based upon the output from a depth of field – step size calculator that I now realize is fatally flawed. Honestly I can’t remember which calculator I used, but I can tell you this — after using Rik Littlefield’s DOF Calculator to determine the safe step size for the same macro rig is 58.038 microns, I knew 200 microns must not have worked as well as I thought. And as you can see in Rik’s annotated image, a step size of 200 microns is too big. Sincere thanks to Rik for his feedback!

Copyright © 2023 Walter Sanford. All rights reserved.

Connections

I’m not as dumb as I look, you know. (I have a face for blogging, not vlogging.) But I am a little slow sometimes. For example, I was slow to make the connection between the size and shape of two lens adapters I own.

When I bought the Laowa 25mm f/2.8 2.5-5X Ultra Macro lens for Canon EOS cameras, I also bought a Laowa Lens Mount Adapter for Canon EF lenses to Fuji X Series cameras. I remember thinking the adapter is oddly shaped and wondered why it wasn’t designed to be shorter/thinner.

That was before I purchased the Fringer EF-FX Pro II lens mount adapter (Canon EF lenses – Fuji X Series cameras).

The following photo shows two Canon EF to Fujifilm X Series lens adapters: the Laowa EOS-FX (shown left); and the Fringer EF-FX Pro II (shown right).

Canon EF to Fujifilm X-Series lens adapters.

Notice the two lens adapters are the same diameter and thickness (26.3 mm): the former is due to the Canon EF mount (top) and Fujifilm X Mount (bottom); the latter is due to something called flange focal distance (FFD).

The 17.7 mm FFD of my Fujifilm X Series digital cameras combines with the 26.3 mm thickness of the lens adapters (shown above), resulting in an FFD of 44 mm — exactly the right FFD for Canon lenses to work properly on a Fujiflm X Series camera body!

The Backstory

The Laowa lens adapter is manual; the Fringer lens adapter is automatic. The former doesn’t feature electronic contacts that enable auto focus, etc.; the latter does.

Soon after I bought the Laowa lens adapter I used it to mount a Canon EF 100mm macro lens on my Fujifilm X-T3 camera. Although the adapter worked to connect the lens and camera, the experiment was a failure because the Canon macro lens doesn’t have a ring for setting aperture manually, and the Laowa lens adapter doesn’t have electronic contacts that enable a camera to set the aperture of the lens. Same problem with my Canon MP-E 65mm macro lens.

Enter the Fringer lens adapter.

Copyright © 2022 Walter Sanford. All rights reserved.