Alice in Telecentricity Land (plus Post Update)

In a recent blog post, I wrote …

The best advantage of a truly telecentric lens is there should be little or no “focus breathing” as the camera moves closer to/farther from the subject. Essentially that means the apparent size of the subject should remain the same. That should enable better focus stacking because the outline of the subject is constant. Source Credit: Experimenting with a telecentric lens rig (plus Post Update).

Using my clone of Rik Littlefield’s 0.8x magnification telecentric lens rig, there was little or no “focus breathing” in the test focus bracket that I created from 63 JPGs, as shown in the following slideshow.

First, a brief explanation of what is shown in the slideshow. The first frame is Photo No. 1 of 63 from the focus bracket, edited to make it black and white. The last frame in the slideshow is Photo No. 63 of 63, shown in full color.

I loaded the two photos as a stack in Photoshop. Next I changed the opacity of the last image in the slideshow to 0%, meaning the first image, now black and white, is shown completely. Then I flattened the layers and saved the output. I repeated the process, changing the opacity of the last image to 25%, 50%, 75%, and 100%. At an opacity of 100% the last image is shown completely and the first image cannot be seen.

This slideshow requires JavaScript.

Look closely at the slideshow and you might notice the subject shifts slightly to the right (from first to last slide), but nothing like the “focus breathing” that typically occurs when a non-telecentric lens is used to do focus bracketing. This means the photo composition that I saw in the first photograph is essentially the same in the last photo.

The following photo gallery features full-size versions of the same images used to create the slideshow, in order of increasing opacity.

0%

25%

50%

75%

100%

Let’s pause to review. We know the subject should appear to be larger when the camera moves closer to the subject. But in this case, the subject appears to be the same size in both the first and last shots of the focus bracket. Why? Well, this is the point where I might be beyond the limit of my expertise but based upon my understanding of telecentricity I’d say it’s because most of the light rays that pass through the lens rig are parallel.

Things are getting curiouser and curiouser

If my [educated?] guess is true, then parallel lines in a subject should remain parallel from foreground to background.

Let’s start with a thought experiment. Think about a pair of parallel railroad tracks. Many, if not most people have noticed that railroad tracks appear to converge toward a vanishing point in the distance. The same thing happens when you photograph parallel lines. Or does it? Not when a truly telecentric lens is used to shoot the photograph! Let’s look at an example.

I didn’t have time to shoot and post process an entire focus bracket of a small plastic ruler, so I shot two quick and dirty photos near the end points of the ruler. The first photo shows the foreground; the last photo shows the background.

I could have used Photoshop to edit the images so that the vertical blue lines are aligned, but I didn’t because I decided it’s more important to show another example that illustrates lack of “focus breathing.” Plus I think it’s easy to see at a glance the lines are in fact parallel, not convergent.

Yeah, yeah — I could have and should have done a better job of posing the ruler but like I said, the photos are quick and dirty. Expediency trumps perfectionism.

Post Update

Consistent with the “quick and dirty” theme for this post, I used Apple Preview to edit the preceding photos of a small plastic ruler.

I started with the first photo. I drew a horizontal red line between two vertical blue lines on the ruler. Next, I selected and copied a small area from the bottom of the photo.

Finally, I pasted the selected/copied area from the first photo onto the second photo. As you can see the vertical blues lines are virtually the same distance apart at both ends of the ruler. Therefore my Rube Goldberg lens rig is almost perfectly telecentric.

Related Resources

• Experimenting with a telecentric lens rig (plus Post Update)
• Telecentric lens rig revisited
• Telecentric combo at 0.8x to 1.69x, by Rik Littlefield – root of a long thread on photomacrography.net

Copyright © 2023 Walter Sanford. All rights reserved.

Telecentric lens rig revisited

The following composite images show the results of my first test using a new telecentric lens rig, cloned from a similar rig designed by Rik Littlefield.

Helicon Focus was used to focus stack 63 “as is” JPGs from my Fujifilm X-T3 mirrorless digital camera (focused on the head only). “As is” is a descriptor that I use often in my photoblog, but that doesn’t mean the images weren’t edited — rather it means the JPGs were edited in camera using one of the Fujifilm film simulations (PROVIA / STANDARD).

63 JPGs | Helicon Focus | Rendering Method B

In my limited experience using Helicon Focus, rendering Method C seems to work better than Method B. (For what it’s worth, rendering Method A never produces good results for me.) In this case, I can’t see a clear difference in the quality of the output. Do you think one version looks better than the other?

63 JPGs | Helicon Focus | Rendering Method C

Look closely at the full-size versions of the preceding composite images and I think you will agree with me that the image quality is excellent!

Tech Tips

In a recent blog post, I wrote …

Rik [Littlefield] developed another telecentric lens rig that results in lower magnification (0.8x versus 1.69x) but better image quality. I need to order some inexpensive parts before I can build and test that rig. Source Credit: Experimenting with a telecentric lens rig (plus Post Update).

The last part I needed was delivered a few days ago, and much to my amazement all of the parts fit together! (See parts list, below.)

I used my Apple iPad mini 6 to shoot the following quick-and-dirty photos of the new telecentric lens rig.

Here’s a parts list (shown from left-to-right in the preceding photos).

• Fujifilm X-T3 (APS-C) mirrorless digital camera [not shown]
• Fringer EF-FX Pro II
• [1] Canon EF 100mm f/2.8 Macro lens
• [2] 67mm to 52mm step-down ring
• [3] M52-M42 step-down ring
• [4] Fotasy M42-M42 helicoid [15-26 mm long (11 mm travel).]
• [5] M42 tube (7 mm long) [WeMacro 42mm tube set: 7, 14, 28 mm long.]
• [6] 42mm to 52mm step-up ring
• [7] 52mm-43mm step-down ring
• [8] Raynox DCR-250 close-up filter (43mm thread)

Notice the focus ring on my Canon Macro lens is set for infinity [highlighted by a green rectangle]. The distance between the front of the Canon lens and front of the Raynox close-up filter is ~54 mm, based upon guidance from Rik Littlefield.

With the Canon Macro lens set for infinity, the parts in front of the Canon lens work together with the lens to make it telecentric. Adding the Fringer adapter has no effect on the telecentricity of the Canon lens — it’s only used to enable my Canon lens to work with the Fujifilm X-T3 camera.

Safe step size

I used Rik Littlefield’s excellent DOF Calculator plus personal guidance from Rik to determine the safe step size to use for focus bracketing with the new telecentric lens rig.

My input is highlighted by a red rectangle; the calculator output is highlighted in green.

Notice I input a 20% step overlap (0.2) to be sure there was no “focus banding.” The calculator suggested a step size of 0.17589 mm. That’s equivalent to 175.89 µm (micrometers).

Since the smallest increment on my NiSi NM-200 manual focus rail is 10 µm, I divided 175.89 by 10 in order to determine the number of increments to turn the larger adjustment knob on the NM-200. The answer is 17.589 increments. For simplicity and safety, I turned the knob 15 increments between shots.

Copyright © 2023 Walter Sanford. All rights reserved.

Experimenting with a telecentric lens rig (plus Post Update)

I’ve been experimenting with a telecentric lens rig. My rig is cloned from a similar one created by Rik Littlefield, using gear I already own.

I’m guessing you’re thinking “What is a telecentric lens?” The honest answer is “I don’t know.” I’m not sure I’ll ever understand what telecentric lenses are and how they work. I’m hoping practical experience will result in better understanding of the theoretical.

So why have I written a blog post about a topic I don’t really understand? Good question! The simple answer is because I have learned enough, mostly from Rik Littlefield, to know there are practical advantages to using a telecentric lens for macro photography.

The best advantage of a truly telecentric lens is there should be little or no “focus breathing” as the camera moves closer to/farther from the subject. Essentially that means the apparent size of the subject should remain the same. That should enable better focus stacking because the outline of the subject is constant.

My Rube Goldberg telecentric lens rig

Rik Littlefield’s telecentric lens rig features the same gear as mine (described in the next paragraph) minus the Canon-to-Fujifilm lens adapter because he uses a Canon EOS Rebel T1i DSLR camera body with his rig.

My Rube Goldberg telecentric lens rig is cobbled together using a Raynox DCR-250 close-up filter attached to my Canon EF 100mm macro lens using the plastic clip-on adapter supplied by Raynox. The lens assembly is mounted on my Fujifilm X-T3 APS-C digital camera using a Fringer EF-FX Pro II adapter.

Rik developed another telecentric lens rig that results in lower magnification (0.8x versus 1.69x) but better image quality. I need to order some inexpensive parts before I can build and test that rig.

Testing 1, 2, 3.

The following closely-cropped composite image shows the result of my first test of the telecentric lens rig.

I shot 57 images of a toy plastic lizard using my NiSi NM-200 manual focus rail. I used an aperture of f/8 and a step-size of 100 microns, as recommended by Rik Littlefield.

Helcion Focus Method B was used to focus stack the “as is” JPGs from my camera. The resulting TIF file was cropped using Apple “Preview” — that’s about as quick and dirty as cropping gets!

Post Update

The first time I heard about telecentric lenses is when Allan Walls teased the topic during one of his YouTube live-streams. During a subsequent live-stream, Allan demonstrated how to make a lens telecentric using a rig similar to one that Rik Littlefield created.

Telecentric Lenses – Macro Talk Too – from Allan Walls Photography, June 29, 2023 (1:12:10)

Allan’s YouTube live-streams are one hour in duration, but there’s usually a lot of chit-chat during a typical live-stream that might not interest readers of my blog.

In this case, I recommend that you watch the segment from 11:22 to 30:21. A lot of what I have learned about telecentric lenses from Rik Littlefield and Allan Walls is covered during that part of the video. (If you continue watching the video beyond the 30:21 mark, then you will hear my name mentioned twice.)

Copyright © 2023 Walter Sanford. All rights reserved.

L-bracket for Fujifilm X-T5

In a recent blog post, I said …

l use Arca Swiss L-brackets for all of my cameras. Good L-brackets are designed so the bracket doesn’t block any camera doors or ports. But I don’t have one for the [Fujifilm] X-T5 because it’s new enough that the selection of compatible L-brackets is poor. Source Credit: Walter Sanford, Comedy of Errors.

My urgent need for an L-bracket trumped my anxiety about ordering one from AliExpress in China. I decided to buy an L-bracket for my X-T5 from the “GoGlory Store.” US $27.55 plus free shipping helped to incentivize me. I placed my order on 12 March 2023; it was delivered on 20 March. Shipment from China to the east coast of the United States in eight (8) days was a pleasant surprise!

The L-bracket is well-made and fits my Fujifilm X-T5 perfectly without extending the vertical rail (as shown in the top photo, below).

Photo Credit: “GoGlory Store.”

The bracket comes with two Allen wrenches: a larger wrench (shown above); and a smaller one. The “GoGlory Store” Web page says the Allen wrenches are magnetic; they aren’t. Look closely at the full-size version of the preceding photos. Notice two small silver circles on the bottom of the horizontal rail — those are magnets in a groove that fits the larger Allen wrench.

The larger wrench is used to tighten/un-tighten a larger bolt that connects the L-bracket to the 1/4″-20 threaded tripod socket of your camera. The same bolt has a groove for a flat-head screwdriver.

The larger Allen wrench is also used to tighten/un-tighten a slightly smaller bolt that enables you to extend/contract the length of the L-bracket. That bolt does not have a groove for a screwdriver.

The smaller Allen wrench is used for two small bolts that enable you to remove the vertical rail completely.

Battery-chamber door

The following photo shows the L-bracket mounted on my Fujifilm X-T5; the opening in the horizontal rail enables the camera battery-chamber door to open/close freely without removing the L-bracket.

L-bracket, showing opening for camera battery-chamber door.

Camera Connectors (side doors)

The next photo shows the vertical rail of the L-bracket and the left side of my camera. The large cut-out in the L-bracket enables easy access to two small doors on the left side of the camera, and doesn’t block the built-in speaker. Both doors to the camera connectors are open in the following photo.

L-bracket, showing cut-out for camera connectors (side doors).

The vertical rail features four 1/4″-20 threaded sockets (taps) for mounting camera accessories.

What are the take-aways?

During limited testing, I am completely satisfied with the L-bracket I bought from AliExpress. Really, how often do you hear me say that about camera gear? A well-made product that does what it’s supposed to do, all for a good price plus free shipping — what’s not to like?

Copyright © 2023 Walter Sanford. All rights reserved.

Making progress (on a steep learning curve)

OK, let me say right at the outset that using a manual focus rail like my new-ish NiSi NM-200 to create a 328-photo focus stack is insane! So I regrouped, made a new plan, and conducted some tests.

I discovered, albeit too late, that I needed to shoot a lot of  photos for my last focus stack because I chose to use an aperture of f/8 and the “safe step size” for f/8 (at 1x magnification) is 40 µm (micrometers, or microns) — a relatively small step size.

In contrast, at 1x magnification the safe step size for f/11 is 800 µm — during limited testing that seems to be the sweet spot for creating focus stacks that look fairly good using fewer photos.

Canon EOD 5D Mark II DSLR camera plus Canon EF 100mm macro lens (1x, f/11)

The following composite image was created from 20 photos.

The background is the non-reflective side of a piece of black plastic. It’s textured surface appears to be a bad fit for macro photography — notice lots of little white specks on the background. Not good.

f/11 | 1/200 s | ISO 100 | Manual WB (Flash)

But wait, there’s one more thing. Did you notice the copper penny hiding underneath the quarter? Well, it was supposed to be hiding. I borrowed the idea from another photographer whose name I can’t remember. The point is to create some visual relief for the coin in the photo. The plan might have turned out OK if I’d noticed the misalignment of the penny before I did the focus bracketing.

Fujifilm X-T5 mirrorless digital camera plus Fujinon 80mm macro lens (1x, f/11)

The following composite image was created from 26 photos.

For the background, I used the white reference card from a Vello White Balance Card Set (Small). I set the white balance for AUTO WHITE PRIORITY WBW — a new setting (at least new to me) that’s supposed to result in whiter whites.

f/11 | 1/250 s | ISO 125 | WBW

The subject is in focus from back-to-front, and I like the white background. I think this is the best composite image I’ve created so far, but as always, you be the judge.

Fujifilm X-T5 mirrorless digital camera plus Fujinon 80mm macro lens (1x, f/11)

The following composite image was created from 21 photos.

For the background, I used the black reference card from a Vello White Balance Card Set (Small). I think it looks better than the textured black plastic background in the first photo, although I think the white background looks best.

f/11 | 1/250 s | ISO 125 | WBW

Pixel-peepers will notice the far end of the nickel isn’t as sharp as the rest of the coin. That’s because a man-caused disaster forced me to leave out the first two photos in the set. I hope the man responsible for this sloppy work will be held accountable for his actions!

Tech Tips

I think it’s worth noting that all three composite images were created using unedited JPGs straight out of the camera. All of the composite images could have been improved by making a few edits to the RAW files such as adjusting exposure, increasing contrast, and adding a little sharpening, to name a few.

In these test cases, I was looking for focus banding caused by using a step size that’s too big and glitches caused by Helicon Focus, the focus stacking software I used. As far as I can see, no problems.

My NiSi NM-200 is mounted on a Manfrotto 405 3-Way, Geared Pan-and-Tilt Head. The camera line of sight was inclined at a 45° angle relative to the staging surface. That’s less important in this case and more important for an upcoming review of the NiSi NM-200 focus rail.

Both cameras were set for manual exposure. Both lenses were set for manual focus; the combination of manual focus and back-button [auto]focus gives me the best of both worlds.

I use single point focus nearly all the time. I moved the focus point to the farthest point of each subject, then used back-button focus to autofocus on the subject and shoot a photo. Without changing focus from the first photo, I used the focus rail to move across the subject from back-to-front in 800 µm increments (eight numbered increments on the NiSi larger adjustment knob), taking a photo at each step.

More light is required for proper exposure at f/11 than f/8. I used one Sunpak LED-160, one Godox TT685C external flash unit (plus Altura flash modifier), and one Godox MF-12 external flash to light the first subject (Virginia quarter). Two Sunpak-160s and two Godox TT685C external flash units (using Altura and Lastolite flash modifiers) were used to light the last two subjects (quarter and nickel coins).

Related Resources

• Zerene Stacker DOF Calculator
• Fujifilm Colors: Auto White vs Auto Ambience, by pal2tech (12:47)
• Helicon Focus – Quick Start on Mac OS, by HeliconSoft (2:20)

Copyright © 2023 Walter Sanford. All rights reserved.

Comedy of errors

My first big focus stack turned out to be a comedy of errors. Lots of little things, all of them avoidable, but the one that broke the stack was when the camera battery died approximately two-thirds of the way through the project.

My new Fujifilm X-T5 has a much larger battery than my Fujifilm X-T3 so I never imagined it wouldn’t last long enough to create the stack.

I might have been able to salvage the stack by changing the battery without removing the camera from the focus rail, but the Manfrotto quick release plate partially blocked the battery door. Doh!

l use Arca Swiss L-brackets for all of my cameras. Good L-brackets are designed so the bracket doesn’t block any camera doors or ports. But I don’t have one for the X-T5 because it’s new enough that the selection of compatible L-brackets is poor.

I have two ways to provide continuous power for the X-T5 but I couldn’t use them because the battery door was partially blocked. Double doh!

Making lemonade from lemons

Long story short I used Helicon Focus to stack all the photos up until the power failure and the results look fairly good, as shown below. Oh what might have been. Triple doh!

ISO 400 | 80mm | 0 ev | f/8 | 1/250 s

The preceding composite image was created from 192 of 328 photos. I used a safe step size of 50 µm (microns) between photos. Each JPG photo is ~13 MB, 7728 × 5152 pixels.

The coin is acceptably in focus from the top of the coin to a point about two-thirds of the way toward the bottom. Zoom in on the horse’s head and you should notice sharp focus is lost beginning below its eye.

The amount of detail in the composite image is astounding, as shown in the close-up of the upper-right quadrant.

Close-up, upper-right quadrant.

Related Resource: Post update on 11 April 2023.

Copyright © 2023 Walter Sanford. All rights reserved.

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

Post update: What is it?

The mystery object shown in my last blog post is a macro composite image of the right eye of Benjamin Franklin, as he appears on a $100 bill. The $100 bill is the largest denomination Federal Reserve note currently issued for public circulation.

Image Credit: Wikimedia Commons.

Tech Tips

2.5x magification | aperture f/4 | shutter speed 1/250 s | ISO 160

The preceding image is a focus stacked composite of 77 JPG photos taken with my Fujifilm X-T3 digital camera plus a 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.

The camera was mounted on my NiSi NM-200 manual focus rail. A safe step size of 50 microns was used in order to avoid focus banding, as determined by using Zerene Stacker DOF Calculator.

For better composition of the final composite image, I created the stack by focusing past the farthest focus point and moving the rail backward to slightly beyond the closest focus point. (Remember, the subject looks bigger at the farthest focus point than the closest. This almost certainly means it will be necessary to crop the final image if you shoot front-to-back. Going back-to-front helps to avoid this problem.)

The carriage of the focus rail traveled a total distance of 3.85 mm.

77 steps/1 x 50 microns/step = 3,850 microns

3,850 microns/1 x 1 mm/1,000 microns = 3.85 mm

77 steps is probably more than necessary but I wanted to be sure the entire image is acceptably in focus.

Helicon Focus was used to create the focus stack. The final rendering is saved as a TIF file, by default. I converted the TIF to JPG for posting in my photoblog. The final output, shown above, is unedited otherwise.

Sidebar

A micrometer (also known as a micron) equals 0.001 of a millimeter, or 1/1,000 of a millimeter. In other words, there are 1,000 micrometers in one millimeter. The symbol for micrometer is µm.

Related Resources

• Zerene Stacker DOF Calculator
• Helicon Focus – Quick Start on Mac OS, by HeliconSoft (2:20)

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.

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