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.

Did you know … ? (plus Post Update)

Did you know that flash power ratios are relative, not absolute? I didn’t, that is until I bought a Godox MF12 macro flash and was testing it in combination with a Godox TT685C Speedlite.

Are flash power ratios absolute or relative? In other words, is 1/16 power the same strength across all devices? When I set my MF12 and TT685C for 1/16 power, the MF12 doesn’t look as bright as the TT685C. Thanks for answering my question! Source Credit: Godox User Group on Facebook.

Sincere thanks to all the members of the group who kindly answered my question! One answer stood out from the others.

Walter Sanford – The TT685 is closer to 65 W, and the MF12 is roughly 12 W. The TT685 at 1/8 + 3 should be close to the MF12 at 1/1. But that can still be off, as the difference in reflector shape can change the output. Source Credit: Samuel Gibson.

The guide number of the TT685C is 197′ (power ratio 1/128 – 1/1); the guide number for the MF12 is 16′ (power ratio 1/128 – 1/1). Clearly the TT685C is the more powerful flash.

Post Update

The Godox MF12 Macro Flash is underpowered, doesn’t support high-speed sync, and doesn’t feature removable batteries. Perhaps now it’s clear why I said “I won’t buy more MF12s.”

Copyright © 2023 Walter Sanford. All rights reserved.

Godox MF12 Macro Flash (plus Post Update)

Do you remember when I announced I bought a Godox MF12 Macro Flash? That’s because I didn’t. I just bought one and started using it.

Maybe you noticed I created a new Category called “Godox MF12.” It’s more likely you didn’t. Please know that I use Categories and Tags in order to make it easier for readers to search for and find specific information.

Testing 1, 2, 3 …

I’m already heavily invested in the Godox flash ecosystem, so when a “usually trusted source” gave high ratings to his new Godox MF12s I decided to buy one for testing. Full disclosure: I hesitated to pull the trigger when I realized the MF12 costs almost as much as full-size flashes such as the TT685 series. That just doesn’t seem fair/right to me!

I think the intended use for Godox MF12s is to mount one or more flash units on a system of rings that fit on lenses with different filter thread sizes. I know a lot of photographers who own MF12s but as far as I know no one actually uses them mounted on a lens, and no one uses them for macro photography in the field.

Instead, the macro photographers I know use their Godox MF12s as small, lightweight flashes perfect for macro photography in the studio. They say several MF12s, set for low power, add up to nice soft light that’s both bright and relatively free of specular highlights. When used that way, the MF12s seem to work well.

Photo courtesy B&H Photo.

I think it’s fair to ask “Do the MF12s work better than larger, more powerful flash units used at lower power ratios with lots of diffusion?” The objective answer is, “No, not really.” During limited testing using flash equipment I own already, my results are comparable to theirs.

No high-speed sync.

But wait, there’s more. Recently I discovered the MF12 doesn’t support high-speed sync (HSS). That’s on me — I just assumed any modern external flash unit would support HSS, especially since most (if not all) Godox flashes do. But the MF12 doesn’t and that’s a deal-breaker for me. Post Update: I think it’s worth noting that macro flashes available from Canon and Nikon do support HSS, although they cost much more than the Godox MF12.

Slower shutter speeds aren’t a problem in the studio when my camera is mounted on a tripod, but when I’m in the field I prefer to use shutter speeds faster than the default sync speed of my cameras. For this reason alone, I won’t buy more MF12s.

There is one “pro.”

Notice the button labeled with an icon that looks like an asterisk. That button toggles a modeling light on/off. Better, some flash triggers such as my new-ish Godox XProF II can remotely power on/off the modeling light plus set the relative power of the modeling light (from 1 to 10).

Photo courtesy B&H Photo.

ALL external flash units should include a modeling light. The MF12 does but in my opinion that’s insufficient for me to recommend the product.

Post Update

In an effort to get right to the point about what I dislike most about the Godox MF12 Macro Flash, I didn’t gripe about its built-in Lithium ion battery. I think it would be better if the MF12 featured a removable battery of some type.

As designed, the internal battery can be recharged by connecting the flash unit (via USB cable) to either an AC power source or portable power brick such as the Anker PowerCore+ 26800 PD 45W.

In my opinion, the fact that you can’t simply swap in a fresh battery makes this flash less suitable for use in the field.

How does the flash perform when its battery is fully charged?

The powerful built-in lithium battery supports approximately 500 full-power flashes with a 0.01 to 1.7 second recycling time. Source Credit: B&H Photo.

I would say 500 flashes might be overly optimistic, based upon my experience using the Godox MF12 for focus bracketing. I don’t have lab testing equipment so I can’t confirm the flash recycling time, but I can say it’s fast enough to fire continuously in burst mode when using lower power ratios.

Related Resource: Godox: #MF12 Macro Flash Operational Tutorial, by GODOX Global (3:25).

Copyright © 2023 Walter Sanford. All rights reserved.

“Magic Mylar” Moonlight

In a recent blog post entitled “Magic Mylar” diffusion material (plus Post Update), I shared the results my initial experimentation with a new material for light diffusion. Since then I added more mylar for multiple layers of diffusion and I must say I’m liking the results!

Toy dinosaur.

I used single point focus, positioned over the eye of the dinosaur. See why it’s necessary to use focus bracketing/focus stacking?

By now, some of you might be tired of looking at my toy dinosaur. That’s OK, he has thick skin [Get it?] and can withstand a little good natured griping. But seriously, he’s the perfect model for testing light diffusers due to the highly reflective plastic of which he is made.

“Magic Mylar” — where it all began

A friend and expert in macro photography kindly shared several sheets of diffusion material with which he is getting great results. The material is made of mylar plastic, matte on both sides.

Tunnel of Light II

I created a variation of my friend’s “Tunnel of Light.” Using my set-up, the mylar is almost perfectly round and surprisingly rigid.

Tunnel of Light (front/side view). Don’t mind the background clutter!

A single sheet of mylar is clamped to the white plastic top from a big jug of pretzels. The round top is ~4.5″ in diameter.

The jar top is held in place by a Wemberley The Plamp II. At a price point of $49.00, I don’t recommend buying a Plamp in order to make your “Tunnel of Light” — I just happened to have one on-hand and it does the job. I’m sure you can find a suitable clamp using off-the-shelf materials.

Tunnel of Light (rear/side view).

Three Impact ABS 3.75″ Small Spring Clamps (6-Pack) are used to hold the mylar in place. The orange “pivoting nylon pads for uneven surfaces” snap on/off, and as you might expect, tend to snap off at the worst times! For that reason, I DO NOT recommend these clamps. The price was right [$5.40] but you can’t count on them to perform in a pinch without fail. [See what I did there?]

I’m thinking about replacing the white plastic jar top with a PVC pipe fitting, the advantage being it would support the mylar while allowing a view of interchangeable backgrounds through the tunnel of light.

“Magic Mylar” everywhere …

How I got the shot

The toy dinosaur was placed inside the “Tunnel of Light II.” Two small LED light panels were used to light the scene for both setting exposure and focusing. Two external flash units were added for “pop.” All of the light sources were diffused with “Magic Mylar” plus one or more additional light diffusers such as the Altura flash modifier, shown in the preceding photo.

The goal is to use several light sources, set for low power, that add up to nice soft light that’s both bright and relatively free of specular highlights. Looks like I’m on the right track.

Copyright © 2023 Walter Sanford. All rights reserved.

Helicon Focus: Rendering in action (plus Post Update)

In my last blog post, I shared a composite image that was created using Helicon Focus to focus stack 99 JPG photos taken automatically using my Fujifilm X-T5 set for AUTO FOCUS BKT.

The following video demonstrates two strengths of Helicon Focus.

1. It’s relatively simple to use. Creating a focus stacked composite image can be as easy as a two-step process: add source images to Helicon Focus by drag-and-drop; click the “Render” button.
2. Rendering works quickly. For example, 99 photos focus stacked in ~50 seconds! (~00:08 s to ~00:58 s.)

The main window features two panels: the panel on the left shows the source images as the focus stack is created; the panel on the right shows the final output.

The right sidebar shows a list of filenames for the source images. When a filename in the list is highlighted, the corresponding image is displayed in the left panel of the main window.

Look closely at the final output, shown in the right panel in the main window. Notice the “ghost” artifact that’s visible near the tip of the toy dinosaur’s tail. Otherwise, the composite image looks perfect.

Click here to see a Screen Recording of the Rendering process.

I have no idea what caused the artifact. For whatever reason, some of the composite images I have created using Helicon Focus have one or more artifacts.

In contrast, every time I have used Fujifilm AUTO FOCUS BKT it has worked perfectly. (He said with fingers crossed.)

Related Resources

• https://youtu.be/jr5SMaO4qWI
• When dinosaurs attack! – This blog post shows the final image after I used Helicon Focus “Retouching” to fix the “ghost” artifact.
• Focus bracketing and focus peaking – When I watched the real-time display of Helicon Focus rendering “Method C” for the first time, I was reminded of a blog post featuring two videos I created to demonstrate how focus peaking can show the way focus bracketing works. Those videos aren’t as steady and smooth as I’d like, but hey, not bad for a manual focus rail!

Post Update

When I tested the link to the video I noticed a problem with “flash dropout.” Two small LED panels and two external flash units were used to light the scene. Notice the flash on the right side of the subject didn’t fire in photo DSCF1214.JPG. That flash was a Godox MF12. Up until now, the MF12 flash has never failed to fire. For those who might be wondering, the Lithium Ion battery in the MF12 was fully charged before I started the focus bracket. I’ll watch it more closely to see whether reliability is an issue.

Copyright © 2023 Walter Sanford. All rights reserved.

When dinosaurs attack!

Run for your life!

Toy dinosaur.

The preceding composite image was created using Helicon Focus to focus stack 99 JPG photos taken automatically using my Fujifilm X-T5 set for AUTO FOCUS BKT. The composite image was created using unedited JPGs straight out of the camera.

When you use AUTO FOCUS BKT, you select two endpoints for your focus bracket (Point A and Point B) and the camera sets the step size between shots automatically.

If your goal is to create a composite image with the subject entirely in focus, here’s a helpful tip. As you are looking through the camera viewfinder, or in my case looking at the LCD on the back of the camera, it can be difficult to be sure which point on the subject is closest to the front of the lens and which point is farthest.

For example, looking at the composite image shown above, can you be certain one of the toy dinosaur’s legs doesn’t extend in front of it’s nose? I couldn’t. So what should you do before starting the photo shoot?

I think it’s helpful to look at the subject perpendicular to the camera/lens line of sight, as shown below. In this straightforward example the nearest and farthest points on the subject are obvious — Point A is the tip of the dinosaur’s nose and Point B is the tip of it’s tail. This tip should be useful for subjects that are more complex than my toy dinosaur.

Toy dinosaur (side view).

For what it’s worth, the preceding photograph was taken using my Apple iPad mini 2.

Tech Tips

“Rendering” Method C in Helicon Focus worked best for this subject/composition, but it didn’t work perfectly. There was one artifact that doesn’t appear in any of the 99 focus bracketed photos used to create this composite image, so I knew that in-camera focus bracketing was working properly in my Fujifilm X-T5.

I used “Retouching” to fix the artifact. This was the first time I have used the retouching tools in Helicon Focus. I must admit the experience wasn’t as painful as I was led to believe, but it took a little experimentation to figure out the process.

At this point, I feel like I don’t have enough experience to share directions for how I removed the artifact. But I did take notes so I can refine the process and you can be sure I’ll do a follow-up blog post related to retouching as soon as I don’t feel as lost as I did this this time!

Copyright © 2023 Walter Sanford. All rights reserved.

Post update: What is it?

The mystery object shown in my last blog post is one of my prized possessions — an enamel lapel pin from the National Oceanographic and Atmospheric Administration (NOAA).

NOAA enamel lapel pin.

The About Me permanent page on my blog, linked from the top of the “Pages” section in the right sidebar, features the following quote.

For more than a decade, I was actively involved with several education outreach initiatives of the American Meteorological Society. Source Credit: About Me page.

As a result of generous funding from the National Science Foundation (NSF), the National Weather Service NWS), and the American Meteorological Society (AMS), I was able to participate in summer workshops for K-12 teachers at many NOAA/NWS facilities such as the National Weather Service Training Center, the NOAA/NWS Storm Prediction Center, the NOAA National Severe Storms Laboratory, the Cooperative Institute for Meteorological Satellite Studies, and the National Center for Atmospheric Research, to name a few. There I received training that enabled me to serve as an AMS Atmospheric Resource Agent for the Commonwealth of Virginia.

I don’t remember exactly when and where I was given the NOAA lapel pin but it’s a treasured memento of a period in my life when I learned a lot from some of the top experts in NOAA, and I experienced significant professional growth.

Copyright © 2023 Walter Sanford. All rights reserved.

What is it?

Ladies and gentlemen, children of all ages. It’s time for another exciting episode of “What is it?”

I will reveal that both photos are “one offs” (not focus stacked composite images) that show different parts of the same object, photographed with a 4x microscope objective mounted on my Fujifilm X-T3.

If you think you know what is shown in these photos, then please leave a comment. The answer will be revealed in a post update.

Copyright © 2023 Walter Sanford. All rights reserved.