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.

What is it?

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

If you think you know the camera part highlighted by a red circle in the preceding photo, then please leave a comment. The answer will be revealed in a post update.

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.

Sometimes you get what you pay for.

I love me some Manfrotto clamps and articulating arms. But — and it’s a big but — two points diminish my enthusiasm for Manfrotto gear.

First and foremost, in my strong opinion many (if not all) Manfrotto products are way overpriced.

Second, Manfrotto seems to be obsessed with slathering many of their products with excessive amounts of grease and lubricants. Almost every Manfrotto product I have purchased required a thorough cleaning before I felt comfortable using it with my cameras and lenses.

SmallRig

On the strength of a rave recommendation from a trusted source (henceforth known as a “usually trusted source”) I bought some clamps and articulating arms made by a company called “SmallRig.”

The price is definitely right and their products work as advertised. I would call SmallRig clamps and articulating arms “less greasy” than comparable Manfrotto gear, but some clean-up is still required before use.

Initially I was pleased with the build quality of the SmallRig clamps and articulating arms. Over time I noticed some of the gear I bought has started to fall apart.

For example, notice the rubber pad on the inside of the jaws of one of my SmallRig Super Clamps has peeled away from the metal.

Close-up of SmallRig Super Clamp.

And the rubber gasket on one end of a small articulating arm has peeled away from the metal. I noticed the problem when a blob of what appeared to be rubber cement got on my fingers when I was setting up external flash units for a photo shoot.

Close-up of SmallRig 5.5″ articulating arm.

What are the take-aways?

Do the products still work? Yes, I guess they do although I must admit my confidence in the brand is gone.

Anyone who knows me well knows I am very gentle with my photography gear so it cannot be said these products are failing due to abuse. Not to belabor the point, but if I should decide to sell any of my equipment then you should buy it STAT because every used item would be fairly rated as “pristine.”

As a service to my fellow photography enthusiasts I am issuing a “Do Not Buy” advisory for SmallRig clamps and articulating arms.

Related Resources

• Manfrotto
• SmallRig Super Clamp w/ 1/4″ and 3/8″ thread 735
• SmallRig 5.5″ Articulating Arm

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.

“Magic Mylar” diffusion material (plus Post Update)

So there I was, working on the next epic sundial-related blog post, when I realized two things: 1) The post needs to be too long to finish before Friday; and 2) The topic probably needs to be covered in a series of posts rather than one long post. Regrettable, because WordPress site statistics shows the sundial-related blog posts are popular with readers of my blog. Anyway, please stay tuned — I hope to finish the next post by Tuesday, 23 May 2023.

In the meantime, I decided to give you a quick update on my never-ending quest for good light diffusers.

“Magic Mylar”

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.

I should have taken some shots of the same subject with- and without diffused light, but I didn’t have time to do a proper test of the new diffusion material. Qualitatively speaking, I like the look and feel of the test shots in diffused light although I concede there are specular highlights that might require either double- or triple layers of diffusion, as recommended by my friend.

Here are a few shots from a quick studio session. The subject is a highly reflective plastic toy dinosaur. I used a small LED light panel (with added diffusion to supplement the built-in diffuser on the LED) and a Godox TT685C plus a small Altura flash modifier to light the scene. The output from the LED light panel is assumed to be constant, while I slightly increased the distance between the subject and the TT685C from the first to last shot. I estimate the front of the Altura was no more than say 5″ to 7″ from the subject. My assumption is the farther the TT685 was from the subject, the more the LED was the dominant light source.

Closest.

Mid-range.

Farthest.

Where can I get some “Magic Mylar?”

I don’t know whether the results of my test are so impressive that you would like to order some of the “Magic Mylar” STAT. The following image shows the label from a big roll of the mylar.

Comstoc Ink Jet Plotter Media | 3 MIL Double Matte

It’s unclear whether this specific product is discontinued. One source says the art supplier Dick Blick sells sheets of similar material. I will do some research and report my findings, if any. Please comment on this post if you find a source before I do.

Tech Tips

Disclaimer: The following photos show no evidence that I’m actually a fairly good photographer.

Here are two quick-and-dirty shots (taken with my Apple iPad mini 6) that show how I used the mylar to diffuse light from a Sunpak LED 160 light panel. I simply taped an ~8.5″ x 11″ sheet of the mylar to the LED. The first photo shows the LED off; the second shows the LED on.

Sunpak LED 160 light panel. (Off.)

Sunpak LED 160 light panel. (On.)

Looks like I didn’t place the subject at the center of the circle of light. In my defense, the circle of light wasn’t as apparent to me as it is in the photo. Hey, I told you it was a quick-and-dirty test!

More later after further testing.

Post Update

I’m a scientist. No really, I am. I know it’s easier to analyze the results of an experiment that has only one variable. My last experiment included another variable that made it impossible to objectively evaluate the quality of light diffused by adding “Magic Mylar” to a small LED panel.

So I ditched the Godox TT685C external flash unit and photographed the subject using only diffused light from the LED panel.

All photos were taken using my Apple iPad mini 2. Same subject, same “stage.” Notice the subject is closer to the center of the circle of light on the background.

Next I moved the iPad closer to the subject for a better look at the specular highlights, if any.

Finally, here’s the same shot cropped for a closer look at the subject. The white balance is way off, but hey, it’s an iPad camera photo! Otherwise the light has what I would describe as a “warm glow” with fewer glaring specular highlights than the shots from the first test. Maybe now you can see why I am excited by the results of my experimentation with the new mylar diffusion material.

Perhaps you’re wondering, “Why was it necessary to use an external flash unit when you took the first test shots?” I used my Fujifilm X-T5 and 80mm macro lens to take those shots. I wanted to use the same settings that I’ve been using for studio macro focus bracketing. Problem is, the photos were underexposed. Since I didn’t want to change the camera/lens settings, my only option was to add more light. And now you know the rest of the story.

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.