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.

iPad/tablet tripod mount

Did you know I suffer from “decision paralysis?” I do. It doesn’t matter whether a product is expensive or inexpensive, I agonize over the decision to pick the one that’s best for me. This time, I made the decision relatively quickly with little angst.

I knew I needed to get some sort of tripod mount for my iPad mini 6. For a while, I was using a small photography clamp to hold my iPad. It was precarious at best and an expensive accident waiting to happen.

A quick Google search turned up a YouTube video that caught my attention.

The build quality looked good and the price point seemed fair, so I ordered one.

After a month or two of usage, I can say this versatile tripod mount works as advertised. I think the parts that actually support the iPad are a little narrow for my comfort, but they do work — just be careful to center your tablet on the mount and be sure it’s clamped down tightly.

The tripod mount came bundled with several “extras.” Most of them are borderline useless, but one item turned out to be a pleasant surprise.

The small wireless remote control is great for starting/stopping time-lapse videos. You can use the built-in timer featured in the Apple “Camera” app to shoot still photos and start video recording, but you still have to touch the iPad to stop recording video. That can result in “camera shake” that you need to edit out of the video, but hey, I don’t need one more thing to do when the “little remote that could” can be used for clean stops.

Is this the “best iPad mount” as the YouTube video title says? I don’t know. But it’s “good” and sometimes all you need to know is when good is good enough. Please comment if you know of a better product than this one.

Related Resources

• THIS is the iPad/Tablet Tripod Mount YOU NEED! by BenoniTech (2:55)
• Aluminum iPad Pro Tripod Mount Adapter Holder With Cold Shoe Ball Head and Bluetooth Shutter for iPad Pro 12.9 11 10.5, iPad Air Mini, Surface Galaxy Tab, Video Recording 3.5 to 13.5″ iPhone Tablet $29.99 (as of this writing)

Copyright © 2023 Walter Sanford. All rights reserved.

Outflow boundary

What goes up must come down.

A simple conceptual model of a thunderstorm includes an updraft and downdraft. Sometimes the downdraft causes an “outflow boundary.”

What is an outflow boundary?

Outflow Boundary

A storm-scale or mesoscale boundary separating thunderstorm-cooled air (outflow) from the surrounding air; similar in effect to a cold front, with passage marked by a wind shift and usually a drop in temperature. Outflow boundaries may persist for 24 hours or more after the thunderstorms that generated them dissipate, and may travel hundreds of miles from their area of origin.

New thunderstorms often develop along outflow boundaries, especially near the point of intersection with another boundary (cold front, dry line, another outflow boundary, etc.; see triple point).

Source Credit: Glossary, NOAA National Weather Service.

Recent outflow boundary near my location

Notice the intense thunderstorm located to the northwest of the blue reticle that marks my location. The large cell produced heavy rainfall, as indicated by the red radar echoes and green polygon that outlines an area where a flash flood warning was issued.

Click on the following image to see a full-screen view of the animated GIF.

05 JUL 2023 | KWLX | Outflow boundary

Now notice the ring of radar echoes that radiate outward from the dissipating thunderstorm cell. That’s an outflow boundary!

If you pour water on a flat surface, then the water will spread out in all directions. Like water, the atmosphere is a fluid (albeit much less dense than water) and behaves similarly.

Also notice another strong thunderstorm that formed along the outlfow boundary (to the southeast of the blue reticle) where the gust front might have interacted with some type of atmospheric boundary that caused uplift and fueled a new thunderstorm cell.

Related Resources

• What Causes a Thunderstorm? [Featuring embedded video (2:38).]
• How Thunderstorms Form
• Life Cycle of a Thunderstorm

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.

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.

Interactive infrared weather satellite image

The AMS interactive infrared [weather] satellite image resulted from the collaboration between the American Meteorological Society (AMS) education initiatives and the Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison.

Infrared imagery is one of three types of weather satellite imagery. Black, white, and shades of gray are used to represent temperatures from the tops of clouds and the land & water surfaces on Earth. Black is the hottest temperature; white is the coldest. Sometimes this type of weather satellite imagery is color-enhanced for use by broadcast meteorologists.

The first image (shown below) is the non-interactive version of two screenshots from my Apple iPad mini 6. All three images in this blog post are from the same date and time.

08 May 2023 at 19:00 UTC (03:00 pm EDT).

As you move the cursor (red reticle) over the interactive image, the temperature (in degrees Celsius) and location (latitude and longitude) are listed.

The first screenshot shows the cursor (red reticle) over a dark area located somewhere along the Florida peninsula where the temperature is 27°C (78.8°F or 299.2 K). At such a warm temperature, we are almost certainly looking at land rather than water.

Cursor (red reticle) located somewhere along the Florida peninsula.

The the second screenshot shows the cursor (red reticle) over a bright white area located somewhere in/above Alabama where the temperature is -55°C (-67°F or ~218.2 K)! At such a cold temperature, we can be certain we are looking at the tops of very high clouds. This could indicate hazardous weather is occurring at the Earth’s surface.

Cursor (red reticle) located somewhere over Alabama.

Science can and should be fun. Have fun exploring using the AMS interactive infrared [weather] satellite image!

Related Resources

• AMS interactive infrared [weather] satellite image – the American Meteorological Society (AMS) and the Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison.
• Weather Calculators, including temperature conversion – a page of interactive calculators that still work, rescued from the Wayback Machine Internet Archive.
• UTC/EST/EDT – a table listing equivalent times among Universal Time Coordinated (UTC), Eastern Standard Time (EST), and Eastern Daylight Time (EDT).
• AMS Interactive Infrared Weather Satellite Image – Making the Invisible Visible. Another resource rescued from the Wayback Machine Internet Archive. I created this activity as an extra credit opportunity for my Grade 8 Physical Science students when we were studying energy and energy transformations. In retrospect the activity is probably too long to use “as is,” but it might serve as a data bank of questions that teachers could use to create their own version of the activity. For non-educators, the activity questions can help to guide your thinking about what you can tell from the interactive infrared imagery.

Tech Tips

The interactive infrared [weather] satellite image was tested using my Apple iPad mini 2 and 6, Apple MacBook Air (13″, M1, 2020), and Apple iMac desktop computer (vintage 2009) and is compatible with all of those devices.

Did you notice both the non-interactive and interactive infrared images are GIF files?

The [GIF] format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. Source Credit: GIF, by Wikipedia.

In the old days before the AMS interactive infrared [weather] satellite image, we would use a scientific image-processing tool such a NIH Image (now ImageJ) to infer temperature from pixel values (0-255). Labor intensive, but it was fun!

Copyright © 2023 Walter Sanford. All rights reserved.

Thunderstorms, mesocyclones, and tornadoes. Oh my!

As a weather enthusiast, RadarScope is my go-to weather app for tracking the approach and passing of weather systems such as the line of strong thunderstorms that affected the Washington, D.C. metropolitan region on Saturday, 22 April 2023.

Animated GIF created by RadarScope app. (11:44 AM to 11:58 AM)

The following annotated screenshot shows a few basic buttons; their function is described below the graphic.

My location, radar sites, and warnings. (12:01 PM)

1. My location. (See blue reticle, center screen.)
2. Radar sites. (KWLX, located in Sterling, Virginia, is the National Weather Service radar site nearest to my location.
3. Warnings. (Two warnings were in effect when this screenshot was captured.)

A fly-out panel appears when you click on the Warnings button. As you can see, there were two Severe Thunderstorm Warnings in effect at the time of the screenshot. If you click on one of the warnings then RadarScope automatically takes you to a zoomed-in view of the warning area. Click on the button for “My location” to return to your home location.

Warnings. (11:58 AM)

Tornado Warning

Soon afterward, a Tornado Warning was issued for Culpeper- and Madison Counties in Virginia, as indicated by the red polygon. Notice the red polygon is nested inside a yellow polygon that outlines an area where a Severe Thunderstorm Warning was issued.

Tornado Warning (red polygon). (12:30 PM)

Click on the red polygon for more information about the Tornado Warning.

Tornado Warning (information). (12:30 PM)

The next screenshot shows the “Super-Res Reflectivity” radar product, zoomed in on the Tornado Warning area. With a lot of imagination, you can almost see something that looks a little like the classic “hook echo” associated with tornadoes. Almost, but not quite.

Super-Res Reflectivity. (12:30 PM)

Time to switch to the Storm Relative Velocity radar product, shown below. This is where Doppler weather radar really shines. Greens indicate radar echoes moving toward the KWLX radar site; reds indicate radar echoes moving away from the radar site (like brake lights on a car driving away from you).

The following image shows the thunderstorm cell is rotating counterclockwise — this is known as a mesocyclone and is the reason for the Tornado Warning.

Storm Relative Velocity. (12:27 PM)

Within the broader area of counterclockwise circulation there is a tighter area of greens and reds, as shown more clearly in the Super-Res Storm Relative Velocity radar product.

Super-Res Storm Relative Velocity. (12:32 PM)

It’s important to note that the orientation of side-by-side greens and reds typical of rotating thunderstorm cells varies depending upon the location of the storm cell relative to the weather radar site. In the example shown above the greens are on the right and the reds are on the left because the warning area is located to the southwest of KWLX. In contrast, if the warning area were located to the northeast of the radar site, then the reds would be on the right and the greens on the left.

As it turns out, there were’nt any official Tornado Reports for Virginia. Later the same day, a small F0 tornado touched down briefly in Montgomery County, Maryland.

Related Resources

The following resources from the National Weather Service provide excellent background information about Doppler weather radar.

• How radar works
• Composite Reflectivity
• Storm Relative Velocity

More RadarScope-specific resources are available from the creators of the app.

• User’s Guide
• Information Articles
• RadarScope Blog

Copyright © 2023 Walter Sanford. All rights reserved.

Minor post updates

How to do screen captures on Apple iOS devices

Since my last blog post, I discovered it’s possible to record a movie of the screen display for Apple iOS devices that features both video and audio.

As you know, when you swipe down from the upper-right corner of the screen, the “Control Center” menu appears. Tap and hold the “Screen Recording” button and the following sub-menu appears.

Apple iOS | Control Center | Screen Recording / Microphone On

Tap the “Microphone” button to toggle recording on/off. As you can see, my iPad mini 6 is currently set for “Microphone On.”

This feature could be useful for creating instructional videos that show and tell how to use apps such as “RadarScope” (shown in the background of the preceding screenshot), my favorite weather app.

Comedy of errors

Going back to mid-March 2023, my blog post entitled Comedy of errors included the following composite image. Did you notice the dark blob on the coin? I did! It’s located in Theodore Roosevelt’s imaginary line of sight, above the horse’s neck. Once you see the blob, you can’t un-see it.

Composite image created from 192 of 328 photos.

The discoloration was a mystery to me, since I washed the coin with soap and water (twice) in preparation for the photo shoot. I’m happy to report the mystery was solved, by accident, when I was watching another YouTube video recently.

Turns out the dark blob is a chemical reaction that can occur on some coins as they age. In this case, the quarter is made of silver (in part) and the simplest explanation of the dark blob is it’s a place where the coin is tarnished. It’s not exactly the same thing as tarnish, but you understand.

Some coin collectors refer to the discoloration as a “burn.” In most cases, a burn doesn’t reduce the value of a coin, but in some rare cases it can add to the value substantially.

Related Resources

• How to Record iPad Screen With Sound, by Howfinity (2:43)
• Value of 1968 Kennedy Half Dollar, by BigDCoins (6:26)
• RadarScope app – a blog post by Walter Sanford

Copyright © 2023 Walter Sanford. All rights reserved.