Iberian odonate larvae

During late-October 2021, I was contacted by Miguel A. Conesa-García, PhD, Profesor Tutor Biología, Diversidad Animal, Ciencias Ambientales, UNED-Málaga.

Miguel was working on finishing the second edition of his book about odonate larvae in the Iberian Peninsula (Spain and Portugal). When Miguel was almost finished, an adult male Wandering Glider dragonfly (Pantala flavescens) was spotted in Spain. P. flavescens is a new species of odonate for the region, so Miguel decided to add the new discovery to the species list in his book.

Cover photo, courtesy Amazon Books.

The following screen capture shows the search string I used to find the book on Amazon.

Screen capture, Amazon Books.

The book is richly illustrated with beautiful photos and diagrams. It’s abundantly evident I could learn a lot from the book — I wish there were an English Edition!

Miguel requested permission to use a photo of a Wandering Glider exuvia in my photoblog, published on 14 November 2018. I was, of course, willing to help.

Page excerpt from Miguel’s book, featuring my photo.

I’m mentioned in the acknowledgements at the end of the book. Regrettably my first name is misspelled and the Web address cited is no longer current. I took the liberty of annotating the page from Miguel’s book to provide the correct information.

Acknowledgements, p. 539 (annotated).

Acknowledgements, p. 539 (original).

Migratory Dragonflies

Wandering Glider is one of at least five major species of dragonflies known to be migratory in North America. P. flavescens is the only species of odonate known to occur on every continent except Antarctica.

The exuvia that I photographed is the “cast skin” from an odonate larva (nymph) that was collected in the field by Andy Davidson, a graduate student at Virginia Commonwealth University in Richmond, Virginia USA. Andy reared the larva in the laboratory as part of a research project entitled “Predator-Prey Interactions in a Changing World.”

Part of the value in rearing odonate larvae in the laboratory is knowing with certainty that an exuvia is from a particular species. This is perhaps the reason that Miguel chose to use my photo.

Related Resources

• Test shots: Pantala flavescens exuvia.
• Field Guide to Migratory Dragonflies, by Migratory Dragonfly Partnership.

Copyright © 2022 Walter Sanford. All rights reserved.

Fujifilm/Fringer/Canon MP-E 65mm macro lens

In a recent blog post I mentioned that I was looking forward to testing the Fringer EF-FX Pro II lens mount adapter with my Canon MP-E 65mm Macro lens.

The MP-E 65mm doesn’t have a ring for focusing on the subject — you set the magnification ratio (from 1x to 5x) and move the camera/lens rig back and forth until the subject is in focus. For all photos, I focused on one eye of the model.

Dimetron

The first studio model is a toy Dimetron, photographed at a magnification ratio of 1:1. The toy is ~3.6 cm (~36 mm) long. The size of the APS-C sensor in the Fujifilm X-T3 is 23.5 mm x 15.6 mm. At 1x magnification, the entire length of the toy doesn’t fit on screen.

Dimetron toy | 1:1 magnification | 1/16 flash power ratio

With the camera/lens set for the same f/stop, shutter speed, and ISO (f/5.6, 1/250 s, and 400, respectively), less light reached the sensor when the magnification ratio was increased from 1:1 to 2:1. So I increased the flash power ratio by one stop, from 1/16 power to 1/8 power.

Dimetron toy | 2:1 magnification | 1/8 flash power ratio

Triceratops

The last studio model is a toy Triceratops, photographed at a magnification ratio of 1:1. The toy is ~4.3 cm (~43 mm) long.

Triceratops toy | 1x magnification | 1/16 flash power ratio

As with the first model, when the magnification ratio was increased from 1:1 to 2:1 it was necessary to increase the flash power ratio by one stop.

Triceratops toy | 2x magnification | 1/8 flash power ratio

Gear Talk

The Fringer EF-FX Pro II lens mount adapter enables one to mount Canon lenses on Fujifilm X-Series digital cameras. As you can see, my Canon MP-E 65mm macro lens works well with the Fujifilm X-T3 camera.

The APS-C sensor inside the Fujifilm X-T3 digital camera has a crop factor of 1.5x, so the Canon MP-E 65mm macro lens has a focal length of ~98mm (35mm equivalent) when mounted on an X-T3. The net result is an increase in apparent magnification, …

Post Update Update

Just because something looks like a duck and seems to act like a duck doesn’t mean it’s a duck. And so it is with the Fringer EF-FX Pro II lens mount adapter — although it looks like an extension tube, it isn’t. Why was I deceived by its appearance? Because I didn’t understand something called “flange focal distance.”

For an interchangeable lens camera, the flange focal distance (FFD) … of a lens mount system is the distance from the mounting flange (the interlocking metal rings on the camera and the rear of the lens) to the film or image sensor plane. This value is different for different camera systems. Source Credit: Flange focal distance. Wikipedia.

For example, the FFD for Canon EF-mount is 44 mm and the FFD for Fujifilm X-mount is 17.7 mm. In order to make a Canon EF lens perform properly on a Fujifilm X-series camera body, an adapter must move the Canon lens 26.3 mm farther from the digital sensor. (44 mm – 17.7 mm = 26.3 mm)

Not surprisingly, when I remeasured the thickness of my Fringer EF-FX Pro II lens mount adapter it turns out to be closer to 26 mm than my original course estimate of 30 mm (cited below). The net result is the 17.7 mm FFD of my Fujifilm X-T3 combines with the 26.3 mm thickness of the Fringer adapter, resulting in an FFD of 44 mm — exactly the right FFD for the Canon lens to work properly on a Fujiflm X-series camera body!

It’s worth noting that “apparent magnification” is still a real thing when a camera lens designed for a “full-frame” camera is mounted on a camera with an APS-C size sensor. The image formed by the lens is exactly the same size regardless of the size of the digital sensor used to record the image, but a smaller part of the image is “seen” by an APS-C sensor than a full-frame sensor, resulting in the misperception that the image is magnified.

I hope this sets the record straight. Sincere apologies for any confusion I might have caused — I never heard of “flange focal distance” before I bought the Fringer adapter!

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[Post Update: From this point forward everything I wrote is incorrect. Is my face red, or what? I’ll explain further when I have a chance to use a desktop computer to edit this post.] … although the images appear to be magnified more than can be explained by this fact alone.

In the opinion of this author, the Fringer adapter functions like an extension tube. The adapter is ~3.0 cm (30 mm) in thickness. There aren’t any optics inside the adapter but it does move the lens 30 mm farther from the camera sensor. That, my friends, is an extension tube.

I used an online, interactive Macro Extension Tubes Calculator to estimate the effect of a 30mm extension tube on photos taken with the Canon MP-E 65mm macro lens at magnification ratios of 1:1 and 2:1. The calculator shows the magnification ratio increased from 1:1 to ~1.5:1 and 2:1 to ~2.5:1 respectively.

Macro Extension Tubes Calculator | 1:1 magnification ratio

The values for “new minimum focusing distance” are in millimeters, despite the fact that the second “m” only appears when you click an insertion point in the box and scroll to the right. The values for magnification ratio seem reasonable; the values for new minimum focusing distance, not so much.

Macro Extension Tubes Calculator | 2:1 magnification ratio

[End of segment with information that is incorrect.]

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Related Resources

Full-size photos of the preceding studio models are featured in the following blog posts. Those photos should help to give the reader a better sense of how much the subjects were magnified by the Fujifilm/Fringer/Canon MP-E 65mm macro lens rig.

• What is it? (published on 21 DEC 2020)
• What is it? It’s a toy Dimetrodon. (published on 23 DEC 2020)
• Toy dinosaur: focus-stacked composite image (published on 08 JAN 2021)
• Flange focal distance, by Wikpedia.
• Sensor Size and Magnification – correcting a common misunderstanding, by Allan Walls Photography (20:02). Fast-forward to 5:48. See also Sensor Size Matters – Part 1 (the Front Half) – A Demonstration (19:51).

Copyright © 2022 Walter Sanford. All rights reserved.

Fujifilm X-T3: Focus Peak Highlight

I like to use manual focus to shoot photographs with my Fujifilm X-T3 digital camera. Set the small dial on the front of the camera to “M.” The beauty of manual focus on Fujifilm X-series cameras is back-button auto-focus still works!

When the small dial is set for “M” both manual focusing and back-button auto-focusing can be used in combination with what Fujifilm calls “Focus Peak Highlight,” or more simply, “focus peaking.”

The following YouTube video by pal2tech explains a technique that makes it much easier to see the focus peaking.

BEST Fujifilm Manual Focus Setting, by pal2tech (6:01).

The process is simple. Set the camera to record JPG + RAF [Fujifilm’s proprietary raw format]. Select one of the black-and-white Fujifilm film simulations, e.g., ACROS. [More about Fujifilm film simulations in an upcoming blog post.]

The camera display will be black-and-white. As Chris Lee (pal2tech) explains in the preceding video, it’s much easier to see focus peaking on a black-and-white background.

JPG files saved to a memory card are black-and-white too, as shown below.

Buzz Lightyear plastic toy. [Focus Peak Highlight not shown.]

RAF files are saved in full color, as shown below.

Buzz Lightyear plastic toy.

Tech Tips

“Focus Peak Highlight” can be activated when the camera is set for manual focus mode. Using back-button focus (AF-L button) in manual mode enables one to retain full control of the exposure triangle, focus quickly, and see what’s in focus before shooting a photograph.

Fuji Back Button Focus (4:06), a YouTube video by Ashraf Jandali, provides a clear demonstration of how to use back-button focus on the Fujifilm X-T1. The same technique works with the Fujifilm X-T3.

Related Resources

• BEST Fujifilm Manual Focus Setting, by pal2tech (6:01).
• Fuji Back Button Focus, by Ashraf Jandali (4:06).
• The ultimate guide to Fuji’s Film Simulations; A DEEP dive to de-mystify one of Fuji’s best features, by Dave Etchells, Imaging Resource.

Copyright © 2022 Walter Sanford. All rights reserved.

Sample photos: Fringer EF-FX Pro II lens mount adapter

Oh look, it’s the “Made in the shade” monkey and Buzz Lightyear — two of my favorite studio models! Whenever I need to test new photography gear and/or techniques, they are always willing to help.

As promised in my last blog post, here are a couple of sample photos taken with my Canon EF 100mm macro lens mounted on a Fujifilm X-T3 digital camera body using a Fringer EF-FX Pro II lens mount adapter.

Single point focus was used for both photos. For the first photo, the focus point was located on the monkey’s right eye (bottom eye, relative to the photo). The real world size of the toy monkey is ~4.8 cm long.

“Made in the shade” monkey toy.

The Canon lens is controlled by the Fujifilm digital camera via the Fringer adapter. EXIF information (shown below) is available for each photo. As you can see, the photos in this set were taken using an aperture of f/5.6 and a shutter speed of 1/250 s, the default sync speed for the X-T3.

The “sweet spot” for the Canon EF 100mm macro lens is either f/5.6 or f/8. The depth of field is shallower at f/5.6 than f/8, but I thought the former might be a better test for sharpness than the latter.

Apple Preview | Inspector

Buzz Lightyear reporting for duty, sir. I don’t remember exactly where the focus point was located, but it was probably somewhere near Buzz’s face/head.

Buzz Lightyear plastic toy.

Regular readers of my blog might be happy to know Buzz will be back again for my next blog post.

What are the take-ways?

As you can see, my Canon macro lens works well with the Fujifilm camera. Does it perform better than my Fujinon 80mm macro lens? It’s too early to tell.

The APS-C sensor inside the Fujifilm X-T3 digital camera has a crop factor of 1.5x, so the Canon EF 100mm macro lens has a focal length of 150mm (35mm equivalent) when mounted on an X-T3. The net result is an increase in apparent magnification.

Some of the advantages of mounting the Canon lens on a Fujifim digital camera (rather than my older Canon DSLR camera) are really about features available on the X-T3 that enable me to get more from the same lens.

For example, there are only nine (9) focus points on my Canon EOS 5D Mark II; the Fujifilm X-T3 can be set for either 117 or 425.

The Canon EOS 5D Mark II doesn’t feature focus peaking; the Fujifilm X-T3 does. Focus peaking is a useful aid for focusing the Canon lens manually. More about this topic in my next blog post.

And of course, don’t forget that all of my Canon lenses (including several L-series lenses) can be used with my Fujifilm cameras via the Fringer adapter. I’m especially looking forward to testing the Fringer adapter with my Canon MP-E 65mm Macro lens.

In summary, the Canon/Fringer/Fujifilm rig works as expected. During limited testing, I discovered something that doesn’t work. (Again, more about this topic in an upcoming blog post.) The problem isn’t a deal-breaker and it should be something that can be fixed in a firmware update of the Fringer adapter. Editor’s Note: I just contacted Fringer as of this writing. I’m interested to see whether they are receptive to customer suggestions for improvement. I’ll update this post to include their response. Post Update: Fringer replied to my message promptly. Details in an upcoming blog post.

Related Resources

• How to Find Your Lens’s Sharpest Aperture or Sweet Spot, by Todd Vorenkamp for B&H Photo “Explora.”
• Depth of Field, DOFMaster.

Copyright © 2022 Walter Sanford. All rights reserved.

Thanks, Photopea!

According to The Verge …

Adobe has started testing a free-to-use version of Photoshop on the web and plans to open the service up to everyone as a way to introduce more users to the app. Source Credit: Adobe plans to make Photoshop on the web free to everyone, by Jacob Kastrenakes.

Way to go Photopea — looks like you might have helped to nudge Adobe out of its complacency!

Related Resources

• The Verge: Adobe plans to make Photoshop on the web free to everyone, by Jacob Kastrenakes.
• 9to5Mac: Photoshop on the web free in Canada; more regions on the way, by Allison McDaniel.
• Engadget: Adobe will release a free version of Photoshop for browsers, by A. Khalid.

Copyright © 2022 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 what is shown in these photos, then please leave a comment. The answer will be revealed in a post update.

Copyright © 2022 Walter Sanford. All rights reserved.

Fossil shark tooth, revisited

This blog post features a photo of a fossil shark tooth that I collected from the Lee Creek Phosphate Mine in Aurora, North Carolina. I didn’t record the exact date when I collected this specimen, but it was sometime between 1984 and 1989. The mine is currently open for phosphate mining, but it’s closed to the public for fossil collecting.

At the time I collected the tooth, the species of shark was called Carcharodon megalodon. Subsequently, the scientific name was changed to Carcharocles megalodon.

C. megalodon lived in “shallow” seas approximately 10 million years ago. 10 million years seems like a long time on the human time scale, but isn’t long ago on the Geologic Time Scale.

Size and jaw placement

The following annotated image shows one method for measuring the size of a fossil shark tooth. The “slant height” of the tooth is approximately four and one-quarter inches (~4 1/4″) long, as measured along the straighter edge of the tooth (lower edge, relative to the photo).

According to Gareth Williams, a member of the Megalodon Maniacs Facebook group, the tooth is from the upper jaw (lateral).

Lee Creek Phosphate Mine | C. megalodon (lingual side)

Photoblog post flashback

On 11 May 2020 I published a blog post entitled “Focus bracketing using Fujifilm X-T3” that features the same ruler shown in the preceding photo.

The 7″ plastic ruler is from the Calvert Marine Museum. Do you know why the small ruler is 7″ long rather than the more common 6″ length? Please leave a comment if you know the correct answer. Source Credit: Focus bracketing using Fujifilm X-T3.

The reason the ruler is 7″ inches long is because that’s the length of the largest fossil shark teeth ever collected — the holy grail for fossil hunters!

Tech Tips

The Adobe Photoshop “Ruler Tool” can be used to measure the number of pixels between any two points along the ruler shown in the preceding annotated image.

60s ‘shop: Using the ruler tool to measure distances in Photoshop CC, by Photoshop for the Scientist (1:00) provides a clear and concise explanation of how it’s done.

The resulting value (in pixels) can be used to set a custom scale in Photoshop in order to make other measurements of the tooth virtually.

Related Resources

• Fossil shark tooth, a blog post by Walter Sanford published on 16 September 2011. Whoa, I’ve been blogging a long time! As expected, an 11 year-old blog post includes some broken links.
• Fossil shark tooth, a recent blog post by Walter Sanford
• Saved post from “Megalodon Maniacs” Facebook group
• How to measure a fossilized shark tooth
• 60s ‘shop: Using the ruler tool to measure distances in Photoshop CC, by Photoshop for the Scientist (1:00). See also Setting a Custom Scale and Measuring in Photoshop (7:10).
• The Size Of Megalodon (see section entitled “Worlds Largest Megalodon Teeth“)

Copyright © 2022 Walter Sanford. All rights reserved.

Jumping spider

The following photo shows a tiny spider carcass (~3/16″ long) that was inside an exuvia (~1 3/4” long) from a Common Green Darner dragonfly (Anax junius). The exuvia was collected on 17 June 2021 from a small pond in Prince William County, Virginia USA. I discovered the spider long afterward — too late to save its life.

17 JUN 2021 | PNC. Wm. County, VA | Jumping spider

Thanks to Eva Weiderman and Joseph Girgente — members of the “Odonate Larvae and Exuviae” Facebook group — for their help in identifying the specimen as a jumping spider, Family Saticidae.

Salticidae is one of several families of spiders with eight (8) eyes. My take-away from reading the reference on BugGuide entitled “Spider Eye Arrangements” is identification of this specimen to the genus and species level is challenging at best and impossible at worst.

In contrast, it’s well known that spiders use odonate exuviae for shelter. I wish the jumping spider had come out of its most excellent hidey-hole sooner!

17 JUN 2021 | PNC. Wm. County, VA | Anax junius exuvia

Related Resources

• Spider Eye Arrangements, by BugGuide. See Family Salticidae.
• Nature Abhors a Vacuum, by Douglas Mills.
• Post update: What is it? [Anax junius exuvia, shown above.]

Tech Tips

The tiny jumping spider was photographed using a Panasonic Lumix FZ-300, Raynox DCR-250 close-up filter, Godox X2To/p flash trigger, and Godox TT685F plus Altura flash modifier. Camera settings: ISO 100 | f/7.1 | 1/60 s | 56.9mm (316mm, 35mm equivalent).

“Raynox DCR-250 close-up filter” is a blog post in which I provide more information about how I use the Raynox with my Panasonic Lumix superzoom bridge cameras.

Copyright © 2022 Walter Sanford. All rights reserved.

Twin-spotted Spiketail (terminal appendages)

Male

All male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”) and a lower unpaired epiproct (“inferior appendage”).

Male members of the Family Cordulegastridae (Spiketails), including male Twin-spotted Spiketail dragonflies (Cordulegaster maculata), have relatively small cerci (terminal appendages) that can be mistaken for female cerci.

07 MAY 2018 | Fairfax County, VA | Twin-spotted Spiketail (male)

Male dragonfly secondary genitalia, called hamules, are located below abdominal segments two and three (S2 and S3), as shown in the following annotated image. Hamules come in a variety of sizes and shapes, but their function is identical for all species of odonates.

07 MAY 2018 | Fairfax County, VA | Twin-spotted Spiketail (male)

Female

As far as I know I have never seen a female Twin-Spotted Spiketail. (I have seen several individuals that I was unable to photograph.) No problem. Mike Boatwright kindly allowed me to annotate a couple of his photographs.

Photo used with written permission from Mike Boatwright.

These individuals are female, as indicated by their rounded hind wings, terminal appendages, and prominent subgenital plate (ovipositor) at the tip of their abdomen.

Photo used with written permission from Mike Boatwright.

Copyright © 2022 Walter Sanford. All rights reserved.

Arrowhead Spiketail (terminal appendages)

Arrowhead Spiketail dragonflies (Cordulegaster obliqua) were spotted along small streams at undisclosed locations in Fairfax County and Prince William County, Virginia USA.

Male and female Arrowhead Spiketails are similar in appearance. They can be differentiated based upon several field marks.

Male

This individual is a male, as indicated by his “indented” hind wings and terminal appendages.

07 JUL 2014 | Fairfax County | Arrowhead Spiketail (male)

Arrowhead male and female cerci are similar in appearance, and it can be challenging to see the epiproct clearly from some viewpoints. When in doubt whether an individual is male or female, look for indentations at the base of the hind wings of males.

07 JUL 2014 | Fairfax County | Arrowhead Spiketail (male)

Female

This individual is a female, as indicated by her rounded hind wings, terminal appendages, and prominent subgenital plate (ovipositor) at the tip of her abdomen.

21 MAY 2019 | PNC. Wm. County | Arrowhead Spiketail (female)

Although Arrowhead male and female cerci are similar in appearance, there is no mistaking the subgenital plate of female spiketails! It’s easy to see why “Spiketails” is the common name for Family Cordulegastridae.

21 MAY 2019 | PNC. Wm. County | Arrowhead Spiketail (female)

So the take-away is simple: If you see a subgenital plate then the individual is definitely female; if not, then it’s probably a male.

Copyright © 2022 Walter Sanford. All rights reserved.