Archive for the ‘Photoshop’ Category

Jumping spider

March 15, 2022

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

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)

January 25, 2022

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)

January 21, 2022

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.

Proof of concept, revisited

December 10, 2021

In this blog post I’m going to show you how I used Photopea to annotate one of my photos. The workflow using Photopea is virtually identical to the way I annotate photos using Adobe Photoshop.

The original photo was edited using Apple Aperture (a discontinued photo editor) and Photoshop (for spot removal and sharpening). I could have attempted to edit the photo using Photopea but that wasn’t the point of my “Proof of concept” blog post.

Finished project

The first screen capture shows the finished project — I used it to reverse-engineer the steps that I took to create the annotated image and the settings I made along the way.

The “Layers” panel (located in the right sidebar) shows the finished project is compromised of seven layers, listed from bottom to top in the order they were created.

The “Background” layer is the photo itself. Go to File / Open… and navigate your computer to find a photo you would like to annotate.

View / Rulers

Before proceeding, it’s helpful to turn on “Rulers.” More about that later. In the Photopea menu bar, go to View and check Rulers.

Tech Tips: command-R (macOS) is a keyboard shortcut that can be used to toggle Rulers on/off.

The “View” menu also includes “Zoom In” and “Zoom Out” plus the associated keyboard shortcuts.

Press and hold the spacebar. Notice the arrow-shaped cursor turns into a hand that can be used to drag the canvas around the work space.

Post Update: View / Screen Mode > Fullscreen will scale up the Photopea window to fit the size of your computer screen. Fullscreen mode makes it much easier to work on fine details, especially when used in combination with the “Zoom Tool” and “Hand Tool”; the icon for both tools appears in the lower part of the left sidebar. Try it — you’ll like it! Uncheck “Fullscreen” in order to return to the desktop view. By the way, did you notice I added another guide line and Text layer for a follow-up blog post?

Text Tool settings: Title

The title is the first layer I added using the following selections: IBM Plex Sans (font type); SemiBold (font style); Size = 150 px; Color = Black; and “Aa” = Sharp.

Tech Tips: Text size is measured in pixels, not points. I’m not sure Photopea is calibrated correctly to convert points to pixels. Test it yourself using one of many online points-to-pixels calculators such as PT to PX Converter.

No matter, click the down arrow beside text “Size” and simply use the slider to select a text size that you like. You can also highlight the pixel size and type the exact number you prefer.

To begin adding text to your project, select the “Text Tool” (located in the left sidebar), click an insertion point on the photo and start typing. The default name for the new layer is “Text layer 1, 2, 3, etc.”

When you are finished, either delete the layer by clicking the “Cancel” button (X icon located near the right end of the Photopea menu bar) or save changes made to the layer by clicking the “Confirm” button (checkmark icon located to the right of the X) and the layer name changes so it is the same as the text you typed. In this case, I shortened the name of the layer to “Comet Darner dragonfly.”

With the layer selected, click on the “Move Tool” (left sidebar, at the top) and click-and-drag the text to reposition it exactly where you like.

Text Tool settings: Labels

Next I added a layer for “eye (1 of 2),” one of several labels for parts of the anatomy, using the following selections: IBM Plex Sans (font type); Regular (font style); Size = 100 px; Color = Black; and “Aa” = Sharp.

Tech Tips: The “Sharp” setting is used to avoid text with “jaggies,” that is text with saw tooth edges.

As an aid for aligning text, I created a blue guide line by clicking on the ruler along the top of the screen and dragging down to position the guide line on the photo. The guide line can be repositioned using the “Move Tool.”

Line Tool settings

The next layer I added is an arrow that points from the label to the anatomical part, in this case an eye. The settings I used for “Arrow 1” are shown in the following screen capture.

Tech Tips: Add a new vertical guide line for Arrow 1 by clicking on the ruler along the left side of the screen and dragging to the right to position the guide line on the photo. Right-click on the “Rectangle Tool” and select the “Line Tool.” I used shift-click-and-drag to draw a straight arrow that is aligned with the new blue guide line.

Add more layers

I followed the same steps described above to add a Text layer for “wing pads,” a new guide line for Arrow 2 and an arrow that points from the label to the anatomical part, and another Text layer for “prementum.”

Saving / Exporting

I saved the final image as a Photoshop document by selecting File / Save as PSD. The resulting PSD file can be reopened in Photopea in order to continue working on the project. Post Update: .psd files created by Photopea can be opened in Adobe Photoshop, although it is likely the font(s) you chose to use in Photopea are not available in Photoshop. Photoshop will prompt the user to resolve the problem.

I also saved the file as a PNG by selecting File / Export as.

What are the take-aways?

Open Photopea in a Web browser: www.photopea.com (For what it’s worth, I prefer “Google Chrome.”) Since Photopea is Web-based, it runs on desktop computers, laptop computers, tablets, and smart phones. Having said that, I think it would be challenging to annotate a photo with a tablet or phone unless those devices are used in combination with an external keyboard and mouse. Not impossible, but definitely challenging.

My dear friend Phil Wherry passed away too long ago. Phil was my tech guru for many years. I’m the type of person who suffers from “approach avoidance” — I like to know what will happen BEFORE I do something. One of the best bits of tech advice Phil shared with me is “Don’t be afraid to experiment and see what happens.” That’s exactly what I did when I used Photopea to annotate one of my photos and I encourage you to do likewise. Good luck!

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Proof of concept

December 7, 2021

Can Photopea be used to annotate photographs? Yes!

Do the results look as good as photos of the same subject that were annotated using Adobe Photoshop? You be the judge.

Comet Darner (Anax longipes) | exuvia (lateral)

In my opinion the results are of comparable quality and that’s saying a lot considering this is my first attempt at using Photopea to annotate a photo.

As expected, the workflow flowed slowly since this was the first time I used many of the tools featured in Photopea.

I saved the final image as a Photoshop document by selecting File / Save as PSD. The resulting PSD file can be reopened in Photopea in order to continue working on the project. I also saved the file as a PNG by selecting File / Export as.

The Backstory

The preceding photo shows an exuvia from a Comet Darner dragonfly (Anax longipes) that was collected by Stanley Caveney on 19 July 2021 from a pond at MeadowWoods in West Elgin, Ontario, Canada. Sincere thanks to Stan for kindly sharing this beautiful specimen!

Related Resource: Learn Photopea

Copyright © 2021 Walter Sanford. All rights reserved.

Dark and moody

November 19, 2021

I spotted an emergent Uhler’s Sundragon (Helocordulia uhleri) during a photowalk along a mid-size stream at an undisclosed location in Prince William County, Virginia USA. The following photograph shows the exuvia from which the teneral adult emerged.

13 APR 2021 | PNC. Wm. County, VA | Uhler’s Sundragon | exuvia (ventral)

In the opinion of the author, larvae (nymphs)/exuviae from Family Corduliidae (Emeralds) and Family Libellulidae (Skimmers) can be challenging to differentiate and identify to the family level.

One way to differentiate Emerald from Skimmer larvae/exuvia is to look for a “ventromedial groove” in the prementum: it’s probably Corduliidae (Emeralds) if there is a ventromedial groove; it’s probably Libellulidae if there isn’t.

Look closely at a version of the preceding photo that was reformatted, rotated, and cropped to show an enlarged view of the prementum. You should notice a ventromedial groove on the basal half of the prementum, indicating this specimen is a member of Family Corduliidae (Emeralds).

13 APR 2021 | PNC. Wm. County, VA | Uhler’s Sundragon | exuvia (ventral)

Three raised structures on the underside of the prementum remind me of the hood ornament on a 1949 Lincoln automobile. (No, I wasn’t alive in 1949!)

Related Resources

Tech Tips

One reason I underexposed the photo is to add definition to the ventromedial groove and avoid overexposing the black background.

I prefer a white background for photographing odonate exuviae. Using a black background proved to be more challenging than I expected. More later in a follow-up blog post.

Copyright © 2021 Walter Sanford. All rights reserved.

How to estimate instar, revisited

November 16, 2021

I’m the founder and co-administrator of the Odonate Larvae and Exuviae Facebook group. Friday, 12 November 2021 was the two-year anniversary of the group. As of this writing there are approximately 1,700 members in the group, including people from around the world.

For example, Abiodun Matthew Adedapo from Nigeria. Abiodun began posting to the group relatively recently, sharing information and photos related to his research. Sincere thanks to Abiodun for permission to repurpose two of his photos for another mini-lesson on how to estimate instar.

What is the instar? Not F-0.

The equation for instar equivalent is as follows.

Instar equivalent = HwL / HW

Where HwL is Hind wing Length and HW is Head Width.

 

Photo used with written permission from Abiodun Matthew Adedapo.

I used the Adobe Photoshop “Ruler Tool” to measure the number of pixels along the two double-tipped white arrows shown in the preceding annotated image of a preserved specimen collected and photographed by Abiodun.

HwL is ~132.6 pixels. HW is ~195.12 pixels.

Instar equivalent = 132.6 pixels / 195.12 pixels

The units cancel, so the answer is ~0.68 — close to Ken Tennessen’s  average value for F-1 (final instar minus one).

Abiodun reported the instar as F-2, based upon in situ observations of a cohort of larvae (nymphs) from Family Gomphidae (Clubtails).

For my purpose, it doesn’t matter whether the actual instar is either F-1 or F-2 — the important take-away is we know the instar is not F-0, the final instar. This provides an opportunity to mention a simpler way to estimate final instar.

Larvae in the final stage can be recognized by the length of the wing buds which cover the fourth abdominal segment. Source Credit: Field Guide to the larvae and exuviae of British Dragonflies, by Steve Cham, p. 30.

Look closely at the first annotated image. Notice the length of the wing buds/pads doesn’t reach the fourth abdominal segment (S4) of the specimen therefore this larva is not in its final instar.

Thanks to Freda van den Broek for sharing this method with me!

F-0 (final instar)

The last annotated image shows part of a different larva also collected and photographed by Abiodun. Notice the length of the wing buds/pads does reach S4, therefore this larva is in its final instar.

Photo used with written permission from Abiodun Matthew Adedapo.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Mouth parts – Tiger Spiketail exuvia

November 12, 2021

I revisited a photograph featured in a blog post published several years ago. I wanted to annotate the image to include information that I learned recently.

The following annotated image shows the face and mouth of an exuvia from a Tiger Spiketail dragonfly (Cordulegaster erronea) after its scoop-shaped face mask was pulled away from the head in order to count setae on the inner side of the prementum.

Cordulegaster erronea | exuvia (face and mouth)

There are two mandibles, one located on each side of the labrum. And there are two maxilla, one located below each mandible. Coarse setae make it challenging to see all of the parts clearly.

Sincere thanks to Marla Garrison for verifying my tentative identification of these mouth parts. And of course, thanks to Mike Boatwright for collecting and sharing the specimen with me.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Post update: What is it — emerald or skimmer?

November 5, 2021

An exuvia from a Stygian Shadowdragon dragonfly (Neurocordulia yamaskanensis) was collected by Freda van den Broek on 10 June 2019 along the St. Croix River in Interstate Park, Polk County, Wisconsin USA.

The presence of a ventromedial groove in the prementum suggests this specimen is a member of Family Corduliidae (Emeralds) and in fact it is.

Congratulations to Douglas Mills, who correctly identified the family of this specimen.

Going with corduliidae for the groove. It’s got impressive crenulations — I had to double check they weren’t jagged and this was a trick question 🙂 Source Credit: Douglas Mills.

Douglas successfully avoided the trap that was set when I chose to use a specimen that features deeply-scalloped crenulations along the margins of the palpal lobes. According to Kevin Hemeon, member of the “Odonate Larvae and Exuviae” Facebook group, crenulations like these are a characteristic field mark for Genus Neurocordulia (Shadowdragons) in the Family Corduliidae (Emeralds).

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

What is it — emerald or skimmer?

November 2, 2021

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

I wrote about the “ventromedial groove” in a recent blog post. Based upon what you learned, is the following odonate exuvia a member of Family Corduliidae (Emeralds) or Family Libellulidae (Skimmers)?

Odonata (Suborder Anisoptera) | exuvia (face-head)

If you think you know the family, then please leave a comment. The answer will be revealed in a post update.

Copyright © 2021 Walter Sanford. All rights reserved.


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