Gazania rigens [Gazania]

[cazza132]

Casswell, T. (2022) Gazania rigens (L.) Gaertn. (Asteraceae) Gazania. Flowers photographed in ultraviolet, infrared and visible light. Also with multispectral stack. LINK

 

Location:

17 June 2022

Australia

Collected from a street garden adjacent to the beachfront at Coolum

 

Synonyms:

• several -- see Reference

 

Other Common Names:

• Treasure flower

 

Comment:

This species is recognized as a weed in some areas of Australia, however it is widely used for a groundcover in suburban street gardens, median strips, traffic islands, etc in south eastern Queensland due to its hardy nature and prolific flowers in a variety of colours blooming nearly all year round.

Two samples were taken and placed in a water filled vase approx 20 min after collection. Each was imaged using Baader U, Kolari U, Kolari Hot Mirror V2 & a generic 650nm infrared filter. All eight image runs were focus stacked.

An attempt was made to combine infrared (R), visible (G) & UV (B) into a multispectral image (mantis shrimp vision?), which proved difficult due to the dynamic nature of the flower given its circumstances.

 

Reference:

1. Wikipedia (18 June 2022) Gazania rigens. Wikimedia Foundation, San Francisco, CA.

 

Equipment:

• Converted Canon EOS R5
• EL-Nikkor 105/5.6.
• Baader U, Kolari U, Kolari Hot Mirror V2 & a generic 650nm infrared filters

 

Technique:

• UV, visible & infrared colour balanced using a white PTFE sheet with exposure dialled down to avoid any RGB channel clipping.
• Focus stacked using Helicon Focus 8.
• ISO100, f/11 for all shots.
• Multispectral - aligned using PT Gui with manually placed control points

 

Yellowish White Sample:

Visible light, t = 1/100s

 

UV (Baader U), t = 5s

 

UV (Kolari U), t = 5s (some highlight clipping)

 

650nm Infrared, t = 1/80s

 

Multispectral using the Kolari U for UV (blue channel)

 

Yellow Sample:

Visible light, t = 1/80s (slight overexposure)

 

UV (Baader U), t = 8s

 

UV (Kolari U), t = 8s

 

650nm Infrared, t = 1/80s

 

[dancingcat]

too beautiful to be a weed :-)

 

[Andy Perrin]

Lovely! The infrared shows more than usual here. 
 

I surprised myself by liking the Kolari colors more than the Baader’s. 

[cazza132]

2 hours ago, dancingcat said:

too beautiful to be a weed :-)

 

All the weed talk! Damn, I was looking for some good flowers to give to my partner that wasn't just for me to take photos of.  You have given me an excellent idea - thanks! And, wow, the Gazanias do give the unexpected in UV. Loads of variations in vis & UV colour that don't entirely correspond based on other flowers.  There are some amazing examples on this site - especially the bold stripy / striated variants. Btw, you have been posting some nice work.

[cazza132]

2 hours ago, Andy Perrin said:

Lovely! The infrared shows more than usual here. 
 

I surprised myself by liking the Kolari colors more than the Baader’s. 

I agree! I have tested both filters with a 395nm torch and the Kolari is passing about 3EV more. The Baader claims it's max transmission at 350nm. The Kolari is shifted longer (maybe 360nm). A custom WB is required when switching. WB set to Baader U looks blue/purple with the Kolari in front. The analogy to me in infrared is the Kolari is 680nm and the Baader is 720nm. The further to the extremes, the more monochrome the camera sees it and the less effective the colour filter array becomes - it seems.

[Stefano]

I have never seen a UV-white flower with black nectar guides, really beautiful flower.

[cazza132]

1 hour ago, Stefano said:

I have never seen a UV-white flower with black nectar guides, really beautiful flower.

I am as surprised as you are, even given my limited knowledge and other UV flowers seen and imaged (short time). I remember Andrea posting something recently regarding a study of various flower colour pigments (a list of 10 or so) and how they show up under UV. Carotene is one that gives the yellow under vis and UV if my memory is vaguely correct - not working full tilt in this example as there are other yellow pigments that don't work in UV. Might have to try a carrot under sunlight. Might have spent too much time here under ethanol laced beverages tonight - oops. Free time well spent I hope :)

[cazza132]

1 hour ago, Stefano said:

I have never seen a UV-white flower with black nectar guides, really beautiful flower.

White flowers and white cars show up blue most of the time in UV. The persistent white and that bull's eye landing pad on a white flower is normally seen in yellow flowers. Even if they get classified as a weed, there were plenty of bees homing in on these flowers yesterday! Was good to see. Even felt bad about taking the flowers.

[cazza132]

Bee vision - tweaked the multispectral shot. Keep the UV channel as blue, split the visible channel into blue component (green) & green component (red) into two separate layers and associated channel mixers. UV=blue, visible blue = green & visible green = red. No red and no infrared. A solid visual reference if you're an airborne traveller. Those dark markings! Pretty good communication between flora & fauna for symbiosis!

[colinbm]

Excellent & beautiful series cazza132

[Nate]

Very cool comparisons cazza132. The water droplets add so much to the depth.

[Kai]

Excellent work - thanks for sharing!
Especially the stacking makes a big difference :)

[Andrea B.]

Thanks for this lovely contribution to the botanical section!

 

I made a couple of minor edits. The title, for example, has to be formatted a certain way so that the database can be searched to make an Index for the botanical sections. I added the "author" of the plant. The author abbreviations refer to the botanist(s) who first formally identified and named the plant. The header needed a link to this page.