Monochrome Yellowjacket @~ 1.1X Laowa 65mm

[JohnDownie]

Taken outside, using sunlight.

Dusty, long-dead subject.

Fuji X-T2, ooc jpegs.

I used a Hejnar digital micrometer rail, which was very quick to use.

Pretty happy, overall.

What causes the corona discharge?

[rjlittlefield]

What causes the corona discharge?

I assume you're referring to the bright streak extending from abdomen to hind leg, at lower left.

That looks like what happens when undiffused light from a small source, like direct sunlight, does a specular reflection off a shiny surface and then gets focus stacked. Out-of-focus versions of the specular reflection often appear as streaks which are still sharp even though streaked out at various angles, and then the focus stacking process aggregates the streaks to produce patterns that look like what you have.

Check your source images to be sure.

All that said, I'm bothered by the fact that this pattern only appears at one place in the image. Normally I'd expect to see similar patterns from other shiny spots on hair and cuticle. I wonder what's special about that one spot. Please let us know what you find in the individual source images.

Hejnar digital micrometer rail

This product was new to me. I finally found it on the Hejnar site as "8" Screw Adjusting Macro Rail with Digital Scale", http://www.hejnarphotostore.com/product-p/ms5dsp.htm . It's described as "Lead screw delivers 1.06 mm of travel per full revolution but digital scale let you adjust positioning with 0.001 inch (0.025 mm) increments". That seems oddly low resolution, about 8.6 degrees of rotation per increment on the digital readout. Am I reading things correctly?

--Rik

[Wayne]

Dusty, long-dead subjects are the best --- like most works of art, I find mine floating dead in swimming pools.

[JohnDownie]

What causes the corona discharge?

I assume you're referring to the bright streak extending from abdomen to hind leg, at lower left.

That looks like what happens when undiffused light from a small source, like direct sunlight, does a specular reflection off a shiny surface and then gets focus stacked. Out-of-focus versions of the specular reflection often appear as streaks which are still sharp even though streaked out at various angles, and then the focus stacking process aggregates the streaks to produce patterns that look like what you have.

Check your source images to be sure.

All that said, I'm bothered by the fact that this pattern only appears at one place in the image. Normally I'd expect to see similar patterns from other shiny spots on hair and cuticle. I wonder what's special about that one spot. Please let us know what you find in the individual source images.

Hejnar digital micrometer rail

This product was new to me. I finally found it on the Hejnar site as "8" Screw Adjusting Macro Rail with Digital Scale", http://www.hejnarphotostore.com/product-p/ms5dsp.htm . It's described as "Lead screw delivers 1.06 mm of travel per full revolution but digital scale let you adjust positioning with 0.001 inch (0.025 mm) increments". That seems oddly low resolution, about 8.6 degrees of rotation per increment on the digital readout. Am I reading things correctly?

--Rik

Thanks, Rik, I will check the images later on.

On the inch setting, the readout is @ 0.001, with an additional digit that is either blank or 5 (0.001, 0.0015, 0.002, etc.), suggesting 4.3 degrees per increment.

In mm, 0.01mm resolution = 3.4 degrees.

I can turn it slow enough to get these resolutions, less whatever the inherent error is.

Mr. Hejnar may be being conservative about the confidence window?

[rjlittlefield]

On the inch setting, the readout is @ 0.001, with an additional digit that is either blank or 5 (0.001, 0.0015, 0.002, etc.), suggesting 4.3 degrees per increment.

In mm, 0.01mm resolution = 3.4 degrees.

Excellent, that sounds much better.

Mr. Hejnar may be being conservative about the confidence window?

Could be any of several reasons. I've written to let him know that we noticed.

--Rik

[tahder8]

Scale can read 0.01mm increments ( 0.01 0.02 0.03) mm or 0.0005 inch with increments 0.0005 inch ( last digit can be 0 or 5 ) so 0.001 - 0.0015 - 0.002 - 0.0025 etc
There is another macro available with 0.01mm scale and need 2 rotation of screw for 1mm travel
http://www.hejnarphotostore.com/product-p/ms4-1.htm

[rjlittlefield]

To clarify, "tahder8" is Chris Hejnar himself, posting here under a quite anonymous username as required by some other forums.

(It turns out that photomacrography.net is actually less restrictive than some other places. Who would have thought it?! )

--Rik