On the Subject of Skimmers and Light ...

[Arthur Morris]

Black Skimmer, adult lit by the last rays of the setting sun

This image was created on August 13, 2015 at Nickerson Beach, Long Island, NY with the Induro GIT 304L/Mongoose M3.6-mounted Canon EF 600mm f/4L IS II USM lens, the Canon Extender EF 2X III, and the EOS 7D Mark II (now replaced for me by the Canon EOS 5D Mark IV.) ISO 800. Evaluative metering +1/3 stop: 1/250 sec. at f/9 in Manual mode. AWB at 7:39pm on a clear afternoon.

In the Red Light, Blue Sand ... blog post here, I wrote:


Red Eye Without Flash!

If you look closely you can see some red eye in the skimmer’s eye, similar to what you sometimes get with flash. Red eye results when light bounces off the retina. If you can explain how you can get natural red eye when you are not using flash please leave a comment.

Los of folks have tried to answer the question but so far all have been unsuccessful.

As for the image, don't be shy; all comments are welcome.

with love, artie

[annmpacheco]

no Visine, smoking medical marijuana, or: not all of the light is absorbed; some is reflected back to the camera lens. The light reflects the blood supply behind the pupil... ? "A for effort!"

[Randy Stout]

Artie:

I like the warm light, pop of the orange, crop.

The red reflex all depends on the direction of the light entering the pupil, its reflecting off the retina and the viewer being in line with that reflection. So the low angle of the sun, your low shooting position aligned perfectly. Same principal that gives "red eye " from on camera flash, the angle of the incident light is close enough to viewing angle that you see that reflection. When you put a flash off axis from the camera lens, the reflected light angles away from the lens, hence no "red eye".

Randy

[Arthur Morris]

no Visine, smoking medical marijuana, or: not all of the light is absorbed; some is reflected back to the camera lens. The light reflects the blood supply behind the pupil... ? "A for effort!"

A for effort but that is about it ... Someone on the blog finally nailed it.

with love, artie

[Arthur Morris]

Artie:

I like the warm light, pop of the orange, crop.

The red reflex all depends on the direction of the light entering the pupil, its reflecting off the retina and the viewer being in line with that reflection. So the low angle of the sun, your low shooting position aligned perfectly. Same principal that gives "red eye " from on camera flash, the angle of the incident light is close enough to viewing angle that you see that reflection. When you put a flash off axis from the camera lens, the reflected light angles away from the lens, hence no "red eye".

Randy

Correct-o-mundo.

with love, artie

ps: is this correct?: in low light, the pupil opens wider making red eye more likely.

[Randy Stout]

Artie:

Absolutely true, that when the pupil is larger (low light) that more light enters the eye, and the alignment of light and viewer angles isn't quite as critical. Obviously if the light is too low, the red reflex won't be as bright, so it is a balance of light intensity, pupil diameter and alignment of light source and viewing angle.

Randy