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Offline Rounder

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Re: Solar Eclipse
« Reply #40 on: September 04, 2017, 05:49:28 PM »
You're thinking about the TOTAL energy entering the eye - and I'm talking about the energy hitting each tiny photo-sensitive cell on the retina.

That's a really good point, I hadn't thought of it that way. 

I guess Pete was right and I was wrong, and it actually is more dangerous during the eclipse than not.

This is why I keep coming here, occasionally I'll learn something new!
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Offline 3DGeek

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    • What path do the photons take from the physical location of the sun to my eye at sunset
Re: Solar Eclipse
« Reply #41 on: September 05, 2017, 02:15:40 PM »
You're thinking about the TOTAL energy entering the eye - and I'm talking about the energy hitting each tiny photo-sensitive cell on the retina.

That's a really good point, I hadn't thought of it that way. 

I guess Pete was right and I was wrong, and it actually is more dangerous during the eclipse than not.

This is why I keep coming here, occasionally I'll learn something new!

No problem, it's a very subtle point - and easily misunderstood.  We get used to being able to quickly GLANCE at the sun for a couple of seconds without much more than an after-image that lasts for ~30 seconds - but during the eclipse, that instinct is derailed.   Even a couple of seconds is too long with the iris full-open.  Far *FAR* too many people have either temporary or permanent damage to their eyes as a result.  I've been looking to see if there are any statistical estimates for how many victims there were.   Pre-eclipse estimates ranged from "hundreds" to "at least a million" - but those were wild-assed guesses.   The only kind of post-eclipse data is the spike in Tweets and Google searches for phrases like "My eyes hurt"...but no solid numbers yet.

We know that most people who suffered are reporting a ring of fuzziness.  We know that the human eye 'saccades' (jiggles around a bit) in order to improve spatial resolution to greater than the density of the "pixels" in the retina.  This is a clever trick of the eye/brain that NASA uses (or doesn't if you're an FE'er) to improve image quality from space probes and rovers.

What that does is to spread the damage to the retina over several adjacent cells - to varying degrees depending on how intently the person focussed on the image.   That explains why the damage is "fuzzy" instead of a sharp ring of damaged vision.

People who have an entire circle of damaged vision rather than a hollow ring probably looked into the sun long before or after totality...which is much worse and combines iris-open and iris-closed damage.

My job (and my passion) is photo-realistic real-time 3D computer graphics - which has turned me into something of a student of human vision and how light propagates.  I've worked in both computer games and professional flight simulation - where realism is demanded by our customers.

When simulating bright and dark scenes in 3D computer graphics, there isn't enough light coming from the computer screen to provoke an iris response - and the ambient room lighting prevents the iris from opening fully during dark scenes.   So to make things look realistic in 3D graphics, you have to SIMULATE what the iris does and artificially brighten dark scenes and dim down bright scenes.   Hence I've studied how the pupil responds to light changes.
Hey Tom:  What path do the photons take from the physical location of the sun to my eye at sunset?