Subject: Re: Is there an easy way to stop this light scatter ghosting in allmy photos & videos of engine valves?
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From: PeterN <"peter,newdelete">
Subject: Re: Is there an easy way to stop this light scatter ghosting in all
my photos & videos of engine valves?
Date: Fri, 15 Dec 2017 23:14:41 -0500
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On 12/15/2017 1:18 AM, Arthur Wood wrote:
> PeterN wrote:
>>   I think that your answer is a good response to a real problem.
>> Some here may have encountered it and you provided an answer that would
>> help them.
> I see the solution is a "diffuser" but what's the "problem".
> What I mean by that is why does the light look like it's raining?
> For whatever reason, it's like "sleet" at a 45 degree angle.
> Where is all that "sleet" of light coming from?
> And why always a 45-degree angle?
> I assumed that some "physics" principle is being invoked.
> No matter how I held the camera, I still got a 45-degree "sleet" of light.
> Take this one example from far away:
> Compared with this at 90 degrees:
> Compared with this at a closeup:
> All have this "sleet" of light at the same angle.
> Why the 45-degree "sleet" angle in /all/ the photos?
> I realize the /solution/ is a diffuser but what's the physics problem?
> Is there a physics principle that causes the always 45 degree sleet?

The Duck gave you a pretty good practical resolution. To e e it looks 
like a point source lighting problem. u.e. your lens resolving power is 
insufficient. Diffusion breaks up the point source lightning,

IOW Mathematically an object may be considered a point source if its 
angular size, is much smaller than the resolving power of the lens:
Ether  diffusion, or a lens with higher resolving power should solve 
your problem