# Lens flare...and lens inter-reflections



## EyeDontKnow (Apr 7, 2014)

Can someone please explain the reflections between lens elements......and how they end up in our photographs ?

...Why are some sharply rendered, and why are some blurred.
Is it distance from the focal point ?


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## Jack Henry (Apr 8, 2014)

I think the number of flares is equal to the number of leaves in the cameras iris. For example an iris that has 9 leaves will give you a flare that has 9 'rays'.


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## EyeDontKnow (Apr 8, 2014)

Jack Henry said:


> I think the number of flares is equal to the number of leaves in the cameras iris. For example an iris that has 9 leaves will give you a flare that has 9 'rays'.



I'm referring to inter-lens reflections (though lens/camera iris is at play).
Like when you shoot the sun, or a pinpoint light.
The pin light bounces around the lens insides.

Maybe "flare" and "rays" are not applicable here. 
....the stray dots found with a pinpoint light.....


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## EyeDontKnow (Apr 8, 2014)

I just want to make sure I understand this.
Is this a fair graphic ?






(I understand the "camera sensor" is not where I pointed.....I pointed to the focal apex.....the sensor is beyond that.)
This a rough graphic.


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## siloxr (Apr 17, 2014)

It's just a matter of transmission versus reflection (with some refraction thrown in for good measure). 
http://photographylife.com/what-is-ghosting-and-flare  <---this is a pretty good/clear explanation of what's going on, but the high level version is this:  There is no such thing as a lens that will perfectly transmit (allow to pass through) all light that hits it.  Some of it will hit a given element at just the right angle for it to reflect or be refracted (the changing of the angle because of passing through different media such as air versus the glass of the lens) through one element to the precise angle needed to reflect in the next or some combination thereof.  Of these, some will merely pass back out of the camera, but others will bounce around some.  Of those that bounce around, some will make it back to the sensor and be recorded as a flare.  The more elements in your lens and with filters you have, the greater your "risk" (quotations because in some cases you might want lens flare) of getting lens flare (like if you throw on a GND filter, a UV filter, and a polarizing filter onto a 13 element lens with an extender, you're going to have to deal with MUCH more flare than shooting through a 5 element prime).  This is one of the reasons that some people recommend not keeping a UV filter on all of the time to protect your objective lens.


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