Light Diffusion Issue With My Fuji X-T2 Camera

Christmas Parade; heavily overcast day (click to enlarge)
Notice the flare not only around blue LED lights but significantly out from the area of the lights.
X-T2, 16-55mm f/2.8 lens @ 41.4mm; 1/250th sec. @ f/8; ISO 800

Thanks for coming back and visiting this blog.  I think 2017 will be an exciting photographic year for us.

As I mentioned on Monday, here is second issue I recently discovered with my X-T2.  This has never appeared before in any of my images but only appeared in a few under this particular circumstance.  See the blue color spread way out around the lights on the officers' motorcycles?  It is very apparent.

It appears to be lens flare but I don't think it is.  I don't see the same wide diffusion and light spread in the red LED lights as I do in the blue.  So, there is something different going on here.  I've been photographing for 46 years under most all conditions, directly and indirectly into light sources and this just doesn't seem to be the typical appearance of lens flare.  So what is it?

Flare and ghosting typically occurs when pointing a lens at bright or direct light sources inside or positioned just outside the camera's frame as seen in the viewfinder.  One of the reasons we use lens hoods.

Lens flare is apparent in two ways, as artifact, usually some sort of polygonal shape (normally all or part of the shape of the lens aperture shape), rings, circles or lines as well as a non-specific haze which reduces contrast and color saturation.  We've all seen it.

Usually changing camera position can reduce or eliminate flare.  Moving the camera slightly up, down, left or right can move the position of the light source responsible and reduce or eliminate lens flare.  What a photographer typically does, if possible, is take a step of two left or right to change the angle of the light source to the camera lens.

I expect flare from direct light, but I never had had flare that bled so far out and around the light source.  Below is a crop showing the flared areas with much of the white motorcycle farings/windscreens showing as blue.  There are some other areas as well.

In this example, the positions of the motorcycles changed with every exposure.  The motorcycles were moving obliquely toward me and the handlebars of the bikes were moving left and right as the riders rode very slowly in the parade.  But the anomaly persisted.  

What do I think it is?  I think these are reflections from sensor back onto the rear lens element and back to the sensor  It does not appear to be typical lens flare to me.

See circled areas and arrows showing excessive flare (click to enlarge)

I think there are three reasons this occurred.  First, I believe part of the reason was that the air was very moist and humid.  Not only humid but cold and moist.  You can see a bit of fogginess and haze in the background down the street.  Just below is the OOC RAW image without any increase in contrast, clarity, etc.  Atmospheric humidity can certainly affect image formation.  The excessive moisture in the air can easily diffuse light and make it appear to spread beyond the source.

This is what the original RAW image looked like as far as haze, low
contrast and atmospheric fogginess before I edited it (click to enlarge)

Second, the LED lights on the motorcycles are extremely bright.  If you remember in the past, especially in the blue halogen light days for emergency responders, the blue was almost not visible during daylight. When I was a chief of police and we changed the setup of our light bars on the tops of our patrol cars, we kept the red with the blue as the blue was not very visible during daylight hours.  Blue only became very visible during the day when LED lights were adopted.  These LED lights are much brighter than normal lights.

Third, as I previously mentioned, I think this is the manifestation of reflection of the intense and direct blue LED lights through the lens, hitting and reflecting off the surface of the sensor, reflected back to the rear lens element and then back onto the sensor, spreading out as non-image forming scattered light in a wide area around the light sources.

Am I worried about this?  No.  This occurred in very specific circumstances and would probably happen with most, if not all, digital cameras.

Now, after all of this, am I sure?  No.  But this is my best educated guess as to what I found.  If you see it in your images, you might have a better idea as to what you are seeing.

If you have other ideas, please leave a comment and share with all readers.

Thanks for looking. Enjoy! 

Dennis A. Mook 

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