Blue Moon: Bad photo, simple light question

[zigzag]

I took a photo of the lunar eclipse and got a blue moon beside it. This is some

sort of lens flare. Why blue only? Is it refraction, diffraction or something

else? How does it work?<div></div>

[Ed_Ingold]

This is a case of lens flare, due to internal reflection in the lens. It is blue because of the nature of the coatings on the affected surfaces.

 

It is prominent in this image because the image is grossly overexposed.

[zigzag]

Excellent, thanks, I'll ditch the moon on the left and keep the blue one (luckily I have many others).

[mohammed_abidally]

Interesting, I don't understand this phenomenon, maybe someone can explain it.

[mohammed_abidally]

Oh sorry, I did not see Edwards response when I posted...

[kellyphillips]

Did you have a UV filter on your lens? I had something like this happen to me one night because of my UV filter.

[maciek bernatt-reszczyński]

same here - the UV filter on my 70-300 Tamron

[zigzag]

Ah yes, UV filter on 70-200mm f/4L Canon

[jennifer_durand]

This what they call "once n a blue moon?" It's a funky result.

[lester_wareham]

What make and type of filter and lens model Glen?

 

This sort of problem arises when you have extremely bright lights in frame, it can be due to the lens on its own or to the addition of a filter. Top end filters like Hoya SHMC/Pro 1 and B+W MRC are very good and often do not cause a problem even under extreme conditions such as this.

 

The main problem with the above is you seem to have exposed for the part of the moon in eclipse causing the illuminated half to over expose by many stops along. This has the effect of increasing the brightness of the reflection.

 

For information the dynamic range for ghosting of the typical L-Lens without a filter is about 14-18 stops. A top end filter will probably be better than this, however much depends on the combination of filter and lens, lenses with well sunken front elements suffering more from filter induced ghosting.

 

If you exposed correctly for the illuminated half of the moon I suspect you would not see the the reflection.