What is causing this flare?

[Alan]

Take a look at these two shots....


The light near the bottom is a streak in the one shot, and a point, in the other (a point, for the most part, that is).


These were taken with a 5D Mk 2, 70-200 f/4 IS L, @ f/8, ISO 100. Mirror lock up on both shots.


This image was at 1.6 seconds, EV -0.67. Focal length: 89 mm


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3 minutes later, this shot was taken. 2.0 seconds, EV 0.67, focal length 78 mm (same settings as above).


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It was a windy night.


What would cause the light to look like a point source with the longer shutter speed, yet a flare with the shorter?

[wusstigphoto]

My guess is that its not the shutter speed. the bottom (non-light sabre) is at a wider zoom and you can see the main light source withmultiple little flares which I bleieve is normal forcatchin it at the edge of the lens. Since your zoomed in a little bit more in the upper pic, I believe you just caught the very edge of the glass with the tip of the light source and that caused it to trail up the lens a bit... sorta like a fiber optic effect.


Thats my theory and I'm sticking to it until someone comes up with something better[H]

[wusstigphoto]

nice sunset city-scape btw

[Bob]

Alan,


You should NOT get this condition. Have the lens checked out. Ifthe lens isless than 14 months old Canon will fix it free. I own the same lens on a full frame body and have never seen this. Show this photo to Canon tech support.

[Gian Luca]

Did you have any filter on the lens? UV?

[Alan]

The lens is well over 2 years old.


Typically, on these night shots, I leave the filter off. But, it was on for this event. Could that have contributed to it? Usually, what I see when the filter is on, is less sharp point lights, but not this sort of "light sabre" flare.

[Gian Luca]

I always take the filter off if I have a light direct into the lens, as I always noticed more flaire with the filter. The quality of the filter is very important as well

[Gian Luca]

I looked at the image several times, and to me the different flare is due to the different focal lenght + filter. Try to position a light on that part of the lens with and without the filter, and you will have the answer

[Alan]

Gian, I'll run that experiment soon. Thanks.


I use B + W filters.

[Gian Luca]

B+W are excellent filter they should not give problem. On the other end is the lens had some problem you should have it again in the second picture. This should be even worse as the light is directly in the frame.


I think this was just unlucky and due to the angle + space between lens and filter, I also think that this will be very difficult to reproduce.