Crazy-bad light flare dusk shots, lens to blame?

microbike

microbike

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Tim
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Hi guys,
Something cropped up tonight at dusk (!) and I thought I'd ask the experts!
I had to shoot a dusk shot of a fire station, and it all went OK, apart from an old problem reared it's head.
When I've shot dusk shots before where you're looking into bright lights from a building or vehicle, I've used my trusty 1.4 Canon 50mm. No problems with light, or flare, ever.
But I was squeezed for space tonight and resorted to using my wide-angle fixed 20mm Canon. Brilliant in the daytime. But proved lousy tonight by making crazy shapes all around the place wherever the light was bouncing - look closely, there's messy light spill, circles, weird shapes. Aaargh!
Q1: What's the reason for this?
Q2: Are there other wide angles that don't do this?
Ta!
http://farm3.static.flickr.com/2445/4092857515_438dc02708_o.jpg
 
Have you got a filter on the lens? if you have try taking it off and taking the shot again. could light bouncing between filter and front element of the lens.
 
Dave, I've only got a basic UV filter on it. Could that be the problem? I'll go and check the make. I'll feel a real twit if that's the issue
 
microbike said:
Dave, I've only got a basic UV filter on it. Could that be the problem? I'll go and check the make. I'll feel a real twit if that's the issue
Click to expand...

I am 99.9% sure that if you take the uv filter off that you will find the problems will go away.
 
Flare is caused by the filter, no question. It will always do that with lights that strong against a dark background. Throw it away :)
 
Absolutely agree...
I use a UV filter for 99% of the time and the shot you describe is the 1% of the time I'd take it off...

Especially on a 20mm lens...
 
ok in the interests of learning - can some one tell me and help me understand what the problem is as I'm not sure I can see it?
the only thing i can see is the way the headlights look with the light forming rays rather than an even glow.
thanks
 
Wide angles, even the best, will be subject to flare simply because of the greater chance of oblique impact of the light.

Extra low dispersion glass can only go so far!

But filters won't help either...
 
funky_snowhead said:
ok in the interests of learning - can some one tell me and help me understand what the problem is as I'm not sure I can see it?
the only thing i can see is the way the headlights look with the light forming rays rather than an even glow.
thanks
Click to expand...

Look in the sky and shadow areas of the building. There are coloured circles - flare caused by the light bouncing around off the filter.
 
Yv said:
the most obvious issue is in the sky funky - look just left of centre, there are several overlapping circles of a redish grey hue [you might have to adjust monitor to see them, depending on how good your screen is and calibration]
Click to expand...

Those are almost certainly internal reflections from the vehicles' headlights... just clone them out - they're in a fairly open area so it's a snip to do...
 
funky_snowhead said:
ok in the interests of learning - can some one tell me and help me understand what the problem is as I'm not sure I can see it?
the only thing i can see is the way the headlights look with the light forming rays rather than an even glow.
thanks
Click to expand...

Problem is as described above.

Cause is mostly reflections off the mirror-like surface of the sensor which are normally reflected straight back out of the lens, but the flat rear surface of the filter reflects them back again and you get a double image. Good thread and examples here http://www.talkphotography.co.uk/forums/showthread.php?t=130960 though some of the best (ie worst :eek: ) images are no longer hosted.

Uncoated filters are pretty horrendous. Single coated filters are much better and multi-coated ones take a bit of provoking, but the effect is always there to an extent. For the same reason, lenses that are 'digitally optimised' have extra coatings on the rear element to prevent this but since their surfaces are curved it's not nearly so bad anyway.

The fundamental problem is two mirror-like surfaces facing eachother. But apart from that there are always reflections bouncing around inside any lens but uncontrolled reflections from an additional glass element stuck on the front is never going to do any good. Apart from the specific double-images you get, there is also veiling glare from all the other reflections going on which appear as a light fog. Usually you can't see it unless it's a cheap filter and you do a direct side-by-side comparison, but it's always there to a certain extent. If you want to see how bad it gets, photograph car headlights straight on, with and without the filter, against a dark background.

People think sharpness is the main problem with filters; it's not. It's flare.
 
HoppyUK said:
Problem is as described above.

Cause is mostly reflections off the mirror-like surface of the sensor which are normally reflected straight back out of the lens, but the flat rear surface of the filter reflects them back again and you get a double image. Good thread and examples here http://www.talkphotography.co.uk/forums/showthread.php?t=130960 though some of the best (ie worst :eek: ) images are no longer hosted.

Uncoated filters are pretty horrendous. Single coated filters are much better and multi-coated ones take a bit of provoking, but the effect is always there to an extent. For the same reason, lenses that are 'digitally optimised' have extra coatings on the rear element to prevent this but since their surfaces are curved it's not nearly so bad anyway.

The fundamental problem is two mirror-like surfaces facing eachother. But apart from that there are always reflections bouncing around inside any lens but uncontrolled reflections from an additional glass element stuck on the front is never going to do any good. Apart from the specific double-images you get, there is also veiling glare from all the other reflections going on which appear as a light fog. Usually you can't see it unless it's a cheap filter and you do a direct side-by-side comparison, but it's always there to a certain extent. If you want to see how bad it gets, photograph car headlights straight on, with and without the filter, against a dark background.

People think sharpness is the main problem with filters; it's not. It's flare.
Click to expand...

Hmmm...I don't think so - I noticed these problems back in the 1970's shooting film...it's far more likely to be light reflecting off the front element of the lens , then onto the inner surface of the filter then back into the camera...
That accounts for the off-centre 'ghosting' - if it were reflected off the sensor then it would be almost on top of the original point-source...
 
Arkady said:
Hmmm...I don't think so - I noticed these problems back in the 1970's shooting film...it's far more likely to be light reflecting off the front element of the lens , then onto the inner surface of the filter then back into the camera...
That accounts for the off-centre 'ghosting' - if it were reflected off the sensor then it would be almost on top of the original point-source...
Click to expand...

Sure, it's flare, one way or another. Sorry if I didn't explain it very well. It does come in various forms, like the internal reflections you're describing (and which seem to be the OP's main problem as you say), then you get veiling glare which is the general loss of contrast when reflections of all sorts bounce around and get scrambled into slight fog, and then there is the digital specific one which creates the mirror images shown on the link. Yes, they are usually quite central depending on the angles involved. If they are off-centre they either bounce back through the side of the lens and hopefully get lost in the baffling or the mirror box, or contribute to veiling glare.

With digital you can quite easily get all three at once.
 
thanks for the replies - I finally spotted the ones in the sky which make me think i may need to adjust my monitor.
the red ones in the building shadows - doh - how didn't I see them!
Funny how unless you're looking for something and/or don't know about it the brain just ignores it as unimportant!!!!
 
funky_snowhead said:
thanks for the replies - I finally spotted the ones in the sky which make me think i may need to adjust my monitor.
the red ones in the building shadows - doh - how didn't I see them!
Funny how unless you're looking for something and/or don't know about it the brain just ignores it as unimportant!!!!
Click to expand...

Most flare you notice because it moves around in the viewdinder while you're framing up.

The digital-specific flare, because it originates off the sensor, you cannot see in the viewinder. I think you might have struggled to notice some of those small spots on the LCD image, particularly if you're not looking for them.
 
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