Light spots during night shots

[Justin Hancock]

See the attached picture for an example. This was the first time out with my Canon Rebel XT (w/ kit lens, 18-55mm). As you can see, the lights down the pathway seem to be casting another set of lights on the lens. How can I remove this effect?

Manual Exposure, 1/30sec, 5.6aperture, 49mm, WB auto, ISO 1600.

Come to think of it, could it be the ISO setting being so high?

[jacks]

This has nothing to do with ISO. That produces noise all over the image. Light from one of the lamps is bouncing around inside your lens. Each time some light goes through and makes a faint image, and the rest is reflected inside the lens and back again where it makes another, slightly fainter image and so on. It might not even be one of the lamps in the picture doing this, in which case a lens hood would fix it. If it is one in the picture then try slightly different angles or focal lengths and see if that stops it.

[rey]

I'ts not the ISO. The light spot's pattern looks like a 180 degree reflection of the street lights. Notice how it curves at it fades just like the street lights curve as it fades. Did you have a filter when you shot this? A UV or a clear filter? That could be it.

[Justin Hancock]

Yeah, I had a UV filter on it. So many things to learn from. Is it smart to take off the UV filter when shooting at night? The main purpose for me of having a UV filter on is for protection.

[rey]

As soon I saw it I suspected filter flare, mainly because the spots are in 180-degree off the center of the image. I know I've responded to your filter posts before, but this is one of argument against using a UV filter as a protection for your lens.

Check this out for info about filter flare:

http://www.luminous-landscape.com/co...m-feb-05.shtml

[E.T]

Here's test how different filters cause lens flares

http://www.teknofokus.fi/Foto/suokoe.htm
1: without filter
2: uncoated filter, also shape of flare tells general quality of filter is lousy.
3: multicoated filter, now in this case thickness of filter glass isn't even which caused doubling of flare.
4: multicoated optically good filter

Last four photos show scene photographed with similar setup.

Now I don't know how best multicoated filters work, but if lens (/its elements) can be coated in such way that it itself doesn't cause flares there shouldn't be anything preventing best multilayer coated filters from being equal.

[Jozo]

That kind of things happen with protective lens. Luckily not often.


Here´s a link to Sunday morning photographer´s informative article of protective lenses.

http://www.steves-digicams.com/smp/02062005.html



But I don´t give up my UV-lens... Every choise you make is a compromise: Picture quality - protection etc.


Quality of the lens is not the only thing that affects to flaring. The distance between protective and camera lens is a factor too.

[rjseeney]

This is one of the reasons I don't recommend using protection filters. In reality, they serve no purpose but to add extra income to the filter makers. They add nothing to the image except issues such as flare and softness. In terms of protection, if you bang a filter hard enough to break it, the lens you are protecting will likely suffer serious enough scratches from the broken glass to render it useless anyway. Minor surface scratches have little to no impact on image quality (certainly less than adding a filter). Unless you are in a sandy, windy environment, pass on the protection filters.

[dashboardgyno]

When talking about when to use filters etc, do you think that having a polorizing filter on indoors using flash would cause some ill effects? I did this a long time ago, and forgot that I left the filter on from earlier in the day when I was shooting some cars. When I went ot the hospital to see my new niece.....the pictures were terrible, and I had a terrible time focusing on things close up like the birth card... (if I can find pictures I will post them) but that is what I blamed it on. Am I close?

[rjseeney]

Polarizing filters cause about a two stop loss of light, which make them unsuitable for indoor use. They really don't serve a purpose indoors..they are most useful for reducing reflections and deepening blues and greens.