What causes these phantom lights?

[overseasJJ]

When I use my Canon EF50mm f/1.8 II lens in the situation below I get the phantom lights seen off to the right. When I switched to my EF28mm f/1.8 they go away. So, are the phantom lights a feature of the 50mm lens? What causes it?



Thanks.

[autofocus]

Dirt on your lens, or filter
Try cleaning your lens, and also try shooting with your filter off the lens. These might be reflections off the filter

[sk66]

I think it's a form of "ghosting". If you have a filter on the 50mm take it off, and/or stop down a bit and see if it goes away.

[Digidave]

If you are using a UV filter, that is what's causing this. The lens will pick up on the reflection of the lights on the filter. Even if you are using the filter on both lenses, the difference in focal length may be why you see it on one lens & not the other.

[Doug Sundseth]

As noted, it's ghosting. (You can see the shape of the tree in the reflections, so it's unlikely to be dust.)

This is sometimes exacerbated by filters, especially cheap, uncoated filters, but it can be the result of any sort of internal reflection in the lens, and it can happen whether or not you have filters.

I would start by removing filters, then reduce exposure so the tree lights aren't blooming so much, then, if necessary, add light to bring up the exposure of anything the previous changes have left underexposed.

[ErikUngerPhotography]

I can almost without a doubt tell you it is the filter. I borrowed a friends 50 f/1.4 that had a cheap, and extremely dirty UV filter on it, and discovered many of my photos with extreme back light were ruined because of this same problem. I had used a 50 F/1.4 before with no filter and didn't have any problem.

Everyone feels differently, but I prefer going no filter and instead relying on the lens hood to protect my lens. The only time I may put a filter on is if I am in a very dry and dusty area with strong wind.

[ceremus]

Yeah, I use B&W multicoat filters so it's usually not an issue, but especially when shooting directly into lights in a dark scene such as shooting fireworks or a scene like this, I'll remove the filter. Otherwise I'll get flaring like that.

[ErikUngerPhotography]

Honestly, just keep one of those little air blowers on you at all times, and there is absolutely no need for a filter... unless it serves a purpose like ND. Or if you are in a very windy desert. Those are the only times I ever condone a filter.

[Doug Pardee]

To pile on: it's your filter. This is why you shouldn't use a filter unless it's needed, and when you do use a filter, use a quality filter.

Here's what happens. When the shutter is open, the light coming through the lens hits the sensor. That's what you want, right? But the front of the sensor is somewhat shiny, so some of the light gets reflected back out through the lens. In a perfect world, it just goes out the front of the lens and fades away. But if you have a flat reflective surface on there — like a cheap filter, for example — the light gets re-reflected back through the lens to the sensor. It ends up at a point exactly 180 degrees from the "real" light.

Because the problem only occurs when the sensor is exposed, you can't see it through the viewfinder.

Good filters are multi-coated to try to make them as non-reflective as possible. Most people have very little trouble with multi-coated filters. It's the inexpensive uncoated filters that cause the most grief. But the best solution is no filter at all.

[By the way, almost all affordable lenses have a front element that is flat on the back side, so a ghost could come from there. However, the lens manufacturers understand this situation and usually make sure that surface is really well-coated.]

[overseasJJ]

Thanks for all the replies, especially the explanation about the reflection from the sensor to the filter and back to the sensor again. Interesting. I removed the filter and tried again. The bright green reflections are gone now, but I still have some of the smearing blue spots as can be seen in the original and here:



I guess these are coming form the lens and can't be avoided? Maybe something to do with it being a $99 lens? Interestingly, when I rotated to landscape, I didn't see any ghosting.