Green reflections?

Hi all!

I wasn't sure where to ask this question and groups are really confusing on Flickr, so I hope you all can help me here. I'm currently using a Nikon D40x with a 50mm f/1.8 E series lens mounted. I have a 52mm threaded Sunpak ultraviolet filter screwed on over the lens.

I've noticed that, if I take pictures where there's a bright light source—particularly smaller points, and especially at night—I'll get greenish ghost lights that are reflections of some of the lights. I haven't figured out whether there's a particular angle or intensity or something that produces it, though.

Here are some examples (these were just snapshots, so please excuse the quality :P):

http://backup.cambridgeincolour.com/...960997/wat.jpg

The bottom left one is less obvious, but if you look closely, you'll see that it's an upside-down reflection of the light coming from the kitchen; the part in the middle that doesn't have that green light is from the waitress blocking some of the kitchen light.

Here's a very dramatic, very obvious example:

http://backup.cambridgeincolour.com/...sidonteven.jpg

If I recall correctly, the spots appeared when I had an 18mm–55mm zoom lens mounted using the same UV filter. I haven't yet taken off the filter and tried taking a picture without it on, though; I'll try doing that tomorrow.

In the meantime, does anyone know what it is and how I can prevent it from happening?

Thanks!

Hi SQLU,

Welcome to CiC - it's great to have you with us.

Most won't be able to see your images because I don't think dropbox supports direct linking (I had to copy the image URL to the clipboard and open it in a seperate tab to be able to see them), but that aside, what you're seeing is a reflection from your camera's sensor.

It's quite common, and occurs when light from a bright source enters the lens - bounces off the sensor - travels through the lens in the other direction - bounces off one of the elements - and hit's the sensor for a 2nd time. To find out what light caused it, you need to go to the diametrically opposite portion of the image.

As much as I like UV filters for front-element protection, this is one circumstance where they can make this kind of thing worse.

Hope this helps :)

I ran across this, which discusses angular reflections internal to the lens. It is a discussion concerning the development of Nano Crystal Coating by Nikon, but talks about the problem they were trying to eliminate. At the very bottom of page 2, they show an example which matches your problem.

http://imaging.nikon.com/products/im...e/20/index.htm

Pops