Protection filters.

[Sirius Glass]

If you will merely unscrew the filter while viewing through an SLR and hold it in front of the lens and move it around, you can observe the movements of the reflected ghost highlights. You will see the image degradation that a filter creates. I've got one Pentax branded "ghostless" UV filter that doesn't cause these double-images. But all the flat ones do.

There's a thread here where a photograph was shown of a movie theater marquis where the name of the theater appeared shifted and upside-down.

(there was a url link here which no longer exists)

In most photographs which have already been taken, the artifacts seem to be acceptable, since they are clearly visible but people keep using filters.

But at night, shooting scenes with bright lights and dark backgrounds, take the filter off if you don't want ghost images.

Yes, but when you do that the light is not traveling through the optical axis for which it was designed. If you take a lens and shine a light way off axis and you get a flare, that in itself proves merely that you can abuse a lens with a deviant light beam but you have not demonstrated that the lens is defective nor have you demonstrated that the lens is defective. Furthermore, you can take a fresh roll of 35mm film and in full day light pull it out of the cassette, rewind the film, and develop the film. The film will be fogged but you did not demonstrate that the fogging had anything to do with a defect.

 

[AgX]

Best way to see:
Take out a UV filter pane, cut it in half, set one half back into the ring correctly and then watch the image whilst twisting the filter ring.

 

[rthollenbeck]

Ah, so you want the "natural" light that you cannot see. Does that include infrared as well as uv? How about gamma rays? Neutrinos?

That's awesome!

 

[chip j]

I want light that the FILM sees; we ARE talking about Photography, are'nt we?

 

[cliveh]

Protection filters interfere with the Zen vibrations.

 

[Sirius Glass]

I want light that the FILM sees; we ARE talking about Photography, are'nt we?

No, the UV light that we do not see is just fog in the distance. Infrared light is interesting when we want to shoot infrared film, otherwise just like UV IR is just light noise and fog.

 

[AgX]

As long film can "see" UV radiation there is no reason to look upon UV different from IR.

 

[Sirius Glass]

Yep, except they are on the opposite sides of the visual spectrum. Therefore we need band pass or notch filters to take them out.

 

[Bill Burk]

Yes, but when you do that the light is not traveling through the optical axis for which it was designed. If you take a lens and shine a light way off axis and you get a flare, that in itself proves merely that you can abuse a lens with a deviant light beam but you have not demonstrated that the lens is defective nor have you demonstrated that the lens is defective. Furthermore, you can take a fresh roll of 35mm film and in full day light pull it out of the cassette, rewind the film, and develop the film. The film will be fogged but you did not demonstrate that the fogging had anything to do with a defect.

That's not the purpose of the demonstration. These reflections are there when the filter is in place. You just don't notice them until you see them move.

 

[Bill Burk]

The other thing to consider... these reflections "might" only be 2% total light... so they will show on your photograph when there are specular highlights only. And they will only be really obvious when there is a dark field background where they appear.

So those night-time fireworks and movie marquee shots... that's where you'll see them.

 

[Sirius Glass]

That's not the purpose of the demonstration. These reflections are there when the filter is in place. You just don't notice them until you see them move.

All refractive optical surfaces, even with the best of coatings, reflect some light. A well made filter provides some lens protection without a noticeable image impact.