Greenish Spots

[t0tor0]

hi all,

just want to check with you what causes these green spots on this photo.

Taken with with 28mm f/2.0 @ ISO640.

RAW convert in Aperture.

I had a hard time with the white balance of this picture as well.

Thanks

[Riccis]

It is the IR filter... Go naked and you will not have this problem, this is what I do...

Cheers,

[t0tor0]

oh. ok. Thanks!

Just curious technically...

How did this happen?

Does this happens only in tungsten lighting?

[adan]

It is most visible in contrasty lighting with bright point sources like this shot - often they are tungsten lights but the effect is not depedent on that.

It is simply reflections of those bright lights, off the the front of the lens itself, then off the BACK of the IR filter and through the lens to the sensor. Tinted green by the IR filter's absorption at the red end of the spectrum.

With the filter - green reflections.

Without the filter - the guy's hat would go purple.

Take your pick.

[egibaud]

I had a similar problem with candel lights.

[mustafasoleiman]

This is really silly... I have the same problem when I shoot strong points of light in the night...

I agree it's the filter... but I don't remember ever having this problem, at least sooo obvious with my M6 and filters.

The choice between green spots all over the image and purple synthetic blacks is ludicrous.

Is there an easy way to correct the purple in PP?
Sometimes it's not possible to spot out every little green dot... try Piazza San Marco in Venice at night!!!

[barjohn]

Are you sure it isn't aliens that flew out of the cloud of smoke?

[jaapv]

Originally Posted by mustafasoleiman

This is really silly... I have the same problem when I shoot strong points of light in the night...

I agree it's the filter... but I don't remember ever having this problem, at least sooo obvious with my M6 and filters.

The choice between green spots all over the image and purple synthetic blacks is ludicrous.

Is there an easy way to correct the purple in PP?
Sometimes it's not possible to spot out every little green dot... try Piazza San Marco in Venice at night!!!

There is no simple solution. There are some profiles in Capture one that will go a long way to correct the colours, but that is as far as one can go. Otherwise - well, yes, cloning.... The reason for the intrusiveness of the reflections is that the filters are not simple absorption filters that can be muliticoated. They consist of dozens of layers of coating that reflect and reduce specific wavelengths through interference. That makes them indeed prone to have green highlights "bouncing about" Exactly this habit was one of the main reasons Leica could not use dichroitic filtering in front of the sensor - uncontrollable reflections between the filter and the rear element of the lens.

[adan]

There is another solution, of course. The filters can be unscrewed if reflections are going to be more of a negative factor in a given shot or situation, and put back on when IR color shifts will be the biggest problem.

Piazza San Marco at night sounds like a great place to take the filters off. Piazza San Marco in daylight - put 'em back on.

With no implication about the sample starting THIS thread, in the vast majority of the shots I've seen posted where someone is upset about the reflections, the reflections are the least of the problems with the picture....

That being said - I am sure Leica would love to be able to sell a camera that works with M wideangles but does not need external filters. They don't see a solution right now. If YOU do, (and that's a collective 'you' - again not directed at tOtorO personally) by all means submit it to them.

[gravastar]

One solution might be a filter constructed from a zero power meniscus lens with UV-IR cut coatings. This is a trick used by Canon on the 300mm 2.8 which has a protective glass on the front. A possible problem is the curvature of the lens could introduce color casts similar to the cyan corners with wide angles.

I've found a somewhat hit and miss solution, which requires chimping, is to hold the filter in front of the lens at a slight angle.

Bob.

[misha]

one example where they actually work )