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I've noticed some strange colouring around highlights from lamps when taking photos at night

Taken with a Canon EF 24-105mm L: Taken with a Canon EF 24-105mm L

I think it should look like this one with no artifacts (Taken with a Canon 100mm) : Taken with a Canon 100mm

What can it be? The front and back glass of the lens look clean.

Can you help?

Thank you

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  • \$\begingroup\$ Thank you Alan Marcus and Caleb for your feedback. I should've said that I've before taken photographs with said lens and it never showed that type flare before, which by the way is iridescent and lacking in definition (I'm aware of lens flare; but this is not a 'healthy' one). \$\endgroup\$
    – Joaquin
    Commented Aug 22, 2016 at 13:59
  • \$\begingroup\$ Has the problem never happened before in the same situation, or you've just never pointed it at a lamp quite like this before? If it's the former, do you have any idea when it started? And, please also spell out if you are using any protective (or other) filters attached to your lenses. \$\endgroup\$
    – mattdm
    Commented Aug 22, 2016 at 15:45
  • \$\begingroup\$ Thank you mattdm, No I am not using any filters nor any protective elements. I've noticed this only a few days ago after shooting at night. The lens had a problem a year ago and had a piece replaced by a Canon authorized shop. I believe it was a ribbon connecting some elements, and it gets broken for some reason (There are rumours of Canon having a bad batch of those ribbons). \$\endgroup\$
    – Joaquin
    Commented Aug 23, 2016 at 14:23
  • \$\begingroup\$ To me the rainbow pattern indicates some sort of diffraction is going on. What was the aperture set at, for both pictures? \$\endgroup\$
    – 2012rcampion
    Commented Aug 25, 2016 at 5:48

2 Answers 2

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I think it should look like this one...What can it be? The front and back glass of the lens look clean.

Both lenses exhibit some lens flare. Flare is caused by light bouncing around inside the lens and eventually reaching the sensor. It's natural that two different lenses, constructed with different elements and different coatings, have different lens flare patterns. Indeed, just changing the focal length of your 24-105mm lens (i.e. zooming in or out) will change the arrangement of the elements and the pattern of the lens flare.

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The modern camera lens must be fabricated using several groups of individual lenses. Some are positive, some negative as to their power. Some of these elements have air-space between them, some are glued together. Such complex lens arrangement is necessary to mitigate aberrations. These are defects that prevent us from making an optical system that truly makes a faithful image.

Each lens of the lens array has two polished surfaces. The exposing light as it transverses each lens suffers some loss due to reflection from each surface. This reflected light is staying away from its intended path. It may hit the polished surface of an adjacent lens and be re-reflected. In any event there will be lots of straying of light within the lens. Some will find its way to film and/ or digital sensor and this we call flare.

We mitigate flare by blooming the lens. This is an artificial ageing of the lens. It was discovered that identical lenses, one young and one new, differed in how much light they passed. The older lenses were found to be coated with schmutz. This is atmospheric pollution. A thin coat acted like a thin film on a soap bubble. This coat, if the right thickness, will cancel some of the reflections affording less flare. We call this “lens coating”.

OK we have many surfaces, all contributing to flare, and we also have the fact the figure (curve) of the lens is a compromise of shapes. We also have polished glass that always has microscopic scratches. What we don’t have is a lens that makes a truly faithful image.

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  • \$\begingroup\$ The more complex the lens design, the more likely it is that we will see ghost images. Each polished surface in the path of the image forming rays has the potential to form a ghost image. The digital camera is particularly prone as hovering just over the digital sensor is a flat glass protective cover glass. This surface can act as a mirror and reflect image forming back at the lens. These hit the polished surface of the rear lens and are reflected as a ghost image back at the sensor. Coating all surfaces helps however, we have never been able to eliminate ghost reflections. \$\endgroup\$
    – Alan Marcus
    Commented Aug 22, 2016 at 19:07

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