Seeking kind advice - blue fringing

[Semerka]

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Please could I ask the esteem forum for an opinion on blue fringing in my photo. 
For the first time today I used the new Leica Vario Elmarit 28-70 mm zoom lens to take photo of our dog in a quite contrasty, indoors environment.

The camera is SL2, shot at f/2.8 at 57 mm. There is very pronounced blue fringing of the light hair around her right eye and further on her ear and shoulder. 

I have never come across such bad fringing on such a large area. Do you think that the lens could be faulty? 

Thank you very much! 

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Edited September 25 by Semerka

[jaapv]

No - not the lens This is a sensor effect called blooming. Rare on CMOS sensors, caused by oversaturated pixels. There is a slider in LR to remove it. 

https://sensor.wiki/cmos-sensor-blooming/

[Semerka]

Thank you very much for the quick reply, @jaapv, I will investigate how to prevent it. 

Edited September 25 by Semerka

[jaapv]

It is quite rare, so not a big problem on CMOS, but there is really no specific action to take, except underexpose significantly in high contrast situations, but that is not really desirable either. The best is to remove it in postprocessing, either by using the dedicated slider or by the Color Replacement Brush. 

[adan]

It is unlikely to be an equipment failure.

It is a natural, somewhat common, and expected effect in digital photography.

So common that most digital photography post-processing software includes (at some expense to the software maker) a control exactly intended to get rid of of such color fringing. It can happen any time with any lens/camera/sensor (except the Leica Monochrom-only cameras, obviously 😉 )

This is from Adobe's Camera Raw, but most other editing programs will have a similar set of controls.

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jaapv suggests "blooming" - I suspect color aliasing (a feature of even healthy Bayer-pattern sensors, using extra-sharp lenses)

http://www.tedfelix.com/ColorAliasing/index.html )

.....and/or chromatic aberrations (no such thing as a perfect lens, even for Leicas).

Localized overexposure (such as these sunlit and shiny hairs, compared to the rest of the dog's black fur) can emphasize it.

[jaapv]

5 minutes ago, adan said:

It is unlikely to be an equipment failure.

It is a natural, somewhat common, and expected effect in digital photography.

So common that most digital photography post-processing software includes (at some expense to the software maker) a control exactly intended to get rid of of such color fringing. It can happen any time with any lens/camera/sensor (except the Leica Monochrom-only cameras, obviously 😉 )

This is from Adobe's Camera Raw, but most other editing programs will have a similar set of controls.

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jaapv suggests "blooming" - I suspect color aliasing (a feature of even healthy Bayer-pattern sensors, using extra-sharp lenses)

http://www.tedfelix.com/ColorAliasing/index.html )

.....and/or chromatic aberrations (no such thing as a perfect lens, even for Leicas).

Localized overexposure (such as these sunlit and shiny hairs, compared to the rest of the dog's black fur) can emphasize it.

I suggested blooming because it is blue. Aliasing is more often red-green, purple fringing on its own is a high-contrast sensor effect, purple-yellow  (the yellow often hard to see) fringing longitudinal chromatic aberration. Lateral chromatic aberration is red-green. take your pick, the remedy is always the same: Sliders or colour replacement brush. 

[Semerka]

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Thank you both @jaapv and @adan for giving me the peace of mind that it’s not the equipment that’s broken. 
And I have learnt new facts. 😎

[Stuart Richardson]

It looks more like longitudinal chromatic aberration to me. The reason I say that is that you can see it coming in a bit in the background bokeh as well, which is not blown out and where there is no high frequency detail that could cause moire. And the front of her nose is ever so slightly redder than the point of focus (longitudinal ca is usually greenish behind the focus, reddish in front). Also, a lot of Sigma designed lenses I have used do this, and this zoom is one of their designs. The bluish tone can be a factor of white balance or processing. I think you would get rid of this in two main ways: 1. stopping down a bit. 2. using prime lenses with apochromatic correction, like the apo summicrons. They don't do this. Zooms are hard design and require certain compromises in order to perform well. This is one of them. 

Edited September 26 by Stuart Richardson

[jaapv]

I have never seen this specifically on the Sigma 28-70 but that may well be because of the photographs taken with it. Other zooms like the R 105-280 are more prone. I still think that this is no indication that there is anything wrong with the lens and just an unlucky coincidence easily corrected in post, whatever the cause. 

[Stuart Richardson]

Nothing is wrong with the lens. It is a consequence of trying to balance other aberrations and keep the size, weight and cost manageable. Zoom lenses are always an optical compromise in comparison to an equally well-built prime. This is one of those compromises. Primes are not immune to this effect however. In this case, I think the problem would most certainly be solved by stopping down to f4 or f5.6. The larger depth of field would have minimized the effected area, but lenses also tend to improve in this behavior as they stop down, even with bokeh present. If you want to keep the same depth of field, one thing to try might be to stop down another stop, but then step back slightly and zoom in a bit more. For example, try 70mm at f4 instead of 57mm at f2.8. I certainly can't guarantee that that would have solved it, but it is something to experiment with. 

Edited September 26 by Stuart Richardson

[Semerka]

Thank you for your thoughts, @Stuart Richardson, much appreciated. I am taking it all on board.

I did want a compact zoom lens and am prepared to live with it’s shortcomings for the convenience when on hikes. 

 

[beewee]

On 9/26/2025 at 3:28 AM, Stuart Richardson said:

It looks more like longitudinal chromatic aberration to me.

Yup, I agree.
 

 

On 9/26/2025 at 7:39 AM, Semerka said:

I did want a compact zoom lens and am prepared to live with it’s shortcomings for the convenience when on hikes. 

LOCA is usually more apparent at more telephoto range, at close distances, shooting wide open on high contrast subjects. A good stress test would be close ups of jewelry and chrome accents.

Shouldn’t be that common for landscapes if you’re shooting wide angle, stopped down, and focused far away.

I’d be curious to know how it does though since it is very attractive for a hiking setup.

[Semerka]

Hi @beewee, thank you.  
I will post some sample images later. So far I like it for it’s simplicity, versatility and compactness of the 28-70mm zoom. There’s CA around the edges of objects against bright background, it’s not an APO lens. 

[AKorenc]

Longitudinal Chromatic Abberation at it's best. Nothing to do with "sensor blooming." As the green/cyan/blue colors are absent from this image, simply reduce saturation of these colors by at least 60-70% and it'll be gone.

[Semerka]

Ok, here are some sample images. I like the lens for general purposes when out on walks and recording the happenings of the day. 

f/4 at 68 mm:

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Edited Thursday at 06:31 PM by Semerka
Trying to get all my images in the post.

[Semerka]

Rose: f/4 at 70 mm

Bark: f/2.8 at 70mm

 

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Edited Thursday at 06:25 PM by Semerka

[Semerka]

And our Alfie at f/3.5 at 70mm

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[Semerka]

f/11 at 38mm

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[Semerka]

f/2.8 at 65mm

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[Semerka]

Reposting the sample photo of the strawberry tree fruit because for the first post I did not reduce the size in the correct way and it distorted the bokeh. 

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