APO?

[Ghiry6591]

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I took this photo at the beginning of October and, honestly, I don't know what to think. It is a backlight, obviously, intentionally underexposed in a strong way to create the silhouette effect. What worries me about this photo is the dramatic effect of what seems to be pure and simple purple fringing on the water. Why? Because the photo in question was taken with Apo Summicron SL 75/2 Asph. (original DNG). I thought that an apochromatic lens would protect me from most aberrations, but evidently this lens did not do it. Even if the shooting conditions were difficult I am very, very disappointed by an object that costs 5000 euros.

 

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[adan]

Where do I start?  

1) "Apochromatic" is not an absolute term. Lenses are more or less apochromatic - and generally for three specific colors/wavelengths in the electromagnetic spectrum (sometimes even in the infrared or UV ranges).

2) Overexposure (i.e. an exposure that turns water reflections pure white ("blows out" the highlights)) can produce digital color fringes with any lens. Generally purple/violet/magenta, because that is the most energetic part of the visible spectrum (closest to the UV - which can burn our skin and even cause cancer, over time). The high energy allows the near-UV color to "fringe" more - and more obviously - into the dark surroundings.

3) The structure of digital sensors itself can also produce aliasing that takes on the appearance of fringing. If, for example, a sharp edge between white reflections and darker water falls right on the edge of side-by-side red, blue and green-filtered sensor elements, it may miss the green pixels and be counted/detected by the sensor as red + blue = magenta.

4) Leica has generally said that their designation/branding of recent lenses as "APO" means "really, really excellent" - but not necessarily tied directly to "apochromatic performance" as such. Although in general really well-corrected lenses overall will show less fringing than less well-corrected lenses. But again, "less" does not equal "none."

5) post-processing software now generally has a "remove purple (or cyan) fringes" - it is a fairly easy problem to fix with just a couple of sliders (one for amount/size of the fringe in pixels, the other for the exact color range (some fringes are red and cyan, others are magenta and green (most common), other are blue and yellow, etc.).

That is a rough summation of the key points of many previous discussions here about the subjects of APO, apochromatic, and color fringes in digital pictures (either/both in the sharpest parts, or in the out-of-focus backgrounds/foregrounds.)

Edited October 23 by adan

[otto.f]

Probably shot with an M11

[adan]

1 minute ago, otto.f said:

Probably shot with an M11

In the SL forum? Do keep up. 🤪

[Ghiry6591]

The photo was taken with Leica SL2-S

[Ghiry6591]

Enlargement of the most problematic area of the photo: unacceptable for me.

 

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[jankap]

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Please test the APO property of the lens with a less critical subject. In the given picture, over-exposing could have been a problem of the sensor.

On the other hand, the part of the picture under the bridge seems to be clean and is still more overexposed.

[LocalHero1953]

This looks like the common effect you get when highlights are blown, as here - it has been discussed before.

If I recall the cause correctly, around the edges some frequencies are not blown and the raw conversion algorithms attempt to reconstruct the colour of the partly blown area - and gets it wrong. You often see it with sparkly water and twigs against a white sky. The smaller the blown areas, the greater the proportion of areas with the wrong colour, so it is more noticeable in sparkly water and where there are lots of twigs. Thus (in this case) this is a digital artefact, not an optical aberration.

If you want to check for non-apochromatic behaviour, you should look for somewhere where highlights are not blown.

Lightroom can remove this with a brush and the Defringe tool.

Edited October 23 by LocalHero1953

[Smogg]

As Jim Kasson wrote: “In general, the designation Apo on a lens means that the folks in marketing think that the lens is well corrected by their company’s standards, and that they would like you to think that, too.” 

You shouldn't demand absolute results, they are unattainable.

 

[Ghiry6591]

thanks to everyone for your contributions 👋

[Stuart Richardson]

You may also find some help using the "enhance details" function in Lightroom. That will run a more processor intensive raw conversion, but it should lower the rate of sensor artifacts.

I agree with Andy. I do not believe this is an issue of the lens, it is one of the sensor and software. This is also where higher resolution sensors do better. With more pixels to work with, they are harder to fool and they can make better guesses about what the colors should be. Most everything in photography is a trade off, and this is unfortunately one of those areas.

Edited October 23 by Stuart Richardson

[Virob]

I went through this when getting the 21 APO. What you are seeing is  blooming. Blooming is a function of the sensor and is influenced by pixel size, focal length, the wider, the more the affect, and overexposed area’s. It really has little or nothing to do with the quality of the lens. The effect however can be accentuated by filter's.

A bit of a wake up call after shelling out big bucks on a lens, I agree, nothing is perfect.

 

[Jon Warwick]

I basically agree with what Stuart has already mentioned. The colourful speckles you see remind me of the issues that I encountered with my M240 - I used to often see such speckles embedded into fine detail like moraine (the rubble of rocks next to glaciers) across the valley in my landscape photos, and seemingly exacerbated by higher contrast direct sunlight. I think it's more to do with the camera only being 24mp, and associated issues with the colour filter array etc with the low resolution sensor.

I would imagine a 60mp SL3 would present much less problems here - simply more data for the sensor = more accurate representation of fine detail and colors. For these types of scene, I now encounter far less problems with my 60mp M11 (than I did M240), and by extension it's even less when I use a 100mp medium format.

I'd agree with Stuart on the above re: Enhance in ACR being worth a try (something he helpfully suggested to me in the past and which I commonly deploy) - ie, where i do still get such colorful speckles even with the M11, the Enhance function does a good job of cleaning it up. 

Final thought - it would be interesting if the Pixel Shift mode would have helped here too on your SL2-S? (flowing water not the easiest subject for it, but for other subjects, the high resolution mode does a good job of eliminating and cleaning up "problems" resulting from the color filter array).

Edited October 28 by Jon Warwick

[helged]

1 hour ago, Jon Warwick said:

I basically agree with what Stuart has already mentioned. The colourful speckles you see remind me of the issues that I encountered with my M240 - I used to often see such speckles embedded into fine detail like moraine (the rubble of rocks next to glaciers) across the valley in my landscape photos, and seemingly exacerbated by higher contrast direct sunlight. I think it's more to do with the camera only being 24mp, and associated issues with the colour filter array etc with the low resolution sensor.

I would imagine a 60mp SL3 would present much less problems here - simply more data for the sensor = more accurate representation of fine detail and colors. For these types of scene, I now encounter far less problems with my 60mp M11 (than I did M240), and by extension it's even less when I use a 100mp medium format.

I'd agree with Stuart on the above re: Enhance in ACR being worth a try (something he helpfully suggested to me in the past and which I commonly deploy) - ie, where i do still get such colorful speckles even with the M11, the Enhance function does a good job of cleaning it up. 

Final thought - it would be interesting if the Pixel Shift mode would have helped here too on your SL2-S? (flowing water not the easiest subject for it, but for other subjects, the high resolution mode does a good job of eliminating and cleaning up "problems" resulting from the color filter array).

As a SL2-S and SL3 user, I can also confirm that SL3 is much less prone to showing this artefact. Actually, I have hardly seen miscolouring on SL3; and in the few cases I have seen tendencies of it, quick postprocessing fixes it.

Edited October 28 by helged

[jdlaing]

Water prisms. That’s where the colors are coming from.

[jaapv]

I don’t think so. APO correction is only in the plane of focus and chromatic aberration can easily occur in the DOF zone on an APO lens. 

[jaapv]

8 hours ago, Jon Warwick said:

I basically agree with what Stuart has already mentioned. The colourful speckles you see remind me of the issues that I encountered with my M240 - I used to often see such speckles embedded into fine detail like moraine (the rubble of rocks next to glaciers) across the valley in my landscape photos, and seemingly exacerbated by higher contrast direct sunlight. I think it's more to do with the camera only being 24mp, and associated issues with the colour filter array etc with the low resolution sensor.

I would imagine a 60mp SL3 would present much less problems here - simply more data for the sensor = more accurate representation of fine detail and colors. For these types of scene, I now encounter far less problems with my 60mp M11 (than I did M240), and by extension it's even less when I use a 100mp medium format.

I'd agree with Stuart on the above re: Enhance in ACR being worth a try (something he helpfully suggested to me in the past and which I commonly deploy) - ie, where i do still get such colorful speckles even with the M11, the Enhance function does a good job of cleaning it up. 

Final thought - it would be interesting if the Pixel Shift mode would have helped here too on your SL2-S? (flowing water not the easiest subject for it, but for other subjects, the high resolution mode does a good job of eliminating and cleaning up "problems" resulting from the color filter array).

Simply use the defringe sliders. 

[evikne]

2 minutes ago, jaapv said:

Simply use the defringe sliders. 

Or even easier: use the Defringe pipette. Done with one click!

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Hallo,

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