Do you think this would be spherochromatism?

[ErikKaffehr]

Hi,

Someone suggested the image below shows spherochromatism, I don't think so but what is your view? Actual pixel dumps below.



Zeiss Distagon 40/4 FLE at f/8 on a P45+ (it is not the new IF version of the lens).

it goes away at f/16 - f/22:




Best regards
Erik

[BernardLanguillier]

Someone suggested the image below shows spherochromatism, I don't think so but what is your view? Actual pixel dumps below.

Great, I am about to learn a new word...

What is "spherochromatism" and is it bad to have been taking pictures for 25 years without knowing the word... doctor?  

Cheers,
Bernard

[ErikKaffehr]

Hi Bernard,

I am looking into aliasing from large pixels compared to small pixels. What I see in the image is a Bayer interpolation artefact, thin lines not covering all RGBG pixels. Luminosity is calculated correctly but color is not. That is my guess.

Some suggested that is something called spherochromatism and caused by a bad sample of the lens.

This is taken from the LensRental's site:

"There is one form of spherical aberration that you may have seen if you’ve used very wide aperture lenses: spherochromatism. Like chromatic aberration, some lenses have corrected spherical aberration at some wavelengths better than others. This may result in a magenta tinge for out of focus areas in the foreground and a greenish tinge in the out of focus portion of the background (or vice-versa)."

Best regards
Erik

Great, I am about to learn a new word...

What is "spherochromatism" and is it bad to have been taking pictures for 25 years without knowing the word... doctor?  

Cheers,
Bernard

[Phil Indeblanc]

I would think at that F16-22 range, it is diffraction that takes it away?

Would this be the same on another copy of the lens? Or perhaps a newer type of lens?
I'm not familiar enough with Ziess lenes to know if this is an older lens or most current. Visiting the Ziess website didn't help as I couldn't find this.
But I'm with Brenard, although in general he is far more technical than I, I too have not heard of this.

Is this what someone mentioned on the other thread being the Apo coating issue? Also sounds like a logical reason.

[ErikKaffehr]

Hi,

The lens has significant chromatic aberration that is not fully corrected in Lightroom. I don't think this is chromatic aberration as it is on the pixel level, and follows distinct lines, vertically and horisontally. If it would be chromatic aberration I would say it would be more persistent. But I am asking for an opinons, so I don't argue that much.

Just to mention, there is nothing like 'Apochromatic coating', that term is true nonsense. Apochromatic means that lens focuses three colours in the same point. That can be achieved by a combination of three lenses with different indices of refraction. There are very few true apochromats. The Zeiss Otus may be one and there is the Coastal Optics 60 mm UVIR macro lens. Most lenses labeled Apo don't fulfil the requirement.

Zeiss is out of MF-business so it is clearly an older lens, known to be not very good. It has been replaced with a newer version called Distagon 40/4 FLE IF. The new IF version is a different animal. I was testing at f/16 - f/22 because I knew the lens had bad corners.

Now, just to put things in perspective, this lens makes great images:
Full size: http://echophoto.dnsalias.net/ekr/Articles/MFDJourney/RawImages/Samples3/20130907-CF044069.jpg


Ful size: http://echophoto.dnsalias.net/ekr/Articles/MFDJourney/RawImages/Samples3/20130822-CF043962.jpg


The Zeiss data sheet can be found here: http://www.hasselbladhistorical.eu/pdf/lds/CF40.pdf

I guess that the HC 3.5/35 is the closest one in the recent Hasselblad system: http://www.hasselblad.com/media/6640/hc35%20v3.pdf

I enclose the MTF plots.

I would think at that F16-22 range, it is diffraction that takes it away?

Would this be the same on another copy of the lens? Or perhaps a newer type of lens?
I'm not familiar enough with Ziess lenes to know if this is an older lens or most current. Visiting the Ziess website didn't help as I couldn't find this.
But I'm with Brenard, although in general he is far more technical than I, I too have not heard of this.

Is this what someone mentioned on the other thread being the Apo coating issue? Also sounds like a logical reason.

[jerome_m]

It cannot be spherochromatism as the entire line is at the same distance from the lens, yet the colors vary.

[Bart_van_der_Wolf]

Someone suggested the image below shows spherochromatism, I don't think so but what is your view?
[...]
it goes away at f/16 - f/22:

Hi Erik,

No, it looks nothing like spherochromatism (spherical aberration that varies with wavelength, non-apochromatic correction) because that would result in resolution that varies with wavelength.

What this looks like is simple false color artifacting due to Bayer CFA demosaicing. Note the Magenta/Green and Blue/Yellow artifacting depending on horizontal/vertical orientation. It's a demosaicing artifact, a different Raw converter will probably give different results. The additional diffraction at f/16- f/22 will spread the signal over more sensels, allowing a better color interpolation/demosaicing. That's somewhat similar to the intended function of an OLPF.

Cheers,
Bart

[Bart_van_der_Wolf]

This is taken from the LensRental's site:

"[...]This may result in a magenta tinge for out of focus areas in the foreground and a greenish tinge in the out of focus portion of the background (or vice-versa)."

This is more commonly referred to a Longitudinal Chromatic aberration.

Cheers,
Bart

[ErikKaffehr]

Hi Bart,

That is my take, too, but there was a suggestion that it would something else, so I felt I would ask for opinions.

It seems a bit interesting that I see this but nobody else.

Best regards
Erik

Hi Erik,

No, it looks nothing like spherochromatism (spherical aberration that varies with wavelength, non-apochromatic correction) because that would result in resolution that varies with wavelength.

What this looks like is simple false color artifacting due to Bayer CFA demosaicing. Note the Magenta/Green and Blue/Yellow artifacting depending on horizontal/vertical orientation. It's a demosaicing artifact, a different Raw converter will probably give different results. The additional diffraction at f/16- f/22 will spread the signal over more sensels, allowing a better color interpolation/demosaicing. That's somewhat similar to the intended function of an OLPF.

Cheers,
Bart

[Bart_van_der_Wolf]

It seems a bit interesting that I see this but nobody else.

Maybe they do see it, but camouflage it, and keep silent. A Raw converter like e.g. RawTherapee with AMAZE demosaicing offers user adjustable suppression of such false color artifacts. And when one anticipates such issues, one can always shoot a second image at a much narrower aperture, and use that in a layered (allows different deconvolution than optimal for the wider aperture image) masked edit to locally suppress the issues.

Cheers,
Bart

[Doug Peterson]

One of these days we might win you over to Capture One so you don't have to deal with (nearly as many) issues like this in the quality of your raw processing.

Maybe I need to suck it up and comp you a seat in our C1 class.

[Fine_Art]

Hi,

The lens has significant chromatic aberration that is not fully corrected in Lightroom. I don't think this is chromatic aberration as it is on the pixel level, and follows distinct lines, vertically and horisontally. If it would be chromatic aberration I would say it would be more persistent. But I am asking for an opinons, so I don't argue that much.

Just to mention, there is nothing like 'Apochromatic coating', that term is true nonsense. Apochromatic means that lens focuses three colours in the same point. That can be achieved by a combination of three lenses with different indices of refraction. There are very few true apochromats. The Zeiss Otus may be one and there is the Coastal Optics 60 mm UVIR macro lens. Most lenses labeled Apo don't fulfil the requirement.

There is no such thing as an APO coating. That is a misunderstanding. Lets look at lens coating tech. Typically we are talking about anti-reflective coatings for photography. Some companies use coating chemicals that are highly tuned to specific wavelengths. They have to use a sequence of several to get the effect they want. Others use a broad band coating. The combination of coatings and lens curves are what makes the output of the lens what it is. The coating are an integral part of the lens design. The same lens elements without the coatings would look different, less contrasty. On a multi-coated lens obviously one coating is the most exposed so it will take the brunt of cleaning or anything else that could damage coatings. That will change the colors of the lens as the relative intensities of the colors change a small amount.

The lens element themselves can have color separation in the focus length direction or in the lateral direction. Lateral errors usually are pronounced at the edges.

Lightroom/ACR is the most common software. It has gone through many revisions. I would be surprised to hear it is causing very visible de-bayer errors at this stage. Do others also suffer this issue using manual PS brushing to remove it?

In my experience I have some kit zooms that I never use that have known color issues. Even some of my older primes have some in extreme light. I simply do not have this problem with my best lenses. I pretty much use RT for all RAW work. RT has one problem of being very slow to load thumbnails. I use ViewNX 2 to work the catalog then load RT from it with a right click. View NX2 does not have the color problem either.

[Fine_Art]

ViewNX2 at 100%. No color separation. Some mild sharpening halos.

[Fine_Art]

Maybe they do see it, but camouflage it, and keep silent. A Raw converter like e.g. RawTherapee with AMAZE demosaicing offers user adjustable suppression of such false color artifacts. And when one anticipates such issues, one can always shoot a second image at a much narrower aperture, and use that in a layered (allows different deconvolution than optimal for the wider aperture image) masked edit to locally suppress the issues.

Cheers,
Bart

Sorry Bart, I find that very unlikely. First of all if the software was having problems debayering, why would it only be on a small part of the image? It is not logical. Second of all if everyone was having to correct all their images they would have abandoned ship to other software long ago.

It is far more likely that it is an issue with the lens.

[Bart_van_der_Wolf]

Sorry Bart, I find that very unlikely. First of all if the software was having problems debayering, why would it only be on a small part of the image?

Hi Arthur,

IMHO it's likely because it only shows on high contrast edges in the focus plane. Longitudinal Chromatic aberration produces colored edges in out of focus (OOF) areas also in the image center, often Green in front and Red in the rear of the focus plane. With a shallow DOF, due to relatively longer focal lengths in MFDB shots, or more diffraction blur due to narrower apertures, it does not manifest itself the same in all images.

Otherwise LCA is curable with reducing fringe colors on high contrast edges, false color artifacts have too many different colors for a simple cure in post-processing, so it is best handled when doing the Raw conversion/demosaicing.

It is not logical. Second of all if everyone was having to correct all their images they would have abandoned ship to other software long ago.

It is far more likely that it is an issue with the lens.

If Erik tries a different Raw converter and it goes away or change colors, that would prove false color artifacting, if it stays the same then it's something else. Not everybody uses a camera/back without AA-filter, so many would not be affected to the same degree.

Cheers,
Bart

[Fine_Art]

It seems only Harry Potter gets to find the Download Now button.

FYI I have licenses for Elements 2, 3 and PS CS3. None are still on my computer.

[Christoph C. Feldhaim]

Looks like some heavy supercolorfringielisticexposialidofism to me.
No way to save the image.

[Doug Peterson]

Sorry Bart, I find that very unlikely. First of all if the software was having problems debayering, why would it only be on a small part of the image? It is not logical. Second of all if everyone was having to correct all their images they would have abandoned ship to other software long ago.

It is far more likely that it is an issue with the lens.

This is definitely debayering error. Promise.

[ErikKaffehr]

Hi,

I checked a bit. The lightning conductor is about one pixel wide. The color shifts on the lightning conductor itself, but not on surrounding pixels. I have tested with:

- Lightroom 5.3 RC using PV 2012 (original sample)
- Lightroom 5.3 RC using PV 2003, this has much reduced color aliasing but it is still there
- Capture One 7.1.3 as bad or worse as 5.3 RC using PV 2012

Raw Therapie doesn't open IIQ file.

I am pretty sure this is color aliasing. I have a long experience of optics, having something like 25 lenses (Minolta, Sony, Pentax 67, Zeiss) I have never seen an aberration exactly one pixel wide in two orthogonal direction.

I have tested another of the images. It cleaned up well on LR 5.3RC with PV 2003, but was quite soft. On C1 it was pretty ugly. I have tested that image in RawTherapy and it was best of the bunch. C1 version below.

Best regards
Erik

Hi Arthur,

IMHO it's likely because it only shows on high contrast edges in the focus plane. Longitudinal Chromatic aberration produces colored edges in out of focus (OOF) areas also in the image center, often Green in front and Red in the rear of the focus plane. With a shallow DOF, due to relatively longer focal lengths in MFDB shots, or more diffraction blur due to narrower apertures, it does not manifest itself the same in all images.

Otherwise LCA is curable with reducing fringe colors on high contrast edges, false color artifacts have too many different colors for a simple cure in post-processing, so it is best handled when doing the Raw conversion/demosaicing.

If Erik tries a different Raw converter and it goes away or change colors, that would prove false color artifacting, if it stays the same then it's something else. Not everybody uses a camera/back without AA-filter, so many would not be affected to the same degree.

Cheers,
Bart

[Christoph C. Feldhaim]

This is definitely debayering error. Promise.

+1

Spherochromatism would not cause a color change like presented.
It would most likely cause a color change becoming bigger towards the edge of the image.
The error presented changes with the slight position changes of the cable.
Thats a strong indicator for a debayering error and not an optical aberration.