Anyone know, why does this happen?

[Adam Bonn]

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Occasionally when I shoot a snap of my kid at mid (2000+) ISO, normally under artificial light, parts of her lip loose colour

I can (sort of) fix it with brushing in LR. C1 it's not quite as bad, and C1 tells me the part missing colour has a higher luminance than the rest of her lips.

I've opened affected DNGs in 3 different RAW convertors and the problem is there in each.

No matter which profile I use in LR (embedded, adobe, custom, custom with GM24 derived color matrices) the issue persists.

Anyone any idea why this happens, and what I can do at time of capture to avoid it?

Cheers

(these are all non edited images to rule out any impact of my edits or changes profiling might have caused)

 

 

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[Peter Kilmister]

None of these images seems to be in focus so hard to comment.

Edited May 15, 2021 by Peter Kilmister

[Adam Bonn]

22 minutes ago, Peter Kilmister said:

None of these images seems to be in focus so hard to comment.

they're low res, high iso screen grabs blown up to well in excess of 100%, try just looking at the colour drain from the lips

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are you really not able to see that? do you really think that's caused by a lack of focus? 

 

 

[gbealnz]

I can't help with your quandary Adam, but recall your love of a different brand of APS camera, do you still own one? Why I ask is that maybe try the other brand, in side by side conditions and see? Same time, same lens, different sensor. Same result?

[jaapv]

I also notice yellow and magenta blotches. That points at IR contamination. As the skin is built up in layers of varying IR reflectivity and of varying thickness. the colour cast will vary with the location. For instance areas with a dense capillary network will reflect strongly, as Hemoglobin is highly IR reflective, areas with a more fatty substrate will absorb IR. The discoloration or the lip red indicates a variation in the build-up of the skin layers. Leica's, especially M cameras, have some residual IR sensitivity due to the use of thin filters.

Try using an IR cut filter.

[Lee Rust]

IR reflectivity of hemoglobin vs fatty areas affects skin color in photos? Fascinating! I've never noticed this particular anomaly, but I do have a UV/IR cut filter on all my Leica lenses to prevent a purplish tint in black synthetic fabrics when using my digital M.

Edited May 16, 2021 by Lee Rust

[Cobram]

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4 hours ago, jaapv said:

I also notice yellow and magenta blotches. That points at IR contamination. As the skin is built up in layers of varying IR reflectivity and of varying thickness. the colour cast will vary with the location. For instance areas with a dense capillary network will reflect strongly, as Hemoglobin is highly IR reflective, areas with a more fatty substrate will absorb IR. The discoloration or the lip red indicates a variation in the build-up of the skin layers. Leica's, especially M cameras, have some residual IR sensitivity due to the use of thin filters.

Try using an IR cut filter.

M camera as a medical detecting device? Always something new to learn...

 

[LocalHero1953]

The M9 had this problem a lot - under certain artificial lights the lips of certain people would be strongly magenta-coloured - like bright lipstick. And some people with 'the wrong type of skin' would show a blotchy face - very ugly at times. I found the effect less in the M240, but not always absent. 

I reported it here a long time ago!.

Edited May 16, 2021 by LocalHero1953

[frame-it]

1 hour ago, Lee Rust said:

IR reflectivity of hemoglobin vs fatty areas affects skin color in photos? Fascinating! I've never noticed this particular anomaly, but I do have a UV/IR cut filter on all my Leica lenses to prevent a purplish tint in black synthetic fabrics when using my digital M.

example of IR 850nm, note the blood vessels

 

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[Adam Bonn]

6 hours ago, jaapv said:

I also notice yellow and magenta blotches. That points at IR contamination.

Thanks @jaapv

I wondered this, but (forgive my ignorance) I didn't think IR contamination was a thing away from sunlight? Two of those shots were under indoor (whatever energy saving lightbulbs my other half got from Ikea) lighting. Is IR really a thing with in this case?

6 hours ago, jaapv said:

Try using an IR cut filter.

I do have a Leica UV/IR cut filter, should I use it all the time (not just on days with a high and bright and merciless tropical sun)?

[Adam Bonn]

36 minutes ago, LocalHero1953 said:

The M9 had this problem a lot - under certain artificial lights the lips of certain people would be strongly magenta-coloured

Yes I have an M9 too and quite a few of shots of blokes wearing lipstick 🤣

The problem here with my 240 looks a little different, the lips are de-saturated to the point of (more or less) matching the surrounding skin tones, but only in some areas. 

It's also inconsistent, 🙄 I have other shots taken at the same time that don't have this effect

[frame-it]

1 minute ago, Adam Bonn said:

I didn't think IR contamination was a thing away from sunlight?

indoors with no sunlight, and no IR light..i doubt you would see any IR "patches"

[Adam Bonn]

6 hours ago, gbealnz said:

I can't help with your quandary Adam, but recall your love of a different brand of APS camera, do you still own one? Why I ask is that maybe try the other brand, in side by side conditions and see? Same time, same lens, different sensor. Same result?

Well remembered!

I do still have the X-Pro1, but I don't think I've even turned it on in 18months or shot with it for 3 years, maybe the battery went bad, leaked and effed it up - I've no clue! 😲 (all the XF glass is long gone though, no wait I still have one of the zooms, the XC 230mm one!)

I think a side by side won't help too much to be honest... either 

a) the camera I don't use won't have the problem and that won't help me fix the camera that does

b) both cameras will exhibit the same behaviour and I'll end up wanting to resolve it twice 😒

[Adam Bonn]

4 minutes ago, frame-it said:

indoors with no sunlight, and no IR light..i doubt you would see any IR "patches"

of the 3 pics in my OP, the first was a mixture of indoor and sunlight (it was grey and raining hard though)

The other 2, 100% indoor light (iirc about 2500k using a WhiBal)

[jaapv]

28 minutes ago, frame-it said:

indoors with no sunlight, and no IR light..i doubt you would see any IR "patches"

IR is not something only the sun produces. Artificial lighting can be quite high in IR content. For instance a flash gun can blast out quite a bit. Incandescent lighting produces more heat and IR than light. Use a filter for a while to see if it helps. It won't harm your photographs.

[jaapv]

1 hour ago, LocalHero1953 said:

The M9 had this problem a lot - under certain artificial lights the lips of certain people would be strongly magenta-coloured - like bright lipstick. And some people with 'the wrong type of skin' would show a blotchy face - very ugly at times. I found the effect less in the M240, but not always absent. 

I reported it here a long time ago!.

And dark skin can have a blue cast in places. Melanin will block the transmission of IR to deeper layers. Less displeasing than the yellow and magenta on Caucasian, but still...

[jaapv]

2 hours ago, Cobram said:

M camera as a medical detecting device? Always something new to learn...

 

Nothing new there:

https://pubmed.ncbi.nlm.nih.gov/26691203/

[Adam Bonn]

25 minutes ago, jaapv said:

Use a filter for a while to see if it helps. It won't harm your photographs.

Thanks Jaapv,

I'll give that a try. Like you say shouldn't cause any harm (Hmmmm maybe on my 21mm!!)

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Hallo,

Look here: Leica M

[frame-it]

41 minutes ago, jaapv said:

IR is not something only the sun produces. Artificial lighting can be quite high in IR content. For instance a flash gun can blast out quite a bit. Incandescent lighting produces more heat and IR than light. Use a filter for a while to see if it helps. It won't harm your photographs.

interesting, i have several converted IR cameras, 720nm and 850nm, none of them will show anything except a incandescent light bulb indoors, and that too above ISO 3200, i thought normal flashes have a filter to block IR?

 

[jaapv]

They do - but the effectiveness is variable.

This graph for varying light sources runs up to Red, but IR can easily be extrapolated.

https://www.researchgate.net/figure/Emission-spectra-of-different-light-sources-a-incandescent-tungsten-light-bulb-b_fig1_312320039

It shows that incandescent and halogen, and sunlight have the highest content.
LEDs will emit little to none - or not: see below - (but have a different problem due to a green peak) and fluorescents depend on the Phosphor mix, but often have a small peak around  750 nm. 

https://dothemath.ucsd.edu/2012/05/spectral-extravaganza-the-ultimate-light/

The takeaway: It is completely unpredictable with high efficiency lighting; trial and error is the only thing that works.

 

Don't forget that the highest sensitivity of M cameras lies in near-infrared, the filtering works better the longer the wavelength gets.