M11 Infrared Sensitivity

[J S H]

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Hello all. It's been a few years since I've posted, but I still follow the forum regularly. After several years without an M body, I recently acquired a new M11. Love the camera...I think it's an amazing achievement for Leica. I shoot IR photography professionally and I was curious about the M11 and its general sensitivity to Infrared. I've done some testing and it seems that the M11 has at least as much IR sensitivity as the M240, which was the last M body I owned. I have shot quite a few IR images with the 240 and after shooting some new images with the M11, the exposure times are pretty much equivalent. I never really noticed any issues with the M240 for normal visual light photography and I don't see any issues with the M11 either. I actually think the filtration is just about perfect and probably about the best Leica could do with the thin sensor stack.

I will say that the M11 sensor is amazing. I have multiple Sony bodies that I use for photography and cinematography, both IR converted and standard. The M11 sensor seems like a cut above the A7r4, which is the newest Sony body I shoot with. I can't quite put my finger on it, but it's noticeable. I think it's partly because of the thinner sensor stack and Leica's approach to color. Also the M11 has no phase detect array, which is a total dealbreaker for IR, as it shows up clearly in the infrared spectrum.

Here are a few informal examples that show the same scene in IR and visual light. The IR images were shot with a 780 IR filter, which is fairly restrictive, but still lets a little visual light through.

1) Leica Elmar-M 50 2.8, 1/750 sec F8

2) Leica Elmar-M 50 2.8, 30 sec F8 (780 IR Filter)
 

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[J S H]

2nd set of images...

3) Voigtlander 75 1.5 Nokton, 1/350 sec F4

4) Voigtlander 75 1.5 Nokton, 30 sec F4 (780 IR Filter)

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[jankap]

The colors of the landscape with the Nokton are beautiful. The sky could be less reddish.

An interesting test, but I am an IR layman.

[darylgo]

Thanks for your posts, very interesting to know that the M continues to allow IR without modification.  On occasion, I’ll set ISO at 6400, shoot f1.4, and get iirc 1/30 sec exposure with the M240 in sunlight, similar filter as the 780.  The grain/noise is unacceptable.  I’m curious if the noise has improved with the M11. 
 

 

[J S H]

When time allows, I'll try a few exposures at a higher ISO on a sunny day. I should have mentioned in the original post, but the above images were all at ISO 64. 

[ianforber]

Same here. I shoot IR regularly and use an 830nm or 720nm filter depending on the strength I’m am looking for. I find 800-1600 ISO to be the sweet spot. That said, the first image below is at 5000 ISO with a 720nm filter just to see if I could hand hold the camera. The second image is a stitched panorama of 5 images at 1600 ISO with 830nm filter. Both with 50mm Summicron. Both tests so no artistic merit. Panorama was shot in Spring last year so leaves on the trees to show the full IR effect.
 

 

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[DenverSteve]

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20 hours ago, darylgo said:

Thanks for your posts, very interesting to know that the M continues to allow IR without modification.  On occasion, I’ll set ISO at 6400, shoot f1.4, and get iirc 1/30 sec exposure with the M240 in sunlight, similar filter as the 780.  The grain/noise is unacceptable.  I’m curious if the noise has improved with the M11. 
 

 

It's probably important to mention that your "noise" is due more to the higher ISO than the longer exposure.  Try the same shots at ISO 100 & 6400 and I'm sure you'll see a difference. 

[jaapv]

This also means that the camera is sensitive for IR contamination in colour shots. Use an IR cut filter for high-IR situations like tropical noon sun, some types of artificial light, sunsets and some flashes. Typical is a yellow cast and olive greens. 

[darylgo]

51 minutes ago, DenverSteve said:

It's probably important to mention that your "noise" is due more to the higher ISO than the longer exposure.  Try the same shots at ISO 100 & 6400 and I'm sure you'll see a difference. 

Thanks for the info, makes sense.  The high iso is for portability and shooting handheld without sensor modification.

[hmzimelka]

I can't say I'm very impressed with the IR sensitivity of the M11. It's better than with my D850 but it's certainly not great.

At the edges one can sometimes experience the stair-like interpolation artefacts of fine details. (not sure what the correct technical name for this is) I'll try post an example when I have one that is prominent enough. For now my examples are not prominent enough to be easy to show here.

I had to create a revised M11 DCP colour profile in Adobe DNG Profile Editor, with some adjustments to WB.

Here are some examples taken with my Summicron-M 50mm V with a 720nm filter. One B&W and one Colour. 

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[sdk]

IR sensitivity is not meant to be a feature of the M11, of course, and could be a bug in some situations, necessitating UV-IR cut filters to correctly render some subjects that reflect a lot of IR. Glad to see it takes either very long exposures or high ISO to make IR photography possible, which means ordinary color photography is probably negligibly affected by this trace of sensitivity most of the time.

[MrPaulK]

But aren't those very long exposures really a result of the very high density IR filters, not lack of IR sensitivity? (not that question is not rhetorical, it is a real question)

[hmzimelka]

14 hours ago, sdk said:

IR sensitivity is not meant to be a feature of the M11, of course, and could be a bug in some situations, necessitating UV-IR cut filters to correctly render some subjects that reflect a lot of IR. Glad to see it takes either very long exposures or high ISO to make IR photography possible, which means ordinary color photography is probably negligibly affected by this trace of sensitivity most of the time.

Exactly. The fact that it's not great for IR is actually a positive. I'd rather it be accurate for colour during normal colour photography. I've not seen any odd colour contamination yet. 

[hmzimelka]

9 hours ago, MrPaulK said:

But aren't those very long exposures really a result of the very high density IR filters, not lack of IR sensitivity? (not that question is not rhetorical, it is a real question)

The 720nm filter I use is not high density at all. It's actually probably the lowest IR wavelength IR filter I can find, since anything lower also includes the red spectrum transmission.

I haven't used 850nm or higher transmission filters. I would be curious what others have tried. 

These are the filters I used for B&W infrared film back in the day. EFKE and Rollei IR films. Now those were fun times  

[hmzimelka]

OK, so curiosity led me down this path... 

The first image is with a 720nm IR filter on the Summicron-M 50mm V, f/2.8, 2sec exposure, ISO 64.
The second image has the same settings but with a Leica UV/IR filter attached (13411)
The third image is unfiltered, f/2.8, 1/350sec, ISO 64.

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[jaapv]

One does indeed see a very mild olive cast in the greens, but would not notice it unless alerted.

[hmzimelka]

25 minutes ago, jaapv said:

One does indeed see a very mild olive cast in the greens, but would not notice it unless alerted.

Here are the D850 (top) and M11 (bottom) white balanced on the grey card.

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[jaapv]

Exactly. Minimal, and of no real influence on the image but present. Look at the brighter patch of grass in the foreground. It would be interesting to have such a comparison with high-IR light. I say this because I had images taken on the M240 with bright sun straight under the Equator around noon that had an incorrigible yellow cast from IR. The only thing I could do was convert to B&W. 

[hmzimelka]

17 minutes ago, jaapv said:

Exactly. Minimal, and of no real influence on the image but present. Look at the brighter patch of grass in the foreground. It would be interesting to have such a comparison with high-IR light. I say this because I had images taken on the M240 with bright sun straight under the Equator around noon that had an incorrigible yellow cast from IR. The only thing I could do was convert to B&W. 

Yeah, not denying the existence of IR here. Just a comparison. Not enough to bother me.

We have currently an extremely high UV index at the moment, to the point that most of our plants get burnt. Not sure if that also means high IR levels too. The images above were taken at 12:40. 

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[jaapv]

High UV would reduce the percentage of IR I agree, just something to bear in mind and not to worry about under most conditions. The M240 had an IR filter of about 75% efficiency. The M8 about 60% and that was enough to cause trouble. I would say from your tests that the M11 is similar to the M240.

BTW, it might be interesting to use a UV pass filter. UV photography was quite effective on the M8. You would need a vintage lens as most if not all modern lenses are UV filtered. I used a Summarit 1.5/50 from the early fifties.