Leica M246 IR cut off filter ?

[Greg Law]

Advertisement (gone after registration)

Does anyone know the spectral details of the IR sensitivity of the Leica m246 sensor & if an IR cut off filter is also in place to reduce native sensor IR sensitivity?

 

 

Greg

[fotomas]

Hello Greg,

don't know details but the infrared sensitivity of the M246 is pretty similar to the M240. It went down to 1200 nm or even more. I did a test on the IR capability and got the feeling that it especially matters if you use yellow, orange or red filters. All these filters are transparent for IR and I found skin becomes a bit mushy then.
Even without filtering I have the impression that you get more details and a sharper image with a IR-cut filter in areas with a lot of IR reflectivity.
But the difference is subtile.
 

Regards

 

Frank

 

[jaapv]

Which is not surprising. The IR light will create an out-of-focus "overlay" over your sharp visible light image as IR light will focus in a different plane. As the IR will be underexposed by four or five stops the effect will be very small, but it can affect microcontrast, depending on the intensity of the IR component of the light.

If you use colour filters you are altering the intensity balance between visible light and IR light and the effect may become more critical in extreme situations. It might be worth experimenting with stacking an IR filter to see whether the advantage outweighs the drawbacks.

[algrove]

So to cut to my concern here.

 

Is it better to use an orange B+W say 040 filter versus a 486 B+W filter on an MM1 for landscapes?

[jaapv]

The M8 had an IR filtering that was 50% effective (with the well-known result ), the M9 was 80% effective which is acceptable in normal circumstances and I suspect that the M240 series is around 70%, which means a filter is needed from time to time. It is easy to verify these values by using an IR pass filter like B&W 092 and comparing EV values between the cameras.

[dante]

I measured the sensitivity with almost every available b/w and color correction filter, including an 092. It has extremely little IR sensitivity; using an IR-pass filter is like a heavy ND.

[jaapv]

Advertisement (gone after registration)

70% is quite effective, but it will still allow you to do IR photography. A 093 filter works better, though.

[algrove]

70% is quite effective, but it will still allow you to do IR photography. A 093 filter works better, though.

 

Jaap

 

Does the MM1 have an IR filter in place or does it just have a clear glass filter over the sensor? Sorry for the question, but I do not remember those specs any longer.

[jaapv]

It has an IR filter, the same _{as the M9 AFAIK.} 

[metalgrunt]

@algrove This is a bit of a late reply, but I once found an official brochure called "LEICA M MONOCHROM - The fascination of digital black-and-white photography." It states the following:

"Image format/image sensor: Active area approx. 23.9 × 35.8 mm, 5212 × 3468 pixels (18 megapixels). Infrared blocking filter for invisible light with wavelengths longer than 700 nm, no low-pass filter."

-Lauri