IR Effect on B&W Photography

[Stan Raucher]

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I am interested in using the M8 primarily for B&W work, so the WB and IR issues seemed less troubling to me than to those doing color work.

 

Now, according to this poster IR may cause problems for B&W images as well.

 

He states that IR "causes an overall softening (even Leica lenses aren't corrected for chromatic aberration in the infrared), a lack of overall contrast, increased flare (lens coatings don't perform efficiently in infrared), and a loss of shadow detail."

 

Anyone else care to comment on this?

 

Thanks,

 

Stan

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[carstenw]

I think the Apo lenses *are* meant to be corrected for infrared...

[ho_co]

I think the Apo lenses *are* meant to be corrected for infrared...

I don't think so, Carsten. Check out some of E Puts's lens curves. You may be right, but I seem to recall that even Leica's apochromats follow standard design practice of bringing only three specific and visible wavelengths to the same focus point. (On the other hand, the Zeiss "superapochromats" brought I think five or six wavelengths to the same focus.)

 

But although theoretically the poster is correct, we live with this condition daily. Even Leica's apos bring only three colors into focus; all the others are either before or behind the focus point. IR and UV are both further away from where we want to work, so their effect will be somewhat greater.

 

Have you seen the wonderful tonalities of the Leica b/w shots that have been posted around? If those images have been degraded by increased sensitivity to IR, they would be terrifyingly good with IR filtration.

 

The point is correct, but the IR effect is minimal in practice.

 

--HC

[Vivek Iyer]

Howard is right. The focus shift (IR focus being closer to the camera than the visual focus) will affect the sharpness since most Leica lenses aren't corrected into the IR region.

So, the sharpness and contrast experienced by using film (most color films are senitive upto 650nm in the visible), ortho films, and even panchromatic films will not be readily apparent due to IR contamination. It should be possible to take care of it by using a suitable filter (in most cases, except the ultrawides).

 

There will be a slight loss of contrast. Foliage will look a bit bleached, for example.

It is good for skin tones though.