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Infrared sensitivity and older lenses


dpitt
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I like to experiment with old Leica M and SM lenses on my M8 and M9.

Yesterday I took on a Leica Elmar F3.5 from just after WWII mounted on the M9.

 

This produced stunning results for such an old design. A bit flair prone of course(I forgot to take the lens shade with me) but when everything was just right it was very sharp and even contrasty for an older lens.

 

Of course I used it without filter because I do not have any UV/IR cut filter that fits. But even then I was expecting decent colors on most pictures, as usual with the M9. But to my surprise it showed quite a bit of IR contamination. And I remember trying this lens on my M8 a few years back with very bad results on that point.

Now I ask myself the following questions:

 

- Maybe the light transmission bandwidth of the older lenses was is larger than in the current designs?

- I understand that this was not much of an issue in B&W photography, so maybe these lenses were even designed to make use of IR in someway to enhance contrast? And later on, some coating was added as in my sample, to make color film an option but still not completely cutting of IR?

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It may be that you are seeing UV contamination, which manifests itself in similar colour shifts  as IR on sensors. Lenses before ca. 1950 have no inbuilt UV filtering. After that time Leica used a lens cement that absorbs UV and in some cases UV opaque coatings.

 

Normal lens coatings do not specifically block IR light, the coatings used on IR-cut filters are very specific.

In fact, normal lens coatings can and will produce Infrared flare on many lenses, called the IR Hot Spot. Older lenses, with less effective coatings, will be much more suitable for Infrared photography for this reason. There are lists of suitable lenses to be found on the internet.

One thing that might be of influence may be the number of the lens elements, glass does absorb  and reflect some Infrared. IR  reflection of glass is a surface phenomenon caused by the inclusion of water and other ions in the glass, so the number of elements is of more significance than the actual thickness.

 

Although older lenses did have markings for focus shift due to IR, I do not think they were designed with specific IR use in mind.

 

Film does not react to IR like a sensor that is IR sensitive and needs filtering.

 

There were different spectral response curves of older film. In fact, it was  difficult to get them sensitive to the longer wavelengths. Orthochromatic film struggled with yellow and was blind to orange and red, Isochromatic film rendered yellow and orange better but still no red, Panchromatic was sensitive to red up to about 600 nm, but even Superpanchromatic film cut off at 680 nm.

 

It is true that infrared photography was far more popular before WW II than it is now. The development of IR film for military purposes during the First World War gave rise to a wave of enthusiasm, some would even call it a fad. There were dozens of IR films on the market. This popularity gave rise to the inclusion of IR markings on lenses to indicate the focus shift.

 

However, the need for these markings does indicate that the lens designers did not correct their lenses for infrared light. A modern apochromatic lens will show far less IR focus shift than simpler designs.

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I like to experiment with old Leica M and SM lenses on my M8 and M9.

Yesterday I took on a Leica Elmar F3.5 from just after WWII mounted on the M9.

 

This produced stunning results for such an old design. A bit flair prone of course(I forgot to take the lens shade with me) but when everything was just right it was very sharp and even contrasty for an older lens.

 

Of course I used it without filter because I do not have any UV/IR cut filter that fits. But even then I was expecting decent colors on most pictures, as usual with the M9. But to my surprise it showed quite a bit of IR contamination. And I remember trying this lens on my M8 a few years back with very bad results on that point.

Now I ask myself the following questions:

 

- Maybe the light transmission bandwidth of the older lenses was is larger than in the current designs?

- I understand that this was not much of an issue in B&W photography, so maybe these lenses were even designed to make use of IR in someway to enhance contrast? And later on, some coating was added as in my sample, to make color film an option but still not completely cutting of IR?

 

 

ALSO, your post process is very different --- doesn't work like shooting old kodak hie...  with a little skill, the images are breath taking

 

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