Spectral sensitivity of black-and-white films

[StS]

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Good evening,

 

having played a bit with different films recently (BW400CN, Tri-X and Tmax400), I might have found a point, why we prefer certain films over others. Grain is a common discussion point, and here the colour process based BW400CN certainly behaves differently to classic black-and-white films. However, at least with my film scanner, I could not find any dramatic difference between Tri-X and Tmax, when it comes to grain. This might be due to the fact I tend to over-expose black-and-white films slightly, if in doubt.

 

Having seen some Tri-X photos, which looked like taken through a light yellow filter, I took the data sheet of BW400CN, Tri-X and Tmax400 and copied the spectral sensitivity behaviour in one file.

 

The film having the narrowest spectral response is BW400, cutting even into blue, which should give it a slight yellow-filter effect. The classic BW films's sensitivities, however, reach deep into ultra-violet (there goes my Tri-X-yellow-filter-theory ). Quite interesting is also the lower sensitivity of Tri-X around 500nm (green), which should give less denser negatives (or darker prints) for green.

 

Tmax appears to have the most uniform spectral sensitivity (also the broadest range). Interestingly, it is the film I like least, especially, when taking images of people. It might have its virtues over Tri-X, when taking landscapes, though, but I haven't tried yet.

 

Science aside, I prefer BW400 or Tri-X over Tmax - but this is just my (not calibrated) view...

 

Stefan

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[tgray]

I've found the difference in grain between Tri-X and T-Max are minimized while scanning. It is much more apparent when doing wet prints. The spectral sensitivity in my experience is different, but probably not enough to bother me. T-Max appears to be a bit less sensitive to blue which could be nice in pictures that include the sky.

 

I did notice a large difference in resolution between the two films. Both in scanning and wet printing.

[christer]

It took me quite some time to start liking TMY, but once there it is now one of the two films I use the most. It goes very well with TMAX developer, I developer I disliked ten years ago.

[budrichard]

You may want to look into the history of orthochromatic and panchromatic films if your interested in spectral sensitivity. In particular, I can reccamend C.E. Kenneth Mees, The Theory of the Photographic Process, Macmillan Co., New York, 1942.

The reason that photos of early native Americans look so dark is that they were taken with ortho film and the 'red' was enhanced.-Dick

[adan]

Way back in my college days, the instructor in the sensitometry class (Zone System and the like) always referred to "typical Tri-X white skies" when critiquing shots. He was not a fan of that film without some kind of filtering.

 

As an aside - part of the popularity of yellow filters for B&W work (and not just for skies - David Douglas Duncan shot his Viet Nam news coverage with them), is that lenses pre-1980 still often had a lot of CA, and narrowing the spectrum to the green/red range improved real sharpness by deleting the fuzzy blue fringes we still occasionally see today, as well as darkening shadows to increase the "apparent" sharpness of contrast.

[pico]

[...] As an aside - part of the popularity of yellow filters for B&W work (and not just for skies - David Douglas Duncan shot his Viet Nam news coverage with them), [...]

 

Under the tropical canopy, a blue filter is helpful, too. (There is no sky under the canopy)

[adan]

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Based on his pictures in War Without Heroes, most of the jungle canopy where DDD took his pictures had been removed by Agent Orange or a succession of loud bangs and booms. Mostly big mud piles like the fire base at Khe Sanh.