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I recently read an article about HCB. The writer wrote that Tri-X has an EI of 400 in Daylight & 320 in Tungsten... Is this true? That the temperature of the light will affect the EI in B&W stills?
Thanks for reading & hopefully responding.
Older BW films did have a lower speed in tungsten light because they were too sensitive to blue and not enough to red light. Modern films have a more balanced color response and usually have the same speed in all light. The article's claim of 1/3 stop difference seems too little anyway...thats so little you'll never see it. I think the older films had a much bigger difference between their daylight and tungsten speeds., like a stop or so.
On the other hand, motion picture B&W film gives different ratings for daylight and tungsten. And the difference is... 1/3 of a stop slower in tungsten.
That being said, Chris is correct, 1/3 of a stop isn't anything to sweat about. Though note that in the Kodak tech sheets for still B&W film, while they don't give other ratings for tungsten lighting, they do supply different filter factors for tungsten exposure compared to daylight for filters.
I tend to drop exposures about 1/2 to 2/3 of a stop in tungsten light - and a lot more with some of the new flourescent lights. Haven't checked it with LED lights yet.
Most problems occur when you are shooting indoors in a room. You have bright lights and deep shadows. To keep the light balanced, you usually have to expose for shadows and let the lights fall were they may. Otherwise you have a solid black with 'spots" of bright lights.
The modern films are better, but not infallible. When in doubt - overexpose and be prepared to burn in light sources.
Some developer will work better with this kind of light - flatten the contrast. Stand and semi-stand developing helps, low contrast developers like D23 also will give a less contrasty negative.
Tri X works, but the range is limited - particularly if you are going to 'wet" print. Film has more of a latitude than paper. Scanning and contrast modification in L/R or P/S is easier.
Kodaks XX does indeed give a 200 iso for tungsten and 250 in daylight. Of course, we are looking at staged scenes with big Klieg lights that can be turned up or down to lift shadows and balance the brights.
Watch some of the old classic movies in bl/w and see how the light is balanced - Orson Wells was a master at this "The Third Man" is a great movie in itself - but also a lecture how to light.
If you can, switch films when shooting tungsten and develop it specifically for the situation - either by changing developer or processing.
Also remember that light is not constant - it actually "flickers" usually at 1/60 sec intervals. If you are shooting at speeds around 1/60 you can hit a low glow and shots look underexposed - but another shot, a split second later looks OK.
As with everything, test and note down variations.
In the old days filter manufacturers used to sell a CC filter for tungsten lights on B&W films.
Thank you Tom & Thanks to all the rest for their appreciated info. on this subject.
1/3 F stop is a good average of a modern panchromatic film. However if you have an Orthopan or Ortho film the sensitivity will drop a lot more: 1 F stop.
Look at this Rollei Retro 100 TONAL film. The spectrum of this film will stop just over 600nm.
iso 100 in Daylight
iso 50 in Tungsten light.
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