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  1. #11

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    The eye focuses light better at the red end of the spectrum than the blue (it's a simple lens remember). I would be surprised if this caused any kind of haze in the viewing test you did, but it might. An example of this is little blue LED marker lights which seem to be the fashion in some areas of outdoor public area lighting these days. In the dark they appear to have haze around them when you look at them from a distance of at least about ten metres. Another example is seeing an ambulance from a distance on a dark night: here in Australia they are now using red and blue LEDs for their party lights. The red ones seen at least about 500 metres away appear sharp, the blue ones hazy.

    John.

  2. #12

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    Quote Originally Posted by David Lyga View Post
    There is a difference in contrast when taking pictures under daylight (shade) and indoor tungsten roomlight. When I shoot a roll of BW film under both conditions this situation inevitably manifests.

    Why? I think that it has to do with the bluishness imposing a very slight fog veil over the outdoor image. Even looking at something under the shade, and then immediately placing a K2 (yellow-green) filter over your eye to judge the same scene, shows a slight increase in contrast when using the filter.

    I took photos of a gray scale with color patches under both conditions at the proper exposure. Obviously, the colors imparted somewhat greater contrast with the K2 but the gray scale ALSO did the same. The difference was not much but was at least half a paper grade.

    I prefer the tonal rendition under the lower Kelvin. Indoor tungsten lighting seems to just differentiate the tones better and are actually more believable when printed. It's frustrating to see a roll with negatives with differing contrasts. Are my assessments correct? - David Lyga
    I think you're barking up the wrong tree in blaming degrees K alone. Shaded sunlight is inherently less contrasty than tungsten light. In shade, (fairly even) diffused light is probably approaching the subject from almost 360 degrees. Whereas, under tungsten, there will be a discrete number of small, hard, light sources. So, even accounting for reflections from walls etc, the majority of the light hitting the subject under tungsten will tend to be harder and more directional than shaded sunlight, creating an effectively more contrasty scene.
    Studio photographers spend a lot of effort diffusing hard tungsten and flash sources in order to make them less contrasty. Many would like to use shaded north light instead, but it isn't practical.

    Also, although light temperature may play some part, I'd suggest that flare from scattered light probably plays a more significant role in this contrast difference. There's a lot of incoherent light flying about outdoors in shady conditions. Being sunlight, there's a larger blue component than in tungsten light and, I seem to recall, this wavelength has an even greater tendency to scatter as it strikes dust and water droplets etc in the atmosphere.

    UV filters are useful in combatting scatter but a really good lens hood is probably better. The typical 35mm/MF lens hood is highly compromised. Few photographers would want to carry around a truly efficient lens hood because, in many situations, it would need to be as big, if not bigger, than their camera.

    Regards
    Jerry
    Last edited by jerry lebens; 03-24-2011 at 06:28 AM. Click to view previous post history. Reason: Additional info

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