Colour Correctiongreenspun.com : LUSENET : Large format photography : One Thread
Hello LF user forum
I am shooting a hall that has mercury vapour lamps (coated white)on the inside. I will be doing a double exposure metering for late dusk and then later switching the lights on and filtering for the second exposure. I have a number of filter options, the one I wish to use may only reach me in 3 weeks time, this is the Lee Daylight MV-D. Comments on this filter, good or bad choice?
Info on the lighttec.com site suggests 50m + 30r for RDP but in the 99 Fuji data guide it mentions MV indoor 20m+20r and out door 40r+30m. Why the difference between information sources on the same film type and secondly please explain the indoor and outdoor, is this ito where the lamps are, I will be outdoors shooting the building, but the lamps are indoors which filter set will I use. If I can't get the lee MV-D, I have a lee 30m and a Cokin 002 red filter, with what red number ie 10,20,30,40 or 50 does the Cokin 002 correspond? Is there a site where there are corresponding charts of the Wratten, Lee and Cokin system?
Lastly, I use theoretical exposure times for different lighting situations. For example i have used on a recent shoot 45" at f22 for tungsten lights in a house when I was about 10 metres away shooting toward the hse. The inside exposure measured in the hse was 4" at f22. Is there a way of using the inside reading and distance to hse/bldg to obtain the correct exposure time when outside the hse/bldg? (If it is the inverse square law, plse explain how I wouls use it) Obvioulsy each architectual shoot I will be at a different distance from the bldg. Is there an answer to this?
Thanks for any info Karl Beath
-- Karl Beath (firstname.lastname@example.org), March 13, 2002
It sounds like you're doing a "twi-night" double exposure -- record the outside of the building at twilight, then record the interior lights with a second exposure after dark. This is usually done with NO color correction, because that "tungsten glow" from the windows makes the building look warm and inviting. Color correction formulas and filters don't help much, because the twilight used for the first exposure is not what your film was calibrated for, either. If you apply color correction for the second exposure to make the window light look like 5500 degree daylight, it will just look like a nuclear bomb went off inside. I would scrap the plans to filter the second exposure at all, and just go shoot it and see what comes out.
-- M. Francis (email@example.com), March 13, 2002.
You might just shoot some exposures of the mercury vapor lights with the different filter packs, keep careful notes, get them developed and then choose the best one. Then go reshoot with your information in hand. Keep a record book so next time you'll know. BTW, maybe use roll film for your tests, save some cash. Also, since you are probably going to be using long exposures, you should try tungston film, instead of daylight film. Filter the first exposure to balance the film for day light.
As for shooting at various distances from your subject, I use a spot meter and read the windows from the outside, standing next to the camera and place them accordingly using the zone system. The window glass will cut the interior light so using a reading taken from the interior of the house will probably be too high.
-- Rob Pietri (firstname.lastname@example.org), March 15, 2002.