Anyone have advice for shooting B&W at high altitudes (over 6,000 feet)? I plan to use yellow, orange or red filters, depending on the effect desired. Any special compensations needed for meter readings?

-- Sam (sselkind@home.com), October 01, 1999

Answers

Keep in mind that the cloudless blue sky at high altitudes is much more saturated (i.e. bluer) than at lower ones. This can affect both meter readings and filter factors. Filters that remove blue light, for example, red, yellow and orange filters, will be removing a much greater proportion of light from blue skies and open shadows lit by the blue skylight due to the increased blue component of the light from the sky. Therefore, filter factors should be increased for this situation. You will have to guesstimate/experiment and bracket at first to get a handle on exactly what factors you need. As for metering in general, if you are using a conventional averaging meter which sees a lot of the blue sky area, you may have to increase exposure somewhat due to the high blue sensitivity of the photo cell in most meters. Spot meters exhibit the same blue over-sensitivity and you must take into account when reading the blue sky that the meter may be giving to high a reading. The Zone VI modified spot meters are affected less by this problem since they have special filtration installed to compensate for the blue over-sensitivity, so if you have one of them, you can discount great changes due to photo cell spectral characteristics. Thirdly, photographs made in open shade lit by the open sky (i.e. lit by predominantly blue light) could result in negatives with lower contrast and/or slight underexposure than normal depending on the film you are using due to the spectral sensitivity/contrast of the film you are using. Keep in mind that this only applies to sunny days with clear blue skies. On cloudy or hazy days your meter/filter/film combination will function just as it does at lower altitudes. Hope this helps a little. Regards, ;^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), October 02, 1999.

Also, there is more UV at higher altitudes. Even when not using a red, orange, or other filter, I'd be sure to use a UV filter. UV focuses at a different point, and tends to haze things up.

-- Conrad Hoffman (choffman@rpa.net), October 02, 1999.

I contacted B+W, the filter company, about 3 weeks ago and was told, there should be no problem with TTL metering using b/w filters at high attitude. ( I gave an F2AS to a friend going to nepal ).

Regarding external meters, e.g. a Gossen Variosix, it might depend on the spectral sensitivity. Gossen was kind enough to provide me with a sensitivity versus wavelength graph, which shows highest sensitity around 580 nm, dropping in a gauss curve to almost zero at 380 and 780 nm. So the effect should be rather small for this meter.

-- Wolfram Kollig (kollig@ipfdd.de), October 04, 1999.