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Lighter Construction Filter: Typical particle size and feed concentration range: 0.1-80 /^m and 0.0005-0.3% v/v. These filters are similar in appearance to plate and frame Filter presses (see Section 7.4.2.3), but compound, relatively thick sheets formed from diatomite, glass fibre or combinations of polymers are used in place of Filter cloths to promote depth filtration. As filtration pressures rarely exceed 300 kPa, units are of a lighter construction Filter construction than Filter presses and utilise narrower chambers to provide for the removal of small amounts of fine solids from dilute feeds.
The Kl Filter, very light yellow in color, gives slightly less correction than the Kodak Color Filter. It renders the sky somewhat darker than would be the case with no filter, showing up the clouds but not to such an extent as does the Kodak Color Filter or K2 Filter. Red and yellow subjects such as flowers are rendered lighter construction Filter than with no blue lii>ht from the sky; the G Filter absorbs this blue light and consequently the shadows are rendered darker than they would be if no Filter were used.
Since a Filter absorbs some of the light which would otherwise affect the film, the exposure must be increased. The "filter factor" is a measure of the amount of light absorbed by a Filter with respect to the amount transmitted. The Filter factor represents the number times the exposure must be increased when using a Filter as compai with the exposure required without it. A Filter having a factor o with, say, Kodak Plus-X Film, will thus require twice the exposi necessary without it. |
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