The Subject is Filters

Lars Giertz, our technical advisor, tells when and how to use them.

It is an unfortunate fact that modern black and while films do not render colors in what we gen­erally perceive as correct tones of black, white or gray.

Standard panchromatic films (Tri-X, Panatomic X, HP4, etc.) are very sensitive to blue and ultraviolet light (white skies) and rather insensitive to green light (dark foliage).
Before we try to do something about that problem (and we can), it might, however, be interesting to first have the ability to find out how the film sees our subject be­fore we photograph it.
To adjust our perception of a scene to match that of the film, we need a viewing filter. The fil­ter needs to lighten the blue end of the spectrum, and, at the same time darken the green end.
Since any color filter lightens its own color and darkens its compli­mentary color, we need a viewing filter that is a combination of blue (to lighten the sky) and magenta (opposite of green, to darken the foliage).
So now all you have to do is whip out your Jim Dandy B&W viewing glass and look at your scene to determine whether or not there is reason to modify the film's rendition of the subject to represent the scene the way you want to interpret it.
The only source that I have found for dial kind of a filter is Harrison and Harrison of Holly­wood, California and it is their #23W. It isn't cheap ($15), but then how much would you pay to have gotten a good exposure of that landscape you blew on your last photo trip?
I know that there are purists among us that scoff at the use of filters in black and white photog­raphy. But I submit, dear fellow photographer, that left to its own decision, modem films will render blue subjects one zone too tight, and greens as much as two zones too dark.
Ok, now that we know what the film would give us if we didn't
Well, of course, we fool the film into seeing the way we per­ceive what is the "right" tones of gray. Note that there is no "per­fect" filter that can be used. Sometimes the sky should be white . . . sometimes a more dramatic darkening might capture your feel­ing of the subject. Similarly, a very dark forest might look great against other adjacent lighter tones, but there surely are times when it must be lightened.
Here is a list of the most useful filters for B&W photography using panchromatic film. Keep in mind that each filter has its own effect on the over-all exposure as well, so any time you use one, you will have to make the appropriate ex­posure adjustment.
To check for correct exposure, simply put the filter in front of your light meter and note the dif­ference. Note that each filter will affect each of the colors a differ­ent way. After reviewing the scene you are about to photograph with the viewing filter, select the appropriate filter from the chart.
Then, hold both the viewing fil­ter and the color correction filter together in from of your eye, and you will be able to see the final effect on the film!
The filters are available from most good camera stores. Kodak makes their Wratten Series filter gels in 3 inch by 3 inch squares that can be held in front of the lens if necessary. If you are shoot­ing in large format, it is highly desirable to tape the filter on the back of the lens inside the camera to minimize any light reflections.
Is there a happy medium filter? Do I really have to buy all of those filters to control my subject?
Here is what I recommend in order of usefullness.
B&W viewing filter (Harrison and Harrison #23W, $15.)
213/464-8263, 6363 Santa Monica Blvd., Hollywood, CA 96038.

#12 (medium sky)
#11 (best compromise for medium sky and lighter green)
#8 (light medium sky)
#15 (pretty dark sky. If you are into black skies get a #25,
but greens go darker)
#56 (slightly less than #11)
#58 (dark sky, very light

Try it - you'll get what you want. Question on this or other matters? Call me at home, 723-6463.