Filters for B&W Photog.

[d_f11]

<p>Scenario: It's early afternoon, I'm looking through my viewfinder at/near 90 degrees to the sun at a scene fairly evenly lit across, no shadows, big puffy cumulous clouds in brilliant haze free blue skies, below is a city skyline, or a body of water, perhaps a field with trees. I can visualize what a polarizer will do - to the sky and especially the clouds(make them even more definite), but the red-orange-yellow filter factor - is it all a matter of degrees? Yellow will add alittle contrast/darken the sky, orange even more, red even way way more? I still want to go with Ilford Pan f Plus, so my uneducated guess would be orange or dark yellow, so how would those filters compare with what the poarizer does? I know, go out and try it!</p>

[vilk_inc]

<p>go out and try it. they will do different things--especially if there's (perhaps :)) something else in the frame besides the puffs--and <em>de gustibus non disputandum<br /><br /></em>with the color filters you may also want to pay attention to colour temperature (a.k.a. time of day). just before the sunset the orange may give you mean contrast in the perhaps part of the picture; yellow at the golden hour can be quite like orange at noon<br /><br />did i say go out and try it? :)</p>

[john_shriver]

<p>Very different from what the polarizer does. You can envision it to some degree by looking through the filter.<br>

A light to medium yellow gets the same tonality on film that your eyes see. As you get into yellow-green, orange, and red, the sky will be made even darker.</p>

[d_f11]

<p>Perhaps I'm not being clear enough. I know how and why the polarizer would darken the sky or make MORE definite the clouds(outlines of the clouds), and increase contrast, but how does that differ from the ways the color filters are supposedly doing the same thing? I mean I realize in B&W it's the complimentary color that darkens (enhances?), the same color lightens...?</p>

[paul_hoyt]

<p>The polarizer will darken the blue sky but will not remove light from the shadows, which is reflected blue light. As you increase the strength of the B&W filters from light yellow to yellow to orange and finally red, more blue light is removed from the scene and the shadows become darker and darker. The polarizer is the best filter to separate the sky from the clouds and not lose the shadow detail. A red filter can give you the soot & chalk effect. You do need to evaluate the effect of the polarizer on water when it is in the scene. If you are trying to darken the sky and you have water in the scene, make sure the polarizers effect on the water is what you want; the water can be transparent or is impenetrable.</p>

<p>Paul</p>

[robert lee]

<blockquote>

<p>... but how does that differ from the ways the color filters are supposedly doing the same thing?</p>

</blockquote>

<p>The commonly available B&W film is sensitive to the amount of light incident upon it, but relatively insensitive to the color of that light. So, point a camera up at some puffy white clouds in front of a brilliantly blue sky, and you'll find that the tonal separation between the two isn't actually all that large.</p>

<p>Now, a red filter admits mostly red light, something that that the clouds emits much more of than the blue sky. With the filter in front of the lens, the film recording the sky now receives less energy relative to the clouds. It thus renders the sky much darker tonally.</p>

<p>The easiest way to play with this is to just look at the R, G, and B channels separately of a color image in your photo editor of choice. Play with the channel mixer for more finesse.</p>

[lachaine]

<p>A yellow, orange or red filter in B&W photography has no disadvantages other than its filter factor and whatever it does to the contrast between tones in a scene (which is nevertheless entirely consistent within that scene).</p>

<p>A polarizer has 2 significant disadvantages in addition to loosing about 2 stops of light and in effect adding two glass surfaces in front of your lens rather than just one. First, it greatly limits in which direction you can point the camera if you want the polarizer to work, and it precludes using a wide angle lens because the polarizing effect on the sky won't extend the whole width of the coverage.</p>

<p>Given that, unless you specifically need to eliminate some reflections in the scene you're composing, it's just more practical to use a yellow filter to darken the sky. You just put in on the lens and forget about it. As for red, well, you can't really just forget about the fact you have a red filter on the lens, because the effects are more extreme, but it's still better than using a polarizer if it's just for darkening the sky -- and it will do so more dramatically than the polarizer will.</p>

[tonysvision]

<p>If I'm reading your question right, you are asking how a polarizer works in comparison to colored filters when shooting black-and-white. That's an interesting question, because I generally think of a polarizer as a tool for darkening skies when using color film, because obviously a colored filter won't do the job. Colored filters reduce the amount of light from selected parts of the color spectrum. Most dramatic is the red or deep red filter, which reduces the strength of pretty much all colors except red. Most reduced are the colors on the other side of the color wheel, i.e., the cool colors like blue. I think of it as the "Ansel Adams" filter for getting dramatic skies.</p>

<p>A polarizing filter ignores colors and filters out polarized light instead. Some ancient Eastman Kodak pamphlet taught me to think of polarized light as vibrating only in one direction, as opposed to radially. Skylight reaching us from that 90° angle to the sun and light reflected from nonmetallic objects is polarized. That same old pamphlet taught me to think of a polarizer as a blank disc with a slit in it. so depending on the orientation of the filter, more or less of that polarized light gets through. So when you crank the filter around so that it's "slit" is at right angles to the direction of vibration of the polarized light, the sky becomes dark and reflections are reduced.</p>

<p>Translating all of this to the comparative effects of a polarizer versus colored filters on black-and-white film, the polarizer will darken the sky like a yellow, orange or red filter (but only at that 90° angle, which leads to problems of non-uniformity with a wide angle lens), and would also, depending on its orientation, darken the foliage and water you mentioned by reducing reflections from those surfaces.</p>

<p>Hope this helps – think I'll just go out and try it myself.</p>

<p>Tony Mindling<br>

www.tonysvision.com</p>