polarizing filter

[Greg Miller]

Greg, Thank you of this clarification. As a relative newbie to LF photography, I am at the stage where I plan to go out and purchase some of the basic filters to use in landscape photography with B&W and color films, and I didn't want to buy the wrong polarizing filters (if there had been a significant difference). ....

No problem. Glad to help.

[Doremus Scudder]

Just to clarify:

Yellow, orange and red filters remove blue light (plus more and more green as they progress from yellow to red). If (and only if) the shadows are illuminated by blue light, e.g., from a clear blue sky, these filters will darken the shadows. The effect can be very pronounced at high altitudes and with a very dark blue sky. On the other hand, these filters will have little if any effect on shadows on a cloudy day, when they are illuminated by diffuse light from the clouds. That said, they don't do much for darkening the sky in these conditions either

Polarizing screens remove polarized light from the sky, darkening it in certain areas in relation to the sun (and can darken some cloudy skies as well sometimes). They also remove polarized light from reflections. Removing reflections can be a good idea, e.g., for increasing color saturation, etc. But polarizers need to be used judiciously here, since removing reflections from a scene often renders it lifeless and dull.

Best,

Doremus

[Kevin J. Kolosky]

So again, back to my question. You, meaning any photographer, is faced with a daylight scene and wants to darken the sky. There is a considerable amount of woods, and shadows that are somewhat illuminated by blue light. You want the sky darkened but you don't want the shadows to fall into a lifeless hunk of real dark grey. And you don't want to use a polarizing "screen". So you go back to your red Cadillac by general motors reminder and choose a trusty yellow or red filter to allow those colors to pass but block cyan or blue. Are you going to put those shadows up a zone and then develop a bit less, or are you just going to accept the darker shadows.

[Doremus Scudder]

So again, back to my question. You, meaning any photographer, is faced with a daylight scene and wants to darken the sky. There is a considerable amount of woods, and shadows that are somewhat illuminated by blue light. You want the sky darkened but you don't want the shadows to fall into a lifeless hunk of real dark grey. And you don't want to use a polarizing "screen". So you go back to your red Cadillac by general motors reminder and choose a trusty yellow or red filter to allow those colors to pass but block cyan or blue. Are you going to put those shadows up a zone and then develop a bit less, or are you just going to accept the darker shadows.

There are a couple ways to deal with this. The first is: you multiply your calculated exposure by the filter factor for the filter you are using and then, based on your extensive experience in the field, give a bit more exposure to support the shadows. You also adjust development based on experience with this particular film and filter.

Second: (my preferred method), you meter your scene through the filter with your trusty spotmeter. Then, based on your tests and extensive field experience, arrive at an exposure and development scheme which include adjustments for contrast and exposure changes due to the spectral response of the film you are using.

You can also, however, just support the shadows by giving some extra exposure if you're worried about losing them (which you might easily with a strong filter). Modern films will overexpose a full stop without much of a problem. Then, you just deal with it when printing.

The thing is, if your filter has added a lot of contrast between shadowed and lit portions of your scene, and you deal with this by reducing contrast in the printing phase, you're also reducing the amount of darkening in the sky... which is what you wanted in the first place. That's why it's good to test and get some field experience. I don't "accept the darker shadows." I have a pretty good idea of how tones are going to be distributed in the final print when I release the shutter (or at least where I want them to be ).

Best,

Doremus

[Corran]

I've heard differing accounts on whether spotmetering through a filter is accurate or possible, all from people I would trust. I'm sure that depending on your methodology, type of meter, film type, etc. etc., you might come to varying conclusions.

Personally, I've found that not to work. With most filters I would end up underexposing (the meter was not accounting for the proper amount of filter factor), while with other filters (red spectrum usually) I would grossly overexpose in most situations. So I prefer to use known filter factors combined with a bit of working experience to calculate exposure with filters. By the way, I don't say this to discount the above post, just to add a data point. I'm sure you could meter through a filter and add your own "filter factor" from experience but to me that's an extra step.

Since this thread is about polarizers, I will say here that metering through those filters always gave me underexposed images.

[Heroique]

...and then, based on your extensive experience in the field...

[Applause]

...based on your tests and extensive field experience...

[Applause grows louder]

...That's why it's good to test and get some field experience...

[Applause now thunderous, loud whistles of approval, shouts of "Bravo!"]

[John Olsen]

[Applause]

[Applause grows louder]

[Applause now thunderous, loud whistles of approval, shouts of "Bravo!"]

Experience? That sounds like a lot of work. Doesn't Toyo have an app for that?
This has been a good thread. I think I'll pack my polarizers and give them more tries.

[Lachlan 717]

I use one most times I'm doing forest shots (colour). But I like saturated greens...

[Drew Wiley]

I thought "reflections on leaves, grass, rock, and skin, etc" was the whole point of the photograph to begin with! Interesting to see our different approaches to
the same subject matter. Nobody has converted me to polarizers yet.

[Greg Miller]

I thought "reflections on leaves, grass, rock, and skin, etc" was the whole point of the photograph to begin with! Interesting to see our different approaches to
the same subject matter. Nobody has converted me to polarizers yet.

Some reflections are desirable, some are not. It depends on the photographer and what the photographer is trying to communicate. The polarizer gives the photographer a choice in keeping the reflections or removing some (or sometimes all) of them.

Just one example: sometimes there happens to be a reflection on something that is in the frame and which is not the main subject, and detracts the viewer form the main subject. Using a polarizer to remove the reflection improves the image. THis can mean the difference between making the photo or not. Or making an outstanding photo or making an OK photo.