Jody Forster image in View Cameragreenspun.com : LUSENET : Large format photography : One Thread
In the current View Camera, in the article about 5x7 photography, I saw a very beautiful (to my taste!) landscape from New Zealand by Jody Forster. It's a VERY saturated image shot on Velvia. If you saw it, how do you think she did it? It's extremely saturated color, even for Velvia. I'm a died in the wool B&W person, but this almost inspired me to try some chromes....
-- John Sarsgard (Endive4U@aol.com), February 21, 2000
A polarizing filter used right usually boosts the colour saturation, by removing surface reflections from leaves, paintwork etc. In fact mine's almost welded to the front of my lens for colour work, and I'm considering trying to use it to modify the tonal range in B&W as well.
Anyone tried anything like that?
-- Pete Andrews (firstname.lastname@example.org), February 22, 2000.
I use a polarizing filter with black and white photography (usually landscape or buildings) quite a bit. When the sun is at the right angle the filter will make the sky darker and will make water darker, to mention two common situations in which it alters the tonal range. r
-- Brian Ellis (email@example.com), February 23, 2000.
Thanks, guys. I've used a polarizing filter lots in 35mm. How do you compensate for it in 4x5, since the filter factor depends on the rotation of the filter?
-- John Sarsgard (Endive4U@aol.com), February 23, 2000.
Most places I have read that the polarizer is a constant 2x factor regardless of the amount of "dimming." You might want to check Tiffen for the official word.
-- Tony Brent (firstname.lastname@example.org), February 23, 2000.
That's right. A polarizer essentially acts as an ND filter as far as overall exposure goes, and you can easily get the right factor by sticking it over the cell of your lightmeter. Filters tend to vary quite a bit from maker to maker, but somewhere between 1.5 and 2 stops is the norm. The lighter ones always seem to have a bit of a colour shift to them, so I've settled on Hoyas, which are absolutely neutral.
If you try to make compensation for the darkening of the sky, you just lose the saturation again.
For colour work, I tend to set the angle for best saturation in the subject, usually foliage, and ignore what's happening to the sky. Water's tricky though; it can look really strange if you're not careful.
-- Pete Andrews (email@example.com), February 24, 2000.
Im suprised at how many times people think you need (or want) to compensate for the polarizing. You dont. You just want to compensate for the ND portion. Think about a typical application, such as using it to darken a blue sky (you wanted it darker, right?). The ND portion of a polarizer affects the entire frame equally, while the polarization does not. For instance, the white clouds, which now are very visable against the darkened sky. If you compensated for the polarization, you just bring the sky back to where it was without the polarizer (so whats the point of even using the polarizer?) and burn out the white clouds. I find that 2 stops works out just right for me for compensating for the ND portion. When I initially tried to find a compensation factor, I did what Pete sujested, and simply measured through the filter with my meter. It gave me a 1.3 stop difference. However, the image was still to underexposed. After adjusting my compensation factor I finally found that 2 stops works the best. I dont know if different polarizers have different ND characteristics, so you may need to shoot several frames and find your own factor. Its probably cheaper to do this with 35mm than LF. Shoot a roll with and without the polarizer, bracketing your shots, and you should easily find your factor using one roll of transparency film. Of course, there ARE some situations where compensation for the polarization is necessary, such as removing glare from glass, which may require different compensations, but for most LF images (nature, landscape), compensate for ND, not for polarization.
-- Ron Shaw (firstname.lastname@example.org), February 24, 2000.
Hold the polariser to your eye, rotate it to achieve the required result and then take a reflected light meter reading at the same rotation. This will give you the filter factor. Now fit it to the lens in the same rotational position. Or you can check with a polaroid. Hope this helps.
-- Garry Edwards (email@example.com), February 24, 2000.
The degree of polarization does not affect the filter factor.
If you use the Pentax digital spotmeter, as many do, get a 40.5mm polarizer that will fit the threaded mount in front of the meter lens. Thus you avoid having to use your main pola filter off the camera. I use both the 40.5mm Heliopan for the meter and a 77mm Heliopan for my camera lenses. Works flawlessly.
-- John Costo (firstname.lastname@example.org), February 24, 2000.