polarizer issue and/or uneven development

[Scott Kathe]

I took this image the other day as an exercise a couple of hours before sunset. As you can see by the shadows the sun was behind me and to the right. This was taken with a 150mm lens on a 4x5 with a polarizer to darken the sky. As you can see the sky on the left is lighter, is this due to the polarizer? I would have used an orange filter but I didn't have it with me, I thought my yellow wouldn't darken the sky enough and the red would darken it too much and produce contrast issues in the shadows. I guess I should have tried my two stop soft graduated filter. The sky is uneven as well, is this a development issue? I process in trays. Any thoughts would be greatly appreciated.

Scott

[David A. Goldfarb]

Looks more like uneven development or bellows flare to me. Uneven polarization is more likely to happen with a polarizer and a lens of about 75mm or wider on 4x5".

[Eugene van der Merwe]

Looks to me like it could be from the polarizer, i've had similar results with a 150 and polarizer before, particularly in clear conditions like what you have photographed in.

Eugene

[Brian Vuillemenot]

Looks like uneven polarization to me. The uneven polarization is most pronounced on wider lenses and at a right angle to the sun. You can avoid it by not turning the filter so the effect is so extreme (partially polarized instead of fully polarized), or orient the camera at a more shallow angle to the sun.

[Ken Lee]

Polarization is strongest at 90 degrees to the Sun, and weakest at 180 degrees (and 0 degrees). Your photo is an excellent demonstration.

[Scott Kathe]

I hope it is a polarization issue. The shadows are almost pointing directly at the lightest area of the sky so that would be 180 degrees from the sun. I develop in trays and rotate the stack of film 90 degrees every time I go through the stack-I don't know how to develop more evenly. I also used my 210mm lens but when I was putting the film holder down the darkslide slipped out a bit so my b&w film is pretty messed up I shot some chromes too with the 150 and 210mm lens, if the light sky shows up in the 150mm image and not the 210mm image I think I will have my answer. Thanks for the input.

Scott

[Clay Turtle]

Scott, I am considering (need) using a polarizer, so I am interested. I have a plane polarizer from 35mm work which I will probably use. You didn't state whether you were using a plane or circular polarizer . . . circle seem to have constant exposure factor while plane change according to the plane of the polarizer. So how did you figure your exposure factor?

[Scott Kathe]

Scott, I am considering (need) using a polarizer, so I am interested. I have a plane polarizer from 35mm work which I will probably use. You didn't state whether you were using a plane or circular polarizer . . . circle seem to have constant exposure factor while plane change according to the plane of the polarizer. So how did you figure your exposure factor?

Clay,

The one I used was a Tiffen 52mm circular polarizer and I added 2 stops of exposure to my meter reading. I used a Soligor analog spot meter and metered the shadows for zone III and adjusted for the additional two stops. I'm not really sure what you mean by a plane polarizer unless you mean a linear polarizer. I've used one of those as well with a different lens and again I add 2 stops of exposure. From what I've been led to believe if you use a polarizer, circular or linear, even at less than maximum polarization you have to give full exposure compensation. That is to say if polarizer is set to 1/2 polarization you still have to give a full 2 stops (if that is what your exposure compensation is for your polarizer). Hope that helps.

Scott

[Clay Turtle]

Yes, Scott that does help although I will take the +2 stop factor with a grain of salt for now. Right you are about the linear & circular polarizer. The linear polarizer has a handle extending from the polarizer in order to rotate the lens, the circular came in after the autofocus lens became the way as the rotation of the autofocus would change the polarization. OF course, the 35mm uses thru the lens metering & therefore would automatically adjust or compensate for exposure differences (except if shooting in manual mode).

[Helen Bach]

A circular polarizer is simply a linear polarizer followed by what is effectively a depolarizer (it’s not quite that simple). It behaves exactly like a linear polarizer as far as the outside world goes, so the effect depends on the angle, but it sends circular light (which behaves rather like ‘depolarized’ light in many ways) to the camera instead of linear light. If there is a beam splitter behind the lens (usually for exposure or autofocus) its performance could be affected by linear light, depending on the angle, hence the use of circular polarizers.

An ideal polarizing foil would have a 1-stop filter factor (ie 2x) for randomly polarized (‘depolarized’) light, no matter what the orientation. Real polarizers vary from this value, but their filter factor for depolarized light stays the same no matter what their orientation is.

Best,
Helen