Non-uniform Sky Color - Seeking Advice

Rotation of my Tiffin 67 mm circular polarizing filter, mounted on a Canon EFS 17-85 mm macro lens, does not always produce the desired results; namely, a uniformly darkened sky color (at the widest field of view under hazy atmospheric conditions). In some cases (apparently) I have not been able to find a filter rotation setting that avoids a color gradient; for example, from left to right. Assuming that I cannot re-orientate the line of vision 90 deg to the light source, or do not want to sacrifice field of view, are there any other technical fixes to this problem ?

Thanks for your reply.

There is no fix for the this. As you noted above, the polarization band in the sky (light that is able to be polarized by your filter) runs a 90 degrees to the sun's rays therefore the only what to get solidly polarized skies it to be facing north or south at a 90 degree angle to the sun's path with a narrow field-of-view. With a wide angle lens this becomes more problematic as you can see more of the sky. This is simple physics and there's not really a simple in-camera or on-lens fix that I'm aware of. Is that Mount Hood?

Mark

Reply to Mark Cohran;

Thanks for your reply. Yes, the background image is Mt. Hood. I had hoped you might suggest the shooting the image thu a separate sheet of polarizing film, say mounted at a slight angle from the line of sight. Also I assume that a the use of a lens hood + polarizer would not produce the desired effect.

Like Mark said, a polarizer has different effects on the sky in different directions. They're pretty much unusable at wide angles.

Personally, I've quit using my CP altogether. I get results that I like just fine by being careful of exposure. Even a slight overexposure (1/3 Ev) can wash out a blue sky. By removing the CP I get faster shutter speeds, lower ISOs, and/or smaller apertures—all of which can be valuable in landscape photography.

If you must use a filter for this, a gradient neutral density filter is about the only option.

You've discovered why polarisers are not generally recommended for wide angle lenses. Your better alternatives in this case would be a neutral density grad or post processing the sky. The grad would also darken the clouds a little, which the polariser would not, but post processing could improve that.

As Mark C says, it's simple physics. The sky is not evenly polarised, so using a polariser to darken the polarised parts of the sky will show that unevenness. As you move away from the 90-degree-to-the-sun band, a polariser has progressively less effect on the sky.

Another option is to bracket exposure (easiest with tripod) and blend sky in PP - effectively a digital GND filter.

zircon100 wrote in post #4283954
Reply to Mark Cohran;

Thanks for your reply. Yes, the background image is Mt. Hood. I had hoped you might suggest the shooting the image thu a separate sheet of polarizing film, say mounted at a slight angle from the line of sight. Also I assume that a the use of a lens hood + polarizer would not produce the desired effect.

Use of a separate sheet of polarizing film isn't going to help with the physics, I'm afraid. There will still be an uneven band of polarization due to the wide expanse of the sky. The hood will help with flare control and lens protection, but not with this issue.

Given your composition, a grad ND isn't really going to help that much since is graduated along a straight line through the center of the filter.

I think post processing is your only solution (at least for this composition)

Mark

Why not use a Graduatd ND Filter? I use the Cokin filter system for all my ND work since I can adjust the gradient line to any angle and height. Using such a filter, you could (in your sample photo), simply mask out either the sky at a diagonal, or the road/trees/hillside at a diagonal, depending on what effect you want. Here are some Cokin sample sky shots using ND filters.


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Pretty tricky to use a GND filter with a varying skyline as in the example - it can be done but probably easier to do in postprocessing. I think people probably underutilize the exposure bracketing feature - pretty easy to take 3 shots in a row with same framing and get the sky right in post.

Speaking of bracketing...you could also take 3 to 9 bracketed captures and blend them using HDR in Photoshop or with Photomatix.

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Beautiful picture Zircon where is that.

Thanks to all for your helpful comments. Next time out (assuming that I can find hazy conditions with similar lighting) I will try aperature priority with exposure bracketing w/wo a polarizing filter. "Blending" photos in photoshop sounds interesting (assuming a stationary subject); however, I'm not an experienced photoshop user.

Message to Silverwolf: 0.5 mi SE of Wahtum Lake, 25 mi SW of Hood RIver, OR.

That's a 10sec job in Bibble, using the free Roy-Colour plugin that comes with the program as standard.

Without any filters used, you draw a slider to select the shade of blue that shows only the sky highlighted and adjust Saturation and perhaps a little of Value. No layers, masks nor skyline outlining with the mouse. Still, you can modify or undo the sky correction even after other adjustments have been done (as you could using layers in Photoshop).

Bibble is a RAW converter, but allows processing of JPEGs as well.