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by Aditya

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According to my knowledge Polarizing filters are mainly used to make sky appear more bluish in the day sunlight which gives more dramatic effect to your pictures.

I don't have polarizing filters yet , But would like to know whether we can achieve same effect(making sky more blue like a polarizing effect) through post processing. If yes any link which explains it from scratch ?

I use GIMP and picasa (open source) in Ubuntu . Any easy solution using these Softwares ? or is it better to buy a polarizing filter itself !

I use Canon EOS 1000D , and mostly use 50mm 1.8 and 70-300sigma lens.

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See also: photo.stackexchange.com/questions/1938/… –  Guffa Mar 11 '11 at 11:15

1 Answer 1

up vote 20 down vote accepted

One result of using a polarizer is the deeper blue skies; that effect isn't hard to replicate using software such as Photoshop, Lightroom, Picasa, or the GIMP.

Another important reason a polarizer might be used is to reduce glare and reflections. The best example of this is if one is photographing a puddle or pond; without a polarizer the surface will reflect the sunlight and result in a lot of glare whereas a polarizer cuts down on that glare and the camera will capture an image that shows some underwater detail.

The second effect (removing glare) is not one that can be replicated in post-processing and requires a polarizer to get it right at the time of capture.

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Oh ! I dint know that it will cut glare and reflection , especially through water ! I wanted to cut down that reflection in my recent trip where I wanted to capture underwater fish :D but was not able to due to reflection ! Thanks for the tip ! –  sat Mar 11 '11 at 3:39
4  
@sat: When light reflects off the surface of a material that isn't electrically conductive, it gets polarized. A crossed polarizer in front of the lens will block (most of) that reflection. There are quite a few filters that purport to give the effect of polarization, but most just bump up the saturation. –  Jerry Coffin Mar 11 '11 at 3:48
    
I thought the deeper blue is a result of stronger contrast between the sky and clouds, from the change the polarizer effects on the image of the clouds. So a picture of a cloudless sky, whether using or not using a polarizer, wouldn't change anything (the camera (in anything other than Manual mode) would just change its exposure to compensate for the 1- to 2-stop ND effect so you wouldn't notice a difference in the final picture). –  drewbenn Mar 11 '11 at 5:21
    
Cutting down reflections works best when the reflection is roughly at a 45 degree angle. –  Kendall Helmstetter Gelner Mar 11 '11 at 5:46
3  
@drewbenn, the picture of the cloudless sky is still changed by the polarizer, especially at 90° to the light. –  sastanin Mar 11 '11 at 8:32

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