Monday, January 11, 2010

Part 2: Photography with Imre Z. Balint: Episode 9 - Polarizing Filters

Ok, I've had my dinner so I'm ready to write my supplemental post to Episode 9 about polarizing filters.

In the video I covered a fair bit about the physics of light polarization, but I'd like to highlight that you really don't need to know it in depth, or almost at all, to be able to successfully use a polarizing filter. But heck, being the geek I am, I love exploring why things work the way they do, hence the physics segment. If you'd like to prod into this subject further, definitely check out some of the links I've provided; Colorado University has very cool interactive sections in their web-based tutorial.

In regard to their use, something that I didn't cover in the video is that this is not usually a filter you want to keep on your lens at all times. The major factor as to why is because of the loss of light through the filter. So for example if you're shooting an area that requires longer exposure times, then the shutter speed may slow to the point where "hand shake" or blurriness could occur. Now if a photographer forgets that s/he has the filter on, s/he may end up with a "bad" photo and potentially a missed chance at taking such a picture again. And let's say a photographer chooses to leave the filter on, but has compensated for the loss of light by opening the aperture wide. Ok, perhaps shutter speed will be acceptable, but keep in mind that the wider you open the aperture the less depth of field you get to work with. Higher sensitivity settings may also keep the shutter speed manageable, but then you might see an increase in noise on the photo.
 
Now the nice part about digital cameras is that during the image preview (if you have that feature enabled) you'd quite likely catch many of these issues, and it's not like it's that difficult to quickly remove the filter, so at least it's not the end of the world (that'll be sometime in 2012 *chuckle*).

Because these filters are generally more expensive than your run of the mill UV filter, or even some other varieties, I always remember to take the filter case with me, so that I can safely put them away when not in use. Also something to watch for is that these filters can be a tad thicker then most, which means that if you stack filters on top of each other for effects purposes or have a UV filter on your lens all the times, then expect the potential that you could get some vignetting. Now if you've never seen one of these filters and are wondering why they are a tad thicker than others, it's usually due to how the filter is constructed. The polarizing material itself is not thick at all, but there are basically two rings that make up the filter. One ring screws onto your lens, while the other rotates freely (well with enough friction to stay put if turned to a specific angle). I've for whatever reason you're an obsessive-compulsive filter stacker, I have seen ultra-thin varieties available on the market.

And there are such things as color polarizing filters, which I completely forgot about when I shot Episode 9 (although if I did remember, it would've made the video too long to upload anyway). But in the next few days, I'll release an informal video showing those off, so stay tuned! This Wednesday (Jan 13th) is my projected upload date.

Also keep my 10th Episode in mind, as I'll be showing you ways that you can create 3D photographs! Seems to be all the rage these days. Oh! And if you have any questions about photography, feel free to send them in; click here to read my post about that. Remember to subscribe to my channel and become a Fan on the Binary Graphite Page on Facebook to keep up to date with my stuff. Cya in a while.

Web Resources
http://nikon.magnet.fsu.edu/articles/polarized/polarizedlightintro.html
http://hyperphysics.phy-astr.gsu.edu/HBASE/phyopt/polarcon.html
http://www.colorado.edu/physics/2000/polarization/index.html
http://www.physicsclassroom.com/class/light/U12l1e.cfm
http://en.wikipedia.org/wiki/Polarization_%28waves%29
http://en.wikipedia.org/wiki/Brewster%27s_angle
http://en.wikipedia.org/wiki/Wave_plate
http://en.wikipedia.org/wiki/Circular_polarization
http://www.bobatkins.com/photography/technical/polarizers.html

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