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07-02-2009, 03:48 PM   #1
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Question about distortion on edges

Hi there, I am a new Pentax user and I love the glass I've been using to date (18-55mm kit, 50mm f1.4, and 50-135mm DA* f2.8), however, there's something I don't quite get yet about distortion.

In some photojournalism shots, ie. of riots and various protest around the world, they exhibit a kind of "curved" feel around the edges, and I'm not talking about the extent of a fisheye, but just slightly "falling" off around the sides and the top and bottom of these pictures.

I'm not sure if this is referred to as "distortion", but I find this makes for a great feel in "walk-around" shots, which I cannot achieve with any of the lenses I have.

I was recently at my boss' place and he has a Nikon D700 with a 24-70mm f2.8. Really nice (and expensive set up) but when I would look through the viewfinder and pan the camera, I could tell that the edges moved in and out of the composition slightly quicker than the center of the image. This is where I noticed the resemblance to a photojouralism "look".

My question is: is this curved edge feel more of an inherent characteristic of wider angle lenses (because the 24mm wide end on the d700 is true as it's a full frame sensor)? Or is there some sort of setting that achieves this effect?

Thanks and I appreciate your help. Please note that I am not looking for the intense, visible effect of the 10-17mm fisheye, but something very tame.... kinda like: http://themostimportantnews.com/wp-content/uploads/2009/06/iran-protests.jpg or http://livingincinema.com/wp-content/uploads/2009/06/Iran-Protest.jpg

Thanks!

07-02-2009, 07:11 PM   #2
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The effect is there on any "super wide angle" lens. It is particularly noticeable with lenses such as my DA 12-24 used at or near 12mm. It is possible to remove the distortion with software if you want to lose it. I have DxO Optics Pro, and when I import the raw images DxO removes the distortion, which is what I personally prefer.
07-02-2009, 09:51 PM   #3
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Well, when you look through your kit lens at 18mm, I would think you would see some of the effect CR just spoke of. The 18mm mark essentially corresponds to a 35mm film SLR focal length of 28mm, which is legitimately wide angle. (In 35mm film dimensions, a 35mm focal length was widely considered the beginnings of wide angle.)

But that's just a hint of the depth of the effect that you can see at wider and wider focal lengths. At 16mm you would notice it more, and that's roughly comparable to the 24mm side of your boss's zoom. By 14mm it would be very strong. Naturally, by 12mm (in our 12-24s) it is a dominant feature of the image.

It's a fascinating perspective to use, by the way, so you should try it. It has its pitfalls, too, if you aren't careful and thoughtful about what to use it on. But all photographers should come to experience and use the wide angle effect sooner or later, IMHO.
07-03-2009, 09:43 AM   #4
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Thanks for that.
Based on the reach of the 16-50mm DA* f2.8, would you expect that the difference between 16mm and the 12mm (on the 12-24mm) would make a huge impact, or could you still expect to experience that curved feel on the 16?

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