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Old Apr 29, 2004, 10:16 AM   #1
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Default D70 barrel distortion ?

Hi folks,

Had the D70 (with 18-70 kit) 3 wks or so now and am very pleased with it; great image quality and loads to grow into as I learn. :lol:

The only problem i've found is with the 18-70mm lens @ 18mm, where barrel distortion seems excessive;

http://homepage.ntlworld.com/jimboje...cape_b_n_w.jpg

Is this just simply because its only 'the bundled' lens and not that great? Or would this be evident with other lenses at 18mm too?

Whatever the case, am pleased I waited for this instead of diving in for the Canon. :lol:
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Old May 2, 2004, 8:55 AM   #2
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When you are dealing with a lens of that range, I think some barrel distortion is to be expected. 18mm is a very wide angle lens even though the camera sees it as 24mm.
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Old May 2, 2004, 11:12 PM   #3
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Correction: 27mm. Not to be pedantic or anything...
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Old May 3, 2004, 10:20 AM   #4
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You are absolutely right! I stand corrected.
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Old May 7, 2004, 7:34 AM   #5
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The barrel distortion can be fixed using postprocessing, in the (unusual in my experience) case where it is a problem. See http://www.caldwellphotographic.com/...rFringing.htmlfor a tutorial on how to do this using the amazingly useful Panorama Tools plugin (freeware, and the tutorial page has a pointer to the source, or if that is dead you can find it using Google) for Photoshop. My parameters for Panorama Tools using the 18-70 at 18mm (right at the moment, they may get tweaked a bit further) are b = -0.01525 and d = 1.01525 for red, green and blue (see the Web page above for what this means). These will straighten out the lamppost nicely.
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Old May 8, 2004, 4:32 PM   #6
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Cheers Ross, this looks great stuff :-)(if not mathematically intimidating!) Gonna have a good sit down and read of this with lots of coffee, try and get my head round it! Much appreciated.
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Old May 9, 2004, 2:13 PM   #7
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OK, had a quick play with this, and the plug in rocks :-)Need to fine tune the settings, but i've managed to get these results out of it in 15-20 minutes.

Here are some before and after examples (apologies for quality of photo, but it was best example of barrel distortion i could find from my shots!)

1. Before

[img]file:///C:/Documents%20and%20Settings/jrs/Desktop/before.jpg[/img]

2. After with Ross Alford's parameters

[img]file:///C:/Documents%20and%20Settings/jrs/Desktop/after%20(ross'%20paramaters).jpg[/img]

3. After with me trying (very clumsily) to correct it back the other way a bit.

[img]file:///C:/Documents%20and%20Settings/jrs/Desktop/after%20-%20v2.jpg[/img]

thoughts anyone? Gotta say I'm impressed, nice one Ross :-)
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Old May 10, 2004, 2:38 AM   #8
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Umm.. you cant link to pictures that are on your own harddrive.

You either need to attach the pictures using the link at the bottom of the reply page, or put them up online somewhere and link to that web address...



Godd Luck
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Old May 10, 2004, 5:33 AM   #9
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ooops, haha spot the newbie! Try again....

http://homepage.ntlworld.com/jimbojetset/example.htm

thoughts? like i said before thanks ross.
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Old May 10, 2004, 7:47 AM   #10
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Panorama Tools is really an amazing bit of software. Not only will it correct barrel and poncusion distortion in small amounts, it can correct chromatic aberration, can remap fisheye shots to swinging-lens panorama camera shots or super-ultra-wideangle shots, and many more things. I've attached a not very exciting example of a remapping from fisheye--the original was taken with a Sigma 8 mm fisheye on the D70, the remapped version is in panoramic-camera mode. The tiny size makes it hard to see image quality, but it gives you an idea of what you can do with the software.
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