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-   -   Can this be corrected? (https://forums.steves-digicams.com/pentax-samsung-dslr-k-mount-mirrorless/159191-can-corrected.html)

cameanee Sep 1, 2009 8:53 AM

Can this be corrected?
 
Handheld K100d w/ Tamron 18-250 ISO1600 @ 18mm. Resized otherwise straight from camera.

Shooting JPEG, already I am aware that I'm limited for post processing. It was night concert in Pershing Square, so noise was expected along with other technical deficiencies.

It's the "leaning" buildings that I was wondering about. If so, what PP tool would I try?


http://www.flickr.com/photos/[email protected]/3878217370/

JimC Sep 1, 2009 9:03 AM

DxO Optics Pro

jnanpentaxfan Sep 1, 2009 9:51 AM

This looks like the classic barrel distortion that is common with the 18-250mm Tamron/Pentax lens. According to my research, it only seems to be a problem when the lens is at it's widest. Here is a good link that provides a useful graph of the distortion at different focal lengths:
http://www.photozone.de/Reviews/Pent...f35-63?start=1

Nice pic, by the way.

JimC Sep 1, 2009 9:57 AM

The leaning buildings the OP was concerned about has nothing to do with barrel distortion. It's a perspective issue because the camera was at the bottom of the building and tilted upwards in order to fit the building into the frame.

Without correction, the only easy way around it is using a tilt and shift type lens (and I don't think Pentax has any in their lens lineup), since it's not really practical in most cases to try and find a vantage point where the camera is more in the middle of the frame in order to keep it "square" to your target without tilting it up to fit a taller building into the frame.

You'll see one example on this page (note how the verticals are moving towards the center of the frame as you look upwards in the image in the upper right on this page):

http://en.wikipedia.org/wiki/Perspective_correction

But, with software designed to correct it, it can be fixed. See this page for more info:

http://www.dxo.com/intl/photo/dxo_op...ons/keystoning

jnanpentaxfan Sep 1, 2009 10:36 AM

Quote:

Originally Posted by JimC (Post 997081)
The leaning buildings the OP was concerned about has nothing to do with barrel distortion. It's a perspective issue because the camera was at the bottom of the building and tilted upwards in order to fit the building into the frame.

Without correction, the only easy way around it is using a tilt and shift type lens (and I don't think Pentax has any in their lens lineup), since it's not really practical in most cases to try and find a vantage point where the camera is more in the middle of the frame in order to keep it "square" to your target without tilting it up to fit a taller building into the frame.

You'll see one example on this page (note how the verticals are moving towards the center of the frame as you look upwards in the image in the upper right on this page):

http://en.wikipedia.org/wiki/Perspective_correction

But, with software designed to correct it, it can be fixed. See this page for more info:

http://www.dxo.com/intl/photo/dxo_op...ons/keystoning

I see your point. The barrel distortion is there as well, as evidenced by the curve most noticeable on the buildings on far right, but that isn't the issue with the leaning building, as you correctly pointed out, and wasn't her question. It's just what has been in my mind as I consider purchasing this lens, so it's what stood out to me. I had my blinders on. :confused-smiley:

JimC Sep 1, 2009 10:37 AM

You'll also see this issue referred to as converging verticals. Here's a google search with lots of hits about it:

http://www.google.com/#hl=en&source=...ging+verticals

beachboy2 Sep 1, 2009 10:43 AM

In similar situations I use a 10mm lens (my Sigma 10-20 EX), keep the camera square as Jim points out, and do any fine adjustment to distortion in Elements 7.
cheers
bb2

snostorm Sep 1, 2009 12:41 PM

3 Attachment(s)
Hi cameanee,

I'd think that most of the major PP programs have a perspective correction tool.

I use Paint Shop Photo Pro X2, and from what I've seen, it's tool for this is pretty standard.

Here's your original, a screenshot of the perspective tool -- I moved the corner points of the tool to make the sides of the trapezoid roughly parallel to the leaning buildings -- and the corrected version. Took about 10 seconds. This is just a quick and dirty illustration, and I think that it might have stretched the center building too much, but that could have been helped by moving the top of the trapezoid down a bit.

Scott

cameanee Sep 1, 2009 12:49 PM

Just checking in for any responses.
You guys are great.

SCOTT: 10 seconds maybe for you. I'm completely PP challenged. Thanks.

cameanee Sep 1, 2009 12:53 PM

Quote:

Originally Posted by jnanpentaxfan (Post 997076)
This looks like the classic barrel distortion that is common with the 18-250mm Tamron/Pentax lens. According to my research, it only seems to be a problem when the lens is at it's widest. Here is a good link that provides a useful graph of the distortion at different focal lengths:
http://www.photozone.de/Reviews/Pent...f35-63?start=1

Nice pic, by the way.


Thank you.


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