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Old 16th July 2009, 16:58   #6001
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I know you have a house in Goa which can accomodate me anytime of the year ! Luckily I am on the left block.

This slanting effect, I recall some mention of this (either in bythom.com or dcreviews)in my review searching days for a DSLR few months back. It was termed as some 'lense aberration' or something.
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Old 16th July 2009, 17:00   #6002
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Vertical lines getting skewed is quite common.

There is a good tutorial on how to correct the problem using editing s/w's here
Tutorial: Rotating Skewed Images Accurately - ClubSNAP Photography Forums

For taking pics of vertical lines opposite each other, you need to work on the angle of taking the picture. Also the location of the camera itself.

Also refer this link
CMOS Rolling Shutter

An excellent demonstration on how the picture is taken by the camera
Quote:
Skew
The easiest way to see Skew is to think about taking a photo of a tall building. As the sensor scans down the frame, the building is “drawn” onto the chips and is represented accurately. But if the camera were to pan horizontally while the sensor was still exposing, what would happen? The top of the building would be on one side of the frame, and the bottom of the building would be on the other. The whole building would look like the Leaning Tower Of Pisa! This is called “Skew” and is one of the more prevalent Rolling Shutter effects. With horizontal camera motion, vertical objects can look like they’re “leaning” one way or the other depending on which way the camera was moving.

Last edited by bblost : 16th July 2009 at 17:05.
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Old 16th July 2009, 17:02   #6003
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Originally Posted by shajufx View Post
This slanting effect, I recall some mention of this (either in bythom.com or dcreviews)in my review searching days for a DSLR few months back. It was termed as some 'lense aberration' or something.
It is called Barrel Distortion. It happens with wide angle lenses at the wide end of the zoom lens.

Barrel Distortion: Optical: Glossary: Learn: Digital Photography Review
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Old 16th July 2009, 17:13   #6004
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Did you shoot that at 18mm? Could be the wide angle distortion at the edges. Similar to the effect here (note the bottom edge is a little skewed),
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Old 16th July 2009, 17:14   #6005
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Originally Posted by shajufx View Post
Gurus, please suggest what went wrong here ? Is it the lens or the camera angle ? D60 with 18-55 kit lens.

I have drawn a red vertical line on the right side block. Notice the gap top to bottom.
Attachment 159752
i had posted a similar query few weeks back and vivekiny pointed me to picasa. it is able to correct some of it during post processing, the "slant" is due to the focal length of the lense being focussed at its wide end
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Old 16th July 2009, 17:29   #6006
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Wow, what a response ? No wonder I am addicted to this forum !!
Thanks for all the guidelines, I think I get the picture now. There are around 50/60 pictures of the similar nature, majority of them have this issue. So, now I am trying to correct them one by one. Double !!
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Old 16th July 2009, 17:51   #6007
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Hmm, but thinking about barrel distortion. Is it because of the image formed by the lens is circular and when projected on a square/rectangular sensor, the distortion happens at the edges? In that case it should happen at tele end as well not only wide end. Anyone has a clue about this?
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Old 16th July 2009, 17:59   #6008
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Similar barrel distortion is seen below.
I tried to correct it with picasa, couldnt do it. Can someone help ?
Attached Images
  

Last edited by abhijitaparadh : 16th July 2009 at 18:01.
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Old 16th July 2009, 18:34   #6009
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Quote:
Originally Posted by HellwratH View Post
Hmm, but thinking about barrel distortion. Is it because of the image formed by the lens is circular and when projected on a square/rectangular sensor, the distortion happens at the edges? In that case it should happen at tele end as well not only wide end. Anyone has a clue about this?
Here you go.

http://en.wikipedia.org/wiki/Perspective_distortion_(photography)
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Old 16th July 2009, 20:23   #6010
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@shajufx Don't you need tilt and shift lens, though I haven't used it due to the exorbitant cost?
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Old 16th July 2009, 20:34   #6011
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Quote:
Originally Posted by shajufx View Post
I know you have a house in Goa which can accomodate me anytime of the year ! Luckily I am on the left block.

This slanting effect, I recall some mention of this (either in bythom.com or dcreviews)in my review searching days for a DSLR few months back. It was termed as some 'lense aberration' or something.
shaju, call it whatever you like, it's just "perspective view". when you see rails going away from you, they seem to converge at infinity.

here is an artificial image without perspective correction. see how weird it looks.

Name:  Og8R.jpg
Views: 267
Size:  83.9 KB
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Old 16th July 2009, 21:12   #6012
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Quote:
Originally Posted by HellwratH View Post
In that case it should happen at tele end as well not only wide end. Anyone has a clue about this?
I have no clue about the technical reason for this. It is the outcome in many photographs of buildings that are 5 floors+.

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Originally Posted by janitha View Post
Don't you need tilt and shift lens, though I haven't used it due to the exorbitant cost?
Same here, I cant think of all those special usage lenses right now. I am sure what we get from the kit lens can be manipulated to a great extend.

Quote:
Originally Posted by vivekiny2k View Post
shaju, call it whatever you like, it's just "perspective view". when you see rails going away from you, they seem to converge at infinity.
Agreed 100%. Now what is the solution to get it back to shape ? I tried irfanview, photoshop (7.0), but cant find any tools to get it into shape. Could anyone throw some light on the stretching/skewing part ! I tried all the links related to this. But the issue is, not the whole picture to be skewed. Related links are mostly explaining skewing the whole image then cropping it. In my example photo above, only the right block buliding is slanting. If I skew the whole image, right block will be straight and left block will slant.

I beg pardon to every poster here. I doubt if I am wasting everyone's time here. People come to this thread only to post or view amazing images, not for an elaborate discussion on post-processing. Sorry folks. May be I have to move to the photoshop thread if required. The only reason for me to post here was by expecting a simple solution to it, but it doesnt look like a simple one anymore. Thanks !

Last edited by shajufx : 16th July 2009 at 21:15.
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Old 16th July 2009, 21:22   #6013
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Quote:
Originally Posted by shajufx View Post

Agreed 100%. Now what is the solution to get it back to shape ? I tried irfanview, photoshop (7.0), but cant find any tools to get it into shape. Could anyone throw some light on the stretching/skewing part ! I tried all the links related to this. But the issue is, not the whole picture to be skewed.
with my example what I wanted to say was that leave it is as it is, may be make it symmetrically slanted on both sides.

if you try to un-skew it, it will look weird.
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Old 17th July 2009, 00:43   #6014
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@Shajufx
In Photoshop CS4 ( i think CS3 too has it) there is a filter called Distort--> lens correction, and when used intuitively, it can help correct barrel distortion.
I normally use this distortion to my advantage by trying to go creative while using them. But then i dont shoot much of architecture..

The Official non-auto Image thread-3580420161_a1424d9142_b.jpg

It is also dependent on the kind of lenses. Some lenses have complex distorting nature unresolvable by a simple correction filter..you will need to go for specific software.

By the wat do you live in Sena Vihar?

Regards,
TG.

Last edited by Torqueguru : 17th July 2009 at 00:44.
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Old 17th July 2009, 01:03   #6015
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My first attempt at HDR.

This is the view from my balcony. The sun was setting very fast on the horizon and the scene was perfect for human eyes. But my camera refused to capture all the details of both sky and landscape at the same time. So I decided to capture 3 images at different exposures (-2, 0, +2) and create an HDR out of it.

Here is the outcome -
The Official non-auto Image thread-3452642306_91c866ca88_b.jpg

The 3 images used to create this HDR can be viewed at - Picasa Web Albums - Ronak Gandhi - HDR attempt

Let me know you views.
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