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- Thread starter Bassy
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VisionLight
Veteran Member
This is not a matter of fault but a combination of perspective and optics. Perspective, because in none of the images of the house are you equi-distant from all four corners of the facade. Some corners are further from you and appear smaller in the image, while closer corners appear larger. You are shooting at a 74º angle of view which expands perspective. As a general rule, the perspective we see most comfortably at is between a 40º and 50º angle of view. Unless the offset point from which you took the image is oblique, these angles will give a reasonably rectangular subject. But the expansion of 74º magnifies the oblique position that you took the images from making the further corners appear even further away and the nearer corners appear nearer. Instant distortion. Also note that decreasing the angle of view below 40º has the opposite effect and compresses perspective, somewhat flattening a subject even when seen from an angle.Bassy wrote:
could someone explain why my saltram house shots taken in devon uk today
some look ok and the others are leaning a lot
is it my fault or a camera fault.thanks bassy taken with canon g1x
The second culprit, optics, comes into play because lenses project a round image on the sensor. When the projection is at 74º, this tends to give a barrel like distortion to the image. Straight lines at the left and right sides tend to bow in and out following the round projection. When the point from which you take the image is not too oblique, the camera (optical formulae or software) can partly correct for this, but not always. And once again, if the angle of view decreases below 40º, the opposite effect happens and the barrel effect is replaced by a pincushion effect.
So, what do you do? No matter what angle of view your lens is capturing, both wide or narrow, place yourself in the middle view of the subject. The closer you are to a point where all corners of your subject, up or down or left or right. are equi-distant from you, the more rectangular the image will be. If you are too close, the top of the subject will always be further away than the bottom and you will get a keystone effect. Back up and use a longer focal length lens (i.e. smaller angle of view). If you can not back up, this will present a problem for a P&S camera and you will not be able to eliminate the distortion. But then that's what dSLRs with Tilt/Shift lenses are for.
Hope this helps,
Vision
M
MurryG
Guest
Just a small add-on to what Vision said. Some of the distortion can be corrected in post processing but you would need to leave ample space around the building to do it properly. BTW some really neat photos can be had by tilting your camera up at high-rise buildings when you are standing very close to them. But of course the distortion is then very extreme.
Murry
Murry
Steen Bay
Veteran Member
Nothing wrong with you camera. The tilting lines (or 'keystoning') is just what happens to the perspective when the camera is tilted upwards, and especially with WA lenses. The wider the FoV, the more 'keystoning' you'll get if the camera isn't level.
When using wide angle the picture gets a lot of barrel distorsion. Please correct by using a pretty high correction value, in PSP appr. 30-33. This goes for all your pictures except the last one, where the correction can be smaller.
The other thing, in all thous pictures is straightening. Choose from the vertical middle of the picture a vertical line, windows, tiles etc., and straghten it in the vertical direction. After these two corrections all your pictures look totally different.
Your original:
The corrected:
It only takes seconds, I have to correct most of my pictures this way, when using wide angle.
The other thing, in all thous pictures is straightening. Choose from the vertical middle of the picture a vertical line, windows, tiles etc., and straghten it in the vertical direction. After these two corrections all your pictures look totally different.
Your original:
The corrected:
It only takes seconds, I have to correct most of my pictures this way, when using wide angle.
Hamdan Abdullah
Senior Member
I want to thank the OP for the posting and the others for the answers as I learned plenty here. I too face similar problems when taking wide-angle shots of buildings. Thanks everyone..
Cheers,
Hamdan Abdullah
Canon G10, Canon 40D, Canon 600D/T3i, G1X and Canon SX50HS.
Cheers,
Hamdan Abdullah
Canon G10, Canon 40D, Canon 600D/T3i, G1X and Canon SX50HS.
VisionLight
Veteran Member
Just for clarification, the size of the P&S sensor is immaterial in this case since the lens being used is matched to and corrected for it. Using a full frame sensor or even a medium format sensor would show the same effects from an offset angle, except when paired with a tilt/shift lens. In the case of a larger sensor, possibly the barrel effect would be lessened by a better corrected optical path within the larger matched lens. The only time the size of the sensor is a factor in this type of distortion is if it is larger than the projected image of the optical design. Then you would have a full fisheye effect with all its requisite distortions.
Vision
I try to keep the camera as straight as possible when taking a pic of a building. Usually, that building is a barn or some other smaller structure related to farming. It varies, keeping the camera straight causes the horizon to be in the middle of the pic a lot of the time. Allowing for cropping in post to either show the sky and small forground or large forground and small amount of sky. This is done in camera at the time the pic is taken.
I understand this can be fixed somewhat with Lightroom or Photo shop but I don't have either. Perhaps other posters could give their thoughts on how they deal with this.
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