distortion problems with a wide angle

Joined
Apr 11, 2011
Messages
12
Location
new jersey
so yea i just purchased a sigma 10-20 and i love the hell out of it but these photos i took got distorted i know thats normal with wide angles but how do i fix it.

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CSC_0970.jpg
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Joined
May 15, 2011
Messages
302
Location
Edmonton, Alberta Canada
Photoshop has a distortion correction tool that works pretty good. You'll have to use trial and error to find the right values for that lens.

Even better—with CS5, there is lens correction in Adobe Camera RAW(ACR). It has a database of camera/lens combinations that can automatically correct for pincushion and barrel distortion, vignetting and chromatic aberration—allowing for fine tuning manually if desired. It also has horizontal and vertical perspective correction built in along with rotation, though you do that manually.

Once the image is open, you have a similar feature under the Filter menu, however, ACR allows these changes to be made to the raw data prior to opening.
 
B

Bill N

Guest
There are other tools are needed to do this job, but PS/LR can't really do that!

What other tool would you use, Tom. PS/LR are the only way I know to work with the issue. Thanks, Bill
 
Joined
Jul 4, 2007
Messages
3,551
Location
Redmond, WA
Isn't most of the distortion you're concerned about perspective distortion, and not just lens distortion (barrel, pincushion)? It's sort of the effect you get when you stare up from the bottom of a skyscraper -- it tapers away from you.

It's going to happen a lot with a UWA especially if you aim the lens up like in the shots.

Most software (such as Photoshop Elements, Photoshop, the GIMP) have tools to correct perspective distortion. However, you lose a lot of the wide angle in the process since you have to crop after the "correction." That's because something like your first shot would become a trapezoid and you have to crop out much of the sides.

Your best bet if you don't want to have that effect is to shoot with the camera level and not pointing up or down. Shoot even wider than you may want so you have some more room to crop after applying perspective distortion correction.
 
Joined
Mar 18, 2008
Messages
5,114
Location
Miami, Florida, USA.
All ultra wide angles distort this badly. There are perspective correction lenses but they are expensive.
The problem compounds when the camera is not held parallel to the subject. Slight tilts make things even worse, clearly documented in your first two shots. The last two ones look more natural.
Try holding the camera parallel to the subject to minimize distortions and always come close to your subject.
I am in agreement that fixing those distortions during editing is a formidable task.

William Rodriguez
Miami, Florida.
 
Joined
Jan 15, 2008
Messages
4,553
Perspective is not distortion, it is perspective. It is not caused by a wide angle lens but the shooting distance.

If you happen to own a plastic slide frame, you could use it to simulate the perspective issue. Keep the slide frame at about 20 mm from your eye and look through it. This roughly simulates a 20 mm wide angle lens on full frame. You will see the same perspective as with the camera/lens combo, and surprise, there's no glass lenses involved.

If you don't like the perspective in your images, you have to move your camera position, since it is the only thing affecting perspective. If you don't like tilted verticals, keep your camera upright. Focal length has nothing to do with these.
 
Joined
Jan 15, 2010
Messages
3,985
Location
UK
As others have said tilting the camera and it not being parallel to the subject makes perspective distortion even more apparent, particularly noticeable when you have buildings in shot.

The converging or even diverging vertical and horizontal lines can be lessened (or even totally eliminated) in post processing however at a cost of losing image real estate which may be of importance to the shot. Depending on the shot it may be possible to fill in (fake!!) the area lost but this can be a lot of work.

Couple of quick samples 'corrected' in Photoshop using Lens correction vertical perspective - due to the crop needed you will see that image information has been lost.
ConvVertical2.jpg
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ConvVertical.jpg
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Joined
Sep 21, 2008
Messages
6,374
Location
Alabama
Isn't one of the reasons to use ultra wide is to get distorted perspectives? I don't see anything wrong with the pics in regards to distortion or perspective.

If you want straight lines, use DXO and run all your pics in batch to correct distortion. You don't have to do a thing as it is an automatic correction.
 

Growltiger

Administrator
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Joined
Apr 26, 2008
Messages
13,378
Location
Up in the hills, Gloucestershire, UK
You don't need to lose all that much image even with such stretched perspectives as this.

Two tips on how not to lose too much image:
1. Make the canvas bigger before you do the correction. Otherwise some of the image falls off the edge of the canvas.
2. After cropping you are left with two missing triangles. You can fake with a bit of content-aware fill or simple cloning.

So here is my attempt at the first image. It took several minutes. It isn't perfect but a bit more work would make the cloning invisible to the eye.

perspectivemod.jpg
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Joined
Jul 16, 2009
Messages
10,094
Location
Newcastle
Isn't one of the reasons to use ultra wide is to get distorted perspectives? I don't see anything wrong with the pics in regards to distortion or perspective.

If you want straight lines, use DXO and run all your pics in batch to correct distortion. You don't have to do a thing as it is an automatic correction.

+1

Don't correct it, exploit it :biggrin:
 
Joined
Sep 21, 2008
Messages
6,374
Location
Alabama
You don't need to lose all that much image even with such stretched perspectives as this.

Two tips on how not to lose too much image:
1. Make the canvas bigger before you do the correction. Otherwise some of the image falls off the edge of the canvas.
2. After cropping you are left with two missing triangles. You can fake with a bit of content-aware fill or simple cloning.

So here is my attempt at the first image. It took several minutes. It isn't perfect but a bit more work would make the cloning invisible to the eye.

I still think the original looks better. If the distortions look that bad to OP, the wrong lens is being used.
 
Joined
Mar 24, 2011
Messages
1,370
Location
Canada
Some review sites have the distortion corrections mapped out. Ken Rockwell tends to have these on his reviews. You can check around online.

Lightroom also has distortion corrections. I agree with AlJohnston, exploit the characteristic of the lens, don't try to fix it.
 
Joined
Nov 10, 2008
Messages
3,969
Location
Chicago
Keystone or straight lines that curve. Keystone is prevented by keeping the camera back vertical or a shift lens. Happens with all lenses, not just wides.

Straight lines becoming curved is built into the lens. PtLens is the best cure.
 

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