Persepctive distortion with a wide angle lens

Hi guys,

Nice forum you have here.

So the other night I went out with my camera and took a photo of some trees at sunset and when I got home I noticed some very bad lens distortion. I've never noticed it in any of my photos before and I guess the lens I was using (Sigma 10-20mm) is not the best lens for a subject so close to me. I have taken similar shots before though at the same distance and not had any noticeable distortion.

Anyway, as i've never dealt with this before any tips on the best way to correct it? I've tried in photoshop but had not alot of luck and I downloaded DxO pro trial version and I had no luck with that either. I tried to read up and figure how to work DxO but it seems to be automated? and then the lens correction settings seemed pretty much the same as photoshop? Forgive me if i'm stupid and missed something here. I'll attach and unedited jpg (the highligts are kind of blown just so you can see how bad the distortion is) Thanks for any advice and help any of you can give!!

Shane

http://backup.cambridgeincolour.com/...25e8c79770.jpg

what method did you try in photoshop? One of the simplest ways is using filter>distortion>lens correction filters that is a stock filter with photoshop.

There are manual ways to do it too in discrete steps which gives you more control over particular steps that the correction filter simplifies or bundles multiple steps together in 1 but most the time for 99% of images the filter should be sufficient. If it's possible to do in another package pshop will do it too so it's more a question of "how" than "can it" in my experience.

If the distortion your referring to is the sloping of the trees, then that's normal for UWA (Ultra Wide Angle) lenses.

To see what I mean, mount the lens and take a look at the straight edges of a building up close while you tilt the camera up and down, and pan from side to side.

If can be corrected in post-processing to a large degree, but you'll and up having to crop bucket loads of pixels off your image. Best approach is to try and minimise it by better composition at time of capture (change the height of the camera, and the distance to the subject).

Thanks for the reply guys.

Davey I did try the lens distortion filter and I could get it to look normal but as Colin said I was cropping a huge amount of pixels to get it normal. I guess it was just a mistake i've got to learn from. I've never had this problem before so next time i'm in a similar situation i'll be sure to pay more attention and adjust my composition, camera height and distance from the subject to suit this. Thanks for your help guys.

Also, about DxO if any of you have used it, is it mostly automatic? I've read of superb lens distortion correction but I coulnd't get very good results, well nothing different to photoshop anyway.

Thanks again.

Shane

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Originally Posted by Shane

Also, about DxO if any of you have used it, is it mostly automatic? I've read of superb lens distortion correction but I coulnd't get very good results, well nothing different to photoshop anyway.

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There are a few here that I know of who use it, so hopefully they'll chip in with some thoughts.

Personally, I've tried it a few times - I really WANT to like it, but it just doesn't "do it" for me ...

- First up, I convert all of my RAW files to the standardised DNG format. DxO can't open DNG files - so immediately that eliminates exactly 100% of my work.

- Second up, I found that it wanted to correct EVERYTHING, whereas I only wanted the lens correction parts (I prefer Adobe's ACR RAW converter for my work).

- Third up, I found the interface nothing short of a nightmare; very counter intuative.

I'm sure that those who know and love the program will disagree with me; as I say, I WANT to like it, but that's just the way I've found it.

I have pretty well the same opinion as Colin as far as DXO is concerned.
It's a very powerful piece of software and I suppose if you have lived with it for some time and not worked with anything else, its great.

However I find the user interface very awkward and counter-intuitive. I started using DXO after giving up on GIMP :) but never really got the hang of it. Ever since I got CS3 with that great ACR software, I haven't looked back in spite of them (DXO) still sending me upgrade notices!

A lot of people obviously think it's great but it didn't really work for me. I think it may be more intended to do batch corrections on large amounts of images without user intervention. The fact that they have characterized the behavior of a large number of camera/lens combinations and can automatically apply corrections is excellent. However the user interface for doing other things is hard to use, at least, in my humble opinion.

Personally, I'd probably use it if it could take DNG as an input file, and let me just "tick some boxes" as to what corrections I'd like (eg distortion correction, vignetting correction, CA correction, but leaving everything else "as is").

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Originally Posted by Colin Southern

Personally, I'd probably use it if it could take DNG as an input file, and let me just "tick some boxes" as to what corrections I'd like (eg distortion correction, vignetting correction, CA correction, but leaving everything else "as is").

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Roger, Colin,

I agree, I was considering giving it a try for the barrel/pincushion distortion, Chromatic Abberation (CA) and vignetting corrections, which is clearly (with the camera/lens database) intended to be it's original forte.

But if it is going to try to second guess my desires on image content corrections too - no thanks.

I do like ACR, just wish I had the full blown version, not the Elements one which doesn't do all of the above.

Thanks for your help guys.

I guess my image was just too bad, my mistake i'll do my best not to let that happen again.

And thanks for your advice and help with DxO. The interface is indeed not very nice and yea, i'll stick with photoshop.

Thanks again for your help.

Shane

Have you tried PTLens ? I'm about to give the 10 image trial version a go myself, because I'm not entirely happy with the results from PS correction (although that could easily be 'operator error' ;))

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Originally Posted by GillR

Have you tried PTLens ?

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I've looked at it briefly - didn't "spin my prop" I'm afraid :(

*grumble* Just looked at it more closely, and XP Pro 64bit is not supported :(

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Originally Posted by GillR

*grumble* Just looked at it more closely, and XP Pro 64bit is not supported :(

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Did you try to run the trial version anyway? XP x64 doesn't support 16 bit programs, but there aren't many of those around these days -- 32 bit programs should run OK in most cases.

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Originally Posted by Colin Southern

Did you try to run the trial version anyway? XP x64 doesn't support 16 bit programs, but there aren't many of those around these days -- 32 bit programs should run OK in most cases.

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I should have said I was going to trial it anyway, sorry. I'm just used to grumbling because XPPro64 "isn't supported". I'm waiting for the new incarnation of Windows to come out and settle down before I change my OS.

Anyway ... PT lens installed fine, offered me the plugin for 32bit PS (which I didn't want and said no to) and I installed the stand-alone version. I then set it as an alternative external editor in LR (the 64bit version, which "isn't supported" ;)) and it worked fine.

However, I found I couldn't get results any better than I can achieve in PS. I'd certainly recommend that anyone using an editing program that doesn't offer an equivalent to PS's distortion correction might want to give it a try.

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Originally Posted by GillR

However, I found I couldn't get results any better than I can achieve in PS. I'd certainly recommend that anyone using an editing program that doesn't offer an equivalent to PS's distortion correction might want to give it a try.

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To be honest, I find that this applies to a lot of programs - in many cases it just comes down to just knowing how to apply the controls in Photoshop to achieve the look that's wanted; Photoshops actual execution of the adjustment is usually as good as any other programs in my opinion. Perhaps Photoshop could benefit from more "wizard" style interfaces that leads people through things step by step?

Quote:

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Originally Posted by Colin Southern

To be honest, I find that this applies to a lot of programs - in many cases it just comes down to just knowing how to apply the controls in Photoshop to achieve the look that's wanted; Photoshops actual execution of the adjustment is usually as good as any other programs in my opinion. Perhaps Photoshop could benefit from more "wizard" style interfaces that leads people through things step by step?

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The problem I'm having is that I have some images I took using an UWA lens for the first time (it was the Sigma 10-20 on a 40D)and I'm really not very certain how far I can go with the distortion correction. I keep looking at the results and wondering if I've "corrected" the image beyond the point at which I should have stopped, if that makes any sense.

Anyway, since I splashed out on the 5D2, my widest lens is 24mm, so I shan't be having similar issues until my bank balance recovers ;)

Quote:

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Originally Posted by GillR

The problem I'm having is that I have some images I took using an UWA lens for the first time (it was the Sigma 10-20 on a 40D)and I'm really not very certain how far I can go with the distortion correction. I keep looking at the results and wondering if I've "corrected" the image beyond the point at which I should have stopped, if that makes any sense.

Anyway, since I splashed out on the 5D2, my widest lens is 24mm, so I shan't be having similar issues until my bank balance recovers ;)

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As a rule with WA and UWA lenses you'll get the most dramatic (and relatively "distortion free") shots (if there is such a thing with these lenses) by keeping your horizon no higher than 1/3 from the top of the frame, and then lowering the camera until your foreground subject takes on a meaningful size (look for foreground objects taking up 20 to 40% of the width and height of the frame as a starting point. Also, if your camera isn't pretty close to the foreground object then watch out for excessive distortions around the edges.

On a final note ... you'll probably get the best images if you make SURE you have something of interest in the foreground - if your just shooting a non-specific scene with the horizon in the middle with a WA or UWA lens you'll find that the distant detail (ie anything more than even a few feet away) is incredibly small - which usually makes for a pretty boring photo. Many seem to think that "wider is better" when it comes to shooting landscape, but that's not the case - and - WA lenses actually introduce quite a few additional challenges to be overcome that you don't get with longer lenses.

Hi Colin,

I should have said that these aren't landscape shots but are images of a building where, with hiindisght, I should probably have taken a number of shots using a smaller fov and stitched them together in PS. But hey: I was on holiday; it was the first day it hadn't rained; I wanted to try the new lens out; I didn't have a great deal of time, and tripods weren't allowed. Live and learn!

I think we're all quite acustomed to seeing photos of buildings with converging verticals, so my issue is that by the time I've got things "straight" or, at least. "straighter" (as straight as a centuries-old building ever is, anyway), I'm beginning to wonder whether that really is the way it looked.

I'm enjoying the process of working it out, it's good learning material, and will post some images when I'm happy with them.

Hi Gill,

Wide-angle lenses don't "cause" perspective distortion any more than any other lens, but they do allow you to get closer to the subject and still retain the same FoV - and it's that decreased distance that causes the distortion due to things that are closer looking bigger, and things that are further away looking dramatically smaller.

So - for best results - shoot the likes of tall buildings from as far away as you can, and get the camera as high as you can ... also helps to leave as much of a safety margin around the image as possible as you'll end up cropping the image severely after you've done the correction.

Personally, I like a bit of correction - but having completly parallel verticals on a very tall building always looks a bit unnatural to my eye.

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Originally Posted by Colin Southern

Personally, I like a bit of correction - but having completly parallel verticals on a very tall building always looks a bit unnatural to my eye.

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:D:D

Canon 17mm TS-E
http://backup.cambridgeincolour.com/.../ROOF9921B.jpg

The Flatiron building looks a bit unnatural by itself though.