Why building perspective correction is important.

[manaheim]

I'm going to share a little secret here. It's something I use to distinguish a part of my work, so if any of you people come and compete with me on this, I'll send my Uncle Tony out to give you and your camera some lovin'.

When we look up at buildings and other vertical structures, our eyes and brains work together to compensate for the odd visual effects that occur. If you stop and pay attention, however, you see that the buildings do not, in fact, appear straight.

When look at 2d pictures, however, the reality becomes extremely noticable... and yet, for some reason people don't seem to bother trying to fix it. We just accept it as normal and move on.

HOWEVER, a properly corrected image can have a much greater impact on the viewer. In many cases, the corrected image will feel significantly better to the viewer than the uncorrected one, and they may not even be able to tell you exactly why that is, unless they compare them side by side.

Now in the past, the process of correction was a manual one and, while not crushingly hard, certainly not terribly easy. Nowadays a company called ePaperPress has a very nice and inexpensive tool called PTLens that greatly simplifies this process. (It still takes some skill and practice, but it's quite managable)

Here is an example of the results...

Here is a picture I took before any perspective correction...

And here is the same image AFTER perspective correction...

EDIT: btw, you may notice a TINY angle on the second shot... I've found it works well to leave the tiniest bit of an angle vs. bolt straight, and also keeps you from overdoing it, resulting in an odd Dr. Seuss-y effect.

 

[icassell]

I'm going to have to try that software. I've been thinking of buying a T/S lens, but this would be alot less expensive!

 

[tirediron]

I'm going to have to try that software. I've been thinking of buying a T/S lens, but this would be alot less expensive!

As usual, this isn't a ten-cent replacement for thousand-dollar tool. Perspective correction software can do a good job (as illustrated above) but there is a price. The image is cropped, the degree of which depends on how severe the correction is. As with so many other software 'solutions' they're good, but not as good as getting it right in the camera. Of course there's a lot to be said for $15 vice $1500+, but...

 

[icassell]

Well, the canon lineup are each a bit under $1200 at Amazon, but there is a Russian line for alot cheaper ($388) that Mitica posted. http://araxfoto.com/lenses/arsat-55-shift/

 

[manaheim]

As usual, this isn't a ten-cent replacement for thousand-dollar tool. Perspective correction software can do a good job (as illustrated above) but there is a price. The image is cropped, the degree of which depends on how severe the correction is. As with so many other software 'solutions' they're good, but not as good as getting it right in the camera. Of course there's a lot to be said for $15 vice $1500+, but...

Yeah, I shoot wider than necessary in these situations to ensure I have some extra space to crop without losing the image. I usually lose maybe 5-10% off the sides. Not too bad.

And yeah... literally $15 instead of even $500 is a pretty significant difference.

 

[William Petruzzo]

Nice. I'll have to give it a try.

 

[Flash Harry]

If possible rather than point the camera/lens upwards, which is what causes converging verticals, go for a higher shooting position if possible, if not move back, less problem, also wide angle lens will accentuate the effect. H

 

[Helen B]

There's a good correction tool in the later versions of Photoshop as well: Filter - Distort - Lens Correction.

Best,
Helen

 

[Flash Harry]

You can also use the Spherize thingy in earlier versions for the same effect. H

 

[manaheim]

There's a good correction tool in the later versions of Photoshop as well: Filter - Distort - Lens Correction.

I'm quite embarrassed to say I didn't know that was there. It wasn't there before, so it never occurred to me to look for it now. Funny.

It looks like it doesn't auto correct based upon lens characteristics, though (such as barrel distortion based upon the focal length of the particular lens).

Still, nice...

 

[Neuner]

There's a good correction tool in the later versions of Photoshop as well: Filter - Distort - Lens Correction.

Best,
Helen

Ah, you beat me to it. I've used the grid lines, barrel distortion and vertical/horizontal correction several times. Works really well, but as stated, you do loose some of the picture.

If the edge of the picture is uniform or relatively easy to match like sky & grass, to save loosing some of the image I've cloned the perimeter to fill in.

 

[manaheim]

Regardless of any of this about what tool you use to do it, I hope the original point isn't lost... this is a GREAT thing to do for pictures of buildings and like objects. (unless of course you're intentionally going for that funky look...)

 

[Helen B]

It looks like it doesn't auto correct based upon lens characteristics, though (such as barrel distortion based upon the focal length of the particular lens).

Still, nice...

The key thing for perspective correction in the Filter-Distort-Lens Correction set is the Tilt adjustment, which transforms the image in an optically-correct way (about the lens axis, if the image is uncropped). There are other ways of correcting converging verticals that are not optically correct, and result in the vertical-horizontal scale being altered (ie the building gets thinner or fatter).

Here's an example of the corrections required if you don't transform about the axis, and a brief discussion of alternatives: link.

Best,
Helen

 

[pm63]

I've found it works well to leave the tiniest bit of an angle vs. bolt straight, and also keeps you from overdoing it, resulting in an odd Dr. Seuss-y effect.

Boy, do I agree on this. I tend to overdo it and then think "aahhh what have I done" before having to start from scratch. Photoshop does indeed do a great job, though I do sometimes find having to crop annoying as I can;t exactly preserve aspect ratio.

 

[Bifurcator]

Ah, you beat me to it.

She beat me three it.