Converging verticals - To see, or not to see

[Ndukes]

'Whether ‘tis nobler in the mind to suffer the bends and angles of outrageous distortions,




Or, by adjusting, mend them.' (with apologies to Mr.Shakespeare)




Any thoughts on which works best?

[Shadowman]

I think both are equally distorted but the second image seems more 3-dimensional, there's something about the way the roof juts out that gives it some added depth. Nice captures.

[george013]

'Whether ‘tis nobler in the mind to suffer the bends and angles of outrageous distortions,




Or, by adjusting, mend them.' (with apologies to Mr.Shakespeare)




Any thoughts on which works best?

Dependng on what you want to archive, but the first one is for me wrong. However, I get a strange feeling with the second too. The verticals are corrected but now the size seems to be compressed.

I didn't know Shakespeare photographed.

George

[Donald]

I didn't know Shakespeare photographed.

Don't be silly, George. No, he was the builder.

[DanK]

Frankly, I find the wide-angle distortion in both somewhat uncomfortable to look at, but the first more than the second.

[Loose Canon]

I think you should go for something in between the two Neville.

When you are this close with a wide angle, correcting verticals is going to make the upper part of the building look disproportionately massive. As in your corrected version.

The eye/brain expects to see some converging verticals up this close.

If you were standing further back and taking the shot where the distortion wasn’t as extreme to begin with, then I would say more correction would be necessary and better tolerated by the shot.

Also it may be advantageous to scale it a bit on top. But unless you have a wider version that would lose some of the building.

I also think that the first version should be rotated such that the edge of the left hand shutter on the middle level window is vertical if you didn’t already for the second version. Probably before any further vertical corrections take place. But this too will lose some of the building.

On the second version, the architectural verticals are still not quite right. It appears that you have “skewed” this and if so I think you have slightly overcorrected the camera left side of the building while the right side retains a slight bit of converging, or under correction.

[george013]

I don't know how the correction was done. If it was just correcting the width of the picture so that the verticals are parallel, then that's only half the work. You should correct the height too.

George

[Manfred M]

Tough call on these, Neville. You are fighting two independent types of distortion. One of these is relatively easy to correct, whereas the second one is driven by the distance to the subject / focal length of the lens.

The reverse keystoning (perspective) comes about because you are not completely level. This is why people use Perspective Correction (PC) lenses or do the corrections in post. We tend to be used to a bit of perspective issues when viewing images like this and usually any correction that turns shows the vertical lines as being close to vertical usually works. A bit of convergence is usually okay, but correct the other way and introduce some divergence and the image will look strange.

The distortion brought on by the use of an ultra-wide angle lens, that is something you really can't do much about other than getting further away from the subject, which of course might not be possible or shoot more or less flat on (again this might not be possible). Shooting with as long a focal length as possible is going to be the desirable approach.

A wide-angle PC-E lens (I shoot with the Nikkor f/3.5 24mm PC-E), shot straight on can work. Likewise a straight on shot with a normal lens where you have allowed enough space on either side to correct the verticals can work as well.

Here is a similar situation, although I suspect I might have had more space to work with.



In terms of which of the two images works best for me, I would go along with Terry's suggestion for you to try to find a happy middle point between the two images.

[TonyW]

I think that in correcting the perspective you have inadvertently changed the width to height ratio which makes the second look too bulky at the top. To me, something in between with the correct aspect ratio is the way to go.

[IzzieK]

Now this is a shot where I really start missing Lytebox with its arrows...for comparison.

[george013]

This kind of distortion comes from the fact that the subject, the house, is not placed in or parallel to the plane you focus on. Meaning the points in another parallel plane further from the sensor are enlarged less.

When I say "parallel to the sensor plane" I really mean "perpendicular to the optical ax". Normally the optocal ax is perpendicular to the sensor plane, so the plane you focus on is parallel.
A PC lens is able to play with the optical ax. If you do the plane you focus on is not parallel to the sensor anymore. Now you can shoot pictures under an angle and it looks like as if you stand just before it, parallel.
I never used a PC-lens. It's just theoretical for me. PC=Perspective Control. An E stands for electronic diafragma.

What you are doing essential when correcting perspective in PP is correcting the difference in magnification when it shouldn't be there. The magnification is 2 dimensional, lines are 1 dimensional.

Correcting lines you've a reference, the physical sides of the picture/view. that will be more difficult for the height.

George

[Dave Humphries]

Hi Neville,

I have just made a post in Izzie's thread about shooting with UWA lens and PP corrections.

In particular, I have experienced what has happened to your 'corrected' shot here myself - whatever you/we did has, as TonyW observed, alter the H/W ratio and after the verticals were corrected, you needed to stretch it vertically (or squash it horizontally I guess), to get that back to natural. This is easy to do if there's something in the shot that is known to be round or square, since you can use that to restore a more natural look. That stone head might be useful.

However, there are adjustment methods available in PS that don't mess up the HV ratio, so perhaps try an alternative method to avoid this issue in future, sorry I can't give the best way, my experience is lacking.


As others have said, this is about as extreme an example of what can go wrong as it is possible to imagine

The other advice above is valid; don't even try to fully correct this one, the distortion is due to a combination of issues.

Cheers, Dave

[george013]

Hi Neville,

I have just made a post in Izzie's thread about shooting with UWA lens and PP corrections.

In particular, I have experienced what has happened to your 'corrected' shot here myself - whatever you/we did has, as TonyW observed, alter the H/W ratio and after the verticals were corrected, you needed to stretch it vertically (or squash it horizontally I guess), to get that back to natural. This is easy to do if there's something in the shot that is known to be round or square, since you can use that to restore a more natural look. That stone head might be useful.

However, there are adjustment methods available in PS that don't mess up the HV ratio, so perhaps try an alternative method to avoid this issue in future, sorry I can't give the best way, my experience is lacking.


As others have said, this is about as extreme an example of what can go wrong as it is possible to imagine

The other advice above is valid; don't even try to fully correct this one, the distortion is due to a combination of issues.

Cheers, Dave

That circle is a good reference. I didn't think of that.

George

[arith]

I always try to keep the camera level but not so easy and always use Helicon Filter to fix perspective as best I can.

I try to choose a middle vertical to rotate to, then vertical and horizontal perspective in that order. If I'm using a wide angle lens I also take out the bulge or barrel/pincushion first.

If you point up it never looks right unless you use a tilt/shift lens unfortunately, just being close makes life hard sometimes.

As you can see, after hours of trying I couldn't get this right.

[xpatUSA]

I always try to keep the camera level but not so easy and always use Helicon Filter to fix perspective as best I can.

I try to choose a middle vertical to rotate to, then vertical and horizontal perspective in that order. If I'm using a wide angle lens I also take out the bulge or barrel/pincushion first.

If you point up it never looks right unless you use a tilt/shift lens unfortunately, just being close makes life hard sometimes.

As you can see, after hours of trying I couldn't get this right.

Nice optical illusion on the Leaning Clock Tower of Pisa . . .

[Ndukes]

Many thanks to all for your interesting and informative feedback on this topic. Based on this, and my own instincts also, I have explored a new approach which I have outlined.

First a few points about the photo:-

1. The building is actually not square at the nearest corner. See street plan detail below.
2. The front wall of the building overhangs between each floor and, of course, the roof. So it is always going to look top-heavy.
3. The streets are very narrow which restrict scope for a good viewpoint.
4. In this shot I wanted to show two sides of the building.



Bearing in mind that the straight out of camera image is what the human eye ‘sees’ and conveys to the brain which subconsciously compensates for ‘distortions’ like converging verticals. This is in much the same way as a person looking at an image of a circle on a TV from way off centre still perceives it as a circle in the absence of information to indicate otherwise.
Once we try to correct something which is already geometrically correct but unacceptable to our perception of what it should look like, we depart from reality and enter the world of ‘fudge’. There is therefore no single correct way to do this and we strive to achieve what looks best.

So, firstly, I opened image file in CS6.



I selected the image and used Transform/Perspective to correct the verticals (which, due to the age and construction of the building are not consistently vertical). In order not to lose any of the roof it was not possible to avoid creating a blank triangle in the bottom right corner which I filled with cloned cobbles.



As I see it, while the proportions appear ok at the same level as the camera viewpoint, the shapes become progressively unnatural towards the top of the image. To achieve a more natural look I used Transform/Warp dragging only the top edge of the image down until the proportions looked more natural.



At this stage the entire image needed to be evenly stretched vertically but not so much as to fill the original canvas.



This left empty space at the top which I filled with cloned sky.



All of this is full of compromises, like life itself, but to my eyes it seems to work.
Thanks again to all. Hope some find this useful.

[george013]

Thanks for the explanation.
I think the editing after the perspective correction is not an improvement. The result is a compressed building.
This is where we differ in thoughts.

As I see it, while the proportions appear ok at the same level as the camera viewpoint, the shapes become progressively unnatural towards the top of the image. To achieve a more natural look I used Transform/Warp dragging only the top edge of the image down until the proportions looked more natural.

George

[TonyW]

I always try to keep the camera level but not so easy and always use Helicon Filter to fix perspective as best I can.

I try to choose a middle vertical to rotate to, then vertical and horizontal perspective in that order. If I'm using a wide angle lens I also take out the bulge or barrel/pincushion first.

If you point up it never looks right unless you use a tilt/shift lens unfortunately, just being close makes life hard sometimes.

As you can see, after hours of trying I couldn't get this right.

But I think you have got it right. All the verticals on the buildings are vertical in the picture. Because you are not square on to the middle section of the building, the roof line slopes down to the left and crosses the clock face on a slant. To me, that is as it should be.

[Loose Canon]

I would agree with George here Neville.

The small cantilevered (overhanging) part of the building is not what is giving the disproportionate look from top to bottom (top heavy).

It is the corrections. It is just a fact of Life of this type of correcting, and here the aggressiveness thereof, that this will produce this compression. Happens for any shot, any building corrected this aggressively, cantilever or no. This is what led me to mention scaling the image (upwards) after the corrections to give it a nicer appearance.

But on the other hand it is also a subjective correction to a large degree.

[Manfred M]

Neville - I'm going to have to agree with George and Terry on this one.

I use the technique that you outline quite frequently to correct reverse keystoning issues.

I don't think this is the primary issue with this image. The problem, in my view, is that you are trying to make a shot work that simply has too many contraints. Your finished piece reminds me of so many "selfies" that one sees on the net; self portraits with a wide angle lens that distort the persons face significantly. Increasing sharpness, dodging and burning and other similar techniques might improve the technical issues with the image, but the basic compositional choices the person made are simply impossible to correct.

Your shooting constrictions, compositional choices (wanting to show two faces), equipment constraints, etc are going to leave you with a somewhat awkward representation of the building. Shooting with a PC lens or shooting from the second floor of a building across the street will help with the reverse keystone distortion, but shooting with an ultra-wide angle lens and shooting so that the one corner of the building is close to the lens is going to result in a bit of a funny looking image.

Here it becomes personal taste. So long as you are happy with the image; great! But be prepared with other viewers not sharing your view. Loosing up on some of the constraints (for example doing a straight on shot) and you are more likely to get a compelling image.