My Constant Battles with Keystoning....

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Greg7579 Veteran Member • Posts: 8,260
My Constant Battles with Keystoning....

The 23 is my most used lens and if any of you have seen the hundreds of boring travel "snapshots" that I post on our trips you know I am often jammed up against something at my back and I have to tilt that 23 up a little, whether it be on the GFX 50r or 100. That causes keystoning,

As all you guys know, Keystoning is a type of perspective distortion also known as converging verticals.

As I read 40 years ago, imagine standing in the middle of a two-lane highway that extends across the desert to the horizon. As the you look down the road, the farther away you look, the narrower the road appears. The road does not physically narrow, but, because distant but equally sized objects appear smaller than closer ones, the road appears to narrow.

Stand at the base of a tall rectangular building and look up. The same thing happens. The top floors appear to be narrower than the bottom floor—the same distortion effect.
Tilting a lens vertically emphasizes this distortion. The same distortion occurs in the human eye, but we do some mental distortion correction in our brains that helps keep it from looking like all buildings are going to fall over backwards when we look up at them. And, of course, to our eyes, this effect is more noticeable in tall skyscrapers than in shorter buildings.

I am on a quest to walk into as many Wats (Buddhist Temples) as I can here in Thailand. We have been here two weeks. I have shot in about 30 Wats now, and the amazing external Chedi (circular towers) are fascinating but hard to shoot. Shooting the indoor Buddhist staures, images and alters is also a joy with the stabilization of the GFX 100 as no tripods or monopods are allowed.

Here is an example from yesterday.  I am also battling bald hazy skies (the smog here is almost as bad as Bangkok, but they say it is from burning fields).  The sun is also straight up most of the day.

Here is an example of the 23 with some serious keystoning and my attempt to fix it a little in post.  What would a TS lens do in this example?  Would it really capture that wide scene in a straight manner?  I'm sure many of you could have fixed this better in post, but no matter what you do, it is going to get severely cropped.

These are all from yesterday at Wat Suan Dok West of Chaing Mai, Old Town.  It is a monastery full of Monks and I waited on all these shots for people to get out of my frame!  I hate other tourists and always believe that I should be the only one there.  🤠🤠  Kidding.....

Wat Suan Dok West of Chaing Mai Old Town.  My attempt to straighten - the circles are still bent.  Straighten those and you have nothing lefty....

The uncorrected raw

Here is one at Wat Suan Dok shot yesterday where I was able to back way off and get the sensor exactly right and square to the image using the 3D level of the GFX 100.  But, that meant I had a lot of boring sky and a lot of boring grass.  So I cut it off, as Chris often does, and made a fake pano that is appealing.  This Chedi are all centuries-old storage shrines for Lanna Royalty ashes over the years....

Here is one where I could get back far enough to level the sensor to the scene using the 3D level.  But I as always, was off a bit and had to straighten it a little.  I think that elongated it just a bit.

Here is a trick I have used with wide angle for years.   Stand square under a big façade and point up.  There will be keystoning but it does not have to be straightened as long as there is no other object or tower in the shot.  It can create a pleasing effect directly under church or cathedral entryways.

Uncorrected version.  I had to tilt the lens up just a little here.

Corrected version but a little elongated.  I ran a line through each Cedi (tower) and it straightened them but I think elongated them a bit.

I am far enough back to square the sensor but I always mess up a little.  That is where auto-align works almost all the time.  It will usually square up those pillars and horizontal beams.  The raw has amazing hand-held detail.

Same thing here with auto-align but I cropped off some ceiling and floor.  Amazing detail when peeking the raw.

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