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Correcting Lateral Distortions using a Canon 24mm 1.4L II

Asher Kelman

OPF Owner/Editor-in-Chief
Hi Asher

well the TSE is kinda MF-lens, so unshiftet, you use the sweet spot only. Must be very good, that's rarely been a problem of a shift lens.

It's the amount of shift with good quality which finally makes a shift lens good or bad.

Using it for people: that lens is not done for fast shooting; it's manual focus and when you shift, exposure will probably be indicated wrongly. With its f = 3.5 wide open, I would think twice before using it for your purpose; it's not made for that, IMO.

Are you - apart from the distortions fine with the 24 1.4?
You could use software to ge rid of that distortion.

Michael,

For shooting an entire orchestra, 24 mm just gives ample coverage from where we shoot and depth of field. I am going to try to correct the images I have as the correction involves shrinking the width at the lateral edges, so resolution shouldn't suffer. Still, if the T/S glass is better, then I will be able to resolve more detail without having to make corrections. It seems it's just a matter of cost. If there's a MF 24 mm I'd get an adapter in a second!

Speed is not an issue as I have time to prefocus and I don't need a lot of shots. I'm perfectly happy with manual focus as I get set this well in advance. I'd use it about f 5.0 or f8 if I'm allowed to use flash in a rehearsal.

BTW, what is your favorite lens correction software that you'd use for the 24mm 1.4?

Asher
 

Michael Fontana

pro member
Michael,
BTW, what is your favorite lens correction software that you'd use for the 24mm 1.4? Asher

Asher, you could use Lensfix from kekus for PPC, PTLens for intelmac, or Lenscorrector, which lets you generate lens profiles yourself. The later is especially interesting, if you have a lot of alt lens.
 

Asher Kelman

OPF Owner/Editor-in-Chief
Asher, you could use Lensfix from kekus for PPC, PTLens for intelmac, or Lenscorrector, which lets you generate lens profiles yourself. The later is especially interesting, if you have a lot of alt lens.
Thanks Michael,

You suggestions are helpful. Likely what I'm seeing is anamorphic correction.

"Volume Anamorphosis"

A photograph of a building taken with the sensor parallel to the target will yield an image with parallel vertical lines. In actual fact the vertical lines converge due to perspective. To maintain parallel lines in the image rectilinear lenses magnify the image near the edges.

While this is desirable when photographing buldings, it's less desirable when taking pictures of people. In this case you may find that individuals near the edge of an image in a group shot may have large odd-shaped heads! This is especially true when using extreme wide-angle lenses.

ana01.jpg


Photo epaperpress.com​

Sometimes referred to as volume anamorphosis, this type of distortion cannot be corrected by PTLens. However it is easily corrected in recent editions of Photoshop using the Free Transform tool. Notice the extra long hands in the following image.

To correct this distortion in Photoshop do the following:

Select > All (Ctrl-A)
Edit > Free Transform (Ctrl-T)
Edit > Transform > Warp (choose the Warp button in Options bar)
Then drag the lines to compress/expanded regions as needed.

ana02.jpg


"Volume Anamorphosis" Corrected in Photoshop



I don't like that it seems to approximate! The hands should become normal in size if the image is simply corrected, or is this not possible with a wide angle lens? IOW, if the stage is to remain parallel, do we expect anamorphic distortion of people?

Asher
 

Michael Fontana

pro member
Asher

that's a different subject!

The lens correction software does correct barrel or pincushioning distortion, but not your WA-°effect°!

It's a phyiscal property of the WA and projection type (remember stitching and FOV > 90 degs. ??) - even more pronounced with UWA - to have that big angles effect of distortions at the left and right side of the image, meanwhile the center beeing somehow normal?

Dont mix them up!
With a FOV of 180 degs and a rectilinear, (planar in APP) (= cameralike) projection, paralell lines would meet in infinity!
 

Asher Kelman

OPF Owner/Editor-in-Chief
Michael,

Unless I'm mistaken, the angle of view for the 24 mm lens is 84 degrees. So are you saying that if the stage is parallel the face will be distorted at the edge?

Asher
 

Michael Fontana

pro member
It's 84 degs diagonal - and 73 degs hor, 53 degs vert.

So are you saying that if the stage is parallel the face will be distorted at the edge?

It shouldn't be much with a 24 mm, but will be with a 16 mm. Your example from PTlens looks to me to have a wider FOV than a 24 mm.

------
just look at the women's example, the hands are closer to the lens than the rest, with a UW, and its foreground-background-relation the hands are distorted.
When doing the same shot with a 50 or 100 mm, you will not have that problem.

The reason is, that you will change position and therefore perspective.
Perspective itself depends only on position, and never on lens!
 

Cem_Usakligil

Well-known member
It's 84 degs diagonal - and 73 degs hor, 53 degs vert.

So are you saying that if the stage is parallel the face will be distorted at the edge?

It shouldn't be much with a 24 mm, but will be with a 16 mm. Your example from PTlens looks to me to have a wider FOV than a 24 mm.

------
just look at the women's example, the hands are closer to the lens than the rest, with a UW, and its foreground-background-relation the hands are distorted.
When doing the same shot with a 50 or 100 mm, you will not have that problem.

The reason is, that you will change position and therefore perspective.
Perspective itself depends only on position, and never on lens!
Yes, I agree fully.

@Asher: take a look at this page of DxO on this topic as well. It is not a process which can be automated as explained in there.

Cheers,
 

Asher Kelman

OPF Owner/Editor-in-Chief
Does anyone have examples of using DXO volume anamorphosis correction? Either cylindrical or spherical volume anamorphosis.

I'm interested in how good these are.

Asher
 

Mark Hampton

New member
Asher,

I like the big hands burn...

why not work the other way and make the subject the same size as the hands are !

cheers
 
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