GR: Lens Calibration (orthoimagery)

[RobBain]

Hi

I'm looking to use my GR for orthoimagery. Has any subscriber calibrated their GR lens to correct for the wide-angle perspective distortion?

TIA.

Rob
http://www.fl4.co.uk/NewUAV/

 

[RobBain]

Re: GR: Lens Calibration (orthoimagery): Update

Hi

Update: I've been speaking to Tom Niemann at PTLens (http://epaperpress.com/ptlens/index.html) about determining the distortion-correcting calibration coefficients for the GR. The GR is not currently supported by PTLens but we aim to change that! This should give us a very effective yet simple and inexpensive fix for pincushion/barrel distortion, vignetting, chromatic aberration and perspective.

Regards,

Rob

BTW: I have no relationship nor interests with Tom nor his company. I do like his software, though.

 

[thelps]

I knew nothing about this till you mentioned it here and I read the Wiki article on the subject.
The article suggested the software was $1000 and more, so it seems if you are getting inexpensive you are doing well.

 

[rogergw187]

Re: GR: Lens Calibration (orthoimagery): Update

I've been speaking to Tom Niemann at PTLens (http://epaperpress.com/ptlens/index.html) about determining the distortion-correcting calibration coefficients for the GR. The GR is not currently supported by PTLens but we aim to change that!

Talking gets you only so far. 8=)

I today uploaded some sample GR files to Tom and the camera's now in the database. Just download and install the latest version (9.0), even if you already have it.

Regards,

Roger (a long-time PTLens user and fan)

 

[riccadonna]

Ho, ho all you men! Perpective distortion, that`s the real quest for superwide photographers. There have been written very thick books on the subject. Lens optical distortions is one thing ( pincushion, barrel, moustache ), perspective distortion another and here I don`t mean keystoning. As a matter of fact extreme wide lenses do not distort, however crazy the picture look. It`s just the nature of laws of 2D spatial projection. The reason it looks weird to us and it should is, that we see the object through a spheric projection (our eye matrix retina is spheric) which results in more natural perpective. to keep it short immagine that you squeeze wide angle distorted ( to you eyes ) picture progresively beginning from edges and gradually less and less toward the center. The simple example of rectilinear and spheric perspective is to draw a straigh line divided in equal parts, then a circular line touching the middle of the rectilinear line. Now connect the center of circle which section touches the straight line with equal division marks of that line. You`ll get set of rays intersecting the cicular line in equal number of divisions. Flatten this circuler line on th rectilinear one and compare divisions of both lines. I guess DoX has a filter based on this principle.
p.s. there was a long ongoing dicussion how wide is wide enough without giving impression of unnatural distotion, general opinion was that it was somewhere between 35mm and 28mm. Of course it depends too on the distance, the closer the more impression of distortion. Old architect

 

[rogergw187]

And your point is?

 

[RobBain]

Re: GR: Lens Calibration (orthoimagery): Update

I've been speaking to Tom Niemann at PTLens (http://epaperpress.com/ptlens/index.html) about determining the distortion-correcting calibration coefficients for the GR. The GR is not currently supported by PTLens but we aim to change that!

Talking gets you only so far. 8=)

I today uploaded some sample GR files to Tom and the camera's now in the database. Just download and install the latest version (9.0), even if you already have it.

Regards,

Roger (a long-time PTLens user and fan)

Well done, Roger. Although I looked at my version (I just purchased it - ie. the full version, not the trial) and it says "Camera has not been calibrated!"!

Any thoughts?

Rob

 

[rogergw187]

> Although I looked at my version (I just purchased it - ie. the full version, not the trial) and it says "Camera has not been calibrated!"!

Did you download it before or after I posted my message?

Roger

 

[RobBain]

After your message, Roger. Ie. earlier today.

Rgds,

Rob

 

[rogergw187]

That's odd. Where does it say "Camera has not been calibrated!"?

Roger

 

[riccadonna]

My point is somewhere near, what we call in perspective, vanishing point. Otherwise everything is fine with me and I do hope there`s calibration solution for all GR weak sides. :roll:

 

[RobBain]

That's odd. Where does it say "Camera has not been calibrated!"?

Roger

In the top right hand box (this football stadium is the pic I want to test for corrections, BTW).

Rgds,

Rob

 

[rogergw187]

Hmm. Here's what I see.

I've included the options window. Is your set-up similar?

Looks like a support message to Tom is needed.

Sorry I can't help further.

Roger

PS If you think it would help, put a file up on Dropbox or similar and PM the link to me. I'll see what happens on my machine.

 

[RobBain]

Hmm. Here's what I see.

I've included the options window. Is your set-up similar?

Looks like a support message to Tom is needed.

Sorry I can't help further.

Roger

PS If you think it would help, put a file up on Dropbox or similar and PM the link to me. I'll see what happens on my machine.

This is helpful, thanks Roger. Yours is the 64-bit version. Mine is 32. Wonder if that is making the difference?

I'll ping Tom.

Rgds,

Rob

 

[rogergw187]

> I'll ping Tom.

Please let us know what he says.

Might help to point him at this thread. (I expect you'd worked that out yourself!)

Cheers,

Roger

 

[rogergw187]

Thanks.

Take care,

Roger

 

[RobBain]

> I'll ping Tom.

Please let us know what he says.

Might help to point him at this thread. (I expect you'd worked that out yourself!)

Cheers,

Roger

Tom suggested that I reinstall PTLens. I did and it's now working fine. Thanks for your help, Roger.

Regards,

Rob

 

[rogergw187]

Tom suggested that I reinstall PTLens. I did and it's now working fine. Thanks for your help, Roger.

Excellent. Thanks for telling us.

Clever piece of software, isn't it? I do my initial processing of Raw files in Capture One Pro, which produces superb results. However, I've found PTLens does a better job of correcting distortions, so I've switched that off in C1P and put the resulting TIFFs through PTL. It means an extra processing step but it's worth it.

Cheers,

Roger