Re: Your work on paroramic corrections

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Thomas Sharpless

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Sep 12, 2011, 9:11:47 AM9/12/11
to panini-...@googlegroups.com, schafphoto.com
Hi Schaf

I'm copying this to panini-...@googlegroups.com because keeping the discussion public helps everyone learn.  Please post there in future rather than replying to this e-mail.

On Mon, Sep 12, 2011 at 4:32 AM, schafphoto.com <sc...@west.net> wrote:
My first try playing with the program. I looked for a way to overlay a transparent or thin grid to help lineup in Panini but couldn't figure that out, of course I didn't read the directions either.


It _would_ help to read the manual, or at least the 2 help screens on mouse and keyboard controls.  There you would have discovered Panini-Pro's reference grid, and its ability to toggle the display between original and reprojected image (there is not a true overlay, but I shall probably provide one in future as I know it can be quite useful).

The Photoshop file has the original layer, and a layer I created to withdraw the edges, I was only able to get so far with my first attempt at Panini.

Hard to tell much from such a small image.  What are the 3 panels? Is the center one an overlay of the other 2? What do the cyan and red stripes signify?

So I took the widened view and then transformed the horizontal scale to match the original. That gave me a wider center and withdrawn or compressed info at the edges.
72mm Schneider XL on 5x7 film... 102 degree x 82.8 degree angle of view for that format. That includes the rebate edge of the film, which is included here.

It is most important that the first thing you do in Panini-Pro is to use the Source Projection dialog to tell it the image parameters, so that you start with the image correctly mapped to the panosphere.    In this case, assuming your image is accurately rectilinear, I'd select the 'rectilinear' projection, and set the horizontal fov to 102 degrees.

Then bring up the View Controls dialog (click the projection-looking icon) ad adjust Cmpr.  At Cmpr = 0 you should get a rectilinear view identical to the source (hit 'I' to toggle between them).  Increasing Cmpr will give the compression you desire -- probably a setting around 30 will look right.

For looking at non-panoramic images like this, it is best to switch the display mode from 'PANO' to 'PHOTO' with the control at the lower right corner of the window.  Then the displayed width stays constant as you adjust Cmpr, and the image changes size along with the screen window (whereas in PANO mode the image width changes with Cmpr, and its size is independent of window size).  Of course Zoom scales the image the same way in both modes.

a screen shot of the projection with the coordinates is included in red.

I need to play around a little more and see about correcting the distortion in the foreground lampshades instead of worrying about the edge compression... another day...

I'd suggest you start with an image having a strong central perspective, looking down a narrow street, for example, or a long room.  That is the kind of picture the Panini projection works best on, and it is easier to judge the compression effects than in a flat face-on  picture like this one.  To make face-on images look really right you need to use Panini-Pro's sector flattening tools, which it will take you a while to figure out.

Thanks for producing such an interesting product!

-Schaf


Stephen Schafer  |  Schaf Photo Architectural Photography   |   www.habsphoto.com


PO Box 24218  |  Ventura, California  93002
Landline:   805-652-1000



On Sep 11, 2011, at 1:59 PM, Thomas Sharpless wrote:

Hi

On Sun, Sep 11, 2011 at 3:57 PM, schafphoto.com <sc...@west.net> wrote:
Yes however visually I can see that the edges are stretched in superwide photos so reducing that edge-stretch is what I'm interested in experimenting with, perhaps creating a "truer" view??? 
 
Very true.  Rectilinear perspective distortion has been a problem ever since rectilinear perspective was invented (ca. 1450). Leonardo da Vinci  wrote that a strict rectilinear perspective over 7 degrees wide would be unacceptably distorted (he actually said width of subject : distance from eyepoint > 1:10).  Of course he drew wider perspectives, and by the 20th century art schools had settled on 60 - 70 degrees as the maximum field of view that would 'not look too distorted'.  Maybe now we accept 80 or 90 degree views as 'not too distorted'; but there has to be a limit.  The point is that the tangent projection distorts all sizes, compared to what we perceive with our own eyes and brains, and it is a matter of experience, judgement and preference just how much of that is too much.

The Panini projection is an alternative that reduces the difference of magnification between center and edge -- much as a fish-eye lens does, but only in the horizontal direction.  The result is often very natural looking even when the field of view is panoramic -- 150 degrees and more -- and almost always so for views in the 80 - 130 degree range of modern superwide- and ultrawide-angle lenses.  These may well be "truer views" in the sense that it is easier to believe "yes, that must be how it really looks".  There will of course be some curves where we would expect straight lines.  Panini-Pro has tools for fixing those in many common cases.

-- Tom

Stephen Schafer  |  Schaf Photo Architectural Photography   |   www.schafphoto.com


PO Box 24218  |  Ventura, California  93002
Landline:   805-652-1000



On Sep 11, 2011, at 12:49 PM, Thomas Sharpless wrote:

PS
Your website is most interesting. As you are evidently highly skilled in view camera photography and have an engineer's regard for standards and accuracy, I will consider your criticisms of Panini-Pro especially significant.  Of course Panini-Pro is aimed at making photos more persuasive, not more accurate, but I believe it is important that it is built on geometrically correct foundations.
-- Tom


On Sun, Sep 11, 2011 at 3:22 PM, Thomas Sharpless <tksha...@gmail.com> wrote:
Hello Schaf

The public beta of Panini-Pro is at http://tksharpless.net/paniniv1/.  Please download and try it. I will add you to the offcicial list of beta testers. Kindly report your reactions to the Panini support mailing list whose links are on that page.  And please don't publicize the url (even though anyone can find it via google) because I want to keep the project focused on the needs of pro photographers for now.

Regards, Tom



On Sun, Sep 11, 2011 at 2:43 PM, schafphoto.com <sc...@west.net> wrote:
Good Day Mr. Sharpless,

I am a photographer in Ventura California and often use 98 degree wide angle optics to produce architectural documentation of historic buildings (72mm lens on 5x7 film). I am very interested in you Panini-pro project and would like more info as soon as you do a public beta. I read your article in Photo Technique with much interest. Thank you for your time.

Please put me on your mailing list for further info.

-Schaf


Stephen Schafer  |  Schaf Photo Architectural Photography   |   www.habsphoto.com


PO Box 24218  |  Ventura, California  93002
Landline:   805-652-1000










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