No Lens

[atomasulo]

I have a very unusual setup where I have an old 4X5 photo enlarger.  Below the enlarger, I have a custom motorized XY table with a camera mounted to it.  The camera points up towards the enlarger lens.  The camera lens is removed so that the enlarger projects directly onto the camera sensor.  The XY table is programmed to move left to right and then up like a typewriter, taking a picture between each move.  The table is controlled by steppers, so that the overlap is approximately 20%.  Whew!  I know that sounds utterly ridiculous to most people, and I am sure to get a lot of "why don't you just use a scanner" responses. There really is a reason for this rig.  See photos.  Inside the silver briefcase in the photo are the electronics to control the XY table rig.

Anyway, it should be trivial to stitch together photos from a rig like this.  I've done it manually in photoshop, and although tedious and slow, it works like a charm.  It requires that there be absolutely no lens correction at all.  Could someone tell me basically how to turn off any correction whatsoever?

When I "Align to Grid" and then choose "Show Seams" the seams are curved towards the edges, resulting in things not lining up.  I tried to fake out the program by experimenting with different focal lengths and multiplier.  So far 460.1mm and 1X multiplier work the best, or 1840.4 and .25X, whatever.  It still doesn't quite work right.  Can someone help me?

Thanks!

[Robert C. Fisher]

This should be very easy for PTGui to stitch this. Ok load the images, under the camera /lens parameters uncheck automatic, make lens type rectilinear (normal lens) call it 50mm, don't worry about the multiplyer it will figure it out. go to the panorama settings tab and make projection - rectilinear make the field of view 100 x 100 you can figure it out later and make a template with all the settings so you can make stitching almost automatic.

I have done tiled images this way for years. It's easy once you get it figured out. There may be a tutorial at PTGui's website you can do as well. I hope you are doing this with large negatives if they are 35mm its a lot of wasted time. this would be one way to scan a 4x5 neg to get a high res image.

Cheers
Robert C. Fisher
VR Photography / Cinematography
rcf...@pacbell.net

[atomasulo]

Thanks for your quick reply!  But I have a few questions.
But first, let me give a quick idea why I am using this setup... I'm not actually creating photos from negatives.  What I am doing is drawing on pieces of glass, projecting light through it, and capturing it digitally.  Sometimes I will crack the glass, which gives really interesting effects.  I just couldn't capture what I was doing with scanning.  I usually use a piece of 6X6" glass and project that.  In some cases, I will have a piece of 12" X 12" glass, and just scooch it around on the enlarger so I get the whole thing.

So I am trying what you recommend... maybe I am missing something.
OK, loaded images. 
Unchecked Automatic (use EXIF data...) under Camera/Lens parameters. 
Went to panorama settings tab. Set to 100 X 100 degrees
Not sure what to do next, so went to "Align to Grid." Set my rows and columns
When I hit apply, the settings on my Projection Settings tab changed itself to 222.5 and 156 degrees.
Viewing it in the Panarama Editor has some totally wacked out warped lines
Kind of corrected it by changing the focal length under "Lens Settings" to 3000mm.  But again I feel like I am trying to fool PTGUI rather than work with it.
Any suggestions?

[Robert C. Fisher]

On Jan 16, 2013, at 8:30 PM, atomasulo wrote:

> Thanks for your quick reply! But I have a few questions.
> But first, let me give a quick idea why I am using this setup... I'm not actually creating photos from negatives. What I am doing is drawing on pieces of glass, projecting light through it, and capturing it digitally. Sometimes I will crack the glass, which gives really interesting effects. I just couldn't capture what I was doing with scanning. I usually use a piece of 6X6" glass and project that. In some cases, I will have a piece of 12" X 12" glass, and just scooch it around on the enlarger so I get the whole thing.
>
> So I am trying what you recommend... maybe I am missing something.
> OK, loaded images.
> Unchecked Automatic (use EXIF data...) under Camera/Lens parameters.

You also need to set the lens to rectilinear and some focal length say 50mm

>
> Went to panorama settings tab. Set to 100 X 100 degrees
> Not sure what to do next, so went to "Align to Grid." Set my rows and columns
> When I hit apply, the settings on my Projection Settings tab changed itself to 222.5 and 156 degrees.
> Viewing it in the Panarama Editor has some totally wacked out warped lines
> Kind of corrected it by changing the focal length under "Lens Settings" to 3000mm. But again I feel like I am trying to fool PTGUI rather than work with it.

How is that fooling it. I also go into preferences and up the control points generated that helps some.
> Any suggestions?

[John Houghton]

On Jan 17, 5:52 am, "Robert C. Fisher" <rcf...@pacbell.net> wrote:
> You also need to set the lens to rectilinear and some focal length say 50mm

It's a flat stitching situation. The camera is being used without a
lens simply to take crops of the image projected onto the enlarger
baseboard. You want a huge focal length specified. See this item from
the PTGui FAQ:

http://www.ptgui.com/support.html#5_6

The preceding item (5.5) is also relevant, as viewpoint correction can
be employed as an alternative way of stitching the images.

A third method is to align the images by varying the lens shift
parameters. Individual lens parameters need to be selected on the
Lens Details tab (in Advanced mode). Then in the Optimizer tab (in
it's own Advanced mode) select only the lens shift parameters and roll
parameters for optimization.

The topic crops up regularly in this forum: a search for "flat
stitching" or "aerial" will bring up many discussions.

If you care to make a set of sample images available, we can try some
stitches for you. Use a service such as http://www.ge.tt/ if you
don't have any private web space to upload to and post a link to the
images here.

Also, you might try the (free) Microsoft ICE stitcher, which does flat
stitching in one of its planar modes.

John

[atomasulo]

Thank you for these references.  Makes a lot of sense.  I will give it a try and report back.

[hdrv]

Le 17 janv. 13 à 08:30, atomasulo a écrit :

> Unchecked Automatic (use EXIF data...) under Camera/Lens parameters.

Verify that the lens parameters a, b, c, d, e,.... are set to Zero.

Romuald

[DaveN]

As John H mentioned, you are stitching a flat image moving the camera
along a plane versus stitching an image by moving the camera around
the lens's no parallax point. The math models are different. In
addition to trying Microsoft's ICE, you may also want to have a look
at Autopano Pro from Kolor.com which is set-up for that type of
stitching.

[Kelly]

@atomasulo

This doesn't sound ridiculous - this sounds fantastic! Please post some of the resulting images :)

And yes, the link John kindly provided is perfect for this situation.

Kind regards,

Kelly

[atomasulo]

Thanks.  I have a lot of work to do, so once I get some good images, I'll make sure to come back to this thread and post some images.  In the meantime, I tried John's suggestions... you pointed me in the right direction.  Results are much improved... but I still had to add a lot of my own control points.  I think PTGUI is just not exactly right for what I want to do.  It wouldn't take much for them to add a true flat stitch option to the program, because otherwise its a nice program.

Anyway I took the advice to take a look at some other packages.  I downloaded Autopano Pro trial, and I have to say it works near flawlessly for what I am doing.  They have an orthographic projection which is exactly what I need.  I set the lens to 1500mm load 150 pictures in, and voila!  Really it worked just like that.  I didn't even need to input in what orientation the photos were taken.

Anyway, once I get some finished photos ready, I'll post some.  If anyone is interested in my enlarger/XY rig I can upload some more details on that as well.

Cheers,

Andrew