Thanks, Simon.  Now that I've read through that, I think I could do that -- but it seems like it would be simpler to write a .lcp file directly.  The vignetting math is very simple, probably describable with just the stCamera:VignetteModelParam1 property.  And then I wouldn't have to fake a file from which to copy EXIF data (which I could do easily enough with Exiftool, but it seems like more work), as these are scans of film rather than files from a digital camera.

Is there some reason not to just write a .lcp file by hand?  I just need a little better understanding of what number to stick in VignetteModelParam1, and perhaps a little more explanation about some of the others.

Whoops, sorry -- I made a mistake in the math.  My points do not fit naturally on a parabola, it is a more complex curve.

For each millimeter off center (d), the light ratio is 1/(((d/ƒ)^2)+1), where ƒ is the focal length.

The graph of that for ƒ=40mm looks like:

The X axis shows the distance from image center in mm; the Y axis shows the falloff as I think it is to be represented in the 5th column of the lens design data interchange file format.

Seems like every image needs this vignetting correction, unless it is already handled by empirical measurements through a standard lens profile.  For most situations the result is pretty small, as in most cameras the sensor isn't three times as wide as the focal length as it is in my pinhole camera (this graph goes out to the corner of my pinhole camera's image frame).

So assuming I now have the math right, my question is just why the profile isn't showing up.

The tool put it in ~/Library/Application Support/Adobe/CameraRaw/LensProfiles/1.0, which is exactly where I think it belongs...

Awesome, that took care of that -- I can now see the profile.

Now the problem is that it has no effect.  Because focus distance in the source data is zero, maybe?

Edit: The profile was created without an <stCamera:FocusDistance> property, though the white paper says it is required.  Is that a bug, or is the documentation wrong?  Adding it by hand had no effect.

I did define it -- as zero, because it's meaningless for a pinhole camera.

I'll experiment with other values.

Aha -- the reason I can apply the Sigma 4.5mm fisheye profile is because there's a non-raw version of this profile in the Nikon folder, in addition to the design-based profiles in the Sigma folder.  I got faked out.  Sorry about that.

So now I'm back to wondering why my profile is visible but has no effect.

Simon, thank you so much for working through this exercise with  me.  Between you and Eric, now I know a whole lot more about lens profiles!

I now have two working profiles, one for 6x9 scans and one for 6x12  scans.  The only assumptions made in the end are that the scans cover  exactly 6x9cm or 6x12cm, and that they’re centered properly.  Scan  resolution doesn’t end up playing a part, which is a bonus for my  workflow.

Turns out that several of the tags marked Required in the docs are not  actually required, at least if you’re only handling vignetting.  Here’s  my final working profile:

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 4.4.0-c007 1.126898, Tue Sep 30 2008 01:00:47        ">
    <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
       <rdf:Description rdf:about=""
             xmlns:photoshop="http://ns.adobe.com/photoshop/1.0/"
             xmlns:stCamera="http://ns.adobe.com/photoshop/1.0/camera-profile">
          <photoshop:CameraProfiles>
             <rdf:Seq>
                <rdf:li rdf:parseType="Resource">
                   <stCamera:Author>Mark Sirota</stCamera:Author>
                   <stCamera:ProfileName>Zero Image 612F @ 6x12</stCamera:ProfileName>
                   <stCamera:Make>Zero Image</stCamera:Make>
                   <stCamera:LensPrettyName>Zero 612F</stCamera:LensPrettyName>
                   <stCamera:CameraPrettyName>Zero 612F @ 6x12</stCamera:CameraPrettyName>
                   <stCamera:CameraRawProfile>False</stCamera:CameraRawProfile>
                   <stCamera:PerspectiveModel rdf:parseType="Resource">
                      <stCamera:Version>2</stCamera:Version>
                      <stCamera:VignetteModel rdf:parseType="Resource">
                         <stCamera:FocalLengthX>0.333333</stCamera:FocalLengthX>
                         <stCamera:FocalLengthY>0.333333</stCamera:FocalLengthY>
                         <stCamera:VignetteModelParam1>-0.817545</stCamera:VignetteModelParam1>
                         <stCamera:VignetteModelParam2>0.365188</stCamera:VignetteModelParam2>
                         <stCamera:VignetteModelParam3>-0.060324</stCamera:VignetteModelParam3>
                         <stCamera:ResidualMeanError>0.009584</stCamera:ResidualMeanError>
                      </stCamera:VignetteModel>
                   </stCamera:PerspectiveModel>
                </rdf:li>
             </rdf:Seq>
          </photoshop:CameraProfiles>
       </rdf:Description>
    </rdf:RDF>
</x:xmpmeta>
<?xpacket end="w"?>

Perhaps I’ll generalize the names, since this would work for any camera with ƒ=40mm and a 6x12cm frame, and upload them.