On 05/11/2014, Tom Fine wrote:
>> I do use a digital camera for photographing album covers, and large
>> posters, etc but I admit that I take pictures outside on cloudy days.
>> No artificial light or refection issues that way.
>
> Hi Paul:
>
> What do you do to avoid perspective distortion (non-squareness)? It
> seems like, for a poster, you'd have to have the camera up so high
> that there would be some shadowing or reflection in a poster with any
> gloss to it.
Put a small spirit level on the camera to make sure it is square on the
copy stand.
For big originals it is safe to use a moderately wide angle lens. Not
too wide and vignetting, distortion etc begin to be problems.
Zoom lenses are only OK if of very good quality -- not the standard
"kit" lenses that come with the camera.
A polarising filter will help with reflections on glossy originals.
The best results I have had from a camera is from a Sigma DP3M. This is
a rather unorthodox model with extremely high resolution. There vis also
a DP2M with a wider angle lens. Both models are more or less
discontinued, and they have recently been available at low prices.
Example here:
http://www.dpreview.com/forums/post/54603316
Click on the image to see it bigger, with option to View Original.
> I would like to know more about this method because I have some
> large-scale schematics I'd love to digitize in some other way than
> trying to tile together 12x18 segments.
>
> My wife had suggested something similar to what I think you are
> saying, using a tripod and spreading the document out on our deck,
> holding the corners down with weights. The problem is, no matter where
> I put the tripod, there was perspective distortion because the lens
> wasn't centered over the center of the document. That is the main
> advantage for a photo stand, centering the camera over the image.
>
> I wonder if it's possible to rig up a mechanism whereby a digital
> camera "flies" over large documents like posters or schematics and
> uses built-in panorama software to stitch the segments together? The
> segments should stitch easily due to rigging a mechanism where the
> camera is kept at a static height and static vertical angle to the
> document, moving on a controlled horizontal path.
>
Regards
--
Don Cox
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