Terry, I assume that the original image is a true rectangle and you want to produce an exact reproduction at whatever scale your resolution provides. That is, you want your stitched end-result also to be an exact rectangle: there should be no, as you put it, "perspective effects"
Isn’t the simplest way to achieve that within Hugin not to rely so much on precise camera or image positioning and/or direction but rather on the use of horizontal and vertical control points (and of course a rectangular projection). I’ve found it remarkably successful to place h and v control points on each individual constituent image, using any suitable rectangular bounding frame that might be included in the original image. Failing that one can use the edges of the original image, making sure that enough of the surrounding background is included to guarantee that they show. But you’d want to do that anyway to be sure that all the original image is included. I rely on the translation parameters X and Y; others may prefer to rely on varying d and e per image. Provided the images are tied together with enough internal control points you don’t even need to have h or v points that connect different images. Rather, you can have the same image in both frames of the control-point window. I’ve found this approach to work well with, for instance, a museum painting photographed from several positions along its length, but from below the level of the painting to avoid tiresome reflections and pointing upwards at it. I’m not saying you shouldn’t be as normal to the image as is reasonably achievable for each shot, because that helps avoid focussing and resolution inconsistencies across each image. I just don’t believe it is critical in order to achieve an exact reproduction of the shape of the original. I have a suspicion, though I’ve not tried any systematic comparisons, that it is better to have enough images to ensure that the edges of the original image don’t end up too close to the edges of the constituent images. But maybe your camera gives an image of sufficient quality throughout for you not to have to worry. Roger Broadie On Wednesday, November 4, 2015 at 11:56:47 PM UTC, Tduell wrote: > > Hello All, > I have become involved in a project to help an artist friend prepare an > image of a painting to be used to make giclee prints, and I'm looking for > > any thoughts on what I should do to get it right and what to avoid. > To date, my friend has had his paintings photographed commercially, with a > > medium to large format film camera, the transparency then scanned on a > drum scanner to produce an image that would print at original size at 300 > > ppi. > I'll be shooting with a Pentax K-3 II (aps-c sensor), and aim to shoot a > 2x2 pattern with about 30% overlap vertically and about 50% overlap > horizontally...that's roughly how it works out from the painting and > sensor proportions. > I'll shoot from a weighted tripod, using pixel shift mode, and at this > stage thinking about using a 150-450 lens at about 300mm. > The intention is to set the painting vertical on a stand, with lighting > each side at about 45 deg. > It is a simple matter to set the camera at the correct height shooting > horizontally, but not quite as simple to ensure we are normal to the > painting in the horizontal plane. I would like to try to minimise any > perspective effects as much as possible. The thinking at the moment is to > > move the painting vertically and horizontally on a fixed easel to align > for each shot, rather than move the camera. I think we can better keep the > > shots normal to the painting by this method. > That's probably enough to be going on with...any thoughts? > > Cheers, > -- > Regards, > Terry Duell > -- A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ --- You received this message because you are subscribed to the Google Groups "hugin and other free panoramic software" group. To unsubscribe from this group and stop receiving emails from it, send an email to hugin-ptx+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/hugin-ptx/add6fbee-9362-4c39-a27e-6115314313bb%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
