Re: Can we 'twist' a digital picture to be square with the camera?
- From: Keith nuttle <keith_nuttle@xxxxxxxxxxxxx>
- Date: Sun, 29 Jul 2007 07:57:52 -0400
Mark F wrote:
"maryanne kehoe" <atlsvo@xxxxxxxxx> wrote in part:My wife also paints and this is the technique I use for photographing her painting.
What 'trick' am I missing to take a photo of my watercolor paintings?
Can we 'twist' the digital photo to be square with the camera?
I must be doing something wrong. When I edit my digital photographs of my
watercolor paintings, I need to crop the photo but I can NEVER get the
crop
edges to be exactly square with the digital camera photograph of the
painting.
Therefore I always find myself losing a few millimeters of painting so
that
the photograph is square. What am I doing wrong?
As other have pointed out:
. you likely aren't taking the picture with the camera sensor exactly
parallel to the painting. If you had a rigid setup you could
probably do better, but likely would still need to use software
to make a final correction, such as Paint Shop Pro.
. your lens is probably not perfect. This can be corrected for with
software such as Paint Shop Pro.
HERE IS MY ADDITION:
Lay a carpenter's square against the painting when you take the
pictures. This could then be used for reference points in when
running the parallax and lens distortion tools. Stanley 45-500
for about US$6 at Home Depot might do the job, or you might want
to spend US$20 or so for a better grade, however I don't know if
the $20 ones are more accurate or just more durable.
Using the same setup, take a photo of an accurate grid and use
that to further help the lens correction software. I didn't
find a good grid in my quick search, but "Popular Photography"
uses them for lens tests.
. your painting is likely not perfectly rectangular. Here you need
to use a photo editing tool to clone things to make the edges fill
the electronic "canvas" with no cropping
Here is how I take the picture.
a) I put my unmatted 30 inch by 22.5 inch watercolor on a white towel lying
on the ground
b) I stand over the painting, sometimes on a step stool, and position the
Canon PowerShot A95 5MP camera over the center of the painting
c) I snap the shot using flash & macro focus making sure I am as square as
possible and taking an extra inch or so of border all around to facilitate
cropping
Back inside the office, each and every time, when I crop the 2592 by 1944
pixel digital results using Irvanview 3.98 on Windows XP, I end up with
edges that are not square at first. I have to lose some of my precious
painting just to get square edges when I crop.
What am I doing wrong?
What's the trick to get a photo that is head-on with the painting?
Is there a way to twist the painting with software so I don't have to crop
edges and lose painting data?
I don't know the answer, but the thought occurs that it might be a parallax
problem.
s97
Using her easel I adjust it so that the painting is perpendicular to the floor. I then set up the camera on a tripod, and move it forward or back until the picture fills the frame. (This can also be done with the optical zoom.)
Use a tape measure I measure the height from the middle of the vertical distance of the picture to the floor and adjust the tripod so the middle of the lens is the same distance.
I then measure the distance from each horizontal edge of the picture to the approximate middle of the sensor on the camera, and adjust until they are equal.
The final adjustment is made by using the viewing screen on the camera. I move a horizontal edge of the camera screen until the edge of picture is touching the edge of the camera screen and make any adjustments necessary so they are parallel.
Usually the only adjust I have to make to the picture is cropping and a slight rotation.
Since it is digital if it does not look right I can be easily retaken.
Lighting is very important. To much light will wash out the colors, Flash usually does not work, and you can not get good reproduction when the paints are under glass.
I have the tripod I used with my old chemical camera, but I have seen some relatively cheap tripods recently.
If you are photographing them for competition, it pays to put a little money into the set up for the photographing the paintings.
--
Keith Nuttle
3110 Marquette Court
Indianapolis, IN 46268
317-802-0699
.
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