proj-imim:
RE: Some questions
Greg Stumph 2001-May-01 21:39:26
I've also experienced problems with variations in brightness and color
between images scanned (and photographed) with fixed settings. I'm using a
Nikon LS-1000 scanner, and a Sigma 8mm MF lens. What I've noticed is that
images that contain a bright light source (the sun, exterior windows, etc.)
will vary from images that don't include the light source. For instance, if
the same wall is visible in two shots 120 degrees apart, one containing a
bright light source and one not, the color of the wall will vary between the
shots. I was expecting though, that the wall would look the same in each
shot, since they were both taken with the same exposure settings, and
scanned with the same settings.
So far, I've mainly been using consumer grade Kodak Gold 200 (or 400) film,
and I'm wondering if I'd get more consistent color and exposure between
images with higher grade, slower film. I plan on shooting some Fuji Velvia
and Provia slides soon, so I guess I'll find out if that makes a difference.
Do any of the more experienced photographers on the list have any thoughts
on this? Also, would aperture setting have any bearing on this? Pardon my
general ignorance, since I'm more of a hobbyist, not a professional
photographer...
Greg Stumph
-----Original Message-----
From: #removed#
[mailto:#removed#]On Behalf Of Daniel Maurer
Sent: Monday, April 30, 2001 11:31 AM
To: #removed#
Subject: Some questions
Hi,
i just want to ask a few questions which always apear during my production
process.
1. With my old camera setup (Sigma 8mm AF EX, self made pano head, portrait
mode) i came to an average FOV of 183.5 degree which is quite reasonable for
this lense. With this setup i had my fixed starting values for FoV, a, b, c
and used this as template in PtGui. So I only had to set about 5 controll
points per seame and i very fast came to a good stitch. Values for FoV, a,
b, c always were in the range of the template file (FOV= 182- 185,
a=negative value between 0.2-0.4, b=positive value between -0.3 and 0.6, c=
negative value between -0.3 - -0.6). Straight lines appeared straight (which
is most significant I think).
With my new setup (new tripod head, Manfrotto QuickTimeVR) the camera is set
to portrait mode and I cannot use my old starting values. Instead I made a
new "master file" (For this i use an indoor photo with a lot of vertical
lines, set a lot of controll points and try to get a good stitch) which led
me to new starting values. The values for a,b,c are also a=negative,
b=positive, c=negativ, but much smaller (down under 0.0) but the value for
FOV is reduced to 173-175 degree. The result of the stitch looks even better
than with the old setup. Stitching is not more work now but what i wonder
about is the field of view. Has someone made the same experiences and can
give me an explanation?
2. During scanning i set one image optimization on one image and keep this
adjustments on the other two images. In theory this would mean that all
three images are of the same brightness and color. After stitching i always
have a lot of brightness and color mismatch in my resulting PSD File. Have
you got the same experiences? I have uploaded a typical series of images on
www.360visits.de/panotools.htm i would be interested in what way your first
stitch looks like.
3. Something about the topic scans from PhotoCDs. I have tried the differnt
CCD scanners from Fuji which are the front end of the Frontier Minilab
series. I cannot advice scans from this machines for stitching because of
the automatic color correction. This will lead you to severe problems when
you try blending the seams. The same problem will be on PhotoCD scans.
But for those of you also shooting on medium format i can advice this very
much, scans are cheap and of a very good quality. (and you should take a
look at: scanning a 6x9" negative to 40 MB takes about 8 seconds )
Bye
Daniel Maurer