This came up on a Spirit-thread where I spoke about having a straightforward workflow for color-matching while there are still sequences that are just plain difficult to match.
Color-brightness matching can be fun. I have probably a dozen ways of attacking the frames, depending on the look and the variety among them for a given panoramic sequence.
I'd like to hear from others how they approach this. I'm handling it primarily as an artist. I rely on my eyes and go for Photoshop. Open the sequence, look for the biggest differences, determine similarity for a big part of the images and then divide the bunch in two or three sets. First I correct the brightness levels by changing the input-output levels via 'levels' in PS. Then I check for color-values in different frames and start by altering the R,G,B levels separately.
For certain pans I made the pan first using PTgui and saving it as a .psd file.
I have found this to be slightly more difficult since you are very dependent on a few frames to adjust all other frames to.
I sometimes also change the brightness values to the grayscale single frames before assembling into color.
What I would like to get to is a routine that works for all sequences since some of them are difficult to match
Anyway, time for bed now but tomorrow I'll continue.
Nico

I have also attempted to make separate pans for each color channel after correcting only brightness values for the raw images. This works VERY well, but, learning to make 3 identical pans and matching them is another thing.
So I am struggling with different methods and would like to find a good routine but for the majority of the sequences I can always just choose one or two frames to choose as anchor frames to a particular row, correct the other ones and then match the rows as a whole.
For the colorisation I use a few adjustment layers.
Oh, yes, I have also tried working with color correction functions in PTgui and Autostitch but that didn't work.
Nico

I havn't much experience with panorama stitching myself but as far as color
issues are concerned I usally attack them in LAB space (although not using photoshop but my own command-line proggis

So: have you tried to do the separation in LAB rather than RGB space: so you could do the brightness matching with the luminance-channels only and later
add the color/chroma-only information from the AB-channels...

just as an idea ... don't know, however if this is supported by the pano-progs...

Thank you Nirgal. I will experiment with it for some next pan and let you know. Some 'matching algorithm' would be nice..programmers?
Nico

Thanks to Nico for sharing infos/experiences!
Perdonnez-moi, I'm not very expert of PS and advanced image elaboration... Wath is the LAB space?

..oops, ignore my request, I already found on the web through a search engine!
However, to me colorimetry is a very hard matter, also because often explainations aren't very clear!
...can someon can suggests a site where all these items are described in the most straightforward way?
Thanks.

wikipedia has a quite comprehensive introduction to color models http://en.wikipedia.org/wiki/Lab_color_space

However the exact formulas and colorimetric details (CIE standard details) are not so important.

The basic concept behind LAB is to create a "perceptual" color model that
seperates luminance from the chromatic/color components of an image
(similar to the well knwon HSL (hue/saturation/lightness) model, where also
only one channel carries brightness information...
Of all color spaces, LAB (an it's various CIE variations/enhancements)
is supposed to offer the "most perceptional" color metric, i.e. small
distances in the the A-B plane of the LAB coordinate system also correspond to "small" difference in "perceived" color.

If I remember correctly, Photoshop should already offer full support of the LAB
color space.

What software do you use dilo? I might look into updating some kind of tutorial on my site but right now I got a few pans awaiting some stitching
Nico

Hi Nico... I know relatively well PaintShopPro and, for this reason, I usually use it; only recently I started to use Photoshop (but I have an old version) and sometime other shareware programs (like PhotoLine32).
PS: Thank you very much to Nirgal!