Here is how to fix this problem for real. If you _really_ want to have a normal exposure through the windows AND inside the shop, you will need to make a HDR (high dynamic range) panorama. It involves a bit more work, but gives impressive results, with nicely exposed windows and shadowed regions. I have been experimenting with this lately using a new application named Photomatix.
You shoot fisheyes at normal exposure, overexposed and underexposed (even more than one level of under and over exposure if you want to make things even better. I use a Nikon 995 and use auto-bracketting to take pics at ev+2, ev+1, ev 0, ev-1 and ev-2 in a manual exposure mode (not as hard as it sounds.) I take all five at one position before moving to the next angle (using three fisheye angles to make a pano). Yes, this means I take fifteen pictures total. I then stitch a pano for each exposure value, starting with the "normal" ev 0 exposure. For the other exposures, I do a manual stitch (have to have the Pro version of Panotools for this, I think) for each of the other panos, setting everything from cropping circles to yaw/pitch/roll to the exact same values I got for the normal exposure. This helps to insure that everything is lined up the same in each of the five panoramas.
Ok, so I have had to stitch five panos instead of one, a fair amount more of work (wish I could afford the batch version of panoweaver!) Let's look at each of the five panos (hope my links work!) Note that all of the images have been reduced to 25% in size and saved at 60% jpeg quality. I do all of my work using uncompressed images until the final panorama. (These were shot in my family room to test out the HDR photography concept, so pardon the mess.)
First the most underexposed (ev-2), to get the brightest parts of the windows and lights under control:
Next, the ev-1 for less-blown-out highlights:
The normally exposed image, exposure found using the meter on the LCD of the camera with manual exposure, with a bright window on the periphery of the scene:
The slightly overexposed image (ev+1):
The very overexposed image (ev+2) which brings out details in the shadows:
Now look at two combinations of these images made using Photomatix. It has several levels of combining images that trade off speed, quality, and "feel". Here is the result of the fastest combination, which takes a couple of minutes:
Here is one of the using the advanced-light method, which takes around 15 minutes (You mileage may vary). Honestly, it doesn't seem terribly different from the fast one to me:
Here is a color corrected version. I did the color correctin using the iCorrect Editlab Photoshop plugin.
I think you can see that the highlights are no longer blown out, nor are the shadows as dark. In a critical situation, this could really improve an important pano. Here is a link to the final panorama in QuickTime format. I used CubicConverter to convert the pano to a cubic QTVR:
Pano with no color correction
Pano with color correction
You may notice that I ended up with a bit of a blue cast on one hemisphere of my panorama