I do not want to advertise inappropriately on the mailing list. But if I may interject, there have been postings on ratio imaging software for confocal systems and I wanted to point out that Noran Instruments has a package tailored for ratiometric analysis. In fact, some of the questions posed identify specific features of our Odyssey XL. The XL stores images at up to 240 pictures a second. It stores ratio images at video rate (30 image pairs/second) while displaying a live pseudocolored ratioed image. The experimenter can also identify regions of interest on the live display and plot the mean ratio values in a strip chart. The user chooses either a simple ratio or the calibrated Grynkiewicz equation for ion concentration (or pH). The InterVision analysis software also provides a suite of tools to perform background subtraction, thresholding, and ratioing of the captured data. Again, I want to be sensitive to posting on the net as a representative. However I urge anyone who wants more information to contact Noran Instruments ([log in to unmask]) for more details on our Odyssey XL system and InterVision software. Todd Deckard Noran Instruments 2551 West Beltline Hwy Middleton, WI 53562 Phone: (608) 831-6511 FAX: (608) 836-7224