analog/digital and offline compesation

Marko Marjanovic mmarjano at
Thu Jul 12 06:14:15 EDT 2007

Dear all,

I use FACSCalibur for all my cytometry needs, which are mostly simple 
but create magic for me :)
Not that long ago I started to use SUMMIT software (thanx Denis P.) for 
offline compensation of my data (usually annexinV/PI) and a colleague of 
mine uses FlowJo for her two color purposes. And it seems to be working 
just fine comparing to direct compesation on the machine where I have to 
compensate FL2/FL1 almost 100% to get a text book picture, and not a 
banana lookin-like dot plot :)
I got 2 questions:

1. I heard that FACSScan and FACSCalibur are analog machines and that it 
is not possible to do offline compensation and that it should only be 
done on the machine? (btw I thought that all machines are analog and 
just have AD converters..?) is that true??

2. What cause could produce an effect that I need to compensate that 
much while doing it on the machine? (geometry of the laser and 
mirrors/detectors, age of the machine...?)

Thanx , Marko.

Marko Marjanovic, B.Sc.
Laboratory of Functional Genomics
Division of Molecular Medicine
Rudjer Boskovic Institute
Bijenicka 54, Zagreb, HR-10000
Phone: +385 1 4561111 (1772)
E-mail: mmarjano at

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