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Caroline Bass wrote:

> So here's the question, I'm visualizing GFP in rat brain, and I have a 
> fabulous signal, but the lowest magnification objective is 10X.  Can 
> someone suggest an objective that would allow me to take a larger view 
> of the signal?  Something in the 2X to 4X range would be good.

Dear Carolyn--

We have an Olympus BX50 upright and have both a 2x/0.05 NA Plan, and a 
4x/0.16 NA UPlan on it.  With strong labeling, the 4x is a nice little 
objective and we use it a lot for run-of-the-mill scanning of 
fluorescently labeling tissue and for low-mag imaging of a variety of 
fluorophores.  The 2x is much less useful.  This is probably due to its 
very low NA.  As you probably know, the brightness of a fluorescent 
imaging system will be directly proportional to NA raised to the 4th 
power and inversely proportional to magnification squared.  In this 
case, that works out to (.16/.05=3.2)^4 = 104.8, divided by 2^2 = 4, or 
26.2.  Thus the 4x objective should give a fluorescence image over 25 
times brighter than the 2x objective.  In my experience, that's probably 
about right.  The 2x just doesn't work well for most fluorescent 
specimens.

I'd get the 4x.

Good luck!

Martin Wessendorf
-- 
Martin Wessendorf, Ph.D.                   office: (612) 626-0145
Assoc Prof, Dept Neuroscience                 lab: (612) 624-2991
University of Minnesota             Preferred FAX: (612) 624-8118
6-145 Jackson Hall, 321 Church St. SE    Dept Fax: (612) 626-5009
Minneapolis, MN  55455             E-mail: martinw[at]med.umn.edu