"Lesley Robertson" <l.a.robertson at tnw.tudelft.nl> wrote in message
news:bmljgu$6ce$1 at news.tudelft.nl...
>> "DKafkewitz" <dkafkewitz at aol.com> wrote in message
> news:20031015145344.09624.00000978 at mb-m25.aol.com...> > Light scattering varies inversely with wavelength. The shorter the wave
> the
> > more the scatter. Hence 440 is more sensitive than 660. But absorbance
of
> the
> > light by the medium is also important. Colorless media abosrb no
visible
> > light: that is why they are colorless. Yellow media absorb in the
shorter
> > range. Therefore you use a longer wave to minimize the false reading of
> > Absorbance rather than scattering.
> >
> If you set zero on a sterile blank of the same medium, or use a double
beam
> with a sterile blank, you cancel the effect of the medium unless the
culture
> is producing a pigment. We always used 430nm with our bacteria because it
> gave a longer linear area of ODs with our spectometers, cutting out the
> amount of dilution needed. One common mistake I've seen students make is
to
> dilute with water rather than sterile medium, thereby introducing another
> variable.
> Lesley Robertson
>http://www.beijerinck.bt.tudelft.nl>>
Also you could try a Nephalometer (Nephalometry)
Best Des
