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Re: Re: Nitrate test kits
> One of the issues I've always struggled with is exactly where do you
> the sample with respect to the white background on the colour chart.
I second the question--this is _exactly_ what I have struggled with for
every test I have ever made! Anyone have the answer?
> The main options that make a difference are:
> 1) Directly against the chart, so the white background is lit by
> passing through the sample (& focussed onto the background, as if
> liquid was a lens);
> 2) Directly against the chart, so the white background is lit by
> passing through the sample (but not focussed onto the background -
> tends to
> make the background quite dark);
> 3) Slightly away from the chart so the white background is lit from
> entering at the side & not through the sample.
I'm not sure what you mean by "focused on the background", the difference
between 1 & 2? Could you clarify?
> This usually changes the reading by quite a large amount depending
> on which
> method is used.
> Presumably, when the charts are designed, one or other of the above
> is the one that is supposed to be used (I assume it's #3)?
> It never tells you on the instruction leaflet - & this is true for
> colour comparison based tests I've used.
Same here for all three paragraphs. :-)
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