Re: Infinity corrected lenses

From: Kevin Cunningham (smskjd_at_mindspring.com)
Date: 10/17/04 

Date: Sun, 17 Oct 2004 12:55:18 GMT

"Copepod" <copepod@blueyonder.co.uk> wrote in message
news:Vfrcd.10005$xb.7384@text.news.blueyonder.co.uk...
> Some help requested please from those who know, from someone who is still
> finding out.
>
> I have been offered a compound microscope which has infinity corrected IOS
> lenses. I am not entirely sure about whether, or not, these are necessary
> for my purposes. I am primarily interested freshwater / marine
microbiology.
> I understand that such optics permit the easy insertion of filters
including
> polarising filters. This is of interest to me as I spend much time
watching
> and identifying ciliates. Further down the line when funds permit I
> understand that DIC illumination would be available should I wish.
>
> I have read that the objectives are neither parcentral nor parfocal, but I
> have no way of knowing whether this is the case, or not. Is anyone able
to
> advise.
>
> Searches which I have made have taken me to manufacturers' websites. But
I
> have been unable to find any objective or critical appraisal of the
feature.
>
> Any help / observations would be much appreciated.
>
> Philip
>
Philip, I hope I am understanding the question here. In general all high
quality microscopes are parcentric and parfocal. If they aren't there is a
huge maintenance issue.

Infinity correction is now used by just about every maker. Non-infinity
corrected instruments are made for highschool use if at all. Every major
maker uses infinity correction.

Manufacturers web sites should be better but there not. Why not let us know
what you want to buy, there are a lot of sharp people on the site, they can
help.

Kevin