Re: objectives/occulars for stereo zoom


"George Pontis" <gpontis@xxxxxxxxxxx> wrote in message
news:43cbd015$0$96009$742ec2ed@xxxxxxxxxxxxxxxxx
> Kevin Cunningham wrote:
>
>>
>> "George Pontis" <gpontis@xxxxxxxxxxx> wrote in message
>> news:43cbbb2b$0$96010$742ec2ed@xxxxxxxxxxxxxxxxx
>> > Here is a rank amateur question about choosing occulars and
>> > objectives for a stereo zoom microscope. In essence: what is the
>> > difference between 10X occulars paired with a 0.5X objective, and
>> > 5X occulars paired with a 1.0X objective ? I understand that
>> > working distance is greater with the lower powered objectives, but
>> > what else ?
>> >
>> > ...
>> >
>> > --
>> Good question! The answer is two fold and you already guessed one.
>> Higher mag objectives whether stereo or compound usually have higher
>> numerical aperatures (NA), that means more resolution. In practice,
>> this is the one you got right 10X eyepieces have more field number
>> than other eyepieces since for every 10X eyepiece about .0000001
>> other eyepieces are built. Its better in practice to to change the
>> front lens than the eyepiece because other eyepieces don't have the
>> same field diameter (field of view).
>>
>
> Bad assumption on my part that "FN" scaled inversely with eyepiece
> magnification. I looked at the numbers for Meiji 10X with 1X objective
> and FN is 23. The 5X eyepiece with same objective is only 26. That
> doesn't seem fair.
>
> The "downside" to having a collection of objective lenses is the cost,
> at least when it comes to the Leica and Nikon. The Meiji (with
> Greenough optics) has a set of auxilliary lenses that are not
> expensive. One option is the 0.5X barlow. In practice it seems to work
> pretty well. Can I assume that resolution (or something else) is lost
> compared to the plain objective ? Does depth of field scale inversely
> with magnification when using such an aux lens ?
>
> Thanks again,
>
> George
>
> --

Resolution does go down with lower NA objectives like a 0,5 but you gets
tons of working distance hence more much greater depth of field.

Kevin Cunningham
SMS


.

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