Stauroneis phoenicenteron

RogelioMoreno · Post by **RogelioMoreno** » Sun Oct 23, 2011 6:46 am

I was trying to use my Nikon Plan Apo 100/1.4 with circular oblique illumination (using a Nikon dark field condenser 0.95-0.80) and got the following single shot of stauroneis phoenicenteron (from test slide):

On this crop the surface looks like porcelain:

Rogelio

Mitch640 · Post by **Mitch640** » Sun Oct 23, 2011 9:17 am

I was under the impression you could not use a condenser with a lower NA than the lens?

This doesn't look to bad though. Does anyone know why some of the holes in certain rows do not form?

rjlittlefield · Post by **rjlittlefield** » Sun Oct 23, 2011 1:14 pm

Mitch640 wrote:I was under the impression you could not use a condenser with a lower NA than the lens?

It works fine -- the only challenge is figuring out what NA to assign to the combination.

One way to think about it is that two kinds of light end up hitting the objective: an undiffracted component direct from the condenser, and a diffracted component that has interacted with the specimen. The undiffracted component strikes only the central part of the objective, using whatever NA the condenser has, while the diffracted component expands as a sphere around the subject and thus uses the whole NA of the objective.

Because the final image is formed as usual by interference between the two components, the effective NA is somewhere between the condenser and the objective. Exactly where depends on how heavily diffracting the subject is, so there's no one "correct" formula.

--Rik

Pau · Post by **Pau** » Sun Oct 23, 2011 2:36 pm

Mitch640 wrote:I was under the impression you could not use a condenser with a lower NA than the lens?

For darkfield yes, but Rogelio is using a darkfield condenser to produce circular oblique illumination like Charles in his recent post:
http://www.photomacrography.net/forum/v ... hp?t=14848

Mitch640 · Post by **Mitch640** » Sun Oct 23, 2011 2:43 pm

And what is circular oblique?

Ah, just looked it up, very cool use of a phase condenser.

rjlittlefield · Post by **rjlittlefield** » Sun Oct 23, 2011 2:52 pm

Ah, sorry -- I misunderstood the question.

--Rik

Charles Krebs · Post by **Charles Krebs** » Mon Oct 24, 2011 11:14 am

Rogelio,

Nicely done! Impressive. (especially for a 100X). Looks like that combination will be very useful to have in your "bag of tricks".

(My personal preference would be a little added "curves" or "levels" to brighten it a bit and boost contrast, but that's a totally subjective choice).

RogelioMoreno · Post by **RogelioMoreno** » Tue Oct 25, 2011 4:45 am

Thank you everyone for your comments.

Rogelio