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Objective Upgrade?
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ChrisR
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PostPosted: Wed Feb 28, 2018 3:53 pm    Post subject: Reply with quote

For an economical finite 10x, the one above: http://www.photomacrography.net/forum/viewtopic.php?p=228128#228128 .
For a "known" 4x, Robert OToole's $17 find, if it's not the same as yours!
http://www.photomacrography.net/forum/viewtopic.php?t=34277
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Ichthyophthirius



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PostPosted: Wed Feb 28, 2018 5:13 pm    Post subject: Reply with quote

Claytown wrote:
What kind of poor performance would I be looking out for on a Plan Apo? Even if the Pol performance was similar to your experience with the CF 20/0.60, how much of an improvement (or lack of improvement) would it be for me compared to my current stock lens?


When you cross the two polarisers on your microscope, take out the eyepiece and look into the back of the objective, you should see a dark cross (see below). If the cross is always distorted (rotate the polarisers a bit until you find the most symmetrical position), the performance in Pol isn't good. This is the case with a lot of older Plan Apos.

A good Pol objective will have a symmetrical, dark cross. When you close the condenser aperture by 1/2 and look at your slide, you should have a homogenous dark background.

The CF Plan Apo 10/0.40 will certainly be a big improvement in brightfield over your Achromat 10/0.25. But because I don't know the performance in Pol, I can't say if it'll be an improvement overall.

Regards, Ichty


© Nikon


Last edited by Ichthyophthirius on Thu Mar 01, 2018 4:31 am; edited 1 time in total
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Claytown



Joined: 25 Feb 2018
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PostPosted: Thu Mar 01, 2018 1:10 am    Post subject: Reply with quote

ChrisR wrote:
For an economical finite 10x, the one above: http://www.photomacrography.net/forum/viewtopic.php?p=228128#228128 .
For a "known" 4x, Robert OToole's $17 find, if it's not the same as yours!
http://www.photomacrography.net/forum/viewtopic.php?t=34277


I think I will take a chance on the 10x version of the Amscope 4x lens you referenced.
http://www.amscope.com/accessories/objective/10x-plan-achromatic-compound-microscope-objective-lens-1.html

For $30, I think it's worth a shot. Baby steps, right? Hopefully this will give me a good bang-for-buck ratio and perhaps I can provide some insight to anyone who was curious about the 10x
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mawyatt



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PostPosted: Thu Mar 01, 2018 6:44 am    Post subject: Reply with quote

Claytown wrote:
ChrisR wrote:
For an economical finite 10x, the one above: http://www.photomacrography.net/forum/viewtopic.php?p=228128#228128 .
For a "known" 4x, Robert OToole's $17 find, if it's not the same as yours!
http://www.photomacrography.net/forum/viewtopic.php?t=34277


I think I will take a chance on the 10x version of the Amscope 4x lens you referenced.
http://www.amscope.com/accessories/objective/10x-plan-achromatic-compound-microscope-objective-lens-1.html

For $30, I think it's worth a shot. Baby steps, right? Hopefully this will give me a good bang-for-buck ratio and perhaps I can provide some insight to anyone who was curious about the 10x


Some others tried the AmScope 10X and didn't find it very good I recall, think it had a 6mm working distance also. I have the 4X and it's very good considering the $, but avoided the 10X for reason mentioned.

Best,
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Claytown



Joined: 25 Feb 2018
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PostPosted: Fri Mar 02, 2018 10:26 am    Post subject: Reply with quote

I think I may have been thinking about this all wrong. If an objective is a plan, is it only the field curvature that is corrected? Being a plan doesn't necessarily indicate anything about the sharpness of edges and corners? Can an objective be non-plan and still have sharp edges and corners?

Would the Wild fluotar be a sharp lens all around even if the edges of the field are warped?
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Pau
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PostPosted: Fri Mar 02, 2018 12:06 pm    Post subject: Reply with quote

Claytown wrote:
I think I may have been thinking about this all wrong. If an objective is a plan, is it only the field curvature that is corrected? Being a plan doesn't necessarily indicate anything about the sharpness of edges and corners? Can an objective be non-plan and still have sharp edges and corners?

Would the Wild fluotar be a sharp lens all around even if the edges of the field are warped?


In principle non flat field objectives can have good edges, just they are in focus at different height than the center, for focus stacking this wouldn't matter a lot.
In some (many?) cases plan objectives are also better corrected for other aberrations at the periphery and so more adequate although this isn't a general rule.
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Ichthyophthirius



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PostPosted: Sat Mar 03, 2018 10:35 am    Post subject: Reply with quote

Claytown wrote:
Would the Wild fluotar be a sharp lens all around even if the edges of the field are warped?


I've tried it out for you. I actually have the 10/0.45, not the 10/0.40. It has strong curvature of field but when you adjust the focus to the edge of the field, the edges are very sharp (tested in combination with a Leitz Periplan 10x/18 eyepiece).

Regards, Ichty
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Claytown



Joined: 25 Feb 2018
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PostPosted: Sat Mar 03, 2018 2:56 pm    Post subject: Reply with quote

Thanks guys!

I prematurely pulled the trigger on the $30 Amscope 10x Plan Achromatic, but it arrived today and although it perhaps not as sharp as I was hoping for, it is definitely a noticeable upgrade, especially around the edges for non-stacked shots.

Thanks for testing the edges of the Wild, Ichty. I believe that lens will be my next upgrade, perhaps sooner than later. But for now I'm going to see what I can achieve with what I have.

Here is a side by side comparison of the stock 10x amscope achro lens and the upgrade:

(I'm not sure why the field of view shifted between objectives)

10x Achro:


10x Plan Achro:


10x Achro 100% Center:


10x Plan Achro 100% Center:


10x Achro 100% Corner:


10x Plan Achro 100% Corner:
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phil m



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PostPosted: Mon Mar 05, 2018 1:44 pm    Post subject: Reply with quote

The f.o.v. shifted , most likely because the objectives are not parcentered. Chinese objectives are manufactured to average 70's to 80's optical standards but finished to the most minimum standards of acceptability, both optically and mechanically. One of the tradeoffs is that parcentering is a crapshoot between individual examples. I have a 60X Chinese planachro that is centered 280 um, N.E. of the 40X planfluorite that I sometimes mount with it. Some bevelled parfocalizing shims, solved the problem more or less but it is one of the features of crappy machining and Q.C.
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Pau
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PostPosted: Mon Mar 05, 2018 2:15 pm    Post subject: Reply with quote

The lack of parcentrecity can also be due to the microscope stand. You can test it switching the position of both objectives.

I have some problems of parcentricity in my old microscopes and it is mainly due to the stands
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