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Leitz paperweight?
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Charles Krebs



Joined: 01 Aug 2006
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Location: Issaquah, WA USA

PostPosted: Sun Mar 22, 2009 6:18 pm    Post subject: Reply with quote

Quote:
Have I just dug hole I'm in a little deeper, or will this help me see the bottom?
Hmmm... let's see...I think you're in the UK. Ever been to New Zealand in their fall?

Here is, I believe, the intended use of that eyepiece:

http://www.leitzmuseum.org/Misc-Leitz/Viewers/1960-PRADO-attachment/slide1.html

http://www.melsobel.com/items.aspx?id=100962
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dmillard



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PostPosted: Sun Mar 22, 2009 7:10 pm    Post subject: Reply with quote

Sorry . . . I hadn't previously looked at this thread, but I have one of those Leitz Prado micro-projectors in my garage that I picked up from LabX (for well under $100) because it looked so cool. I wasn't aware they were still being sold new.

There is currently a Nikon CFN 10X 0.30 objective on eBay for $49 that looks pretty good. The seller states that shipping is only to the continental U.S., but he could possibly be persuaded otherwise.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=280324250344

David
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Charles Krebs



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PostPosted: Sun Mar 22, 2009 7:32 pm    Post subject: Reply with quote

David,

Mel Sobel sells a lot of used older gear. It's probably around 40 years old, but I don't know when they stopped making them. With a 500 watt bulb, you had probably find and focus on any living protists quickly! Crying or Very sad
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ChrisR
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PostPosted: Tue Mar 24, 2009 6:43 am    Post subject: Reply with quote

Quote:
Ever been to New Zealand in their fall?

Yes I have, Stuart Island, even. It rained. (It does that a lot Surprised )

Well I have the Leitz Prado projector, with a Colorplan lens. I converted it to halogen. Sharpest projector I ever saw. I suppose I could get the F2 out and take some Kodachromes ... no maybe not. (Or is that Kodacromes, I'm sloppy with aitches..)

Thanks for the link David.
I have yet to look up what the letters like CFN mean. Anyone got a link?
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lauriek
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PostPosted: Tue Mar 24, 2009 11:49 am    Post subject: Reply with quote

Chris, you know that old saying, the first thing to do when you find yourself in a hole is _stop_digging_! Wink

Seriously, just look out for the Nikon 10x CF non infinity corrected lenses (There are a couple of different models, the N and M - with NA of 0.3 and 0.25, both are fine just as long as you avoid the more common modern infinity corrected versions), one of these is almost certainly the first microscope objective you want to start doing this kind of work with!

Re CF and N, I think the N in this case designates a 'biological' objective (Intended for use with light coming through the subject) as compared to a CF-M which I think stands for Metal, where you would expect light to be shone on the subject from an angle close to the lens),

CF means that CA is corrected for purely in the objective, no additional tube lens is expected/required to 'finish' the CA correction. (Chroma Free maybe?)
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ChrisR
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PostPosted: Tue Mar 24, 2009 11:59 am    Post subject: Reply with quote

Yes Laurie, that was the joke I meant... Wink

I presume the N means a cover glass is expected, spherical aberrations..., etc?

I tried the man withthe CFN lens - won't ship to UK due to time constraints. Confused Confused

Photoshop is supposed to correct chromatic aberrations - someone must have been round that block..?
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lauriek
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PostPosted: Tue Mar 24, 2009 12:37 pm    Post subject: Reply with quote

ChrisR wrote:

I presume the N means a cover glass is expected, spherical aberrations..., etc?


I think that is correct, although the general consensus here is that at the magnification ranges we generally use this lens it's hard to spot any IQ issues caused by the lack of coverglass...

I have two of the Nikon 10x objectives, one is the N which has an NA of 0.3 and expects a 0.17mm coverslip, the other I think is an M PLAN, it has an NA of 0.25. I've only done one direct comparison test, and I think the N was a tad sharper.
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Charles Krebs



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PostPosted: Tue Mar 24, 2009 2:54 pm    Post subject: Reply with quote

CF: is, from Nikon, for "chromatic-aberration-free". Some people also say "chrome-free". Again, this means that there was no additional chromatic correction intended to be applied by eyepieces with these objectives. The degree of color correction intended in the design (achromat or apochromat) was accomplished in the objective.

N: I'm not sure. It has nothing to do with cover slip requirements, although above 4X the biologicals (with specialed exceptions) were designed to be used with a 0.17mm coverslip. I have not found anything directly in Nikon literature, but have heard it stands for "new" or perhaps designates objectives that can be used for extras wide field viewing (corrected for a larger field size.... about 26mm verses 20mm)

The "M" as in CF M Plan is for metallurgical, and would be an indication that no cover slip is to be used. (And in later finite versions, the tube length was 210mm).





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Charles Krebs



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PostPosted: Tue Mar 24, 2009 3:11 pm    Post subject: Reply with quote

Here's a clip from the back of an old Nikon brochure. Not all that pertinent with the objectives we are using, but it really drives home how "touchy" things get when the NA goes up. And you can see clearly why "high-dry" objectives (high NA, no immersion) will typically have cover slip thickness correction collars.

For example an objective with a NA of 0.25 (designed to be used with a 0.17mm cover slip) will still perform at "100%" even with no coverslip. But an objective with a NA of 0.65 (also designed to be used with a 0.17mm cover slip) only performs at 10% of it's potential if used without a cover slip, a 90% drop-off.
(Note for Rik Wink They don't get more specific about exactly what they are measuring here)


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rjlittlefield
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PostPosted: Tue Mar 24, 2009 4:20 pm    Post subject: Reply with quote

ChrisR wrote:
Photoshop is supposed to correct chromatic aberrations - someone must have been round that block..?

Sure. See http://www.photomacrography.net/forum/viewtopic.php?t=2761 and scroll down to the 6th posting.

If you're lucky and the CA is nicely behaved (not guaranteed!), then you can get rid of the color fringes.

However, CA does more to degrade an image than just introduce color fringes. Remember that CA results from the lens having slightly different magnification for different wavelengths. Remember also that each of the RGB bands seen by your camera actually comprises a range of wavelengths. The same difference in magnification that causes color fringing between the bands also causes radial smearing within each band.

Digital processing can easily bring the three bands into alignment with each other to eliminate the color fringes. But the radial smearing remains. In the case of that lacewing egg that I linked to, you'll notice that the end of the egg is not very sharp, even though it no longer has a color fringe. I don't know whether that's entirely due to CA, but I'll bet CA is a significant contributor.

--Rik
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ChrisR
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PostPosted: Tue Mar 24, 2009 4:43 pm    Post subject: Reply with quote

Beautifully executed and explained, thanks Rik, & Charles.
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lothman



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PostPosted: Wed Mar 25, 2009 12:00 pm    Post subject: Reply with quote

Hi,
would #79575 (Plan ACHRO LWD 10x / .25 WD = 10.5) for 178$ of this seller
http://www.buntgrp.com/nikon.htm
work?
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Charles Krebs



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PostPosted: Wed Mar 25, 2009 1:51 pm    Post subject: Reply with quote

lothman,

I'm almost certain that is the one I tried in 2005 before I got the excellent CF N Plan Achro 10/0.30.

If so (and I believe it is!).... avoid it!. The one I had showed severe secondary color problems; a real disappointment. I've seen these sell for $75 as well, and even at that price I wouldn't take it back.
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ChrisR
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PostPosted: Wed Mar 25, 2009 5:56 pm    Post subject: Reply with quote

So is this a version before the CFs?
#85011 Plan ACHRO 10x / .30 WD = 9.2MM Confused

So far I haven't found a listing for new kit
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Charles Krebs



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PostPosted: Wed Mar 25, 2009 8:59 pm    Post subject: Reply with quote

ChrisR,

That sounds like the CF N Plan Achromat we've been discussing (the 0.30 NA and the 9.2 WD match), but without the seller listing all of the designation, or a picture, I can't be positive. (If so, it can be had for much less $)

The sheer number of different objectives made by the large manufacturers is astounding. And when you add them up over several "generations" it's incredible. Sometimes all the info you need is clearly marked on the objective, but sometimes not!

Below are links to an older Nikon brochure, and one for some newer infinity ones. And these brochures cover only one portion of the offerings Nikon had/has available. So you can see why it's sometimes hard to distinguish between some objectives if only partial information is provided. For example... in the older CF brochure below there are twelve 10X objectives listed. Ten of them are "achromats". In the newer CF "infinty" brochure there are thirteen 10X objectives listed, and six of those are "achromats". So if the only description I have is "a 10X Nikon CF" it could be one of 25 different objectives! If it were additionally described as an "achromat" it could still be one of 16 different objectives.

www.krebsmicro.com/Nikon_CF.pdf

www.krebsmicro.com/CFI60_Optics_Brochure.pdf
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