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Check out this classic image

 
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Cyclops



Joined: 05 Aug 2006
Posts: 2968
Location: North East of England

PostPosted: Mon Oct 09, 2006 4:27 pm    Post subject: Check out this classic image Reply with quote

An example of an early photomicrograph, from 1904!
http://www.microscopy-uk.org.uk/mag/imag97b/oldphot2.jpg

and check out the scope used to get it!
http://www.microscopy-uk.org.uk/mag/imag97b/oldphot1.gif

©http://www.microscopy-uk.org.uk/
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Ken Ramos



Joined: 27 Jul 2006
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PostPosted: Mon Oct 09, 2006 5:41 pm    Post subject: Reply with quote

Must say that last link shows how far we have all come in microphotography! Very Happy
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Cyclops



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PostPosted: Wed Oct 11, 2006 12:58 am    Post subject: Reply with quote

Hardly what youd call a field scope eh!
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DaveW



Joined: 04 Aug 2006
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Location: Nottingham, UK

PostPosted: Wed Oct 11, 2006 3:26 am    Post subject: Reply with quote

From what I've seen it looks like George Dingwall's set-up now, at least he's working on getting the bellows that long!

DaveW Very Happy
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salden



Joined: 27 Jul 2006
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PostPosted: Wed Oct 11, 2006 3:41 am    Post subject: Reply with quote

Oh now that is dedication Laughing
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Sue Alden
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Cyclops



Joined: 05 Aug 2006
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PostPosted: Wed Oct 11, 2006 4:35 am    Post subject: Reply with quote

Strangely, looking a the photo of the set up, it seems he is using the complete scope to project the image onto the ground glass screen!
Amazing!
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Wed Oct 11, 2006 7:33 am    Post subject: Reply with quote

Why "strangely"? Stick a piece of sheet film back there, and voila, a photomicrograph!

Long extensions are physically awkward, no doubt.

But compared to adding glass, extending the optical path is remarkably free of distortion, aberration, light loss, and spurious reflections. Wink

--Rik
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DaveW



Joined: 04 Aug 2006
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Location: Nottingham, UK

PostPosted: Wed Oct 11, 2006 8:26 am    Post subject: Reply with quote

It's really no different to adding bellows and a camera on top of the microscope in a vertical position, but rather than needing a 6 foot copy stand to do so it is easier horizontally. The only reason for a microscope being vertical that I can see is gravitational effects on the subject. If the "scope" is vertical the stage is horizontal and gravity acts downwards on the subject on the slide, handy if it is in liquid. Turn the microscope horizontal and unless the subject is stuck to the slide it will slide off due to gravity, particularly if in a liquid.

If you don't have enough extension tubes and should you want to make a 6'-0" to 8'-0" set of bellows to try it out, here's how:-

http://www.cyberbeach.net/~dbardell/bellows.html

http://my.net-link.net/~jsmigiel/bellows.html


Who needs extension tubes! Rolling Eyes Very Happy Very Happy


DaveW
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Wed Oct 11, 2006 8:31 am    Post subject: Reply with quote

DaveW, thanks for those links -- ever since I first saw a bellows, I've wondered exactly how they were made.

--Rik
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Cyclops



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PostPosted: Wed Oct 11, 2006 9:17 am    Post subject: Reply with quote

I'd have thought that you would remove the eyepiece and then project the image onto the screen. No hang on that wouldnt work would it, masive vignetting(in fact thinking about it, you'd be lucky to see anything!)

I guess Im just used to using bellows/extension tubes on a camera where you have to remove the lens.
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rjlittlefield
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PostPosted: Wed Oct 11, 2006 11:50 am    Post subject: Reply with quote

Cyclops,

Actually it works OK with respect to vignetting. Your typical microscope is set up to deliver a roughly 20 mm diameter field at the eyepiece, some 160 mm away from the objective. That ratio, 20/160, applies to longer extensions as well, so if you used a 1 meter extension instead, the field would be around 125 mm diameter.

The big hit is that microscope objectives are designed to work best at a very specific distance corresponding to the tube length. Adding a long extension takes the objective way outside its "sweet spot" and you pick up bad stuff like aberrations and curvature of field. The better the objective, the worse the hit. But in absolute terms, I don't know how bad the degradation would be for any particular lens. Might make an interesting experiment...

--Rik
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Cyclops



Joined: 05 Aug 2006
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PostPosted: Wed Oct 11, 2006 12:04 pm    Post subject: Reply with quote

Quote:
Adding a long extension takes the objective way outside its "sweet spot" and you pick up bad stuff like aberrations and curvature of field. The better the objective, the worse the hit


Makes me wonder how he got such a sharp image!
Must have had a cracker of an lens set!
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