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Hello at all! My first Micro and some questions...

 
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magom



Joined: 25 Jan 2010
Posts: 30
Location: Aachen, Germany

PostPosted: Thu Jan 28, 2010 8:21 am    Post subject: Hello at all! My first Micro and some questions... Reply with quote

Hello @ all!

After reading several threads in this great community I wanted to present myself. I'm Magom and I'm living in Germany.

As you can see on the pictures I'm a fully newbee in this category "Micro". I've done a lot of macros but the smaller World is interesting, too!

I'm working with a APO Rodagon 50mm 2.8 but I notice many problems, when my Canon FD Bellows and the distance rings are fully streched. There a lot of chromatic abberations. I'm getting a Schneider-Kreuznach 35mm f4 these days, and I hope to get better image quality on this high magnifications. Also I'm getting a Schneider Kreuznach Componon S 80mm f4. Will it be better then the APO Rodagon 50mm?

The presented distance between Camera and Lens is about 30cm. What do you think about the first try? And are you okay with the fact, that I'll keep on the board learning from you? Smile

Best wishes,
Magom



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rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 19400
Location: Richland, Washington State, USA

PostPosted: Thu Jan 28, 2010 3:13 pm    Post subject: Reply with quote

magom, welcome aboard!

You are very welcome here -- photomacrography.net is a place to learn!

Thank you for the scale bar. It is a great help to understanding what is going on with this picture.

The first thing to recognize is that with this size subject, you will need to shoot through a microscope objective to get sharp images.

Let me talk through this issue.

Because of diffraction, you need a very wide aperture to capture fine detail. There is no way around it. According to your scale bar, this image spreads 0.5 mm across about 572 pixels, roughly 0.87 microns per pixel. To capture any detail at all at the level of individual pixels will require a lens setting of about f/3 or wider. Even then, pixel level detail will be very low contrast and the image will look fuzzy. To make it look sharp, you need an even wider aperture, equivalent to f/1.5 or wider.

But ordinary lenses do not work well at such a wide aperture because of aberrations. Instead you need a lens that is specially designed for high magnification and wide aperture. This describes a microscope objective.

For this image, a good choice would be 10X NA 0.25 or 0.30. The best lens I know for these conditions is the Nikon CF N Plan Achro 10X NA 0.30, designed for an older "finite" tube length microscope (not the newer "infinity" designs).

The catch is that at such high magnification and wide aperture, the lens will give very shallow depth of field.

To make a good image of a 3D subject, you will have to use "focus stacking". This involves shooting many pictures focused at slightly different distances, then running some software to put them all together. Good stacking software includes Zerene Stacker, CombineZP, and Helicon Focus.

Using a microscope and focus stacking, you can make pictures like shown at http://www.photomacrography.net/forum/viewtopic.php?t=4464 and
http://www.photomacrography.net/forum/viewtopic.php?t=5074.

About the color fringes in your current photo, I think these are not so bad. The strong fringes I see are mostly in out-of-focus background areas, especially around blown-out highlights. (Reflections from a metal pin?) Such fringes around out-of-focus elements occur with many lenses, even when in-focus elements do not have fringes. When you use focus stacking so that everything is in pretty good focus, the fringes tend to get thrown away.

One more comment about your lighting. You will get better results from illumination that more "wraps around" your subject. The diffuser you are currently using may look large compared to your subject, but still all of the light is coming from the upper right at a fairly narrow angle. This is why the shadows at lower left are so dark. You will get better results by wrapping a white diffuser / reflector all around your subject so as to provide some light from all directions. Empty yogurt containers and styrofoam cups work well.

I hope this is helpful. We look forward to seeing more!

--Rik
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magom



Joined: 25 Jan 2010
Posts: 30
Location: Aachen, Germany

PostPosted: Fri Jan 29, 2010 3:39 pm    Post subject: Thank you! Reply with quote

Rik!

Thank you so much for your reply. This is exactly what I've desired: te get such an excellent explanation. You spend a lot of time writing me, so again, thank you!

Your advice with the Nikon CF N Plan Achro 10X NA 0.30 is interesting. I will keep that in mind. Do you think I can get such a lens on ebay?

Today I got the Schneider Kreuznach 35mm f4 but it has fungal. I tried to clean it an it worked. But while trying to open one part of the lens, I made a scratch on the first lens-side (when using it in back-position). That was silly I can tell you! I will try to get another specimen and will use this as replacement. What do you think about the lens? Should I throw it away or is it worth keeping it? I got the lens for 20bucks Very Happy

Best regards,

Manuel


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ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 7955
Location: Near London, UK

PostPosted: Fri Jan 29, 2010 4:27 pm    Post subject: Reply with quote

I find that 50mm lens perfectly good, in unscientific comparisons.
Reversed, lenses often need a lens hood (Old film comtainer, black pvc tape.....)
Scratch - probably it'll make no difference. Try looking down the bellows from the camera end. If you see no bright line it's probably OK.
If you DO see a bright line, try fillling it with black paint.
Ebay - evertything comes up on ebay eventually, but beware!!.
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