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Questions about DIC setup (Images added)
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Charles Krebs



Joined: 01 Aug 2006
Posts: 5805
Location: Issaquah, WA USA

PostPosted: Sun Sep 04, 2011 3:07 pm    Post subject: Reply with quote

Pau,

Wish I could offer some equipment suggestions, but DIC mix-and-match is just too baffling for me! Wink

But even with the "official" Olympus pieces I can get backgrounds that are not as even as I would like to have. Naturally, with Photoshop there are many ways to accomplish essentially the same effect. One plug-in I have found very useful is Photokit ( http://www.pixelgenius.com/products.html . It was created by some people whose names might be somewhat familiar http://www.pixelgenius.com/people.html ).

There are quite a few features, but the dodge/burn is especially nice for uneven backgrounds like this and is very versatile (done in layers and can be tweaked with opacity and opacity masks and such). You can try it free for 7 days, so it is possible to determine if it will do the job for you.

Here's a very fast usage on one of your shots. (If you prefer not to have a modified shot posted, let me know and I'll remove it)




BTW... there is also the Olympus Background Subtraction Toolkit:
http://www.olympusmicro.com/primer/digitalimaging/backgrounddownload.html . But it only works with small images, and sometimes the result is not that great.

I've also played around with Image J a little, but found it too complex or not suitable for large full color images.

Ultimately I just find I prefer to do it in Photoshop.
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Pau
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Joined: 20 Jan 2010
Posts: 4885
Location: Valencia, Spain

PostPosted: Tue Sep 06, 2011 10:42 am    Post subject: Reply with quote

Many thanks Charles for your advice. Knowing the quality of your work it must be spot on. I will try both software tools when I had the setup finished and I would concentrate in taking pictures.
Not only is fine reworking my picture, but I would liked to see it bigger.
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RogelioMoreno



Joined: 20 Nov 2009
Posts: 2962
Location: Panama

PostPosted: Thu Sep 08, 2011 4:16 pm    Post subject: Reply with quote

Pau,

I was testing a Nikon 100x/1.4 objective with my 100x DIC slider and I was getting a dark band (NE-SW) on the field of view when the polarizer were at the crossed position, when the polarizer was rotated the band moved outside the field of view. I checked the position of the objective slider's interference band and it was too low of the back focal plane of the objective, I added some extender to move the objective down and bring the band closer to the back focus plane and the dark band begin to disappear from the field of view at crossed position.

The new Nikon DIC prisms (condenser and objective) do not have interference band visible when you put them between (at 45 degree of the crossed position) to polarizer at crossed position, I think the new design is to avoid the non homogenous background of the older systems.

Rogelio
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Pau
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Joined: 20 Jan 2010
Posts: 4885
Location: Valencia, Spain

PostPosted: Fri Sep 09, 2011 12:12 am    Post subject: Reply with quote

Rogelio, thanks for your new observations.

Convinced by your former post about the need to move vertically the objective prism, and after performing aproximate measurements with the telescopic eyepiece I concluded that it must be lowered about 5-8mm and I figured how to modificate the intermediate piece to allow vertical adjustements. Today it's going to the machinist shop to do that modifications. Because they are usualy busy it may take quite a long time Confused .
...to be continued
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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Wed Oct 26, 2011 10:26 am    Post subject: Reply with quote

After almost destroying Twisted Evil the Zeiss intermediate piece to allow vertical movement of the objective DIC slider, I found that the best position for it is the uppermost one I already had got. Dic stuff seems to be counterintuitive, following my measurements it would need to placed some mm lower, but not Brick wall

The setup isn't already finished, but is functional. Now I found good DIC with the NPL Fluotar 16X/0.40, the 40X/0.75 and the 50X/1. With the 25/0.55 it is still too uneven and with higher and lower magnification ones don't work.

Some more test shots. Please give me your opinion about its DIC quality:

Test diatom slide. Leitz NPL Fluotar 16/0.40 prism II


Elodea leaf tip. Leitz NPL Fluotar 16/0.40 prism II


Elodea leaf cells. Leitz NPL Fluotar 40/0.75 prism III

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Cactusdave



Joined: 09 Jun 2009
Posts: 1631
Location: Bromley, Kent, UK

PostPosted: Thu Oct 27, 2011 12:09 am    Post subject: Reply with quote

Images 2 and 3 good DIC, especially 2, which looks pretty much spot on. Number 1 shows some unevenness of field, which I guess you knew anyway. Number 1 is the lowest power and has quite a wide field, and wide field DIC can be challenging to illuminate evenly even for a good DIC system.

My own experiments with non matched objectives used with the DIC system on my Nikon Diaphot shows that good DIC can sometimes be obtained, for example with a Zeiss X25 0.65 Planapo, but that this is always at the price of some degree of unevenness of field. This unevenness can be acceptable for some specimens, but makes stitching difficult as the stitching software seems to compound the unevenness, making one side of the stitched image way to dark, and the other way too light. I found it was the X40 DIC prism that invariably gave the best DIC with unmatched objectives.

Edit: Refering to Charles' earlier post on adjustment of uneven background in post processing, image 1 would certainly be fine after post processing. I have not tried the software he suggests on larger more extremely uneven stitched DIC images, though I should.
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Pau
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Joined: 20 Jan 2010
Posts: 4885
Location: Valencia, Spain

PostPosted: Fri Oct 28, 2011 4:51 am    Post subject: Reply with quote

Thanks, Dave,
I agree with your observations, as DIC inexpert I highly apreciate the opinion of experimented users like you.
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