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Substitute for the resolution test slide 3000
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Lou Jost



Joined: 04 Sep 2015
Posts: 3637
Location: Ecuador

PostPosted: Sat Feb 18, 2017 5:03 pm    Post subject: Reply with quote

Adalbert, those aren't threaded, but 42mm threaded iris exist. You can also really just use paper disks, with different size holes cut in them. I keep a collection of them. But if you are putting them behind an objective, it is nice to have a 42mm threaded iris you can adjust:

http://www.ebay.com/itm/New-IRIS-DIAPHRAGM-Aperture-blade-with-M42-x1mm-thread-casing-/222384424248?hash=item33c7250538:g:kOMAAOSwyQtVi590

http://www.ebay.com/itm/Adjustable-Iris-aperture-diaphragm-2-44mm-w-M42x1-Thread-For-Camera-/321760757916?hash=item4aea6f889c:g:6M8AAOSwBLlVaRzX [/list]
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Lou Jost



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PostPosted: Sat Feb 18, 2017 5:05 pm    Post subject: Reply with quote

Adalbert, I use cross-polarization almost all the time and I find it reduces or eliminates stray glare and wild reflective highlights.
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Adalbert



Joined: 30 Nov 2015
Posts: 720

PostPosted: Mon Feb 20, 2017 9:51 am    Post subject: Reply with quote

Hello Rik, hello Lou,
As far as I can see you have mentioned two different things.
- Rik: aperture between lens and subject (Posted: Sat Feb 18, 2017 7:07 pm)
- Lou: aperture between lens and tube-lens (Posted: Sat Feb 18, 2017 8:00 pm)
I’m a little bit confused because I have never used any inter-lens aperture up to now.
What are the advantages of using this aperture?
BTW, @Lou: thank you for the links!
BR, ADi
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19966
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PostPosted: Tue Feb 21, 2017 12:15 pm    Post subject: Reply with quote

Adalbert wrote:
Hello Rik, hello Lou,
As far as I can see you have mentioned two different things.

Correct, two completely different things.

Quote:
- Rik: aperture between lens and subject (Posted: Sat Feb 18, 2017 7:07 pm)

Yes, but I mention this technique only as a way of helping people understand how the geometry of the image can change, depending on where light enters the lens.

In the animation at http://www.photomacrography.net/forum/viewtopic.php?p=204973#204973, the chip appears to rotate even though nothing physically moves except the light source.

Playing with an aperture between lens and subject can help to understand why this happens.

Quote:
- Lou: aperture between lens and tube-lens (Posted: Sat Feb 18, 2017 8:00 pm)
I’m a little bit confused because I have never used any inter-lens aperture up to now.
What are the advantages of using this aperture?

There are two completely different reasons for using an aperture between two lenses.

The first reason is when two lenses that are designed to be used separately are used together, often the best position for a limiting aperture lies between the two lenses. In this case the best image quality (least aberrations) can be gotten by opening both lens's built-in apertures, and adding a new aperture that is located between the two lenses.

However, the microscope manufacturers design their objectives to be used with a wide open tube lens. If adding an aperture improves the image quality in an objective + tube lens combo, then it is due to some problem with the tube lens. In that case I suggest looking for a better tube lens.

The second reason for adding an aperture is to stop down an objective so as to get more DOF (at the cost of less resolution). An aperture used for this purpose should be located as close behind the objective as possible, so as to minimize vignetting.

--Rik
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Adalbert



Joined: 30 Nov 2015
Posts: 720

PostPosted: Tue Feb 21, 2017 1:17 pm    Post subject: Reply with quote

Hello Rik,
Thank you for the explanation!
Quote:
”If adding an aperture improves the image quality in an objective + tube lens combo, then it is due to some problem with the tube lens. In that case I suggest looking for a better tube lens.”

OK, I still haven't found the best tube lens for the Nikon Lu-Plans.
Enclosed you will find my current ranking-list :-)
http://www.photomacrography.net/forum/viewtopic.php?t=32929&highlight=
BR, ADi
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mjkzz



Joined: 01 Jul 2015
Posts: 1143
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PostPosted: Sun Mar 12, 2017 12:40 am    Post subject: Reply with quote

Quote:
Yes, but I mention this technique only as a way of helping people understand how the geometry of the image can change, depending on where light enters the lens.

In the animation at http://www.photomacrography.net/forum/viewtopic.php?p=204973#204973, the chip appears to rotate even though nothing physically moves except the light source.


This is something I have been pondering. Now, we know different placements of light can lead to different images. What if we place two lights and place them at exactly the two positions in that animation, what the camera would see? a fuzzy image? because intuitively, this should lead to a super imposition of the two animated images. But this super imposition would be fuzzy and blurry, right?

The above involve two discrete placements of two light sources, what if, then, we place a light strip running from one position to another, maybe divide that strip into 10 discrete light sources, then what?

Now lets put a diffused strip in place, are we going to get a fuzzy images?

Very puzzling.
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rjlittlefield
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PostPosted: Sun Mar 12, 2017 1:12 am    Post subject: Reply with quote

mjkzz wrote:
What if we place two lights and place them at exactly the two positions in that animation, what the camera would see? a fuzzy image? because intuitively, this should lead to a super imposition of the two animated images. But this super imposition would be fuzzy and blurry, right?

It will be just like taking the two images that I show, layering them in Photoshop, and making the top layer 50% transparent. Where the two layers are very similar, near the plane of focus, you may perceive the result as fuzzy and blurry. But where the two layers are clearly different, farther away from the plane of focus, it will look like a combination of two images.

Quote:
Now lets put a diffused strip in place, are we going to get a fuzzy images?

Yes, blurred on the same axis as the strip. But relatively sharp on the other axis, crossing the strip.

--Rik
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mjkzz



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PostPosted: Sun Mar 12, 2017 2:09 am    Post subject: Reply with quote

Thanks Rik!

So does this mean if I use a cylindrical light, I will not be able to get a sharp image of this super smooth reflective surface? I could imagine the image would probably be very hazy if we get anything at all.

Maybe a dome light might work . . . I got to get one of this slide.
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rjlittlefield
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PostPosted: Sun Mar 12, 2017 11:18 am    Post subject: Reply with quote

mjkzz wrote:
So does this mean if I use a cylindrical light, I will not be able to get a sharp image of this super smooth reflective surface? I could imagine the image would probably be very hazy if we get anything at all.

It's important to keep in mind that the most dramatic effects are for parts of the subject that are not in focus. These are the places where moving the light(s) around can make the subject appear to change shape or position. But these are also the places where increased DOF due to highly directional illumination is most obvious. Outside the plane of focus, highly directional illumination combined with a shiny subject can produce a much sharper image. However, it is not necessarily an image that accurately represents the subject. In fact in extreme cases the pattern of "detail" is actually more like a laser speckle pattern: intense and stable, but bearing no resemblance to how the subject would look in normal light. In out-of-focus areas, adding diffusion will make a shiny subject look more blurred.

For parts of the subject that are in focus, moving the lights around will not change the apparent shape or position of the subject, except due to the usual perceptual issues of changing pits into bumps, scratches into ridges, and so on. In these areas, highly directional illumination that gives a smaller utilized aperture will result in less resolution; adding diffusion to utilize a wider aperture will give more.

For a direct illustration, see the third, fourth, and fifth panels at http://www.photomacrography.net/forum/viewtopic.php?p=123487#123487.

--Rik
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Smokedaddy



Joined: 07 Oct 2006
Posts: 1424
Location: Phoenix, Arizona

PostPosted: Mon Aug 14, 2017 8:37 pm    Post subject: Reply with quote

Here's what I came up with.

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rjlittlefield
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PostPosted: Mon Aug 14, 2017 9:18 pm    Post subject: Reply with quote

That's a very interesting discrepancy from the vendor's image at http://www.photomacrography.net/forum/viewtopic.php?p=204881#204881 :



At first glance, it looks like your numbers are about 1.5X larger than the vendor's.

But on closer inspection, I see that you must be measuring a different pattern. At bottom right, the vendor says 10.3 and 12.8 microns. That's a ratio of 1:1.24, and indeed the vendor's pixel counts have that same ratio. But in your image, the numbers are 15.236 and 22.475, a ratio of 1:1.48, and again your pixel counts have that same ratio. There's no way that your numbers could apply to the vendor's image, or vice versa. Even more definitive, I notice that in the vendor's image the innermost set of inverted thin L's lines up with the "10" at upper left, but in your image it lines up with the "9". Similarly the vendor's squares of dots end between "6" and "7"; yours end between "8" and "9".

On the other hand, it looks like your image is showing the same "36" pattern that the vendor's is, and the grid pattern to the left of that also looks the same.

Now I'm wondering if these are different generations of chips, or if there are multiple "36" patterns on each chip.

While you're set up to image this thing, can you look again with these questions in mind?

--Rik
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Smokedaddy



Joined: 07 Oct 2006
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PostPosted: Tue Aug 15, 2017 12:42 am    Post subject: Reply with quote

I bought two. They are extremely fragile. Mine had a lot of smug marks on them and crud. I tried using a blower and a super fine soft artist brush with no results. Anyway, here's what mine looks like.

I'm thinking that maybe a nice decapped CPU chip might be just as good if not better or other such animals (not that I have a good example).









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