Eyepiece projection, yes or not??

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soldevilla
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Eyepiece projection, yes or not??

Post by soldevilla »

I am trying these last days to use a projection eyepiece in my macro system. So far I have used the microscope objective as a lens that focuses on the camera chip. To get more magnification and maybe a flatter field I now built a modification to use objective + eyepiece, like on a compound mycroscope. Apart from a longer working distance, which is already important, I have not noticed any quality differences. I would like to hear some suggestions ...

Pau
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Re: Eyepiece projection, yes or not??

Post by Pau »

In principle microscope objectives are designed to work with eyepieces, so nothing wrong here, but the devil is in the details.

- You need the eyepiece well matched with the objective.
+ If you use finite objectives full corrected like Nikon CF you want eyepieces that don't correct for aberrations, if not you need the matched compensating eyepieces (although these objectives are not adequate for direct projection).
+ If you use infinite objectives you need to use the adequate tube lens between the objective and the eyepiece *, if full corrected like Nikon CFI, Olympus UIS/UIS2 or Mitutoyo this is simple, if not like Zeiss and Leica you need the dedicated tube lens, in both cases you want eyepieces that don't correct for aberrations**.

Most eyepieces are designed to form a virtual image "focused to infinite" to be focused with the eye optics, although there are projective eyepieces designed to focus the image on the film/sensor. A visual type eyepiece can project a finite focused image but not when placed at the right distance of the objective.
Apart from a longer working distance, which is already important, I have not noticed any quality differences
If as you say you're getting longer WD you're using the objective outside its design parameters (either now or before...or both). This can work well with low NA objectives like a 10/0.25 but will degrade the image with higher NA ones because spherical aberration. If you are getting the quality you want, that's fine

But this is too general, what equipment are you using?

* With full corrected infinites increasing the tube lens focal length could be more adequate in many cases.
** with older infinite metallurgical objectives from Leitz and Olympus you still need compensating eyepieces

Admin note: Thread moved from Technical and Studio Photography -- Macro and Close-up forum
Pau

soldevilla
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Re: Eyepiece projection, yes or not??

Post by soldevilla »

Hi Pau
my equipment is very simple, a Chinese x4, a Nikon x10, a Nikon x20 LWD and a Nikon x40 VLWD. I bought the projection eyepiece from someone in here but I can't remember who.
In general I am not dissatisfied with the results, but if someone's experience can help me move faster, then better for me. When I use the lens alone, projecting to the sensor, I always try not to go beyond the nominal 160mm and if possible, use something less, I have the feeling that it produces something more of quality. I am not very clear if this premise can be used for the compound microscope, nor if there is a critical distance from the projection eyepiece to the sensor ... this is all new to me now.

I have only a few test in this way. I like if they was a bit more crisp, but this is my level and I no find how to upgrade the results.

Image

Pau
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Re: Eyepiece projection, yes or not??

Post by Pau »

What kind of projective?, please

Your Nikon objectives, are marked 160/0.17...210/0 or...?

If you get more magnification this can easily lead to less crisp image, in particular with your 40X you can easily get empty magnification
Pau

Ichthyophthirius
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Re: Eyepiece projection, yes or not??

Post by Ichthyophthirius »

I agree.

The higher the NA, the more important it is to follow in objective labels for tube length and cover glass. Above NA 0.35, presence/absence of the cover glass is important and above NA 0.55, the tube length needs to be within millimeters of the design (for example for direct projection, 150 mm for DIN 160 mm and 200 mm vor 210 mm objectives).

For eyepiece projection, the eyepiece needs to be raised slightly = longer tube length. A 10x eyepiece would have to be lifted by 5 mm. Therefore it is usually not a good choice for high NA objectives. Afocal setups and projectives, in contrast, allow you to maintain the correct tube length.

soldevilla
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Re: Eyepiece projection, yes or not??

Post by soldevilla »

Pau wrote:
Wed Sep 30, 2020 10:25 am
What kind of projective?, please

Your Nikon objectives, are marked 160/0.17...210/0 or...?
easy...:
x4 no brand, chinese. 160
x10 Nikon, 0,25 LWD 160 (I suspect that is a "clonic" because the letters are erasing, it no seem a Nikon quality)
x20 Nikon M Plan, 0,4 LWD 210/0 (with the letters engraved, no printed...)
x40 Nikon M Plan, 0,5 ELWD 210/0

and the eyepiece projection is a no brand x2,5

Any suggestion?

Pau
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Re: Eyepiece projection, yes or not??

Post by Pau »

The reference tube length is the distance from the objective shoulder to the eyepiece shoulder.

In most systems including Nikon the primary image is expected 10mm below the eyepiece shoulder -this is why Itchty recommends 150mm for 160 objectives and 200mm for 210 ones-, but this matters without eyepiece when you directly project the image onto the sensor. If you use an eyepiece, just measure the nominal length between both shoulders.
Assuming that with your no brand x2,5 this is the same, follow Itchty's advice: you can play with this tube length to some extent with your 4x and 10x but don't deviate more than few millimeters with your 20X and 40X
x10 Nikon, 0,25 LWD 160 (I suspect that is a "clonic" because the letters are erasing, it no seem a Nikon quality)
Many Nikon (and other maker's) modern objectives have it printed (some of them easy to erase) Time of engraving belongs to the past...so likely it isn't a fake

The quality of your sample picture has some issues: chromatic aberration and coma, not sure about the cause
Pau

dolmadis
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Re: Eyepiece projection, yes or not??

Post by dolmadis »

Pau wrote:
Fri Oct 02, 2020 1:24 am
..................., but this matters without eyepiece when you directly project the image onto the sensor.
Hi Pau

I have highlighted that piece of your text because I want to understand more about the tube length used with direct projection and why.

Thanks


John

Ichthyophthirius
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Re: Eyepiece projection, yes or not??

Post by Ichthyophthirius »

Hi John,

Can you also say what camera you use? It helps with telling you exactly what distances to use.

dolmadis
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Re: Eyepiece projection, yes or not??

Post by dolmadis »

Hi

Thanks for replying.

I have Canon APSC and Olympus M4/3 but I also i have eye on a Sony A6300 APSC body at the right price.

Thanks

John

Scarodactyl
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Re: Eyepiece projection, yes or not??

Post by Scarodactyl »

A genuine Nikon pl 2.5x is not that expensive. It would be worth trying the correct one for your system.

Ichthyophthirius
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Re: Eyepiece projection, yes or not??

Post by Ichthyophthirius »

Hi John,

You haven't mentioned any microscope yet. I assume you have tried to attach the objective directly to your camera?

The Nikon objectives produce an intermediate image of good quality with a diameter of something like 20 ... 25 mm. That's similar to both m4/3 and APS-C sensors. An easy way to use the M Plan 20 and M Plan 40 is to place the sensor directly at the position of the intermediate image. http://www.photomacrography.net/forum/v ... hp?t=12147

For the M Plan 20 and 40, the intermediate image will be located 200 mm behind the objective flange (see Pau's reply). That's 210 mm (as written on the label) minus 10 mm from where the eyepiece would be.

This means a distance of 180.75 mm between the objective flange and the front of your Olympus m4/3 camera (200 mm - 19.25 flange focal distance = 180.75 mm) https://en.wikipedia.org/wiki/Flange_focal_distance I recommend not changing the 200 mm distance (for example to change the magnification) as 200 mm should give the best image quality. If you want to cover a larger area, you will need to stich.

The M Plan 40/0.5 will probably always be a bit disappointing, as the NA is quite low for a 40:1 objective. You can't fix that by decreasing the 200 mm distance to cover a larger area. You need to stich and downsample the resulting image to make it look better.

----

Maybe start with the Nikon 10/0.25 (distance: 150 mm) as that will probably be more satisfying.

dolmadis
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Re: Eyepiece projection, yes or not??

Post by dolmadis »

Thanks for showing how this is established.

John

Adalbert
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Re: Eyepiece projection, yes or not??

Post by Adalbert »

Hi Soldevilla,
I’m afraid I don’t know what you want to achieve but the resolution depends on the NA of the lens.
And you can zoom the picture on the display as you want.
Best,
ADi

soldevilla
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Re: Eyepiece projection, yes or not??

Post by soldevilla »

Thank you all very much for the help. I did not understand the importance of respecting the distances exactly. Even I suspected, according to some tests I did) that sacrificing a little of that distance offered a little less magnification but more sharpness.

I have not fully understood the distance that I should leave between the projection eyepiece and the sensor (sorry, my English is poor) and that also modifies the final magnification. But now I move from home for 6 weeks and until the end of November I will not be able to do tests again.

When I return, I will show you my new attempts. Thank you

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