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Afocal fail
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Sun Dec 10, 2017 11:24 pm    Post subject: Afocal fail Reply with quote

Sometime ago, it was recommended that I try the afocal technique for photographing subjects through a microscope. Since I'm using the Micro 4/3 format, it was suggested here that I use a 30mm lens in conjunction with a 10x eyepiece. A few days ago, I received a monocular microscope and just now, I set my 14-45mm lens to 30mm and positioned it in extremely close proximity to the 10x eyepiece. Looking through the camera's rear lcd screen, I was pretty disappointed by the results. A large proportion of the image is taken up with the black outer rim of the eyepiece. Meanwhile, the actual magnified image only takes up a very small portion of the middle of the screen. Vignetting at it's most extreme. I zoomed in to 45mm but this didn't really make a perceivable difference.

Is there something I'm doing wrong? I guess many of you will say move in closer. Though I can't move the lens any closer without hitting the eyepiece with the front glass element.

I'll take a photo and post it to show what I mean.
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zzffnn



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PostPosted: Mon Dec 11, 2017 5:48 am    Post subject: Reply with quote

If you have moved the camera/lens horizontally and vertically and never found larger image cone, then your combination may not work well.

Not every combination works. What I tested was a Olympus 14-42mm kit zoom, along with wide field high eye point eyepiece. You used a Panasonic 14-45mm zoom lens, which is different.
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Last edited by zzffnn on Mon Dec 11, 2017 7:30 am; edited 2 times in total
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Pau
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PostPosted: Mon Dec 11, 2017 7:07 am    Post subject: Reply with quote

Quote:
A large proportion of the image is taken up with the black outer rim of the eyepiece. Meanwhile, the actual magnified image only takes up a very small portion of the middle of the screen. Vignetting at it's most extreme. I zoomed in to 45mm but this didn't really make a perceivable difference.


This sounds weird, are you sure that the camera lens is set wide open?, if you close its aperture diaphragm it will vignette for sure, set the camera in AV or M and set the max aperture.
Even with a phone camera, although round you would get a decent image of the field

Did you read my post? http://www.photomacrography.net/forum/viewtopic.php?t=15607
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Mon Dec 11, 2017 7:45 am    Post subject: Reply with quote

zzffnn wrote:
What I tested was a Olympus 14-42mm kit zoom, along with wide field high eye point eyepiece. You used a Panasonic 14-45mm zoom lens, which is different.


Yes a different lens. But a short zoom nonetheless. Of course not all short zooms are guaranteed to work but I don't think I noticed vignetting that was caused specifically by the lens.

Pau wrote:

This sounds weird, are you sure that the camera lens is set wide open?


Yes, aperture was wide open, and camera was set to full manual exposure.

Pau wrote:
if you close its aperture diaphragm it will vignette for sure


It looks like the vignetting is caused by the eyepiece rather than the camera lens. I will post a photo tomorrow.

Pau wrote:
Did you read my post? http://www.photomacrography.net/forum/viewtopic.php?t=15607


Yes, I did read that post. Very informative.

Could it be that my eyepiece is not a high eyepoint version? I mistakenly thought it was when I ordered the microscope. It does say "WF" so I assume it's wide field. Though when I look through it, I have to position my eye really close to it so perhaps it's not designed for people with glasses.

I do recall reading on this forum that ideally, eyepieces and objectives should match each other so that any optical flaws in the objectives are compensated by the eyepiece. The objectives on my scope are semi-plan. If I ordered a high eyepoint eyepiece from another manufacturer that was intended for semi-plan objectives, would that be a good match for my objectives in regards to minimising optical flaws? Or would I have to use an eyepiece that was made by the same manufacturer as the objectives?
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rjlittlefield
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PostPosted: Mon Dec 11, 2017 9:25 am    Post subject: Reply with quote

dragonblade wrote:
It looks like the vignetting is caused by the eyepiece rather than the camera lens.

Vignetting is caused by the interaction between the eyepiece and the camera lens. It is not caused by either one alone.

What happens is that for some combinations of eyepiece and camera lens, there is no path for light to leave the eyepiece, get through the aperture of the camera lens, and strike the edges of the sensor. That same camera lens would work fine without the eyepiece, and the eyepiece would work fine with a different lens -- say, the one in your eye, or a properly positioned cell phone. The key requirement is that the entrance pupil of the camera lens -- the place where the aperture appears to be -- can be positioned at about the same point where the pupil of your eye would have to be for visual observation.

The combination of a low eye point eyepiece and a zoom lens is particularly troublesome, because zoom lenses usually have their entrance pupil located far behind the front element.

--Rik
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Mon Dec 11, 2017 4:49 pm    Post subject: Reply with quote

rjlittlefield wrote:
The key requirement is that the entrance pupil of the camera lens -- the place where the aperture appears to be -- can be positioned at about the same point where the pupil of your eye would have to be for visual observation.



In my case, I'd prefer my pupil to be a bit further away. It does start to get a bit uncomfortable having my eye so close to this eyepiece.

Like I queried before, would there potentially be any quality issues if I ordered a high eyepoint eyepiece from a different manufacturer?
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rjlittlefield
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PostPosted: Mon Dec 11, 2017 5:18 pm    Post subject: Reply with quote

dragonblade wrote:
would there potentially be any quality issues if I ordered a high eyepoint eyepiece from a different manufacturer?

Potentially, sure. But it depends on details of the optics, and I don't know anything about the optics on this particular scope.

Doesn't the manufacturer sell high eyepoint eyepieces for their scopes?

--Rik
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zzffnn



Joined: 22 May 2014
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PostPosted: Mon Dec 11, 2017 5:36 pm    Post subject: Reply with quote

Many (but not all) microscope eyepieces/objectives combinations have optical compensation built in. So it is best to use high eye point wide field eyepiece made by the same manufacturer, for the same scope model.

Does the scope has manufacturer/model names on its body anywhere? If so, you may google it or search eBay for a macthing eyepiece.

Your monocular scope's shape looks like old Zeiss' mechanical design. It is hard to say what the design of the optics is.
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dragonblade



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PostPosted: Mon Dec 11, 2017 7:50 pm    Post subject: Reply with quote

rjlittlefield wrote:

Potentially, sure. But it depends on details of the optics, and I don't know anything about the optics on this particular scope.


My microscope has got a 10x widefield eyepiece.

The objectives are Semi-Plan and have the following details engraved on them:

Objective 1 - SP4 / 0.10, 160 / 0.17

Objective 2 - SP10 / 0.25, 160 / 0.17

Objective 3 - SP40 / 0.65, 160 / 0.17

Though the odd thing is when I go to the website, www.radicalscientific.com, and look up the microscope model (RM-600), it indicates that it's equipped with Achromatic objectives. Though it does state Semi-Plan objectives in the eBay description.

rjlittlefield wrote:
Doesn't the manufacturer sell high eyepoint eyepieces for their scopes?

--Rik


I'm trying to find that out. There's a list of optional accessories for 'biological laboratory microscope' on the website and I can't see a high eyepoint eyepiece specifically mentioned. There is a "micrometer eyepiece: 10x with helix focusing having reticle 10 / 100."

Ive asked the seller if his company produces high eyepoint eyepices. Currently waiting for his reply.
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dragonblade



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PostPosted: Mon Dec 11, 2017 8:23 pm    Post subject: Reply with quote

Ive just done some googling and Ive come across this catalogue from the same company:

http://www.radicalscientific.com/pdf/2.pdf

There's a list of microscope accessories here and it includes a "micrometer eyepiece H 10x (graticule 10mm / 100 parts.)" I suppose the 'H' might stand for 'high eyepoint' but unfortunately, there is no 'WF' designation. There is a 10x WF eyepiece in the same list but it has no 'H.' Regardless, it doesn't state which microscope models these particular eyepieces are intended for.

Elsewhere in the catalogue, it's mentioned that there is both a WF 10x eyepiece and also a H 10x eyepiece available for the RM-600 and RM-600B microscopes. That sort of sounds like they can be one or the other but not both. I could be wrong. I'll ask the seller if the H eyepiece is also wide field.

Though surely, a high eyepoint eyepiece would likely to be wide field as well? I could well be wrong but given that people with glasses would be viewing the eyepiece at an increased distance, I would think that they would have a wide viewing field so that you could see the entire image area at that distance. Correct me if I'm wrong.

Regardless, even though it's stated that those eyepieces are intended for my RM-600 microscope, it doesn't mention if they're designed for use with the Achromatic objectives or the Semi-Plan objectives. The listing for the RM-600 in that same catalogue states that the microscope comes supplied with Achromatic objectives. No mention of Semi-Plan objectives for that model.
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Pau
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PostPosted: Tue Dec 12, 2017 2:24 am    Post subject: Reply with quote

WF (Wide Field) in that range of eyepieces means almost nothing, just that they are superior to the simpler old fashioned Huygens type. In fact the field of view is not really wide. I've often seen the WF marks wrongly used for high eyepoint eyepieces in chinese stuff, but it dosen't seem to be your case.

Field width (diameter of the eyepiece field stop) and eyepoint placement are different parameters although as I said some confusion between them is not rare.

It's easy to determine if your eyepiece is compensating (for chromatic aberration) or not:
Take the eyepiece outside the microscope, point it to a white illuminated surface and look through it. If at the round limit you see an orangeish halo it is compensating, if there is a very faint blue halo it is non compensating and it there isn't any halo at all it is a good quality non compensating.
If it is non compensating you can substitute it for a higher quality non compensating high eyepoint (for example a Nikon CF)
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dragonblade



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PostPosted: Tue Dec 12, 2017 5:47 am    Post subject: Reply with quote

Pau wrote:

If it is non compensating you can substitute it for a higher quality non compensating high eyepoint (for example a Nikon CF)


Great, thanks. Are there any other good quality high eyepoint non compensating eyepieces that you would recommend?
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Tue Dec 12, 2017 7:00 am    Post subject: Reply with quote

By the way, this is one of the photos I took in my failed afocal attempt. I tried to embed the image but it didn't work out.

https://imgur.com/a/ucHi2
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zzffnn



Joined: 22 May 2014
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PostPosted: Tue Dec 12, 2017 9:08 am    Post subject: Reply with quote

dragonblade wrote:
Pau wrote:

If it is non compensating you can substitute it for a higher quality non compensating high eyepoint (for example a Nikon CF)


Great, thanks. Are there any other good quality high eyepoint non compensating eyepieces that you would recommend?


Pau meant one like this (Nikon CFW10x):
https://www.ebay.com/i/382252688140
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zzffnn



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PostPosted: Tue Dec 12, 2017 9:13 am    Post subject: Reply with quote

And the H in your "micrometer eyepiece H 10x" may refer to helical focusing (and not high eye point).

High eye point is usually indicated by an eyeglasses sign on body of eyepiece.
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