Comparison of projection lens and wide field oculars for imaging.

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The QCC
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Comparison of projection lens and wide field oculars for imaging.

#1 Post by The QCC » Tue Sep 01, 2015 1:26 am

This is actually two tests. One is a comparison of wide field oculars and projection lens for imaging on a microscope using a DSLR.
The second is a stability (vibration) test using a light weight DSLR body as the camera.
The oculars in the comparison are:
A Labomed 10x Wide Field 22mm eyepiece. (30MM dia.) No estimated cost. Came with the microscope.
An OMAX 10x Wide Field 18mm eyepiece. (23.2MM dia.) Approx. $40.00
The projection lens are:
An OMAX 2.5x direct mount camera adapter (23.2MM dia.). Approx $145.00
A Meiji 2.5x projection lens. Approx.(23.2MM dia.) $190.00
A Nikon 2.5x projection lens. Approx. (23.2MM dia.) $250.00

The camera is a Canon XS (1000D) 10mp body. Approx. $120.00
The microscope is a Labomed LB-592 polarizing microscope with a 4x Plan Pol objective.
The specimen is a thin section of Peridotite.
Ocular comparison
The images in the web pages are untouched. Just resampled down for web viewing.
For the nitpicky, you can download a half size composite image (1.4MB) here. It is in JPEG format. Right Click, select Save As

I am leaving myself wide open, but "What do you think?".
This is the setup.
IMG_0831.jpg[/attachment [attachment=2]IMG_0832.jpg
Mounted on the photo tube
Mounted on the photo tube
IMG_0833.jpg (65.92 KiB) Viewed 4808 times
IMG_0833.jpg
Attachments
Computer and microscope setup
Computer and microscope setup
IMG_0831.jpg (84.61 KiB) Viewed 4808 times
LB-592 wide field
LB-592 wide field
IMG_0832.jpg (72.07 KiB) Viewed 4808 times

einman
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Re: Comparison of projection lens and wide field oculars for imaging.

#2 Post by einman » Tue Sep 01, 2015 3:26 am

Hmm..appears to be different magnifications and some are not too clear. If all is the same and you have a 4X objective and 10X eyepiece shouldn't they be the same size ? Or do i not understand teh question?

apochronaut
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Re: Comparison of projection lens and wide field oculars for imaging.

#3 Post by apochronaut » Tue Sep 01, 2015 7:55 am

It's hard to get an organized idea of what is happening here. The magnification differences don't seem to make sense, as Einman pointed out.

There does seem to be a considerable amount of vibration, leading to blurry pictures. One would assume, that would be the case with a long exposure when the camera was mounted over an eyepiece but one of the worst as far as blurriness is at 1/250 , with the camera mounted on the trinocular,where stability should be guaranteed.

I do think I detect a lack of corner sharpness with the Omax eyepiece but the sample is a pretty busy sample, so it is hard to use as a basis for assessment.

#4 and #6 are labeled as having been created with the same optics and shutter speed, yet the results seem to be magnified about 4 fold in #6 and super blurry. Is # 6 a crop of #4?

The QCC
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Re: Comparison of projection lens and wide field oculars for imaging.

#4 Post by The QCC » Tue Sep 01, 2015 12:05 pm

Photos 6-10 are left side center crops of their respective full frame shots.
They are approx. 1024 x 800 in size. The full size of the first five is 3800 x 2600 pixels.
Unfortunately, the first five have been resampled to 1024 x 800.
The download composite shows the first five at half size.

There will be differences in magnification. I kept the same length of camera tube for all eyepieces and the eyepieces are 10x and the projection lens are 2.5x.
The Nikon is way off in its magnification because it requires a much longer camera tube that I used.

My intention was to show you can use a good 10x eyepiece as a camera lens. Comparing them to high quality projection lens.
In the tests, the Nikon 2.5xPL is the best and should be, but the Labomed 10x eyepiece is no slouch.
The poorest performers were the inexpensive OMAX 10x eyepiece and OMAX 2.5x direct camera lens.

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gekko
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Re: Comparison of projection lens and wide field oculars for imaging.

#5 Post by gekko » Tue Sep 01, 2015 1:26 pm

The QCC wrote:The Nikon is way off in its magnification because it requires a much longer camera tube that I used.
The QCC, I know that I will sound like a broken record, but for your comparision to be strictly valid, one (of the many other) conditions that have to be satisfied is that the microscope be focused on the slide using your eyes, then the camera should be installed such that the image is in focus on the camera sensor without changing the original (by eye) focus setting of the microscope (that is, parfocality between eye and camera sensor). Not doing this will be equivalent to using the wrong optical tube length or the wrong cover glass thickness (i.e. it will result in an increase in spherical aberration; the optical corrections for an objective are calculated for a given working distance, cover glass thickness, and tube length).

The QCC
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Re: Comparison of projection lens and wide field oculars for imaging.

#6 Post by The QCC » Tue Sep 01, 2015 2:17 pm

Gekko:
I never use the eyepieces to view a slide. I am not interested in things being parfocal. To me it is the image I see on the print that counts.
The comparison was to show you can use a wide field eyepiece as a camera lens in lieu of specialized optics. Although the image may suffer a bit, eyepieces work as a camera lens. Admittedly, the Nikon specialized lens works best for image quality.

Technically you may be correct, but has little relevance when the oculars are not used for viewing.
Not everyone has matched optics on their microscope. Anyone using a USB camera not made by their microscope manufacturer will run into the situation you describe. Very few USB cameras have focal adjustments.

I was trying to show something practical, not theoretical. It appears I am in the minority.

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gekko
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Re: Comparison of projection lens and wide field oculars for imaging.

#7 Post by gekko » Tue Sep 01, 2015 3:20 pm

With all due respect, I don't think the introduction of spherical aberration in your comparison is "merely" a theoretical matter.

apochronaut
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Re: Comparison of projection lens and wide field oculars for imaging.

#8 Post by apochronaut » Tue Sep 01, 2015 3:42 pm

Your idea to do this test, is a practical thing but only with your set of equipment. For someone with a Spencer 15 for instance , with a set of Zeiss KPL eyepieces and a set of mis-matched achromatic eyepieces , it isn't of any value at all. The fact that you show that a W.F. microscope eyepiece can be used as a good tube lens for photography was a known fact. What aren't known facts are which eyepiece and objective combinations, and on what stands with what kind of lighting and condenser can one expect acceptable or even good to great results. For that, one has to theorize the possibilities based on optical and mechanical laws and if enough stray parameters that skew results can be excluded , then that theory can be converted to a practical possibility.
To put it another way. If I inherited a Weddig monocular microscope with a 3 position nosepiece, fitted with 10X, 47.5X and 90X Bausch & Lomb apochromatic objectives and a Bausch & Lomb 10X W.F. eyepiece, as well as a Spencer hi-eyepoint 10X eyepiece, from my grandfather, does your test tell me if I can use that system for good photomicrography?

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gekko
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Re: Comparison of projection lens and wide field oculars for imaging.

#9 Post by gekko » Tue Sep 01, 2015 9:07 pm

apochronaut wrote:The fact that you show that a W.F. microscope eyepiece can be used as a good tube lens for photography was a known fact.
Actually, I think the correct compensating eyepiece for a given (set of) objective(s) used for projecting the image on a camera sensor will likely give better results than a generic or the wrong projection lens. The eyepiece, when used as a projection lens, should be raised a few millimeters from its fully inserted position in the eyetube in order for it to form a real image (this assumes that the microscope is properly focused on the slide using the eyepiece in its normal, fully inserted position, as it ought to be for the reasons I mentioned above).

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lorez
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Re: Comparison of projection lens and wide field oculars for imaging.

#10 Post by lorez » Tue Sep 01, 2015 9:32 pm

The eyepiece, when used as a projection lens, should be raised a few millimeters from its fully inserted position in the eyetube in order for it to form a real image
gekko, I'm a bit confused here. How does raising the eyepiece change it's image forming capacity ? Wouldn't raising the eyepiece be similar to extending the draw tube ?

lorez

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gekko
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Re: Comparison of projection lens and wide field oculars for imaging.

#11 Post by gekko » Tue Sep 01, 2015 10:43 pm

lorez wrote:
The eyepiece, when used as a projection lens, should be raised a few millimeters from its fully inserted position in the eyetube in order for it to form a real image
gekko, I'm a bit confused here. How does raising the eyepiece change it's image forming capacity ? Wouldn't raising the eyepiece be similar to extending the draw tube ?
lorez
Hi lorez,
A very good question: I had not thought of that. The answer is Yes and No. Yes, if you refocus the microscope as you look through the raised eyepiece (= extended draw tube). No if, as I stated, you focus the microscope with the eyepiece fully inserted (as is normal), then, without refocusing the microscope, you raise the eyepiece. In that case, the intermediate image will be below the focal plane of the eyepiece, so instead of forming a virtual image, the eyepiece will project a real image (presumably on the camera sensor). Does that make sense?

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Re: Comparison of projection lens and wide field oculars for imaging.

#12 Post by JimT » Tue Sep 01, 2015 11:10 pm

QCC, hard for me to judge. Perhaps a better way to compare would be to photo a micrometer slide with the different lenses and techniques. That way the subject is constant through out.

That is if you want to do it again :)

The QCC
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Re: Comparison of projection lens and wide field oculars for imaging.

#13 Post by The QCC » Tue Sep 01, 2015 11:24 pm

I feel I must apologize.
I just do not use a microscope the way most of you do.
To me it is an extension of my cameras. Just five inter-changeable lens.
Chromatic aberration in some of my work is a bonus and is used for effect.
Thanks.
Thanks.
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lorez
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Re: Comparison of projection lens and wide field oculars for imaging.

#14 Post by lorez » Wed Sep 02, 2015 12:10 am

Thanks gekko,

If I read more than the headline I'd have seen the rest of the explanation. I have never tried the technique so I have something new to do.

lorez

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gekko
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Re: Comparison of projection lens and wide field oculars for imaging.

#15 Post by gekko » Wed Sep 02, 2015 8:37 am

The QCC, you are not leaving us, are you? Please don't. I agree that sometimes we get carried away with technical matters even as we know that your interest lies in the artistic side. I apologize for that. I, for one, promise never to mention spherical aberration or chromatic aberration or the like in connection with any of your posts in the future. Please keep enriching us with your beautiful work of rock art and science. I very much hope you will reconsider.

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Re: Comparison of projection lens and wide field oculars for imaging.

#16 Post by apochronaut » Wed Sep 02, 2015 2:57 pm

I spent 6 years in art school, after spending 2 years in biology. I wasn't very good at either, for different reasons. I was driven out of science, because I didn't have the singleness of mind ,to hone in and to persist in it and I left the artistic world because it was packed full of ego trippers, many of whom were also fools. My perception now, 40 years later,is that pure science is dominated by people who presume they know nothing and pure art is dominated by people who think they see everything. One takes a lot of work to climb out of, the other takes a lot of work to climb down from. Getting into the middle ground between those two, is the challenge and those that can do that are rare individuals. Gerald Domingue might be one , worthy of discussion here, Ernst Abbe too, Temple Grandin. These are a few I can think of offhand .

The problem here, is part and parcel of the above. The scientist should look to present data that have proofs, in order that they can be shared for the benefit of all. The artist should present opinion that needs no proof , so that it can stimulate thought for all. The word all, is the important word here.

It is very hard to become a scientist. You need to have your ducks in a row, otherwise your peers will notice that you don't and point that out.

It is very easy to become an artist, All you need to do is proclaim yourself as one. Your peers may still point out that you don't have your ducks in a row but it doesn't really matter because you have artistic license. I suppose the phrase " successful artist " or some other catch phrase might come to mind, which tends to cover for that slight deficiency in qualification that the burgeoning world of artists holds dear.

The thing is you never really hear the term "successful scientist. " . You kind of are or you are not one. So, what this really means is that , when an artist, whether, self proclaimed or peer revued , branches over into the world of science, they too need to have their ducks in a row .

So, this little muddle here, is what it is . I don't think anyone need apologize or change their line of reasoning on anything here. The test was not the best test, plain and simple. Maybe the next one is more controlled. I did try to view the re-dos but I couldn't get them to download, otherwise I would have viewed and possibly commented on them .

I would like to add this. The use of a microscope ocular , as a camera lens is something I know a little about. I have , probably, 500 objectives at the moment and around 200 eyepieces. So, I have had the opportunity to test a good many of them for afocal photography and can assure you that many of them are completely unsuitable and many of them are very suitable and that suitability can vary widely, depending on the stand employed and the objective match employed. That's why I am a stickler for that. Good results depend on accurate matching. There are theoretical rules, that govern the optical and photographic performance and those theoretical rules can be used to fairly closely predict, an outcome of matching. To use those theoretical rules , however, you need optical data, not the name of a manufacturer but optical data. The data given on objectives is pretty clear and concise. You can make a lot of assumptions based on that data but there are always things missing, which makes the extrapolation of such tests difficult. One piece of info. always missing on infinity objectives for instance is the tube length( most seem to be 180 or 200) and are the objectives fully or only partially corrected. Eyepieces are a whole other thing. Aside from the known characteristics of a huygens eyepiece as opposed to a ramsden, the eyepieces made since the 1950's ,most of which have W.F. designations or komp., or plancomp, or kpl or whatever on them, are mostly proprietary designs, with corrections for specific optical aberrations inherent in the system they were designed for. Sometimes you can swap them into another system and sometimes you cannot, so due to these technical factors the post that started this thread was a specific test that purported a conclusion that was already known and had no practical value outside of the specifics of the test and the education of the tester. No one needs to apologize for it or their response to it.

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