Diatom test with Swift FM-31 40x objective

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hkv
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Diatom test with Swift FM-31 40x objective

#1 Post by hkv » Sat Aug 13, 2016 12:45 pm

I was asked to test my Swift FM-31 field microscope with Klaus Kemps diatom slides to show how well the 40x objective performs in terms of resolution.

I have two versions of these field microscopes. One equipped with normal (4x, 10x and 40x) objectives where you use regular slides and cover glasses. The cover glass needs to be put facing down because the microscope is inverted.

The other version have LWD lenses (long working distance) and is supposed to be used with a petri dish or similar looking through the bottom of the dish.

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I used a SnapZoom camera adapter to mount the iPhone 6 to the microscope. First time I tried this as I normally use the SnapZoom on my binoculars.

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Here are the resulting images. No stacking, no photoshopping, just raw as they came from the iPhone.

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Re: Diatom test with Swift FM-31 40x objective

#2 Post by zzffnn » Sat Aug 13, 2016 1:54 pm

^ Thank you very much, hkv.

Sorry for misleading you. What I meant was 8 form test diatoms. Yours seems to be a type plate, which is not as standardized as test plate (and difficult to show resolution).

I assume you used "count down timer" to eliminate vibration caused by finger touching iPhone? Does your FM-31s have filter trays close to condenser diaphragm, would you be able to try oblique illumination to boost contrast?

You seem to have a Navicula diatom there. Usually, 40x NA 0.65 can resolve it to dots, under oblique illumination.
Nitschia or Pleurosigma can also be used for 40x objective.

Some diatoms in photo #3 and #5 are very interesting, by the way. I had a 50 form KK exhibition plate, but did not see them there.
Last edited by zzffnn on Sat Aug 13, 2016 2:02 pm, edited 2 times in total.

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Re: Diatom test with Swift FM-31 40x objective

#3 Post by rabitt » Sat Aug 13, 2016 1:59 pm

As a newbie I'm really impressed with the clarity and sharpness of the photos.
Also with the diatoms on Klaus Kemps slide.
Thank you.

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Re: Diatom test with Swift FM-31 40x objective

#4 Post by hkv » Sat Aug 13, 2016 3:53 pm

Ok, I'll do it over again. This time with the "test" slide and with delayed triggering. Perhaps that will improve the sharpness a bit. Also, I will try to get better white balance. I will cut a cardboard piece and see if I can get oblique illumination. There are two slots just above the condenser lens. Normally used for blue filters and dark field stops. I think that would work.
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Re: Diatom test with Swift FM-31 40x objective

#5 Post by 75RR » Sat Aug 13, 2016 5:09 pm

There are two slots just above the condenser lens. Normally used for blue filters and dark field stops. I think that would work.
That should work fine for oblique. By the way, using the blue filter should help with the white balance, in case you had omitted it in these images.
You seem to have a Navicula diatom there. Usually, 40x NA 0.65 can resolve it to dots, under oblique illumination.
Would be nice if it did resolve the Navicula but surely that is not necessary in a Field Microscope. Besides, even if it could do so "at home", viewing conditions in the field are usually less than ideal.
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Re: Diatom test with Swift FM-31 40x objective

#6 Post by zzffnn » Sat Aug 13, 2016 5:58 pm

75RR wrote:Would be nice if it did resolve the Navicula but surely that is not necessary in a Field Microscope. Besides, even if it could do so "at home", viewing conditions in the field are usually less than ideal.
Yes, it would be nice.

My point is this:
A Swift FM-31 costs at least $250 USD (more likely > $350). If I pay that much for a field scope that has a real condenser lens, I personally would expect good NA 0.65 resolution and contrast. Otherwise, my other $45 pocket scope with 400x total magnification (and no condenser) would work just fine for casual scan.

A good field scope, like the Swift FM-31, Nikon H or TWX-1, would allow microscopist to record live protists on site. Oftentime, after you bring sample home, environment changes, many original protists disappeare and diversity drop significantly. In that case, I would rather sacrifice image quality slightly and keep original biology by firstly recording with a good field scope on site.

With a good smartphone camera and carefully configured field rig, resolution close to (though not better than) home rig is possible.

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Re: Diatom test with Swift FM-31 40x objective

#7 Post by zzffnn » Sat Aug 13, 2016 6:05 pm

hkv wrote:Ok, I'll do it over again. This time with the "test" slide and with delayed triggering. Perhaps that will improve the sharpness a bit. Also, I will try to get better white balance. I will cut a cardboard piece and see if I can get oblique illumination. There are two slots just above the condenser lens. Normally used for blue filters and dark field stops. I think that would work.
Thank you!
I assure you that delayed triggering alone would improve resolution. At least that I saw that in my test. A good darkfield NA 0.65 can resolve many test diatoms too.

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Re: Diatom test with Swift FM-31 40x objective

#8 Post by hkv » Sun Aug 14, 2016 4:51 pm

OK, here we go again. I tried oblique but had a hard time increasing resolution. I used the Klaus Kemp "test plate" and the big diatom with very fine mesh inside did not resolve. I included an image from the BX51 as a comparison which (barely) managed to resolve the criss-cross pattern.

I think the components of the Swift FM-31 has so many weak links.

1. The light source is tiny battery lamp with no possibility to adjust the brightness.
2. There are no condenser diaphragm to adjust NA. (Available as an option)
3. The iPhone adapter and iPhone itself is not the best. There are real camera adapters for the Swift, but I do not have these options.

Apologies for the dust spots. Seems like my older Swift has a dirty mirror, but I need to disassembly it to clean it. Next project...

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From the BX51 with Uplan fluorites objective.

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Re: Diatom test with Swift FM-31 40x objective

#9 Post by gekko » Sun Aug 14, 2016 5:01 pm

Amazing what a difference an objective makes! What is the power/NA of the fluorite objective?

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Re: Diatom test with Swift FM-31 40x objective

#10 Post by zzffnn » Sun Aug 14, 2016 5:27 pm

Thank you very much, hkv.

:evil: That means there is no good pocket scope at under $300 USD. And I don't want to spend more for a field scope. TWX-1, Nikon H or McArthur will perform better but cost much more.

Maybe I will have to find a beaten-up Tiyoda MKH, which is light but not pocketable though.

I suspect the condenser of Swift FM-31 may be a single lens design and cannot go up to NA 0.65. Or the light source is too weak (which you can swapped out with a more powerful LED, should you feel like to in the future).

I once added a cheap two-lens Abbé condenser (NA 1.25 if immersed in oil, around NA 0.7-0.8 when dry) to a toy LED scope with miniature (non-RMS) objectives. I though the combo did not perform worse that the Swift. The DIY scope is light at 3.3 lbs and cheap at $50 in total, but is not pocketable :| I still used it as a field scope.

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Re: Diatom test with Swift FM-31 40x objective

#11 Post by hkv » Sun Aug 14, 2016 8:06 pm

On the other hand, in most cases, a field microscope is used to quickly browse through the samples to see if you have anything of interest. I would say that the ability to achieve contrast would be more important to be able to see transparent objects. That is why I think the Phase-Contrast objectives for the Swift FM-31 would be the best option. I do have a LED light to my Swift. You can stick a Mini-MAG-lite LED or lamp. into the condenser. The condenser housing is built to fit both types of illumination. However, for me, that lamp is too strong for most use. Perhaps if I make a dark field stop it would be useful.

Overall, the FM-31 is very well built. Sturdy and feels solid. Mechanics is smooth and backlash is virtually nonexistent. Image is clear. It also works decent without condenser in daylight. At least with 4x and 10x. However, I guess the Nikon Model H would be better, but then we are talking thousands of dollar... Here is on on ebay for $4450... :?

http://www.ebay.com/itm/Nikon-Field-Mic ... SwXrhXmuo6

If you are looking for a equivalent to large research or educational compound producing great photomicrographic images, the FM-31 is not the right tool. If you need something small, sturdy, lightweight with the ability to quickly scan samples, the FM-31 does a decent job.
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Re: Diatom test with Swift FM-31 40x objective

#12 Post by hkv » Sun Aug 14, 2016 8:15 pm

gekko wrote:Amazing what a difference an objective makes! What is the power/NA of the fluorite objective?
Yes, agree. The 40X fluorite has NA 0.75. Remember thought that it is not only the objective that differs. The light source, condenser is designed for high aperture. Also in that image the camera is mounted on a trinoc head with a Canon 6D full frame camera. The whole system is different...and better... Also a big price difference. :shock:
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Re: Diatom test with Swift FM-31 40x objective

#13 Post by zzffnn » Sun Aug 14, 2016 9:14 pm

hkv wrote: I would say that the ability to achieve contrast would be more important to be able to see transparent objects.
^ Precisely. That is why I wonder how good the Swift condenser is - a good condenser would allow you to use many contrast techniques, such as phase, darkfield or oblique. A single lens condenser may or may not work well with contrast filter/stops.

Actually, besides Nikon H, TWX-1 works just as well. Years ago, some lucky local people snatched a few at or below $300 USD. But now, one may have to go to TaiYuan China to hunt for it.

I also think DIY darkfield stop may work well with the FM-31. LED head lamps like this one: https://www.amazon.com/gp/product/B00SW ... UTF8&psc=1 may provide more light than mini mag lite, while weighting less (if you take it apart - I use one for my portable scope and love it).

I am not expecting image quality comparable to a home rig. But I would like to get close, if I spend $300.

Your darkfield image from home rig looks great, by the way. Was that done with an oil immersion darkfield condenser? Oil darkfield can resolve the Frustulia diatom, which is the second smallest of the 8 forms.

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Re: Diatom test with Swift FM-31 40x objective

#14 Post by hkv » Sun Aug 14, 2016 9:31 pm

zzffnn wrote:
hkv wrote:

I also think DIY darkfield stop may work well with the FM-31. LED head lamps like this one: https://www.amazon.com/gp/product/B00SW ... UTF8&psc=1 may provide more light than mini mag lite, while weighting less (if you take it apart - I use one for my portable scope and love it).

Your darkfield image from home rig looks great, by the way. Was that done with an oil immersion darkfield condenser? Oil darkfield can resolve the Frustulia diatom, which is the second smallest of the 8 forms.
There were swift original dark field stops sold. They fit in the condenser slot. Also a field diaphragm was sold. However, I have never seen those with any scope on ebay nor as stand alone items. I will have to go DYI I guess.

The "dark field" image was actually DIC, no oil, with the 40X objective. I think DIC actually make the situation worse in this case. I have the "general" DIC prism (U-DICTS). There is also a high resolution version where you sacrify other parameters in favor of resolution. This leads me to believe that my DIC system does not squeeze max resolution out of the objectives.
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Re: Diatom test with Swift FM-31 40x objective

#15 Post by 75RR » Sun Aug 14, 2016 10:23 pm

I was surprised at how many accessories the Swift FM31 has: http://microscopeinternational.com/manu ... series.pdf

The more I see of it the more I like it. It is quite ingenious.
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Re: Diatom test with Swift FM-31 40x objective

#16 Post by hkv » Sun Aug 14, 2016 11:05 pm

I found this article. Talks about the use of the FM-31. I agree with you 75RR. I like the FM-31 more and more. It has potential, even though I have not managed to get all the parts for it yet.

http://www.microscopy-uk.org.uk/mag/ind ... field.html
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Re: Diatom test with Swift FM-31 40x objective

#17 Post by zzffnn » Sun Aug 14, 2016 11:26 pm

Based on the manual cited by 75RR, the defaut condenser seems to be a doublet. And the 40x clearly says NA 0.65. On paper, that looks good.

hkv, what difficulties did you have with using DIY oblique filter with the FM-31? I am just curious.

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Re: Diatom test with Swift FM-31 40x objective

#18 Post by gekko » Mon Aug 15, 2016 11:23 am

hkv wrote:
gekko wrote:Amazing what a difference an objective makes! What is the power/NA of the fluorite objective?
Yes, agree. The 40X fluorite has NA 0.75. Remember thought that it is not only the objective that differs. The light source, condenser is designed for high aperture. Also in that image the camera is mounted on a trinoc head with a Canon 6D full frame camera. The whole system is different...and better... Also a big price difference. :shock:
Thenk you, yes. Excellent image and contrast.

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Re: Diatom test with Swift FM-31 40x objective

#19 Post by billbillt » Mon Aug 15, 2016 2:01 pm

WOW!... These all very good!!..

BillT

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