More DF.65

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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Phill Brown
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Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

More DF.65

#1 Post by Phill Brown » Fri Mar 31, 2023 11:15 am

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In the interest of what is realistically achievable on a modest budget.
Mosquito wing.
Easily available.
1mm slide. Cover slip. Canada balsam.
40x .65 Watson para from around 1965.
Microsystem 70 stand.
DIY DF patch in an abbe condenser filter holder
No oil.
Lumix G3 with NDPL2X eyepiece mounted.
No photo shop or processing.
AWB, can be improved by selecting incandescent.

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#2 Post by Phill Brown » Sat Apr 08, 2023 7:42 pm

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If anyone is interested in the DIY patch.
Thin aluminium. Based roughly on the DF element in Nikon phase condenser.
Fixed to 32mm X 1mm watch glass for 32mm holder.
Outside ring is measured to the inside of the condenser,all held together with industrial super glue, satin black paint. Thin strips cut with scissors to hold it together,got repaired a few times so stuck to glass before it all gets too blobby with glue.
Cut out with a DIY blade in the compass, takes a few passes but it's a good way to worry through up to 0.5mm without too much trouble.
Light gap is about 1mm.
Probably not fair to expect anything above n/a .65 dry.

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#3 Post by Phill Brown » Sun Apr 09, 2023 10:41 am

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More challenging.
Radiolarian using a dry Achro condenser.
Same Watson x40 .65.
Only using Lumix G3 onboard processor for monochrome.
I didn't make the slide, came from a junk shop.
Not cropped so f.o.v is around 0.3mm.

Chas
Posts: 422
Joined: Tue Jan 19, 2021 3:11 pm

Re: More DF.65

#4 Post by Chas » Sun Apr 09, 2023 1:13 pm

It is interesting that the dry achro is more colourful than the Abbe condenser .
I dont think that darkfield plays too well with deep refractive objects because of the flair from the out of focus but refractive parts.....sometimes they are better stacked in brightfield and then the colours inverted.
Polycistina are a really enjoyable and rewarding things to focus stack (if you are after something bomb proof to try; have a go with Zerene Stacker .. it 30 days free, and then I think it just watermarks ).

What I dont understand is why some setups work ok with stops but then others dont seem to work (?)
Last edited by Chas on Sun Apr 09, 2023 6:54 pm, edited 1 time in total.

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#5 Post by Phill Brown » Sun Apr 09, 2023 4:19 pm

For a dry condenser the n/a is likely to be 0.9 or less, that would make 0.65 near the limit with the top lens being flat against the bottom of the slide.
A condenser with 1.25 for oil is a better bet dry up to 0.8.
Low power condenser with an air gap is the least likely to work.
Stacking and a DG oil condenser would be preferable for sure.

Chas
Posts: 422
Joined: Tue Jan 19, 2021 3:11 pm

Re: More DF.65

#6 Post by Chas » Wed Apr 12, 2023 11:53 am

I dont know how many iterations there are of Watson Universal condensers, but the rear lens element of the No.1 and No.3 that I have are quite a bit smaller than the ordinary condenser's rear element... this is was the cause of my problems:
Anything as large as 1 pence coin (~20mm) will completely block the light to one side or another of the rear lens. Using an 18mm stop in the swing-out filter holder was still a bit difficult to get right.
Putting the stop right behind the rear lens of the condenser made everything much easier and (perhaps because I am using a diffuse light source) closing down the iris makes the background blacker without diminishing the brightness of the objects.
I am trying out a Dry Zonal darkfield condenser .. it looks quite promising even though I cant get it through the hole in the middle of the stage! ( I have it on a Bausch & Lomb stand which looks as if it has spent some period of its life on a rubbish dump ).

There seems to enough of a gap between the condenser head and the condenser holder to allow the stop to held on with a push-on cap type arrangement.

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#7 Post by Phill Brown » Wed Apr 12, 2023 12:19 pm

I think the universal dry Achro is a 6 element condenser with a n/a of 0.9.
The abbe 1.25 with the flat top lens is by far the easiest.

Sure Squintsalot
Posts: 393
Joined: Mon May 16, 2022 3:44 pm

Re: More DF.65

#8 Post by Sure Squintsalot » Wed Apr 12, 2023 6:12 pm

Phill Brown wrote:
Sun Apr 09, 2023 10:41 am

More challenging.
Radiolarian using a dry Achro condenser.
Same Watson x40 .65.
I find that an inexpensive photographic lens polarizer placed over the field lens does a good job of cutting down glare around the brightest elements of a subject and helps darken the background. It works especially well when used in tandem with an analyzer placed between the objective and the eyepiece.

BTW that DIY darkfield patch is absolutely killer!

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#9 Post by Phill Brown » Wed Apr 12, 2023 9:25 pm

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This was a while ago.
CPL
DF polarised thread.

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#10 Post by Phill Brown » Fri Apr 14, 2023 8:22 am

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IMG- Mosquito wing in Canada balsam with polarised, shows dust picked up from flight. 20230414-WA0002.jpg
IMG-20230414- Radiolarian using oil DF condenser WA0001.jpg
The parts are all there for stacking,so far no day has been long enough.
In my defense these are 60 year old optics.
Attachments
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Chas
Posts: 422
Joined: Tue Jan 19, 2021 3:11 pm

Re: More DF.65

#11 Post by Chas » Wed Apr 19, 2023 7:35 pm

The oil darkfield photographs dont look so different to the those taken using your home made stop.
What was your impression when you were looking through the microscope?
(Was the oil darkfield condenser a Watson Zonal or some other?).

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#12 Post by Phill Brown » Wed Apr 19, 2023 7:49 pm

Yes it's a Watson zonal. The edges don't have the same aberrations.
Only good for na .5 to.95, just a bright centre for
Lower na.

Phill Brown
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: More DF.65

#13 Post by Phill Brown » Thu Apr 20, 2023 9:25 pm

New project.
Same subject, mosquito wing.
Using a Watson abbe with a minor mod.
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Might look similar to patch but
first image is filament projected from the Kohler a 4x .30.
Second image 20x .50, it's a better example of old objective than the 40x used.
Third image is 40x .65
Resolution is better, enough light for 1/80th second at 800 iso on the little Lumix G3.
Will add a mirror next to test the idea it can work at faster shutter without a flash.
Edit. The G3 suffers from shutter shock badly.
I have a Canon 50D which does a better job of it with live view.
This part of the project has added another £1.50 so trying to keep a lid on the spend.

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