LED flashlight makes a great Zeiss-Winkel illuminator

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wporter
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LED flashlight makes a great Zeiss-Winkel illuminator

#1 Post by wporter » Sat Jun 23, 2018 11:52 pm

I bring to everyone's attention a cool serendipitous find, FWIW: I recently found an LED flashlight ('electric torch', I think, to you guys across the Pond, lol) that fits in the bottom back illumination port of my Zeiss-Winkel GFL microscope so well, with such a nice slip-fit, that one would suspect it had been machined for that purpose. (It's a miracle! No machining!)

The flashlight (a Coast G25) has:

1)a spot-beam formed via a nice condenser lens on the front;
2) 330 lumens on high, 80 on low (that's a real 330 lumens, not the hyperbolic figure often seen in cheap ebay flashlights), much more than the 6v15w incandescent bulb that is original equipment has;
3) great build quality;
4) a good color of its LED;
5) a switch that goes high-off-low-off, etc, no annoying strobe or SOS positions;
6) widely available for about $15 here in the U.S.; the company is at coastportland.com.

The second image shows how the front outer diameter of the flashlight has a straight section (see O.D. in mm on the calipers) that keeps it aligned in the bore nicely, no flopping around. Also shown is the original bulb holder tube that the flashlight replaces, and the package. I bought mine from Home Depot here in SoCal.

With 10x objectives, it's too bright, so I use the low setting; at 40x you can switch to High.

I don't have any affiliation with Coast, but their lights are all over the place in the US, & have a good reputation.
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MichaelG.
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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#2 Post by MichaelG. » Sun Jun 24, 2018 12:26 am

That's very tidy ... Thanks for the info.

One has to wonder why they [both] chose the 25.7mm diameter.

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75RR
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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#3 Post by 75RR » Sun Jun 24, 2018 5:11 am

One has to wonder why they [both] chose the 25.7mm diameter.
25.7mm = 1 inch
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#4 Post by MichaelG. » Sun Jun 24, 2018 5:28 am

75RR wrote:25.7mm = 1 inch
Where in the world is that ^^^ true ?

25.4mm = 1 inch

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#5 Post by 75RR » Sun Jun 24, 2018 5:42 am

Oops! Should have said roughly an inch

25.7mm = 1,01181102362314 inch
25,4mm = 1,00000000000108 inch
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#6 Post by MichaelG. » Sun Jun 24, 2018 5:53 am

75RR wrote:Oops! Should have said roughly an inch
That's a relief ... Thanks for restoring my sanity.

MichaelG.
.
http://www.npl.co.uk/reference/faqs/on- ... aq-length)
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Hobbyst46
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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#7 Post by Hobbyst46 » Sun Jun 24, 2018 7:56 am

@wporter
Thanks for the information.
A year ago I purchased my GFL and the original 6V 15W, which failed within a few weeks, so I played a little with flashlights, read about every forum post on LED conversion, and finally paid more than $150 for a retroDiode 10W LED illuminator which serves me very well. The color temperature is 6500K so I can use it for strong blue light if I wish or, alternatively, filter out the blue by means of an orange filter.

However, I have a second GFL stand without illumination, so I may adopt the flashlight idea.

Please do post about your working experience with it. I notice that you took out the original collector lens holder tube, and rely on the built in collimator of the flashlight instead?

Do you get anything close to a Kohler illumination?

Is the light cool white or warm white?

Thanks in advance for answers.
Last edited by Hobbyst46 on Sun Jun 24, 2018 9:02 am, edited 2 times in total.

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#8 Post by Hobbyst46 » Sun Jun 24, 2018 8:49 am

MichaelG. wrote:That's very tidy ... Thanks for the info.

One has to wonder why they [both] chose the 25.7mm diameter.

MichaelG.
Coast chose the 25.7, while in the 1950's Zeiss had already prepared the scope base for future LED flashlight upgrades, so in spite of their habit of using mm and cm sizes, chose a close approximation of the imperial inch. :lol:

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#9 Post by MichaelG. » Sun Jun 24, 2018 9:01 am

Hobbyst46 wrote:Coast chose the 25.7, while in the 1950's Zeiss had already prepared the scope base for future LED flashlight upgrades ...
I would really love to believe that.

MichaelG.
.
P.S. a Google image search for 25.7mm reveals some interesting occurences; Watch glasses, Coins, LED lamps, etc. ... There must be something significant about that number.
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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#10 Post by Hobbyst46 » Sun Jun 24, 2018 9:44 am

The "G25" specification appears to be somewhat flexible. I searched Amazon, eBay, Home Depot, light intensity is 83 Lumens, or 101, or 120 Lumens, some do not mention focusability nor high-low selector switches etc.

On the other hand, I see a huge selection of models, including rechargable ones, on the Coast web site itself. The WIDTH is included in the specs, but if it is given as 1", does it really mean a diameter of 25.7mm?

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#11 Post by MichaelG. » Sun Jun 24, 2018 10:21 am

Hobbyst46 wrote:... on the Coast web site itself. The WIDTH is included in the specs, but if it is given as 1", does it really mean a diameter of 25.7mm?
:oops: I must confess to assuming that the reading on the open calliper was relevant.

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#12 Post by Hobbyst46 » Sun Jun 24, 2018 10:38 am

I will re-check the inner diameter of the back lamp opening in the microscope base.

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#13 Post by 75RR » Sun Jun 24, 2018 2:00 pm

Do you get anything close to a Kohler illumination?
Do not think it can, unless the torch is focusable, as the filament needs to be focused on the front focal plane of the condenser (i.e. the diaphragm) and the LED filament does not look to be in the same plane as that of the original bulb.
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#14 Post by wporter » Sun Jun 24, 2018 10:20 pm

About mm vs inches, and the foot-dragging US reluctance to declare the metric system the winner (except in science), here is a gentleman who has mounted a protest in his own way: http://www.sandiegouniontribune.com/com ... story.html)

Hobbyst46, here are some answers as best as I can provide:

1) the model may have been discontinued (?!) by Coast. Home Depot has plenty of them, but their description of the G25 in their online store is completely wrong. See the image below for the specs on the package (HD SKU # HD7547CP, same as on the HD website); the light is not focusable, has 330 lumens on high, is a spot and not a flood, etc;

2) The color temp seems about 4600K or so, not very warm, but not actinic & bluish like "daylight'6000K;

3) Kohler is not exactly achievable, more Nelsonian (critical), because the built-in illuminator optical path of the microscope has a frosted condenser lens (see images) between the lamp and the right-angle mirror in the base (the mirror is second-surface, BTW). But I didn't have any problem getting an even illumination, after focusing on the field diaphragm, by selecting the appropriate condenser lenses (this scope has a swing-over 0.9 lens over the condenser and a filter-tray aux lens for low-power under the condenser.)

This scope is slightly different regarding in-base lenses as compared to the usual GFL model (non-Winkel?), which has a lamp holder that has 3 lenses in the removable lamp tube (see image from manual).

4) I remeasured the O.D. of the flashlight, now I'm getting 1.020-1.022 inches, or 25.95-25.98mm.

5) the beam is definitely a nice spotlight. See the image; the hole into the right angle mirror housing captures about 80-90% of the beam diameter, so not much light is wasted (the picture is way overexposed & doesn't make this clear).
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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#15 Post by wporter » Sun Jun 24, 2018 10:21 pm

More photos.
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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#16 Post by PeteM » Mon Jun 25, 2018 6:17 am

Kohler illumination can be maintained with a LED flashight, by putting the LED die at the same position as the old bulb filament. I've adapted about a dozen LED flashlights, with just a bit of lathe work. First, to turn off the end and expose the LED die (sometimes a bit more complicated, depending upon how it is retained) so it can move forward into the proper depth. Second, by turning down the diameter or making a bushing to get the right outside diameter. What's especially nice about wporter's find is the high output, the modest price, and the absence of a strobe mode. Thanks.

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#17 Post by PeteM » Mon Jun 25, 2018 6:29 am

If anyone finds an online source for these, would appreciate knowing. All I could find were 3 LED (not "Bulls-Eye") G25 units with 120 lumens. Kohler illumination wants a single LED die, around the size of the filament it replaces.

Maybe the 330 lumen one was discontinued?? Overheated on high? A typo on the package?

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Re: LED flashlight makes a great Zeiss-Winkel illuminator

#18 Post by Hobbyst46 » Mon Jun 25, 2018 6:42 am

@wporter
Many thanks for the detailed info!

Indeed, the base and illumination housings of your GFL scope differ from those of mine. The base of my scope is marked "Carl Zeiss",
not Winkel. The outer diameter of the lamp collector tube is 26.88mm, so the inner diameter of the base opening is ~27.0mm. And on my scope, the newly installed first-surface mirror has improved illumination, relative to its second-surface predecessor.
PeteM wrote:What's especially nice about wporter's find is the high output, the modest price, and the absence of a strobe mode.
Yes for all!! But, for those without access to lathe and mill work, the diameter counts as well.
I will look for a Coast or similar flashlights.

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