Small portable bright LED light source: What is not to love?

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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xioz
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Small portable bright LED light source: What is not to love?

#1 Post by xioz » Sat Sep 17, 2022 12:47 am

Hi All,
I thought I would share a solution I found what has worked for me. I bought a Olympus CHB with the halogen bulb and blue light filter, but found the result less then natural color temperature and brightness was limited by the filter.

Looking around for a low investment solution while still getting into the hobby I bought a LED replacement bulb which (just) fits in the same space, *and* this
Ulanzi L2 Cute Lite Mini Video Light
Screenshot 2022-09-17 100225.jpg
Screenshot 2022-09-17 100225.jpg (52.18 KiB) Viewed 2215 times
The trouble with the LED bulb is the Olympus slider being voltage based doesn't linearly dim or brighten the light though it works to some degree. And secondly you get the strobe/ flicker effect on photo & video, more then my mobile camera can compensate for on many combinations of brightness & objectives. Though I can still get useful images and for eyepiece work it is fine.

Enter the L2 Cute Lite! It fits under the stage, has adjustable light levels, has no flicker effect being battery powered and the manufacturer claims a Colour Rendering Index (CRI) of 95. I can also experiment with different lighting effects with the accessories, putting a coin on the light and moving the light around. Works well in my beginners humble opinion and is useful for many other things as well, so is a good option.

If I stick with hobby, I will probably replace the circuitry in the microscope for a neater built in solution, but this works well in the meantime.

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xioz
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Re: Small portable bright LED light source: What is not to love?

#2 Post by xioz » Sat Sep 17, 2022 12:52 am

Forgot to add a link I found with more info
https://www.ulanzi.com/blogs/news/ulanz ... -led-light

I brought it on Aliexpress.

Hobbyst46
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Re: Small portable bright LED light source: What is not to love?

#3 Post by Hobbyst46 » Sat Sep 17, 2022 12:28 pm

xioz wrote:
Sat Sep 17, 2022 12:52 am
Forgot to add a link I found with more info
https://www.ulanzi.com/blogs/news/ulanz ... -led-light

I brought it on Aliexpress.
What is not to love : according to what I have learnt from the Ulanzi site -
(a) It gets very hot after 20 minutes of use
(b) It is very thick - ~4cm - too thick to install inside the base of the microscope, IMHO.

Besides, for microscopy, a single LED die is better, which I am not sure if the Cute offers.

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xioz
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Re: Small portable bright LED light source: What is not to love?

#4 Post by xioz » Sun Sep 18, 2022 3:42 am

Fortunately this model remains cool to the touch even after an hour, though I mostly use it on the lowest brightness setting as this is more then enough for brightfield.

I actually bought it to fit in the base of the CHB which it should do with a little work. What I forgot to mention is that I found just sitting it on the light exit tube it fits underneath the condenser & works just fine.
If I had higher objectives the stage & condenser may start hitting it, but for 40x it works. I might just remove the CHB's light exit tube instead. I would have to look into whether keeping the lenses in the light exit tube is preferable before I make more permanent changes though.

Why is a single LED die preferable? More even lighting?
PXL_20220918_032945494b.jpg
PXL_20220918_032945494b.jpg (40.84 KiB) Viewed 2109 times

Chas
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Re: Small portable bright LED light source: What is not to love?

#5 Post by Chas » Mon Sep 19, 2022 3:53 pm

Thanks for posting this.
I am after something to go underneath the condenser of a Baker version of a Vickers Patholette..it might just fit in the base nicely. The Ulanzi model seems to be temporarily unavailable on amazon so I have gone for a Smallrig one (interestingly it seems that the Ulanzi model,with its magnetic charging coupling is fully submersible, whereas the smallrig one is USB-C ..so maybe not such a good idea to put mine underwater!).

In your photo you have the cube underneath the condenser without a diffuser ...isnt this a bit of a vicious sort of lighting ??

apochronaut
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Re: Small portable bright LED light source: What is not to love?

#6 Post by apochronaut » Tue Sep 20, 2022 6:26 am

Every time someone posts that they have to use some absurdly bright led light source because their existing halogen or incandescent illuminator has certain defects; I wonder if the problem is due to a faulty illumination system, not a badly engineered one.
At this point in time, probably north of 99% of scientific advancements made with the aid of a microscope were not made using led microscope illumination, so if properly engineered, filament illumination systems were suitable for those applications, I suspect that a halogen system in a simple CHB with shorty objectives used for BF, might also be quite suitable : if the microscope was clean, the equipment was to spec. and the user knew how to use it.

Microscope illumination is not supposed to be blue, nor is it supposed to be yellow. It is supposed to be about like the sky on a cloudy day, something easily obtained with a LIGHT blue CLEAR filter, plus halogen or even incandescent, when the correct and properly aligned bulb is used, the system is clean and powered at the most efficient voltage. It isn't advisable to run either type of filament illumination at voltages much less than about 85% and if running a 15 or 20 watt bulb in any microscope I have ever used and that is a lot, that is also lots if illumination for even a 100X objective in BF.

Another point that has to be brought up is the physiology of vision. We evolved under daylight plus a small amount for about the last 100,000 years under fire light. It doesn't take the eye and brain very long to adapt to light that is even quite far off that of daylight, otherwise we wouldn't have survived sodium vapour streetlamps for the past 70 years. I work a lot out of doors under daylight and under various types of artificial light too. If I go straight from being out in a bright sunny day to a 60 year old microscope that I use quite a bit, sporting an 18 watt incandescent bulb plus a light blue clear filter, the image looks a bit yellow. However, after about 2 or 3 minutes, it no longer does. It looks quite white because my eyes and brain have adapted and normalized the colour. What I do notice though, is that when going from certain fluorescent or led room lighting to such a microscope, the adaption takes a lot longer. There is something about lighting that leans more towards the monochrome that tricks the eye and brain, eliciting a form of colour adaption atrophy. For this and a couple of other reasons too, I make limited use of led room lighting.

I actually own one of the poster's lights. I find it useful as an incident fill light, best employed in concert with a filament light when a microscope photo is imminent but much less useful for visual observation on it's own. Sometimes I have to test a 160 or 170mm objective and for this I prefer to use a horseshoe stand with mirror and a straight through adjustable optical tube. I have the lamp mounted on an octopus tripod and in this format it can easily be adjusted to give good illumination to the mirror for a quick resolution evaluation. It is also useful in that format as a quick transmitted illuminator for something like a Cycloptic but in all applications I have to be wary of it's more monochrome characteristics.

The 60 year old microscope mentioned above is only noteworthy because I have ended up acquiring a very complete system for it, so it has reached that stage of being more of a permanent fixture than I. For some time, I fancied upgrading the illumination to led from it's pedestrian 18 watt incandescent rear mounted bulb but each time that determination reared it's head, I found that something had crept in that was affecting the performance of the system. One time it was a slightly poor bulb contact, lowering the wattage slightly, the next time it was an 80/20 head I switched to that turned out was not as internally clean as the seller had said( old microscopes get a film on lenses, windows and prisms). Each time restoring the system to spec., straightened my head out too, although I still plan on making an easily swappable alternate rear entry 50 watt halogen illuminator, so I can add 1425X DF to the microscope's capability. The rest of the parts are already there.

I did trial that led as an understage light source with that microscope for phase contrast. Firstly, the illumination beam is divergent, not parallel and infinity corrected, so it creates a whole different quality of beam, which causes a degree of understage glare. I never rigourously evaluated the phase contrast performance but I would say, it was not any better than the factory engineered system. Second, the four step intensity setting is cumbersome due to it's bottom location. Refined, careful microscopy requires a continuous control anyway, so some sort of variable amperage control would need to be applied to it.Third, I wasn't excited about the quality of the light. Not sure why but I think it is due to the contrast, which for want of a better term seems artificial.I can't really explain it, just that I don't like it. It isn't surprising that most images that support the quality of led microscope lighting are made with stained slides. Stained slides are like a fruit cocktail in a well lit vending machine. Lots of instant brilliance and contrast, while the true nature of the assemblage is yet to be revealed. The only way to evaluate a microscope system is with subjects that lack contrast, not those with it painted on.

So, this thing is only about 50.00 delivered or the equivalent of about 20 light bulbs. It might be allright if you spent most of your life under harsh led room lighting anyway, the kind of light that requires about 10 javas to make it through the day. Not my cup of tea really, nor would I spend any more time adapting it to any stand.
It does make a useful flashlight and on it's mini octopus tripod is quite adaptable to various positions and angles as a portable temporary work light and next time I do under water stereo microscopy , I will be sure to give it a go. For sure I will keep you posted on that one.

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Re: Small portable bright LED light source: What is not to love?

#7 Post by jfiresto » Tue Sep 20, 2022 9:31 am

apochronaut wrote:
Tue Sep 20, 2022 6:26 am
... It isn't advisable to run either type of filament illumination at voltages much less than about 85% and if running a 15 or 20 watt bulb in any microscope I have ever used and that is a lot....
Thank you for that helpful information. 85% of nominal voltage would be roughly 60% intensity. The standard intensity range on a Schott KL 1500 150W halogen light source is 50–79%. I think I will grow to like an incandescent light source.
-John

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xioz
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Re: Small portable bright LED light source: What is not to love?

#8 Post by xioz » Tue Sep 20, 2022 11:17 am

In your photo you have the cube underneath the condenser without a diffuser ...isnt this a bit of a vicious sort of lighting ??
I normally have the silicon diffusor or the white filter on the light, see the accessories you get with it, this softens the light down and I get better results then.

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Re: Small portable bright LED light source: What is not to love?

#9 Post by xioz » Tue Sep 20, 2022 12:33 pm

It is amazing how the brain adapts to see a light colour as normal. I used to have orange lens in my Ski Goggles. I would notice the colour for the first couple of minutes when putting them on, and then didn't notice at all, and then when I took them off, everything was blue!
absurdly bright led light source because their existing halogen or incandescent illuminator has certain defects
On the lowest setting I use, it is about 250 Lumens (at 50cms). Some halogen bulbs for microscopes go up to 400 Lumens.
The Olympus CHB uses a 20W tungsten light source by default which I believe is around 200-300 Lumens going by the wattage. Does anyone have figures in Lumens for the Olympus CH series light sources?

The main reasons to replace it are using the tungsten light bulb and then the 'colour correcting' blue filter that came with the 'scope gives a dimmer light and the colour is nowhere near a daylight white. The bulb is probably old, but finding a new replacement bulb (side mirrored, small bayonet fitting) with shipping to Australia is difficult.
I am also using a camera extensively so the eyes/brain adjusting to the light would not apply in this case. I only have a monocular model and my vision is full of distracting floaters, so viewing with a camera is much more preferable.
microscope for phase contrast. Firstly, the illumination beam is divergent, not parallel and infinity corrected
I have been wondering about this. So the lens in the light exit tube are designed to create parallel light beams which reduce glare under the stage. Is this also important for brightfield & darkfield? And what does infinity corrected mean when talking about the light source?

For using the Cute cube under the stage, the brightness is on the side, not that I change it much. However building it into the base would mean making room to turn it off and on, or devising a mechanical pusher. So I will probably keep it portable and come up with a another solution. The LED bulb I also bought works fine, but the microscope electronics is not designed for it, so there is flicker and banding from the AC frequency on camera and it will probably reduce the life of the bulb.

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Re: Small portable bright LED light source: What is not to love?

#10 Post by Sure Squintsalot » Tue Sep 20, 2022 6:44 pm

My opinion, for what it's worth, is that up until LED illumination, microscopes were entirely built around the limitations of filament lighting: needed color compensation filters? Then you needed a bright, halogen source. Needed heat dissipation? Then you needed a cooling fan. But wait....fans vibrate, so you needed a conductive thermal mass and a heavy cast aluminum microscope body.

Taking fine-grained film photos at high magnification also required bright lighting to reduce blurring of long exposure times.

The brighter the light needed, the more massive that microscope needed to be. Nevermind the framing to compensate for twisting caused by all of that heating.

That white-hot, eight dollar, 95% inefficient filament bulb caused an ever spiraling of build costs that probably resulted in a few manufacturer bankruptcies!

I'm glad for LED lighting and wish for the day a manufacturer makes an all purpose, high CRI, dimmable, tunable, semi-coherent, focusable, 1,000 lumen monster of a light that can burn off my floaters at the flick of a switch!

Chas
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Re: Small portable bright LED light source: What is not to love?

#11 Post by Chas » Fri Sep 23, 2022 7:53 pm

Just a word of caution..... the Smallrig version of this little light, with the thin white diffuser in front of it seems quite a bit too bright for comfortable viewing with a monocular..my sight is quite 'bleached' after looking through it for a minute.
In the situation that I am using it the light sits about 3 inches below the bottom of the condenser.

However putting a ~3 stop (about a factor of 10 reduction) Neutral Density filter on top of the light makes it very comfortable to use.
I guess that a binocular-headed scope might only need 'half as dark' an ND filter.
On ebay there are inexpensive Wratten Gelatin filters (No.96) which ought to be OK with this pretty cold lightsource
The 96's come in various densities .. the density numbering on them is a bit unusal with, for example, a 3-stop filter having ND number of about 1.0 (I think).
https://en.wikipedia.org/wiki/Neutral-density_filter
and
https://www.watchprosite.com/photograph ... 1.9813306/

[As a reference; a photograph of the white diffuser's surface at ISO 100 and F8.0 takes about 1/1600 of a second].

I have an elderly acquaintance who claims that the vision in her right eye was impaired by spending too long looking down a (monocular) microscope when she was studying botany...presumably by too bright a source.

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