LED lighting....why the hate?

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Sure Squintsalot
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LED lighting....why the hate?

#1 Post by Sure Squintsalot » Mon May 23, 2022 8:49 pm

Reading through this forum I get the sense that a lot of people deeply dislike LED illumination, or at best, are pretty ambivalent. Which confuses me.

I'd have thought getting a super-brite, pure white light was wanted, above all else.

Now that I've gotten a serious microscope of my own and am looking to convert the incandescent lighting to LED, I'm also looking to getting rid of all of the (old tech) filters used for color correction of dimmed filament lighting.

Funny....it almost seems medieval.

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Re: LED lighting....why the hate?

#2 Post by Scarodactyl » Mon May 23, 2022 9:14 pm

LED tech has improved a lot in recent years, so some of what you'll see is based on older LED tech. LEDs generally have a bumpy spectrum of light output, they are definitely not 'pure white' even now. Compare their spectrum with a black body emitter. They especially put out a lot of blue. Other issues likely come down to poor implementation in some products, especially using pwm dimming when a constant current driver is called for.

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Re: LED lighting....why the hate?

#3 Post by blekenbleu » Mon May 23, 2022 9:38 pm

Sure Squintsalot wrote:
Mon May 23, 2022 8:49 pm
Funny....it almost seems medieval.
White LED color rendering can be problematic;
here is a comparison for good white LED:
Image
https://www.researchgate.net/publicatio ... ting_diode
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Re: LED lighting....why the hate?

#4 Post by MichaelG. » Mon May 23, 2022 9:42 pm

Sure Squintsalot wrote:
Mon May 23, 2022 8:49 pm

I'd have thought getting a super-brite, pure white light was wanted, above all else.
That is probably the essence of people’s dislike of LEDs
… until comparatively recently, the output from ‘white’ LEDs was far from pure !

Read-up on Colour Rendering Index

LEDs have many advantages, but colour fidelity is usually not one of them.

MichaelG.
.

Scarodactyl and Blekenbleu beat me to it, but I will post this anyway
Too many 'projects'

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Re: LED lighting....why the hate?

#5 Post by Sure Squintsalot » Mon May 23, 2022 10:02 pm

Are there not "lab quality" LEDs with high CRI approaching 99?
What about the pro studio photographer comunity? You'd think they wanted high-fidelity lighting!

I can get screw-in LED lights from Home Depot with a CRI of around 90....is that not enough?

Besides, how does one of these "crappy" Home Depot LEDs compare with a conventional halogen light at 50%? I remember that kind of lighting looking disctincly bronze-ish in color.

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Re: LED lighting....why the hate?

#6 Post by Greg Howald » Mon May 23, 2022 10:22 pm

I notice things seem less blue when I am using warm white led color. Others may have different experiences. Color seems to differ between manufacturers. Warm white, bright white,,,, not standardized. If I find what actually works I order ten of them just to have the assurance of having them in the drawer. But I don't like halogen as much as led. Some scopes, such as the metallurgical or the petrographic, come with halogen and this should not be converted to led because color is imperative for proper identification. Greg

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Re: LED lighting....why the hate?

#7 Post by Sure Squintsalot » Mon May 23, 2022 10:40 pm

Thanks for that link, blekenbleu!

From the conclusion of that paper:

Nevertheless, very high brightness LEDs are
starting to be commercially available and broadband LEDs such as the one used here but with
higher outputs are most likely to be produced soon. Those could definitely replace halogen
lamps in FF-OCM, considering the numerous advantages of LEDs, including cheapness,
compactness, lifetime and energy efficiency, that already ruled out halogen lamps in most of
today’s applications requiring white light.


As I may have mentioned elsewhere on this forum, I plan on converting my unit to LED and do NOT want to waste time with the
"wrong" LED! Unfortunately, I still don't know what that is!

Hell, I don't even know what I don't know.

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Re: LED lighting....why the hate?

#8 Post by apochronaut » Mon May 23, 2022 11:24 pm

Many people just discovering microscopes, measure the range of possibilities in microscope technology by what is available for a few hundred dollars, sometimes even less. A quality led illumination system from any of the reputable manufacturers built expressly for a specific type of microscopy will cost in the thousands, much more than most people on this forum will shell out for their entire microscope. So will a halogen system but amongst professional microscopists I would bet that halogen illumination still outsells led by a considerable margin. Five to one at least, if not more, 100 :1 just a few short years ago.

New quality microscope illumination systems of any kind are not cheap, nor should they be. New led illumination systems found in amazon grade stencil microscopes are cheap and perform that way. Fortunately, high end research grade halogen systems with all the necessary bells and whistles are quite inexpensive due to the generally high volume of quality used systems out there selling for 10 cents on the dollar. Filtering to a desirable colour temperature takes about 10 minutes to figure out if it hasn't already been done, so the acquisition of a first rate illumination system at genuine amazon prices is within the grasp of even the most budget conscious microscope purchaser.

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Re: LED lighting....why the hate?

#9 Post by LouiseScot » Tue May 24, 2022 12:02 am

As it happens I just earlier today converted my Amscope T680 to LED viewtopic.php?p=122464#p122464
I've used a 3W warm white LED for now. The power spectrum has a big dip in the blue-green and a not huge spike in the blue end of the spectrum:
WarmWhite.jpg
WarmWhite.jpg (17.03 KiB) Viewed 6565 times
NB bear in mind the visible spectrum spans from just over 400nm (violet) to about 700nm (deep red)

I will do a comparison with another scope that comes with LED lighting to see if there is any noticeable difference. Perhaps the proper comparison to do is really with daylight rather than halogen, so I might try to do that with a mirror. I think LED lighting is actually fine for most microscopy since specimen colours are likely limited compared to, say, viewing a scene with the naked eye that contains all colours. I may be technically wrong but that's just my intuitive view! If I do find the particular white LED isn't so good for colour imaging it won't be difficult to change it later. I've also left it open to easily re-insert a halogen bulb.

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Last edited by LouiseScot on Tue May 24, 2022 12:26 am, edited 1 time in total.
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Re: LED lighting....why the hate?

#10 Post by Greg Howald » Tue May 24, 2022 12:09 am

I agree with you Louise in pretty much all you said. My scopes which were originally halogen have all of the power elements intact so that, if necessary, all I need do is re-mount the halogen bulb and plug it in. Greg

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Re: LED lighting....why the hate?

#11 Post by LouiseScot » Tue May 24, 2022 12:17 am

Greg Howald wrote:
Tue May 24, 2022 12:09 am
I agree with you Louise in pretty much all you said. My scopes which were originally halogen have all of the power elements intact so that, if necessary, all I need do is re-mount the halogen bulb and plug it in. Greg
Hi Greg

I only really care what a camera sees and reproduces, and images/colours can be edited easily enough. Yep, keeping the halogen option open or being able to use daylight if needed probably covers all bases!
Louise
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Re: LED lighting....why the hate?

#12 Post by EYE C U » Tue May 24, 2022 1:03 am

99% sure I damaged my left eye using a led source that turned out to have high uv.. the only reason i didn't damage both is my right eye was all fogged up with blood from a internal blood leak. I was right eye blind for about 6 months.. now the right is better but the left still has a greyed out area. went back to a reg bulb source

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Re: LED lighting....why the hate?

#13 Post by blekenbleu » Tue May 24, 2022 1:34 am

Sure Squintsalot wrote:
Mon May 23, 2022 10:40 pm
I plan on converting my unit to LED and do NOT want to waste time with the
"wrong" LED! Unfortunately, I still don't know what that is!
Hell, I don't even know what I don't know.
First, color rendering index may not be that critical for many folks.
It is most important when color is wanted for distinguishing among materials,
where a gap in illumination intensity at some wavelength makes some LED
effectively blind for some key reflectance, absorption or fluorescence.
Otherwise, even with poor color rendering, tweaking for acceptable color balance
can be done fairly easily with many software imaging apps.

Using some objectives which focus red, green and blue at appreciably different wavelengths,
I occasionally capture separate images with red, green, then blue LED illumination,
but more often only using green.
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Re: LED lighting....why the hate?

#14 Post by blekenbleu » Tue May 24, 2022 1:41 am

LouiseScot wrote:
Tue May 24, 2022 12:02 am
The power spectrum has a big dip in the blue-green and a not huge spike in the blue end of the spectrum
That distribution is typical of many white LEDs engineered for efficient illumination,
very like differences between fluorescent tubes tuned for accurate color rendering
and those designed for energy efficiency.
That blue spike is from the actual LED, and the broad longer wavelength response is from phosphors.
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Re: LED lighting....why the hate?

#15 Post by LouiseScot » Tue May 24, 2022 2:15 am

blekenbleu wrote:
Tue May 24, 2022 1:41 am
LouiseScot wrote:
Tue May 24, 2022 12:02 am
The power spectrum has a big dip in the blue-green and a not huge spike in the blue end of the spectrum
That distribution is typical of many white LEDs engineered for efficient illumination,
very like differences between fluorescent tubes tuned for accurate color rendering
and those designed for energy efficiency.
That blue spike is from the actual LED, and the broad longer wavelength response is from phosphors.
Yes, but the power spectrum varies according to the fixed colour temperature of the particular device. I chose this warm white because it has less blue and more power distributed across the rest of the spectrum. There could be other LEDs around that are better but I'm sure this one will be ok.
Louise
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Re: LED lighting....why the hate?

#16 Post by MichaelG. » Tue May 24, 2022 7:01 am

Sure Squintsalot wrote:
Mon May 23, 2022 10:02 pm
Are there not "lab quality" LEDs with high CRI approaching 99?
Yes, but [as I hoped I had made clear in my first response] they are a comparatively recent introduction.
The ‘Hate’ that you mention probably dates back to people’s early experience.

MichaelG.
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Re: LED lighting....why the hate?

#17 Post by MichaelG. » Tue May 24, 2022 7:07 am

This [which dates back to 2012] may be of interest:
https://www.getty.edu/conservation/publ ... ghting.pdf

Appendix_1 is particularly informative
… but it really depends upon how much you care about such things.

MichaelG.
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Re: LED lighting....why the hate?

#18 Post by MichaelG. » Tue May 24, 2022 7:25 am

Sure Squintsalot wrote:
Mon May 23, 2022 10:02 pm

Besides, how does one of these "crappy" Home Depot LEDs compare with a conventional halogen light at 50%? I remember that kind of lighting looking disctincly bronze-ish in color.
.

I think perhaps you need to read-up on ‘Colour Temperature’ [with or without the first u] and ‘Black Body Radiation’
… it should make this discussion easier.

MichaelG.
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Re: LED lighting....why the hate?

#19 Post by LouiseScot » Tue May 24, 2022 9:09 am

LouiseScot wrote:
Tue May 24, 2022 12:02 am
As it happens I just earlier today converted my Amscope T680 to LED viewtopic.php?p=122464#p122464
I've used a 3W warm white LED for now. The power spectrum has a big dip in the blue-green and a not huge spike in the blue end of the spectrum:

WarmWhite.jpg

NB bear in mind the visible spectrum spans from just over 400nm (violet) to about 700nm (deep red)

I will do a comparison with another scope that comes with LED lighting to see if there is any noticeable difference. Perhaps the proper comparison to do is really with daylight rather than halogen, so I might try to do that with a mirror. I think LED lighting is actually fine for most microscopy since specimen colours are likely limited compared to, say, viewing a scene with the naked eye that contains all colours. I may be technically wrong but that's just my intuitive view! If I do find the particular white LED isn't so good for colour imaging it won't be difficult to change it later. I've also left it open to easily re-insert a halogen bulb.

Louise
If anyone is interested, this is the warm white 3W LED I just bought and fitted - on the left you can see its power spectrum along with other 'cooler' whites. I have to admit I haven't done any research into what other/better white LEDs might be available. But for my purposes... I've previously used the violet and short blue single wavelength LEDs for mono imaging.

https://www.ebay.co.uk/itm/131345637382 ... 0664558132

Louise
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Re: LED lighting....why the hate?

#20 Post by SWmicro » Tue May 24, 2022 4:09 pm

LouiseScot wrote:
Tue May 24, 2022 9:09 am
If anyone is interested, this is
Yes I am ! :) thanks for the link.
My lighting is in need of an upgrade.
I have also been following your new toys topics and will comment some more there.

As for "colour temp." etc here - - I can say, with a smile, y'all dont realise how lucky you are to have all this efficient and cool LED tech. I remember the days when fluorescent tubes with "Northlight" phosphors were introduced, costing a fortune but good for growing plants in tropical fish tanks (and fabric matching), otherwise it was fearsome mercury vapour lamps !! :)

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Re: LED lighting....why the hate?

#21 Post by BramHuntingNematodes » Tue May 24, 2022 4:19 pm

Another thing is if you read any journal articles or descriptions or use like some color chart for interference colors or look at old photographs these were all produced and calibrated with incandescent light in mind if written prior to I don't know 2010?
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Re: LED lighting....why the hate?

#22 Post by LouiseScot » Tue May 24, 2022 4:21 pm

SWmicro wrote:
Tue May 24, 2022 4:09 pm
LouiseScot wrote:
Tue May 24, 2022 9:09 am
If anyone is interested, this is
Yes I am ! :) thanks for the link.
My lighting is in need of an upgrade.
I have also been following your new toys topics and will comment some more there.

As for "colour temp." etc here - - I can say, with a smile, y'all dont realise how lucky you are to have all this efficient and cool LED tech. I remember the days when fluorescent tubes with "Northlight" phosphors were introduced, costing a fortune but good for growing plants in tropical fish tanks (and fabric matching), otherwise it was fearsome mercury vapour lamps !! :)
Well, I'm 70 and my first microscopes just had tilting mirrors - not to be pointed at the sun! I've just spent some of today taking some images on two different LED scopes and using a mirror to capture some of today's mostly overcast daylight! I'll post them on here when I get around to it - will try and do it this evening :)

Louise
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Re: LED lighting....why the hate?

#23 Post by BramHuntingNematodes » Tue May 24, 2022 4:22 pm

I usually get a nicely binned high cri Cree high power single die led and hook it up myself all the parts together might cost $50 you would therefore not find the same on a $200 new microscope, particularly if it had been manufactured ten years or even five years ago.
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Re: LED lighting....why the hate?

#24 Post by BramHuntingNematodes » Tue May 24, 2022 4:29 pm

Oh and maybe last thing is that a first attempt at an led fitting is often a flashlight which often has highly undesirable qualities as far as the color, optimized for brightness and efficiency in favor of color reproduction, but also in the arrangement of LEDs. Flashlights use.arrays frequently, as do bulbs, to increase light flux and an array is exactly what you do not what in an ideal microscope light source
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Re: LED lighting....why the hate?

#25 Post by dtsh » Tue May 24, 2022 5:06 pm

BramHuntingNematodes wrote:
Tue May 24, 2022 4:22 pm
I usually get a nicely binned high cri Cree high power single die led and hook it up myself all the parts together might cost $50 you would therefore not find the same on a $200 new microscope, particularly if it had been manufactured ten years or even five years ago.
I do the same thing. Sure it's a bit more, but compared to the rest of the cost of the instrument and the increased utility I get, it still seems like a very inexpensive upgrade.

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Re: LED lighting....why the hate?

#26 Post by BramHuntingNematodes » Tue May 24, 2022 5:18 pm

There are not too many opportunities for the amateur hack to really fill a niche in precision optics but figuring out a decent LED system that costs less than a hundo I think is definitely one of them.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

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Re: LED lighting....why the hate?

#27 Post by apochronaut » Tue May 24, 2022 5:41 pm

An unfortunate aspect of cheap led illumination systems is the loss of information due to the limited number of spectral lines that they produce. The eye has evolved to utilize the full spectrum of daylight in order to be provided with the maximum amount of information available and while no artificial illumination system can duplicate the spectrum of daylight, filament lamp systems provide a more continuous spectrum rather than one made up of an assemblage of discreet spectral lines, such as simple leds provide. The lack of sufficient spectral data will reduce the overall potential for the optical system to transmit maximum detail to the eye or sensor, the latter modelled on the sensitivity of the eye.
Compromises in image quality result. False contrast, missing colour data resulting in unusual transparencies where details should be, uneven contrast due to missing details and unusual visual artifacts. While these effects can be subtle, they are real and result in an otherwise usefull potential tool functioning below par due to an economy design.
Professional led systems use as complete a combination of spectral lines as is possible in order to attempt to cover the similar but more gradual transition across spectra that filament lamps provide in order to produce as contrasty and high resolution imaging as is possible.

Unfortunately, many images provided that display the quality of led illumination systems are not very good and those that do look decent are of stained subjects usually. Using stained material is an old trick of the trade , masking inadequacies, imparting an artificial contrast and filtering to the image. In order to evaluate how an illumination or optical system is performing one of the best easily available subjects are unstained epithelium cells from the mouth. Yeast is good too. Both provide an attainable unbiased evaluatory tool that can be comparatively assessed.

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Re: LED lighting....why the hate?

#28 Post by BramHuntingNematodes » Tue May 24, 2022 6:19 pm

And yet another complication is that eyeballs work differently than cameras as anyone that has had a photo turn out so much worse than their eye saw or had a photo that revealed hidden detail invisible to the eye can attest
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Re: LED lighting....why the hate?

#29 Post by viktor j nilsson » Tue May 24, 2022 6:46 pm

apochronaut wrote:
Tue May 24, 2022 5:41 pm
Professional led systems use as complete a combination of spectral lines as is possible in order to attempt to cover the similar but more gradual transition across spectra that filament lamps provide in order to produce as contrasty and high resolution imaging as is possible.
The LEDs in the professional systems likely come from Nichia or Yuji. There's not exactly a ton of quality LED manufacturers out there. I did a little overview of high-CRI LED options a couple of years back:

viewtopic.php?f=5&t=9135

Not quite as cheap and easy as Cree XML's, that often come pre-mounted on star PCBs, but readily available online if someone really wants to build a high-quality LED illumination system.

(I never bothered to go down that road, I'm quite happy with my 100W halogen and LED+flash combo).

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Re: LED lighting....why the hate?

#30 Post by MicroBob » Tue May 24, 2022 7:46 pm

In my personal view a good Cree LED gives a very nice illumination for the average variety of uses. Louise posted an LED spectrum that is quite typical. White LEDs are actually blue emitters with a fluorescence layer. Apparently they can't reach "white" without the dip at 500nm at the moment with this technique. This dip at blue-green leads to a limited color vision at the opposite end of the spectrum, ca. orange. So the poor pathologist who stares at haematoxilin-eosin stained sections all day will not be happy with the common LEDs.
The CRI values don't really show this limitation so it is always worth to look at the spectrum in the datasheet.

I really like my self built LEDs conversions, they consume little energy, they last, never wore one out so far, they can be adjusted over a wide range of power (which you shouldn't do with a halogen lamp), they are easy to build for me and I have no spares problem with exotic and expensive bulbs. But of cause a good working halogen setup is good too...

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