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

Posted: Thu Aug 11, 2022 3:54 am
by Finelld
There are pluses and minuses to all lighting technologies. I am a degreed professional photographer and electronics engineer.

From a photography perspective the number of spectral lines within the bandwidth of a given light source is less important than the bandwidth and color temperature. Keep in mind that color imaging sensors see only RGB. Most have IR blocking filters because CCD and CMOS sensors are particularly sensitive to red wavelengths. Many LED light sources used by photographers have adjustable color temperatures. This is achieved by having an array of two different color temperatures of “white” LEDs and adjusting the ratio between them. Photographers are experts at modifying lights and lighting with the use of flags, gels, reflectors, and a whole host of light sources. But 99.9% of them aren’t concerned with spectral purity, linearity or if a given line is present or missing. LEDs are more efficient at producing many of the lines used in fluorescence and diode solid state lasers are often used to pump other lasers or non linear optics to get higher optical frequencies and shorter wavelengths. One nice thing about LED illumination is that the color spectrum is comparatively constant over their output power levels when compared to incandescent illumination.

Black body illumination has the benefit of having a more complete spectrum in relation to LEDs but it is weighted towards the IR and thermal IR spectrums. As a result it is very inefficient for optical illumination. Another serious draw back is the spectrum or color temperatures changes as the brightness is adjusted. In order to radiate in the shorter wavelengths like greens and blues you need to dump more power to generate higher quantum energy states to emit these wavelengths. The use of gasses like halogens can improve this but it isn’t a perfect solution.

The last light source I will cover can be considered as two light sources. They are arc lamps and fluorescent lamps. For higher power lights these can encompass the best of both worlds or at least create a compromise between the two previous technologies. They require more support components to work but they are more efficient than incandescent lights. They can be designed to have a phenomenally complete optical spectrum. They lack the amount of dimming capability of LEDs and incandescents. They can also have strong lines in the UV spectrum. HID lamps fall into this category. In the 1980s Streamlight made a light called the Streamlight 1,000,000. It was a bulky handheld HID light that required an external battery pack or belt. It was used by NASA and law enforcement. At the time it had the closest spectral completeness to the sun of any other light source. It was featured in NASAs annual spin-off magazine for technologies spun off from the space program.

Most types of illumination are fine for most types of microscopy. The biggest time you need to worry about specific spectral lines is when doing fluorescence microscopy. The other time is when measuring spectral absorption of parts of a sample.

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

Posted: Fri Sep 23, 2022 2:35 pm
by Dubious
ashamartin wrote:
Fri Sep 23, 2022 11:26 am
The reason behind hating LED light is this flicker that is still far too rapid to be seen directly, but some people can see multiple images of the lamps every time they make a saccade, which is unpleasantly distracting. The flickering of these LEDs may limit the uptake of the bulbs, just as many people dislike energy-saving fluorescent lamps.
That subliminal flicker is caused by PWM--pulse width modulation--used to vary the light output of some LEDs by varying the duty cycle. But, PWM should no longer be an issue, as today there are many constant-current LEDs whose brightness is adjusted by varying the voltage, or that use PWM at such a high frequency as not to cause eyestrain. You just need to be careful in selecting the LED and driver. Note that PWM was also until recently a serious problem with the backlighting for many laptops/monitors/TVs, and still is with some...

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

Posted: Fri Sep 23, 2022 2:38 pm
by LouiseScot
Dubious wrote:
Fri Sep 23, 2022 2:35 pm
ashamartin wrote:
Fri Sep 23, 2022 11:26 am
The reason behind hating LED light is this flicker that is still far too rapid to be seen directly, but some people can see multiple images of the lamps every time they make a saccade, which is unpleasantly distracting. The flickering of these LEDs may limit the uptake of the bulbs, just as many people dislike energy-saving fluorescent lamps.
That subliminal flicker is caused by PWM--pulse width modulation--used to vary the light output of some LEDs by varying the duty cycle. But, PWM should no longer be an issue, as today there are many constant-current LEDs whose brightness is adjusted by varying the voltage, or that use PWM at such a high frequency as not to cause eyestrain. You just need to be careful in selecting the LED and driver. Note that PWM was also until recently a serious problem with the backlighting for many laptops/monitors/TVs, and still is with some...
The previous post was spam which I reported earlier
Louise

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

Posted: Mon Sep 26, 2022 7:12 pm
by richbart
I switched toLED On my BH2 BHTU.I think the photos are better. I sold a microscope to someone in histology, and they wanted halogen, because specific features showed up better with halogen. Just depends on what your doing.

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

Posted: Mon Sep 26, 2022 7:39 pm
by Dubious
All in all, my eyes prefer halogen. But from any engineering point of view, LED lighting has to be vastly superior--just take a look at the size/weight of the external power supply for the Nikon E800's 100w halogen lamp.

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

Posted: Fri Oct 14, 2022 10:06 am
by Antartica
I’m looking to upgrade my Olympus bh2 to led. Which option below is better?

1) https://www.ebay.com/itm/265362785969?h ... R_q_9d76YA

2) https://www.ebay.com/itm/255616141644#v ... cvip-panel

3) does anyone know any other good options?

Thanks

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

Posted: Fri Oct 14, 2022 12:41 pm
by Scarodactyl
I have bought the retrodiode before and found it to be adequate. Baurus posts here as Saul and comes up with some very cool designs so I would expect his to be quite good.

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

Posted: Fri Oct 14, 2022 1:52 pm
by Hobbyst46
retroDiode is a good and reliable supplier IMO.

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

Posted: Fri Oct 14, 2022 4:55 pm
by Antartica
Thank you. Baurus is only 4000-4200k and 95 cri. Retro diode is 5000k and a Cree. Is one better than the other? I’m not sure what that all means so I wanted some advice.

I just want to get rid of the yellow tint given off by my halogen. It makes all my photos look old or dirty.

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

Posted: Fri Oct 14, 2022 5:43 pm
by Scarodactyl
I don't think a yellow tint will be an issue with either. My retrodiode is maybe a bit blue but well made and nice to use.

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

Posted: Fri Oct 14, 2022 6:34 pm
by Saul
Antartica wrote:
Fri Oct 14, 2022 4:55 pm
Thank you. Baurus is only 4000-4200k and 95 cri. Retro diode is 5000k and a Cree. Is one better than the other? I’m not sure what that all means so I wanted some advice.
I can make with the 5000-5500K & 98CRI LED, goes up to real 27W (but you have to be careful checking heatsink temperature), for continuous work is better to keep around 18-20w.
Power supply is not PWM based, no flickering.
I just want to get rid of the yellow tint given off by my halogen. It makes all my photos look old or dirty.
Adjust your WB in the RAW converter

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

Posted: Fri Oct 14, 2022 9:58 pm
by Antartica
Yeah, I figured the 5000k was better. But unfortunately it is out of stock and he’s not answered any of my emails. I’m not sure how else to reach him. Is he still active here?

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

Posted: Sun Oct 16, 2022 8:00 pm
by Chas
Somehow, incandescent lights can be kinder, here are some pics of a nigrosin mount that has broken up, illuminated with a an Ulanzi led light:
This light works fine with older objectives, but with new Chinese objectives the effect is very jarring.
X40 direct projection:
In focus (on the litle bird beak shape , bottom left):
Chin 40 in focus.jpg
Chin 40 in focus.jpg (51.81 KiB) Viewed 2146 times
Focussed above:
Cin 40 above.jpg
Cin 40 above.jpg (43.76 KiB) Viewed 2146 times
Focussed below:
Chin 40 below.jpg
Chin 40 below.jpg (44.63 KiB) Viewed 2146 times
The blue/green margins effect can be very jarring with insect mounts......though you can easily guess whether you need to focus up or down for any particular appendage :roll:
With a tungsten light the blues and greens morph into much less vibrant colours, the blue becomes a sort of pink.
(Yes the white balance is a bit wrong ,it was set to 'flash' but this is not a bad setting for older objectives using this light).