flickering problems, how do you deal with it?

[Aenima]

Hi,

Not found much online about this issue, so i wanted to ask you guys.
What is the deal with the horrible flickering that seems to come from the light sources, especially when using live view or recording video?

Really hard to get good footage because of it. :/ think it might be related to the framerate/refresh rate? but only a vague guess, based on something i read once.


Are there any ways around it or to avoid it?

[MichaelG.]

Basically it's a 'Beat Frequency' between the refresh rate of the camera and the frequency of the lamp supply.

What lighting are you using, and what [if any] dimming ?

Especially if you are using LEDs ... the easy answer is to use either a DC supply, or a very high frequency PWM supply.

MichaelG.

[desertrat]

Flickering can be caused by the illumination intensity of a light source changing with each cycle of alternating current from the mains. Our eyes don't notice it, but a video capture device with a fast "shutter speed", for lack of the proper term, can record it. Incandescent lamps, fluorescent lamps, and LED lamps all do this to varying degrees.

One solution would be to power your light source with smooth direct current, if the light source will allow it. The best source of smooth DC is a battery, preferably a storage battery when current drain is high. A power supply like the kind used for electronic equipment, equipped with a filter to smooth out the ripples of rectified alternating current can also be used.

First, the voltage and current that the light source uses needs to be determined.

[GaryB]

As others mentioned, if it's an LED, it'll be it's power supply/dimmer circuit.
Normally when running LED's I use a Buckpuck with dimmer from led supply
https://www.ledsupply.com/led-drivers/b ... ed-drivers

They cost about $16 with all the options and eliminate flickering completely. I don't know what lighting you actually have so until you let us know it's as far as we can go.

[Hobbyst46]

I am using a 21 KHz PWM dimmer that I bought from retroDiode, along with my LED light.
It enables shooting at a low shutter speed - say, no faster than about 1/250 sec, most of the time, without flickering.
However: The better solution in my opinion is indeed a constant current source. Not necessarily a battery-based device, but constant current.

[Aenima]

Thank you for the replies. It sounds like you guys have a handle on the situation RE flickering, which is reassuring, knowing there are fixes for the problem. Some great info. thank u.
I don't fully understand all of the tech stuff, but i can at least provide the model of 'scope and the illumination -

I use a leitz SM-LUX which has a 6v 10w round filament bulb, and internal transformer (so that the 240v U.K.. mains goes directly into the back via 'kettle lead' cable)

I also have a BHTU olympus, which has a slot-in housing in the back accepting 6v 20w halogen g4 bulbs. This was an american model i believe, and it requires a 110v - 240v transformer separate to the microscope's stand. It sits a few feet away, and makes a gentle hum.

I should take a closer look at that transformer for any specs that might be helpful.

In both cases the means of dimming is on the base of the stand itself.

hth

[desertrat]

Since the transformer primary winding, which connects to the mains, needs alternating current to function, you'll need to bypass the transformer and connect 6 volts DC directly to the dimmer unit or bulb. If the dimmer unit is solid state electronic, you'll probably need to connect the DC supply directly to the bulb. This would apply to both microscopes.

Being a low tech, steam punk, antique technology enthusiast myself, I would probably go with a 6 volt golf cart battery or other deep cycle battery and get a battery charger to recharge it. If the dimmer control on the microscope doesn't want to work with DC, a big honkin' power rheostat can be used for a dimmer control.

Otherwise you could go to an electronics supplier and buy a regulated 6 volt DC "laboratory" type power supply. These won't be cheap, but might not cost more than the battery, charger, and rheostat.

Other members might have advice based on more modern technology.

[MicroBob]

Do you have a dimmer in your microscope lights? In this case you would get the least flicker the higher you turn the power up.

When you feed your bulbs with rectified and evened out power, there will be no flicker.
Laboratory power supplies are not that expensive any more and you can use them for many other things.
It would also be possible to add a rectifier and capacity to your existing transformer.

[hebele]

This is an old thread. But just in case it helps others that ended up here...

I have tried to put a full wave rectifier and a capacitor between power supply and the lamp. It lighted up but was significantly dimmer. Not usable.
Because silicone diodes of the rectifier drops about 1.4V. And this is a lot for a 6V bulb. It turns out there are alternatives for lossless AC to DC conversion but they look complicated for me.

I also realised there are led replacements for the bulb I have: https://www.aliexpress.com/item/4000739 ... 4c4dbD5V7y
I've ordered a pair to try. If I get really lucky, the led might work OK even with the rectifier I got.

[BramHuntingNematodes]

People throw away old laptop power supplies all the time. Nice, clean 18v DC at about 3-6 amps is very good for led constant current drivers.

[Greg Howald]

If you are using a usb microscope camera and the software that came with it, check...
1. The power frequency. If it is set at 50hz when it should be 60, that will add to flickering.
2. The other possibility is to check the frame rate setting in the software. If it is too low I promise it will flicker.
3. Check camera resolution.

Don't rule out the possibility of software issues like this causing a noticable increase in such a problem.

Greg

[hebele]

Thanks for suggestions.

External DC supply is definitely an option. But that also means an external dimmer or using an ND filter for light intensity. I also don't want to carry around a power supply with the microscope. Final option would be full LED conversion by replacing all electronics inside the microscope.

I am aware, in theory, I can match the mains' frequency with the camera. But I am trying to use a smartphone to record some simple videos. And it doesn't have much flexibility.

[Leitzcycler]

Would this be of any help to get new ideas?
https://www.microbehunter.com/microscop ... 24&t=11044

[hebele]

Leitzcycler, the servicing of that Olympus FHT looks great! I think your rectifier is very similar to mine. But you also did a led conversion. I might end up with something very similar.

I have a Leitz SM Lux. Electronics of it is very simple really. It has a transformer inside and a 5 way switch connected to that transformer. No external supply. If it had a 12V lamp instead of 6V, I think the rectifier I tried would be enough.

Someday I also want to disassemble it to clean and lubricate, mostly as a learning exercise. But for now it works fine.

[PeteM]

FWIW, it would be rare for the cause of flickering in a tungsten filament or tungsten-halogen bulb to be an AC rather than DC supply. The filament typically doesn't cool down that much as the current passes zero every 1/60th of a second. Rather, the causes Greg and others mentioned are more likely.

[EYE C U]

REGULAR INCANDESCENT BULBS ARE THE BEST WAY TO GO...THE LIGHT YOU SEE IS THE BULB ELEMENT HEATING AND COOLING EVERY CYCLE (AC)
BUT SINCE THE METAL ELEMENTS ARE SLOW TO REACT IT IS NOT NOTICEABLE. (DC) ON THE OTHER HAND IS CONSTANT.(MOST CONTROLLERS)

WITH LED'S JUST DROP THE SHUTTER SPEED BASICALLY GIVING YOUR SENSOR AN AVERAGE OF THE LIGHT EMITED

[Sir]

The way I deal with this is after I've figured out what shutter speeds to avoid, I bump or lower the ISO so that I can use the same exposures without having to deal with the shutter speeds that don't work with my light source. This of course can introduce a bit more noise to the image, but I haven't found it to be too much of a problem yet.

[Aenima]

I forgot about this post, until it got a reply recently. As an update: however the result was achieved, either a chance usage of a different power supply or something to do with the led, but now I'm using the led mod from forum member Saul, that annoying flicker has gone. I can use whatever shutter speed I want, which is a relief.
Funnily enough I'm still using the old transformer that the olympus halogen was powered by (I bought a USA to UK converter as my olympus came with the USA fitting on the back) and just plugged the led mod power supply straight into that, as Sauls Led device was American also. But together this setup is flicker free