flickering problems, how do you deal with it?

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Aenima
Posts: 214
Joined: Sun May 07, 2017 12:01 am
Location: sunny UK

flickering problems, how do you deal with it?

#1 Post by Aenima » Mon Apr 16, 2018 9:47 pm

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.
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Location: NorthWest England

Re: flickering problems, how do you deal with it?

#2 Post by MichaelG. » Mon Apr 16, 2018 10:00 pm

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.
Too many 'projects'

desertrat
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Location: Idaho

Re: flickering problems, how do you deal with it?

#3 Post by desertrat » Mon Apr 16, 2018 10:04 pm

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.
Rick

A/O 10 Series Microstar
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Several old monocular scopes in more or less decrepit but usable condition

GaryB
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Re: flickering problems, how do you deal with it?

#4 Post by GaryB » Tue Apr 17, 2018 3:29 am

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
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Re: flickering problems, how do you deal with it?

#5 Post by Hobbyst46 » Tue Apr 17, 2018 3:10 pm

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.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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Aenima
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Re: flickering problems, how do you deal with it?

#6 Post by Aenima » Tue Apr 17, 2018 5:25 pm

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
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Location: Idaho

Re: flickering problems, how do you deal with it?

#7 Post by desertrat » Tue Apr 17, 2018 5:51 pm

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.
Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition

MicroBob
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Re: flickering problems, how do you deal with it?

#8 Post by MicroBob » Tue Apr 17, 2018 7:20 pm

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.

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