Whats causing this? (Page 6): In particular, the shutter speed in the frame that shows all the lights is 1/25, meaning the shutter was open through an AC cycle of 1/60. The shutter...

Robg

CHG_CANON wrote:

I didn't go through every last possible difference, but the difference in the metering mode in Aperture Priority likely caused the camera to expose the same scene differently.

In particular, the shutter speed in the frame that shows all the lights is 1/25, meaning the shutter was open through an AC cycle of 1/60. The shutter speed in the frame that shows some lights off was 1/160 and so that was not long enough to capture a full 1/60 cycle.

SuperflyTNT Loc: Manassas VA

DirtFarmer wrote:

Electricity travels pretty fast, close to the spee... (show quote)

I’m not saying the diagram is wrong, just not completely clear. It would be easy to assume each bulb represents one bulb. Also while I agree that theoretically the signal wave should be traveling too fast for the scenario I postulated I also disagree that it appears to be a function of the shutter. The shutter travels vertically so the left and right sides should match. I guess it’s possible that some of the LED’s were installed in one direction and others in the opposite direction but there doesn’t seem to be a pattern and if it were random you wouldn’t expect them to be grouped as well.

PhotogHobbyist Loc: Bradford, PA

Longshadow wrote:

Need picture.

But I'll guess if they are LED lights and on a duty cycle (not constantly on), the shutter speed caught some LEDs on the off cycle. The duty cycle is fast enough that the image retention in our eyes sees them as constantly on.
A different shutter speed may have been used in AP mode. Which I'll guess to be slower.

I guessed along the same lines, alternating current causes some flickering of bulbs and it is not distinctly detected by the human eye. however a camera with a very fast shutter speed could catch the bulbs when the current is making the switch and not illuminated.

DirtFarmer Loc: Escaped from the NYC area, back to MA

SuperflyTNT wrote:

I’m not saying the diagram is wrong, just not comp... (show quote)

I will accept the lack of clarity in the diagram. I produced it pretty quickly and didn't take time to explain it well. The colored blobs are supposed to represent a string of lights, different colors wired in opposite polarity.

It appears there are four groups of lights, two groups wired one way and two the other way. It may be one string with four groups or two strings of two groups or even four strings.

The shutter explanation may not be right because the OP stated that this was taken with his R6, a mirrorless camera, so I assume the shutter is electronic.

Longshadow Loc: Audubon, PA, United States

SuperflyTNT wrote:

I understand what you’re trying to demonstrate but... (show quote)

LED's wired 'aiming to the left' will light on the one side of zero; LEDs wired 'aiming to the right' will light on the other side of zero.
Speed delay due to resistance is quite negligible,
unless it's going through a wire delay line, then it will be 1 nanosecond per foot. I don't know of any engineer or circuit designer in 50 years that worried about any delay through a carbon resistor.

David_E Loc: Maryland Eastern Shore

Longshadow wrote:

Need picture.

But I'll guess if they are LED lights and on a duty cycle (not constantly on), the shutter speed caught some LEDs on the off cycle. The duty cycle is fast enough that the image retention in our eyes sees them as constantly on.
A different shutter speed may have been used in AP mode. Which I'll guess to be slower.

100% correct...exactly what happened here

PHRubin Loc: Nashville TN USA

Longshadow wrote:

Incandescent lights are so slow to cool down and "turn off" compared to 60Hz that they never really go dark between cycles. I'd question if they even dim.
LEDs, being a semiconductor, are closer to instantaneous on and off. Look at the difference between LED and incandescent bulb brake lights. Incandescent "ramp up" and down while LEDs are "bam", on, bam, off.

When I was in school, I conducted an experiment. I was able to transmit speech using an incandescent bulb in a flashlight like reflector to a photocell. I was surprised how well it worked. That doesn't imply that the light went completely "off", but it certainly "dimmed".

Actually, LED's dim when the current is low. But they do "bam" off on cars' stop lights when the current stops unlike incandescent bulbs that dim down to off as they cool.

k2edm Loc: FN32AD

DirtFarmer wrote:

LED lights running on AC. An LED only lights up when current is flowing in one direction. When it flows the other direction they are dark. This happens 60 times per second so your eyes will not see the flickering. The flicker threshold varies with individuals but is generally below 30/second, which is why that is the movie frame rate.

Use a slower shutter speed.

I am not sure that they hafta be LEDs, I suspect filament bulbs flash also, but LEd is the correct answer.. BTW, film (movie) projectors have a frame rate of about 25/sec but EACH frame is exposed TWICE therefore the flicker rate is about 50/sec... somebody was thinking years and years ago.....

Longshadow Loc: Audubon, PA, United States

PHRubin wrote:

When I was in school, I conducted an experiment. I was able to transmit speech using an incandescent bulb in a flashlight like reflector to a photocell. I was surprised how well it worked. That doesn't imply that the light went completely "off", but it certainly "dimmed".

Actually, LED's dim when the current is low. But they do "bam" off on cars' stop lights when the current stops unlike incandescent bulbs that dim down to off as they cool.

Yes, the speech modulated the light intensity, the receiver decoded it.
Similar to playing music in/with a gas fireplace. The gas flow is modulated with the audio of the music.
Same effect/principle of sending signals down a fiber optic cable. The light is modulated with the data.

Longshadow Loc: Audubon, PA, United States

PHRubin wrote:

When I was in school, I conducted an experiment. I was able to transmit speech using an incandescent bulb in a flashlight like reflector to a photocell. I was surprised how well it worked. That doesn't imply that the light went completely "off", but it certainly "dimmed".

Actually, LED's dim when the current is low. But they do "bam" off on cars' stop lights when the current stops unlike incandescent bulbs that dim down to off as they cool.

LEDs bam on and off wherever used in a digital application, it's just that brake lights are the most commonly observed as a comparison to incandescent. And yes, the brake light power is a digital signal, on or off. The only place where they MAY be driven by an analog signal might be a VU indicator.

Architect1776 Loc: In my mind

Longshadow wrote:

Need picture.

But I'll guess if they are LED lights and on a duty cycle (not constantly on), the shutter speed caught some LEDs on the off cycle. The duty cycle is fast enough that the image retention in our eyes sees them as constantly on.
A different shutter speed may have been used in AP mode. Which I'll guess to be slower.