topic Re: Black Line on Photos at high Shutter in EOS DSLR & Mirrorless Cameras

Black Line on Photos at high Shutter

athorat — Sat, 02 Feb 2019 13:24:14 GMT

Got this new canon5d markiv on amazon and sometimes at high shutter speed it gives a distinct black line in between the photos. is this ok at high shutter speed assuming light not passing through? but should it not darken all the image instead of just one black strip?

shutter speed 1/1600 f7.1 iso400

https://www.flickr.com/photos/156126577@N03/39992084913/in/pool-canondslr/

shutter speed 1/300 f7.1 iso400 works fine

https://www.flickr.com/photos/156126577@N03/46042557115/in/dateposted-public/

Re: Black Line on Photos at high Shutter

Ray-uk — Sat, 02 Feb 2019 11:06:44 GMT

Difficult to tell what's happening from the pics because it seems to be a spinning subject, can you make it do it again if you take pictures of a static subject in daylight without using flash or artificial light and then post that on here.

Re: Black Line on Photos at high Shutter

TCampbell — Sat, 02 Feb 2019 15:25:17 GMT

Out of curiosity ... what is the subject in the photo?

The black band isn’t a digital artifact ...so this does not appear to be a camera defect.

However... due to the way the camera is designed to work at high speed, you may be seeing consequences of the camera’s “rolling shutter” mechanism.

To make sense of that, watch this video: https://youtu.be/CmjeCchGRQo

(Note to mods: video embedding feature has changed and now appears to be broken so I'm just inserting this link instead)

My guess is that the lighting on this subject (whatever it is) is flickering at high speed and the you’re seeing things get bright / dark / bright as the camera shutter sweeps across and you are seeing this as banding.

Similar things happen with certain types of lighting systems at arenas, etc. To the human eye they appear to provide continuous light ... when in reality they are flickering at high speed (specifically at the cycling rate of the AC power ... here in the USA 60-cycles per second). This means at high speeds, it’s possible to get a photo at an odd moment and you end up with some photos looking perfect and others looking light they have messed up lighting even though they were taking at the same event on the same day using the same settings. Some Canon models have an anti-flicker mode to deal with the problem (but that feature is based on the flicker being the result of AC power cycling rate or hertz and isn’t meant to deal with things that flicker randomly.

Re: Black Line on Photos at high Shutter

athorat — Sat, 02 Feb 2019 23:10:46 GMT

Thanks for the reply guys, the subject is not moving just the angle while shooting makes it feel like.

This had happened previously even in my living room and dismissed but now its bothering....

If you look at this snap, its big glass sphere and has glass blown LED light inside. which circular (moving klike motion inside)

https://www.flickr.com/photos/156126577@N03/33088114408/in/dateposted-public/

I was underneath this big glass ball and shot vertically.

Re: Black Line on Photos at high Shutter

BurnUnit — Sun, 03 Feb 2019 06:45:58 GMT

LED lamps do flicker. Not as noticeably as fluorescent lamps but they can still cause problems for camera shutters. Digital camcorders will especially show the flickering effect if the wrong frame rate is used with LED lights.

Is the dark area in your photos always horizontal or can it also appear at different angles?

Re: Black Line on Photos at high Shutter

ebiggs1 — Sun, 03 Feb 2019 15:23:28 GMT

"...you may be seeing consequences of the camera’s “rolling shutter” mechanism."

Re: Black Line on Photos at high Shutter

Waddizzle — Sun, 03 Feb 2019 15:36:07 GMT

@athorat wrote:
Thanks for the reply guys, the subject is not moving just the angle while shooting makes it feel like.
This had happened previously even in my living room and dismissed but now its bothering....

If you look at this snap, its big glass sphere and has glass blown LED light inside. which circular (moving klike motion inside)
https://www.flickr.com/photos/156126577@N03/33088114408/in/dateposted-public/

I was underneath this big glass ball and shot vertically.

If light flicker is the problem, I am pretty sure the 5D4 has “Flicker Compensation” that you can enable. It can help with multiple light sources that are flickering in synch, but not with multiple sources that are out of synch.

Re: Black Line on Photos at high Shutter

athorat — Mon, 04 Feb 2019 01:57:37 GMT

is that a problem or is it something which is by design.

I had seen these lines even in my lving room with different light sources...

I have tried to enable the flicker setting and not tried to shoot the same light source yet.

Re: Black Line on Photos at high Shutter

TCampbell — Mon, 04 Feb 2019 02:13:26 GMT

Basically your light meter on the camera is faster than your eye. Your eye doesn't really notice the flicker. But the camera can meter the light hundreds (thousands?) of times per-second and detect the flickering.

Presumably the flicker is genated by the AC power hertz. In the US, the AC power is 110 volts AC power cycling at 60 Hertz. That means 60 times per second the voltage switches from positive to negative and back on the two wire pair.

There are some unlikely complexities. Power from the utility company doesn't enter your home as 110v power ... it is almost always a 220v line which is split into two 110v "phases". This means some rooms may be on one phase and other rooms are on the other phase. I mention this because those two havles of your power are both cycling at 60Hz... just not at precisely the same moment (they are out of phase). I suppose it could be possible where half of a room is on one phase and another half is on a different phase so the lights don't flicker at precisely the same moment. But I suspect that's somewhat unlikely.

The camera would not be able to compensate for both at the same time.

I would suggest reducing your shutter speed to the camera's max "flash" sync speed. This is the fastest shutter speed at which the camera is still fast enough to completely open the first curtain so that the ENTIRE sensor is exposed before it has to close the 2nd curtain.

For some Canon cameras that's 1/250th, for others it's 1/200th, and for others it's 1/160th. It depends on camera model.

Re: Black Line on Photos at high Shutter

Ray-uk — Mon, 04 Feb 2019 14:50:25 GMT

@TCampbell wrote:

There are some unlikely complexities. Power from the utility company doesn't enter your home as 110v power ... it is almost always a 220v line which is split into two 110v "phases". This means some rooms may be on one phase and other rooms are on the other phase. I mention this because those two havles of your power are both cycling at 60Hz... just not at precisely the same moment (they are out of phase). I suppose it could be possible where half of a room is on one phase and another half is on a different phase so the lights don't flicker at precisely the same moment. But I suspect that's somewhat unlikely.

Does this really happen in the USA ? I live in the UK where the normal domestic supply is 240V AC, each house is supplied from a single phase even though my neighbours house could be supplied from another phase. I find it strange that 2 or more different phases could be supplied to one house.

Re: Black Line on Photos at high Shutter

wq9nsc — Mon, 04 Feb 2019 15:37:02 GMT

Ray,

As Tim points out, typical for U.S. homes is for the house to be fed from a medium voltage power distribution line via a step down transformer. This transformer has a center tapped secondary with the center tap forming a neutral between the two secondary winding halves. 240 volts is available across the entire secondary winding for large demand loads (air conditioning, electric clothes dryer, etc.) while 120 volts is available between either side and neutral for lighting and other appliances.

In this case the transformer is functioning as a phase splitter so that as the AC waveform is approaching a positive peak on one side of neutral, it is going towards a negative peak on the other side. The two phases are a creation of the transformer and stay perfectly 180 degrees out of sync due to the split transformer winding. Lower cost LED lighting can use a half wave rectifier so that it only is supplied voltage on half of the waveform and if two of these lights are on different halves of the 120 circuit then you will have them emitting peak brightness 180 degrees out of phase with each other creating some odd effects. Note that the full 240 volt available is a single phase and the split phase is purely a construct of the transformer reversing one side with respect to neutral.

Although you won't typically find it for a home; businesses, farms, and large power consumers will use tri-phase power with three "hot" lines all out of phase with one another. This is true multiple phase power unlike that "pseudo-split" created by the typical home transformer.

Quality LED lighting is fed regulated DC and this isn't a problem, the worst are stuff like cheap Christmas lights where the LED itself acts as a rectifier diode and flickering is very obvious to the human eye. Incandescent lighting has significant thermal lag so even though the power through it is changing throughout the AC cycle the human eye (and camera) don't perceive a difference in illumination unlike sources that respond quickly in response to applied voltage changes.

It is a little more complex than the UK but the U.S. system has some advantages and some difficulties. For best power utilization the house load should be as evenly distributed across each side of neutral because any current imbalance flows back through the neutral line. AND if there is a fault with the neutral line, bad things can occur because the voltage will no longer split evenly across the two 120 volt sides which can cause one side to rise to a damagingly high voltage while the other side drops to voltage low enough to damage motors. In terms of damage to electrical gear, the loss of neutral is about the worst in terms of carnage.

Rodger

Re: Black Line on Photos at high Shutter

kvbarkley — Mon, 04 Feb 2019 15:34:52 GMT

This is done so that you have 220 available where you need it (like an electric oven) and 110 for most of the house.

Re: Black Line on Photos at high Shutter

ebiggs1 — Mon, 04 Feb 2019 15:39:56 GMT

"... it is almost always a 220v line which is split into two 110v "phases"

I know of no instance where a USA house gets a single 220v line. It is always two 110v lines. Each is 180 degrees out of phase with the other. These two seperate lines a connected to seperate poles on our 200v receptibles. Breaker panels have two busses so there is two seperate legs each 110v.

Re: Black Line on Photos at high Shutter

kvbarkley — Mon, 04 Feb 2019 15:52:30 GMT

Nonsense. As said above, they all get a center-tapped 220 V signal that is split at the center tap into two 110 V circuits.

Re: Black Line on Photos at high Shutter

ebiggs1 — Mon, 04 Feb 2019 16:08:14 GMT

"Nonsense." I don't know what you consider nonsense but this is how it works in Kansas at least.

There are two hot wires and a neutral wire. The hot wires each carry 120 volts and are different phases. These phases are normally called "A" and "B" phases. The total voltage, when measured between them, is around 240 volts. Therefor two lines coming in not a single one. It has nothing to do with what happens before the transformer. That's it and this a a photography board not an electrical engineering board.

Re: Black Line on Photos at high Shutter

Ray-uk — Mon, 04 Feb 2019 16:19:07 GMT

@ebiggs1 wrote:
That's it and this a a photography board not an electrical engineering board.

That's true but it has answered my query, I am now much better informed, thankyou.

Re: Black Line on Photos at high Shutter

TCampbell — Mon, 04 Feb 2019 16:26:10 GMT

I didn't expect this to turn into a discussion on electrical systems, but there you go.

Anyway, this is a bit off topic ... but a YouTube channel I enjoy had an espisode that explained a bit about the UK's crazy bulky power plug and how, when you a buy a common appliance (such as a toaster) it doesn't actually include a plug, you have to wire the plug on yourself (is this still true in the UK?)

The story goes that while in the US, all the wiring in the house routes to the fuze box (now breaker box -- we haven't used fuses in years), that requries a lot of extra wiring to place recepticals around the home. During the war years, metal was at a premium and that excess wire was considred wasteful. So instead, the whole house got wired in one giant continous loop (do they still do this?). The problem is... now you don't have individual breakers for each section of the house. To solve that problem, the UK designed plugs with the fuse located in the individual plug (in the US, our plugs typically don't have fuses in them. The only exception I can think of is holiday lighting strings.)

Meanwhile back to the topic ... flickering tends to be based on the AC power cycling rate (if you have AC power at 60Hz then your flickering is probably happening 60 times per second. If you're on 50Hz then you're flickering is probably happening 50 times per second.)

Re: Black Line on Photos at high Shutter

kvbarkley — Mon, 04 Feb 2019 16:28:48 GMT

I *am* an Electrical Engineer.

Where do you think the two phases come from? Do you have two transformers? If you really had two "separate" phases you would have 4 wires coming into the box.

Do you even know what "Center-tapped Transformer" means?

Re: Black Line on Photos at high Shutter

CaliforniaDream — Tue, 05 Feb 2019 15:38:53 GMT

BTW some LED lighting use full wave rectification so the flicker rate is at 120 HZ.