Canon 7DII - Red Shading in images

[klazarski]

So....I'm trying to nail down what this is....

1. This occurred at the USA Rink in Lake Placid, NY

2. When I took shots in the 1980 rink, it did not happen and I tested it outside at the venue AND I just took about 400 burst shots just now and it did not occur (both indoors and out)

3. It did not happen on every shot, but about 40-50% of them

4. It makes me think about the lighting in the rink...
5. I initially had AWB on but did switch to "White fluorescent light" and "Tungsten" and it still occurred.

Gear:
1. Canon 7DII
2. Canon 70-200mm 2.8

Images:  I included one with a sample of the banding and one taking a few seconds later without....no editing.


Thoughts?

[wq9nsc]

Pretty sure that color cast is coming from flicker from the lighting, gas discharge type bulbs (and sometimes LEDs depending upon the driver module) will flicker at a multiple of the 60 hertz AC line frequency rate and where your exposure occurs in the flicker cycle will cause a color shift.

Some of the Canon models have an anti-flicker setting to combat this problem by syncing the exposure with the detected flicker rate; not sure if the 7D2 has that capability but it likely does.  The rink where the problem did not occur probably had a different light source that didn't create the flicker issue. 

Tungsten light filaments have a high thermal lag that doesn't create a flicker visible to cameras or humans but high intensity discharge lighting output changes over the AC waveform and the flicker is very noticeable to the camera.  Highly reflective surfaces like ice and snow often make the color shift more apparent AND as discharge type tubes (includes florescent lighting) age, the apparent flicker will grow worse.

Rodger

[klazarski]

Thank you for the reply!

The 7DII does have an anti-flicker feature and I did turn it on, but it didn't seem to curb it at all.  However, I am getting replies confirming that newer LEDs are a pain in the rear with this.

[wq9nsc]

A lot of the LED flicker issues at home are due to poorly designed bulbs (actually their power supply) and using dimmers and/or LED bulbs that aren't dimmer compatible or don't play well with dimmers even when dimmer compatible meaning that although the bulb power supply won't overheat when dimmed it still won't produce stable light output. Light Emitting Diodes need a DC source and for best results it should be of the constant current type which provides the best device life but a constant voltage source will also provide relatively steady and flicker free illumination.  The problem with the more commonly used constant voltage driver is the current level will change with heat and the device is far more likely to die from thermal runaway.  The really cheap LED replacement bulb manufacturers don't really care about any of these issues and focus only upon the price point so buy with care because their simple supplies are neither constant current nor voltage and light output (and device life) will vary wildly as line voltage and temperature change.

I shot one game at a LED lit outdoor field and the lighting was great with no flicker issue and a properly designed commercial system uses very stable DC constant current drivers for the high intensity LED lights so flicker shouldn't be a problem.  A really good LED system won't have a flicker problem because they are DC operated unlike florescent and mercury/sodium vapor HID lights which are directly AC powered and thus change light output over the sine wave cycle.  However some of the LED driver modules don't behave well when fed with really dirty power and I remember reading one case where a commercial facility had a huge flickering issue with their new LED lighting system which was tracked to a few old CFL fixtures which were impressing a lot of harmonic garbage on the AC line creating issues with the LED constant current power supplies.

In most homes, if you look at the AC line using a scope instead of a pure sine wave you will see all sort of "garbage" distorting the sine wave from the dirty and poorly designed devices (i.e. cheap power supplies in consumer electronics).  Several years I bought a small heater to put in my basement radio workshop and when set to its lower heat setting it distorted the AC waveform in the house so badly that you could hear its "tone" through the hum in transformers in other equipment and the high end mil spec whole house surge protectors I use also made an interesting sound with that device in use.  It quickly went into the garbage but if you have anything like that in your house along with LED (or most CFL) illumination sources then you will have some interesting lighting effects revealed by your camera.

I am surprised their haven't been complaints about that facility if professional games are being held in the facility because none of the major brand cameras have flicker avoidance programming that will work with random or non-standard flicker repetition rates.

The worst of the flicker group are cheap strings of LED Christmas lights most of which use the LED bulbs as self rectifying elements and these will flicker at a rate noticeable to the human eye.  Other common flicker issues are seen when taking photographs of current vehicles with LED brake lights where the diodes are driven with a pulsed current level that provides maximum available brightness without destroying the devices which would happen if they were driven continuously at that level.

Rodger

[Waddizzle]

I understand that Canon's anti-flicker setting works at 120 Hz.  Besides, flicker should only affect the exposure.  It should not have any efffect on WB or color.  I would guess that the pink just might be coming from EXIT signs.

[klazarski]

I will look into more with the anti-flicker setting, but I am 100% certain it's not the exit signs giving off the red rolling hue.  Too far away, not powerful enough and too inconsistent.

[wq9nsc]

Flicker can and definitely does cause color shift during photography, here is a site that provides a good example of it:  https://www.dpmag.com/how-to/tip-of-the-week/fight-color-shifts-at-high-shutter-speeds/

Canon cameras with the anti-flicker system will sync up to either 100 or 120 hz flicker rates which corresponds to the rate at which the sine wave passes through the zero voltage points on its way to peak positive and peak negative with respect to the zero point thus two flickers per cycle. 

The rate will be detected by the camera and is based upon the base AC line frequency of 50 or 60 hertz.  It won't work with irregular flicker or flicker far removed from one of these standards (i.e. a lower quality portable generator with poor frequency regulation).  It also won't work with irregular flicker created by problematic noise on the AC line or with some high efficiency light drivers which provide a variable pulsed duty cycle to create the desired illumination level.

I only enable flicker reduction when necessary because it will drop the peak shooting rate with the faster bodies and it will also cause noticeable "stutter" as the shutter release is synchronized to the line frequency/flicker rate.

Rodger

[Waddizzle]

"Flicker can and definitely does cause color shift during photography, here is a site that provides a good example of it:"

Are you referring to how LED lighting may create different colors by switching between different base colors.  I am thinking of a "tri-color" LED, which had red, green, and yelllow.  In truth, all it had was red and green.  It created yellow by quickly switching between red and green faster than the human eye could detect.

[wq9nsc]

Unfortunately it can happen with any "fast response" lightt emitter and is due to the pulsed light output and not from designed blended color output like you get with multi-color  single source LED designs.  Here is an informative post on color shift from someone who went to the trouble of shooting a series of images under a flickering light, be sure and follow the link within this link to see the photos:  http://www.sportsshooter.com/message_display.html?tid=20873

Some light sources are worse about this flicker created color shift than others.  I have rarely run into major issues with florescent but I have had the color shift happen at times particularly noticeable during a rapid burst of images.  One outdoor football field I shoot at sometimes has some pretty "high hour" mercury vapor lamps and they do create some issues although the anti-flicker setting tames it at the expense of camera responsiveness. In theory very large facilities are less likely to have this problem because they are using three phase power and if the lighting is fairly equally divided between phases then the flicker magnitude will be far less. This is true of AC operated devices (high and low pressure sodium, mercury vapor, traditional florescent) but of little impact when using LED sources which are flickering either through design or shortcomings of the driver or power source.

I can picture LED lighting potentially being a major problem because it has the fastest response of any common light source to changes in drive level (useful in information display applications but lousy for photography when what you want is a steady light source).  It is still a rapidly evolving technology for wide area high intensity lighting so there will be some growing pains with unexpected and undesired consequences including those for photographers who often aren't considered in initial design of these systems where economy of operation is the big driver.  Switch mode type LED drivers are extremely efficient and effective at obtaining the desired average light output level with no visible flicker as perceived by humans but depending upon shutter speed it can result in total scene color shift or shifting of part of the scene.   I don't know how much investigation was done but I do recall reading of some concerns early in the development of these high efficiency controllers where there were comfort impacts upon humans even when they didn't perceive the actual flicker and it probably something like the fatigue factor that occurs with a distorted audio source where the distortion level is not readily perceived by most listeners.

Rodger