08-25-2020 03:07 PM
I tried to see if it happens outside, and it does not. Also, apparently High Burst or Normal Burst does not represent a factor, but the lack of light is a problem. If there is enough light, there is no problem. As soon as the light goes down (inside), then the issue appears.
It might be light flickering, but the camera setting about it does not solve the problem. Is there any other way to resolve it or is there no getting around it?
08-25-2020 05:02 PM - edited 08-25-2020 05:28 PM
Because the flickering of your lighting source is random, the only work around is to change to a different bulb that flickers at the line frequency (or go with old school incandescent lighting) or use an artificial light source that doesn't flicker or flickers at the line rate (pretty much any of the old CFL will flicker at the line rate).
The only way to know for sure which bulb will flicker at the line rate is to test them which is expensive and impractical although you could try with different bulbs you already own and if you find one then try more of that brand HOWEVER the manufacturers are constantly revising these bulbs so that is no guarantee that a new bulb will be like the one you currently own. Cheaper bulbs are more likely to use a simpler largely passive voltage reduction/current limiting network which WILL have a flicker rate synced to the line frequency while dimmable bulbs are more likely to use a higher efficiency switching type source that will flicker randomly.
The in camera flicker reject senses a triggering flicker and then it expects the ensuing flicker to occur at a base rate of 50 or 60 hertz (cycles per second) based upon the power grid in the country and it will modify shutter triggering to avoid triggering when flicker is problematic, that is why the frame rate will slow when anti-flicker is operational. Because the flicker of your lighting does not have this regular fixed rate there is nothing your Canon (or any other) camera can do to avoid the issue. This issue has become increasingly common with the use of higher efficiency power converters for LED and HID lighting.
It can be somewhat addressed in post by shooting in RAW and adjusting exposure and color temperature however in some cases the change will be uneven across the exposure making near perfect cleanup in post exceedingly tedious. Because I primarily shoot sports where timing is critical, I don't use anti-flicker and it is VERY rarely an issue for the type of shooting that I do. In your case it sounds like you need to use a sequence of frames instead of capturing a single frame from an action sequence so you will need to do something to address flicker pre-capture for best results and that involves either changing bulbs or using artificial lighting.
If you see a youtube video of a modern car with LED tail lights, you will see them flickering because the LEDs are driven by a PWM (pulse width modulation) controller driven from DC that controls pulse frequency and duration to provide the desired brightness without damage to the individual LED emitters. Many of the current screw in household bulbs use this same system with a PWM controller that converts the AC input to DC which the PWM controller then uses to achieve the desired perceived brightness by varying the duty cycle of the power to the LED elements. It is typical in these cases to over drive the LED during the on time with a low enough duty cycle not to damage the element by providing sufficient cooling time between high power pulses. PWM controllers are extremely power efficient because they are either on or off with very little resistive loss making them more "green" but they are also the reason that some people are bothered by screw in LED bulbs because although the flicker rate is too fast to be noticeable as flicker, your eyes and brain can respond to a flicker rate that is too high to be consciously noticed. Simple LED light sources like simple flashlights don't have this flicker because the LED is driven by pure, steady direct current that is limited via the power source to a level that is safe for the LED to be driven at continuously. More sophisticated devices pulse the the drive to the LED(s).
08-31-2020 08:29 AM - edited 08-31-2020 08:36 AM
The setting controls are sometimes to difficult to ascertain and use properly, atleast for me. .
I thought I had mine set on ISO 100, a setting that i thought that only I could change, and was not auto, but I was getting over exposed blow outs on occaision, almost at random
When I started comparing the metadata, the ISO was jumping up to 400 or higher, then back to 100 or 200.
Turns out that I had one [that appeared incorrectly unrelated to me] setting clicked on that was causing the ISO to jump up to 400 or higher, then back to 100 or 200, discovered when I started comparing the metadata.
The instruction manual has some details buried somewhere in obscurity within its 600 pages that i used to change to stop the problem that invovled exposure, apperture, time, and ISO
Sorry, i am where i do not have acess to manual, but please look in there first on iso exposures and iso settings, plus auto adjustment settings, but it is hard to find.
Very difficult and hard to find and properly fix or so it was for me, and completely counterintuitive to me.
BTW I could not see the ISO or other settings in your photos.
Just my suggestion.
08-31-2020 09:09 AM
Those are the "safety shift" settings which allow the camera to make a setting on its own if the selected setting will result in signficant over or under exposure. I keep those turned off in all of my camera bodies. They are useful in certain situations but not when you want to exercise full control over exposure.
08-31-2020 10:59 AM
I think light flicker is a likely contributing factor to your issue. But, i would like to see whether or not using Spot Metering is an issue, too. The camera spot meters only at the center AF point, no matter which AF point has been selected.
You can use Canon's DPP4 software to check what part of the scene the center AF point is covering, because that is where the camera will look when it is spot metering to set your ISO. As you say, your ISO seemingly has a mind of its' own. It could be the effects of spot metering.
BTW, I almost never use spot metering handheld. I only use it on a tripod, if then. I get better results with center weighted average metering mode compared to spot metering, which is a little too narrowly measured for most of my scenarios.