Today we are talking about Shutter angles and Flicker Free settings on the GH5. I’m going to go on a slight tangent here and talk briefly about the recent discussions on the use of Shutter Angles in relation to getting faster Auto focus on the GH5 but we won’t be covering auto focus performance today just as a baseline to start our conversation. Back to basics.
When shooting film or cinematic looking footage, the rule of thumb was always to double your shutter speed of your video frame rate. It was discovered that using 179 degree on the GH5 under Shutter angle the GH5 would indeed speed up the auto focus.
Now i have tried this and it indeed does speed things up however i am more curious about the amount of motion blur.
So that’s great and we have a new shutter angle to use that will improve auto focus speeds but what if you don’t care about auto focus and shoot manual or actually care about what the shutter angle represents, which is how much motion blur in your moving pictures (ie video)?
To begin I recently shot an event that friends of ours were at and noticed some flickering of the lights and on someones Computer screen, ruining my shots. I did not see this problem until later on when reviewing it on my full sized screen.
I started looking into the problem and realized that the issue was do to my shutter angle. At that time i was adhering to the 180 degree rule but using the camera in seconds mode and not angle mode.
What other Shutter angles should we use and why?
But first, the easiest way is to first explain what a shutter angle is. A shutter angle is a left over concept from analog film days when movie cameras actually had a 360 disc that spun when taking moving pictures. The technical reason is that the Human Eye would see all images blurry as the picture was moving if that spinning disc wasn’t there. Now divide the disc up into degrees (remember your math from highschool), every circle has 360 degrees. the shutter angle is therefore the open part of that spinning disc and how many degrees it is. To measure a real one, you could use a protractor.
The main point to take away is: The shorter the shutter angle or less open sector of the circle, the less motion blur your picture will have (when you either move the camera or someone is moving in your scene). This can affect how your final movie looks and is one element that makes a film cinematic (there are a lot others as it is an entire process).
So in general:
So shorter shutter angle = less blur = less exposure time
Larger angle = more blur = more exposure time
So how does that relate to the 180 degree rule. Well 180 degrees is the mid point and what most cinematographers use in their movie and films.
So what happens if you were to use less or more of a shutter angle !
This is where things get interesting!
Less = less motion blur.. but by how much ? Will your eye notice it?
I would bet that most people will not notice much of a change but it depends on how much of an angle you use. The same goes for over the 180 degree, how much more blur will your eye notice.
Its a very subjective subject and in most cases a creative decision however, flickering lights changes the equation.
So why bother with anything less or more than 180 degrees (or 179 degress on the GH5)
The answer (for North America) is a technical one.
Have you ever shot indoors with Fluorescent lighting or Shot a scene and noticed that a computer screen was causing some flickering in the image?
If the answer is yes then you a different shutter angle can help you!
Why does this matter today since we don’t have a physical shutter?
The answer is that it matters even more today than before because an Electronic shutter goes by the frequency of the NTSC (in North America) which is roughly 59.98Hz.
That is the same frequency as the Power coming into your home, office etc. A standard electric receptacle that you plug everything into. It also happens to be the same frequency as those flourescent lights and the same frequency of most computer LCD screens. There are also some LED light ballasts that operate at that frequency as well.
The result is that you get flickering or banding lights even at 180 degree shutter angle because you are inline or “in phase” with an existing source even if you are half of the phase. This creates problems for CCD image sensors because they also operate on electric signals and will pick up this pattern.
You can try this yourself to see the problem, if you have a digital video camera, try taking video of a computer monitor set to 60 Hz refresh rate or take video of fluorescent lighting that is running on 60Hz as well. you will get banding and flicking.
How to solve this issue?
While 180 degree (179 degree shutter angle) on the GH5 is good for autofocus performance, it is not going to cancel flickering of lights.
Is there a setting on the GH5 that works well all around or will cancel that strobing or banding effect?
Yes there is! However it depends on what frame rate you are shooting at.
To enable: Use Synchro SCAN setting in the GH5 under the Creative Movie Menu to set your shutter angle, or you can simply use the back control dial as you would change your Cameras shutter speed normally. Synchro scan has to be set to on however first. Also you need to set your GH5 to choose Angle/ISO mode in order to show the shutter angle.
I have compiled the list of the common frame rates and the shutter angles that I am currently using on the GH5 to avoid flicker:
|Framerate (NTSC 59.98Hz)||Shutter angle|
|23.976 fps (24 fps)||144 degrees|
|29.97 fps (30 fps)||120 degrees|
|47.98 fps (48 fps)||288 degrees|
|59.98 fps (60 fps)||240 degrees|
|119.88 fps (120 fps)||288 degrees|
I’ve tested all of these against my 60Hz monitor and they do not produce the flicker any longer.
Why does this work ? Well in technical/electrical terms choosing an angle that is “out of alignment” or “out of phase” means that the frequency of the 60Hz cycle no longer lines up (usually aproximately 90 degrees out of phase) which has the effect of not interfering or seeing the 60 Hz cycle of the source light or monitor you are shooting, which is what you want otherwise you see the banding or flickering effects.
What about Higher Frame rates?
So you may notice a larger degree shutter angle on higher frame rate. Consider our initial conversation about longer shutter angles having more blur. What if the frame rate is quicker? Well there would be less blur because the camera is able to capture more detail in a quicker period of time. The values in the table represent the closest approximation to each other in terms of motion blur that i can come up with. If you want less blur half the number in the table, more blur double it however you can’t go past 360 degrees!
I encourage everyone to try this on their own and see what works best for them.
I for one will most likely leave the settings i have in place then i never have to worry about flickering again and i get a decent amount of motion blur to the footage for cinematic purposes.
If you shoot 23.976 and 47.98 like me, this will definitely help your footage in those scenarios.
I recently found this calculator on RED Cinema cameras site and used this as a baseline for testing. My numbers show real world usage however and do not exactly correspond to the numbers from Red Camera’s site due to not using a RED camera shutter. I specifically tested my numbers on the GH5 with the latest firmware version 2.1. Your mileage may vary depending on the camera you use.
Red Cinema camera calculator:
Stay tuned for an upcoming Youtube Video where i test these settings out in more detail and try to show the differences in motion blur and how they differ from the 179/180 degree shutter rule!
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Until next time! Keep learning!