Eliminating the GoPro prop

Silvaire

Silvaire

En-Route
Joined
Oct 10, 2012
Messages
4,679
Display Name
Display name:
Silvaire
I've been working on adjustments to the GoPro Hero 7 to make videos that look more like they do in real life which means trying to eliminate the propeller strobe effects that are caused by the high shutter speeds the camera uses in the auto mode. The way to do it is to use the Protune feature to control the frames per second and shutter speed (slow them down) and then use a neutral density filter to prevent the over-exposure created by the slow shutter speed. There are problems with it though. For one thing, since the settings are manual there is no compensation for exposure when the scene changes - such as you fly into the sun and then away from it and the GoPro screen is so small, you can only guess at what the results are going to be. Also, the very cool hyperstabilization that the GoPro has doesn't work at slow shutter speeds.

Anyway I compared these two video clips, taken at the same place but on different days (actually about a month apart) and that led me to do an hour of flying around in a circle over a spot and trying a wide range of settings. My conclusion for a bright sunny day: the best results were 30 frames per second, 1/60th shutter speed and an ND16 filter. Anything over 1/60th shutter and the prop starts to show up but still you need a steady mount or it will blur with vibration as the stabilization will be compromised. If you have one of those DJI Osmos that would probably solve that problem.

 
Last edited:
A neutral density filter can help with that.
You can get them on Amazon, of course.
 
Enable supermegahyperstabilization and put the go pro on the spinner. Problem solved.
 
Shepherd said:
A neutral density filter can help with that.
You can get them on Amazon, of course.
Click to expand...

You have to use a ND filter or the picture will be overexposed but, like I said, it's guesswork because the GoPro isn't like an SLR, you don't have a meter. All you have to go by is what you see on that tiny 1.5 inch screen. In the video I posted I used an ND16 but it probably should have been the ND8.
 
Silvaire said:
Eliminating the GoPro prop
Click to expand...
fly a twin

Silvaire said:
use a neutral density filter
Click to expand...
my super low-rent hack for this was to take pictures through the Rosen© sun visor.. it usually works decently well, at least on Pixel phones


..as a geek thought I've wondered about placing the camera in the cowling itself and finding a way to time the shutter with the prop sweeps, sort of like the old WW1 fighter planes so the gun wouldn't shred the prop
 
Tantalum said:
fly a twin...
Click to expand...

Still going to get prop strobes every time you look out the side, it's actually worse since you've got twice as many propellers getting in the way of the shot. Shooting through visor will only bring the GoPro down to about 1/240, not slow enough to get rid of the prop. Honestly, I've tried it. Also, ND filter is about six bucks, Rosen Visors a bit more so not sure if it qualifies as a "low rent" solution.
 
Silvaire said:
not sure if it qualifies as a "low rent" solution
Click to expand...
"low rent" as in its already part of the airplane I rent. The sun visor trick is not great, but works 'okay' it often will at least blur the prop as opposed to those crazy black lines. I haven't seen any phone camera clip on ones that cheap but might be worth another look
 
Silvaire said:
You have to use a ND filter or the picture will be overexposed but, like I said, it's guesswork because the GoPro isn't like an SLR, you don't have a meter. All you have to go by is what you see on that tiny 1.5 inch screen. In the video I posted I used an ND16 but it probably should have been the ND8.
Click to expand...

I bought an adjustable ND filter from Amazon. It wasn't expensive.
The problem was every time you turned the plane you needed to adjust the filter. I set it to near minimum to eliminate the shimmy and I learned to love the prop.
 
Silvaire said:
I've been working on adjustments to the GoPro Hero 7 to make videos that look more like they do in real life which means trying to eliminate the propeller strobe effects that are caused by the high shutter speeds the camera uses in the auto mode. The way to do it is to use the Protune feature to control the frames per second and shutter speed (slow them down) and then use a neutral density filter to prevent the over-exposure created by the slow shutter speed. There are problems with it though. For one thing, since the settings are manual there is no compensation for exposure when the scene changes - such as you fly into the sun and then away from it and the GoPro screen is so small, you can only guess at what the results are going to be. Also, the very cool hyperstabilization that the GoPro has doesn't work at slow shutter speeds.

Anyway I compared these two video clips, taken at the same place but on different days (actually about a month apart) and that led me to do an hour of flying around in a circle over a spot and trying a wide range of settings. My conclusion for a bright sunny day: the best results were 30 frames per second, 1/60th shutter speed and an ND16 filter. Anything over 1/60th shutter and the prop starts to show up but still you need a steady mount or it will blur with vibration as the stabilization will be compromised. If you have one of those DJI Osmos that would probably solve that problem.

Click to expand...
Can you go down to 1/30 shutter? I think that would look even better, you'd need a darker filter though I guess.
 
Shepherd said:
...I learned to love the prop.
Click to expand...

I tried that too but it just bugs me. I've been taking aerial videos as far back as the late 60's with the old 8mm film cameras and even with the Sony 8mm tape the prop was never a problem, they came out looking normal. Of course the new digital cameras have far superior picture quality, no question about that and the image stabilization is fantastic but the weird looking propeller blades creeping back and forth just ruin it. Even worse with rolling shutter cellphones that give you those bizarre venetian blind looking bands across the picture.

exncsurfer said:
Can you go down to 1/30 shutter?...
Click to expand...

You can but there is a formula that says for best results you double the frame rate so if you go down to 24 fps you should use 1/48 shutter. I did some of that but it came out over exposed because the highest filter I have is an ND16, I would need an ND32. Another thing you can control on the GoPro is the ISO so if you limit to a max of say 200 you can get by with a lower filter. The thing you cannot adjust on GoPro is the aperture, it's fixed.
 
Last edited:
Tantalum said:
"low rent" as in its already part of the airplane I rent. The sun visor trick is not great, but works 'okay' it often will at least blur the prop as opposed to those crazy black lines. ...
Click to expand...

Yes, it works, I tried this afternoon.

* Orest
 
ND8 + Circular Polarizer in front is my favorite combo. Its probably like a ND10. Bonus is that glare off of instruments, Rosen visors, windshield and water down below looks nicer.

Variable ND like @Shepherd uses can be the most practical. But can't go as dark with out the 'X'. And cheapo ones really can really kill sharpness.
 
It’s a video out the front of an airplane. You don’t remove the cowl why would you remove the prop, it’s part of the experience.
 
Because this looks ridiculous

Screenshot_20210904-182042~2.png
 
I clamp my GoPro onto my left wing's tie-down ring. I figure the last thing the Internet needs is its 1,000,001st in-cockpit video of a middle-aged man flying a light piston, so I angle the camera slightly downwards and film the (much-more-interesting) scenery from outside the airframe instead.
 
The problem stems from the difference between an SLR's global shutter and GoPro's rolling shutter. In an SLR's global shutter, the entire frame is exposed at the same instant. A rolling shutter sweeps a slit across the frame, exposing, for example, the left edge well before the right edge.
 
Domenick said:
In an SLR's global shutter, the entire frame is exposed at the same instant.
Click to expand...

You're right that rolling shutter causes the artifact, but most digital mirrorless and SLRs actually don't have global shutters. They just have better sensors and processors, so you notice it less. Even high end cine cameras like the Arri Alexa Mini LF (arguably one of the top cameras money can buy) has a rolling shutter. With sensor tech where it is currently, rolling shutter cameras often yield better dynamic range, and lower noise than global shutter sensors. (not an expert in sensor tech, but I work with some, and at least that's what they tell me :)
 
Here is a good example of rolling shutter artifacts using different shutter speeds. It shows how they can be nearly eliminated with a slower shutter. So, while you can do this with the GoPro (select a slower shutter speed) what you cannot do is adjust the aperture and because of that the image is overexposed. The ND filter is used to compensate for that issue. It's not ideal though since video is a dynamic environment and so the settings need to adjust for changing conditions. If the GoPro had aperture adjustment and a shutter priority setting (S) like SLR's do it would work perfect but then they'd probably cost $1500.

 
David Megginson said:
...I figure the last thing the Internet needs is its 1,000,001st in-cockpit video of a middle-aged man flying a light piston...
Click to expand...

Probably true but I meant this thread to be about photography rather than social media and as such my opinion is that for aerial pictures to capture the real concept they can't just be landscape. You need to frame it in a perspective and I think the cockpit, instruments and people make it way more interesting. There might be a million other guys out there doing the same thing but what does that matter to you? It's just a hobby. Money is worthless if it isn't getting passed around.
 
David Megginson said:
I clamp my GoPro onto my left wing's tie-down ring. I figure the last thing the Internet needs is its 1,000,001st in-cockpit video of a middle-aged man flying a light piston, so I angle the camera slightly downwards and film the (much-more-interesting) scenery from outside the airframe instead.
Click to expand...
That’s more or less what I do. This video was taken with a ND16 filter at 2.7K x 60fps with the shutter speed set to 120.
 
Does anyone make action cameras with CCDs? I don't remember rolling shutter artifacts with those sensors.
 
You must log in or register to reply here.
Back
Top