Backcountry Pilot • ND filter

ND filter

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ND filter

So if you add a filter to remove the prop blur does the frame rate have any effect on the picture? Would the addition of a filter be noticeable when changing from 30 FPS to 60 FPS?
I'm curious. I'm just getting started with video and I'm playing around with different settings.
Are there any other quality issues that are affected by the addition of a prop filter?
Thanks,
RR
Rezrider offline
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Re: ND filter

Rezrider wrote:So if you add a filter to remove the prop blur does the frame rate have any effect on the picture? Would the addition of a filter be noticeable when changing from 30 FPS to 60 FPS?
I'm curious. I'm just getting started with video and I'm playing around with different settings.
Are there any other quality issues that are affected by the addition of a prop filter?
Thanks,
RR


In a nutshell... yes. Adding an filter will degrade the quality of the image. It will also cause the camera to vignette in certain settings. To change the prop, you are basically "tricking' the camera to shoot at a slower shutter speed at the expense of quality (higher ISO.) Some do this with an ND (Neutral Density)which will "stop" the camera down. If you are going to do this, a better solution would be to use a circular polarizer which will also help saturate the blues (sky.)

Good luck!
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Re: ND filter

These videos were taken with and without ND filtering mode using a Cannon S100 Powershot camera which is basically just a small pocket camera that also takes video. So it isn't the best quality, but at least give some idea of the effect. It doesn't use an actual filter, but simulates the effect probably by electronically stopping down the shutter speed similar to what BigR describes.

Without ND:



With ND:
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Re: ND filter

Rezrider wrote:So if you add a filter to remove the prop blur does the frame rate have any effect on the picture? Would the addition of a filter be noticeable when changing from 30 FPS to 60 FPS?
I'm curious. I'm just getting started with video and I'm playing around with different settings.
Are there any other quality issues that are affected by the addition of a prop filter?
Thanks,
RR


It's not just a prop filter, it reduces light to the sensor causing the scan rate to slow down, capturing fewer "slices of time." The prop thus becomes a blur by appearing to move faster from point A to point B along its arc. A higher frame rate will have to scan faster to make more images per second, so your stop-down of light entering the sensor will need to be even more aggressive.... I think.

To be honest, I haven't experimented with 60 fps and a ND filter and compared to the 24fps I normally shoot at.

I stacked my circular polarizer on my ND8 and in addition to a little vignetting like Greg said, I saw pronounced blurring from vibration. The scan rate was so slow that a single point being deflected X amount by vibration turned into blur instead of mild jello. Neither is preferable, but I noticed it changed with RPM, as it's the source of vibration.

I sure would like to see an action cam come out with a global/rotary shutter like my Black Magic has. It makes props look amazing!

Here's an old GoPro Hero 3 video. you can see some of the vibration induced blurring as I get on the power down near the river.



This video by comparison is circular polarizer only, which is only around 2 stops of light reduction. Near the end of a day when the sun is low, it can be plenty to blur the prop.

Last edited by Zzz on Wed Feb 10, 2016 8:44 pm, edited 3 times in total.
Reason: Fixed video link...thanks Blackrock.
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Re: ND filter

2nd vid, broke link
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Re: ND filter

All excellent replies, thanks folks. More research for me to come, coupled with trial and error too!
Thanks again,
RR
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Re: ND filter

There are different "densities" of ND filters. Use the least dark grade that does the job. I experienced "jello effect" with a Go Pro, and fixed it by going to 60 GPS.

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Re: ND filter

First I don't know anything when it comes to videography. But I do know I haven't been happy with using a ND filter and what it does to colors and sharpness. So I decided to try shooting a video at 100fps without the filter to see if the propellor artifacts improved, and they did. Next time I'll shoot at 120fps.

You can see the results at this thread:
https://www.backcountrypilot.org/community/forum/latest/sq2-n-around-16728?start=60#p260192
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Re: ND filter

Hey Rez: I've got ND2, ND4 & ND8 filters (light, darker and darkest) for varying light conditions, but I almost never use anything other than my circular polarizer now. It is about as dark as an ND3 filter would be, but I vastly prefer the results I get with it. It's all subjective though. I'd suggest lots of trial and error with your particular camera, mount and filter combinations and decide what works best for you in various lighting conditions. Like flying itself, good aerial photography is a perpetual learning process.
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Re: ND filter

I've only got what was sold as a "prop filter." I'm pretty sure it's some kind of ND filter.

This thing:

https://buy.garmin.com/en-US/US/shop-by ... 57070.html

After all the comments here I'm going to try and find a circular thingamajigger to try.
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Re: ND filter

CamTom12 wrote:I've only got what was sold as a "prop filter." I'm pretty sure it's some kind of ND filter.

This thing:

https://buy.garmin.com/en-US/US/shop-by ... 57070.html

After all the comments here I'm going to try and find a circular thingamajigger to try.


I have the same virb camera so the filter options are limited as to what you can bolt on. I did see a stick on filter for action cameras but I'm not sure how well those work.
I have gotten rid of the jello effect by going to 60 FPS and tweeking the mount a bit.
It's like Flyhound says, a learning process for sure!
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Re: ND filter

I saw a press fit circular polarizer adaptor on eBay, but I didn't look into it much aside from a cursory search.
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