Autofocus issues, only with ND filters attached

[christiand]

Today, i flew at this amazing place in here in Switzerland called the Landwasser Viadukt. When i got back this evening, and looked at the footage, I noticed that a lot of the clips where a bit washed out. I compared to older footage that still was on my SD card, and if I had not used ND filters, or if there was an extreme amount of light, autofocus was never an issue.

I tried to see only if it was an issue only when using ND filters, or if it was a general autofocus issue. I'm always pretty cautious to tap and focus everytime before i start recording, but this evening i noticed that the AF C setting was on, instead of just.

Just like any other normal human being, i hate when my footage gets ruined. I use the TACO RC ND filters. I guess it has nothing to do with ND filters. Is it just because of the stupid AF C setting, or what might i be doing wrong?

 

[Lake_Flyer]

I feel your pain. I hate it too to find out it wasn't 100% focussed. I tend to forget to tap the screen to focus. I'm so used to an Inspire1 X3 camera with fixed focus.
i don't think ND filters would hinder autofocus, unless they are distorted or warped.

 

[christiand]

I feel your pain. I hate it too to find out it wasn't 100% focussed. I tend to forget to tap the screen to focus. I'm so used to an Inspire1 X3 camera with fixed focus.
i don't think ND filters would hinder autofocus, unless they are distorted or warped.

Thanks for your reply. Yeah, it really sucks!

I went back to the same spot again today, to refill the footage. This time, I used a different ND filter, and the result wasn't really that different.
Looking at the footage again, it struck me that it was the same features that were blurry - the trees and the cliff was blurry, where as the railway, the bridge and the mountain in the background was all perfect. I don't know if the compression of the Mavic simply is too aggressive?

I have uploaded a sample file to youtube here:

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[forsythem]

I've been starting to play with my MP video setting, and post editing, to try and remove the same things you're talking about. Have yet to get it right.

Read about and played with D-Log, D-Cinelike, and have been using fixed ISO/shutter speed with ND filters as recommended, and always end up still having those blurry patches, in trees and grass that don't have high contrast.

 

[Lake_Flyer]

I set sharpness +1, keeping the rest on zero, usually D-Log and manual exposure. In post I play with the contrast and sharpness until aliasing is minimal. It's always a compromise.

 

[4wd]

There wasn't any need for the NDs with light levels such as that Switzerland scene.
The result has been underexposure and noise reduction kicking in rather than out of focus.
With the NDs on it would still have been better if exposed correctly.
Regardless of what video 'experts' think about frame rates and shutter speed, with this fixed aperture camera, you will get consistently better results using auto exposure, and unless you want it to look dark have it set on +0.3 to +1.0 as a guide.
+1 sharpening is a good tip but you generally need to apply some noise reduction when editing.
With 4K especially this will take a while on less capable computers.

 

[christiand]

There wasn't any need for the NDs with light levels such as that Switzerland scene.
The result has been underexposure and noise reduction kicking in rather than out of focus.
With the NDs on it would still have been better if exposed correctly.
Regardless of what video 'experts' think about frame rates and shutter speed, with this fixed aperture camera, you will get consistently better results using auto exposure, and unless you want it to look dark have it set on +0.3 to +1.0 as a guide.
+1 sharpening is a good tip but you generally need to apply some noise reduction when editing.
With 4K especially this will take a while on less capable computers.

Thank you for your thorough reply and explanation!

Just to give you some info on the shutter speed and the ND filter: I used an ND8 in the above shot, after trying with an ND16 the first day. I remember that the Shutter speed was always between either 100 or 200 and the ISO was always always 100. If I set the camera to auto, it would go to a shutter speed of 100 and an ISO of 200, which was why I did not use the aut exposure.

For me, it doesn't make a lot of sense that the noise reduction would kick in, since I was on ISO 100. I agree with you that the shot is dark, but the auto exposure wanted it to be way darker, because of the high dynamic range scenery, with the mountains in the background.

 

[4wd]

With this camera, Noise Reduction starts to affect darker areas and is applied automatically unless you set sharpening to +1 At zero you see it some times more than others, worse if light is poor and not much contrast e.g. overcast sky.
Obviously that's not ideal but we have to work around it.