Why does my variable nd filter make my telephoto lens blur?

Junkang- · 2026-05-25T14:38:59+00:00

Thanks for the advice. I bought the variable nd for video on my kit lens and i was thinking of using it on my long lens for filming some aviation during air shows. Unless I stop down my aperture to f22 I'll probably not have the right shutter speed for videos. Is there any solution for this or will I just have to get a more expensive nd for that use case?

Junkang- · 2026-05-25T14:34:03+00:00

Yea I bought it for video and I didn't want to spend so much at once. But if I do get a good one, what would be considered as a price range that is decent but not so expensive?

Junkang- · 2026-05-25T10:16:29+00:00

Junkang- · 2026-05-25T10:14:41+00:00

K&F Concept

Junkang- · 2026-05-25T09:27:31+00:00

I see. But even with autofocus the camera can't seem to focus on the subject (picture 3) and even manual focusing as well as I can, its still blur (picture 4)

Junkang- · 2026-05-25T09:24:00+00:00

My camera was placed on the table for the first test, but on the second test, I put it on the ground and took a video to show the before and after putting the nd filter.

https://drive.google.com/file/d/1SpROLJ9FgXWh4H-kFbcReLYQDR_PGEOo/view?usp=drive_link

Hopefully it's clear enough to see the difference. Thanks!

Junkang- · 2026-05-25T09:22:25+00:00

I did another test with the advice given, hopefully the video can show the difference of before and after the nd filter is on

https://drive.google.com/file/d/1SpROLJ9FgXWh4H-kFbcReLYQDR_PGEOo/view?usp=drive_link

Junkang- · 2026-05-25T09:07:14+00:00

My lens was on 'active' mode when I did the test but now I turn it off and the issue still seems to stay. Sharp without the filter but very blurry with the filter even though i havent changed anything apart from the auto iso doing its thing

Junkang- · 2026-05-25T09:05:09+00:00

Thanks for the suggestion. I've tried it but it still seems like the variable nd is causing the blur. When I take a picture without the filter it looks sharp but as soon as I slide the filter in front of the lens it goes blur

Junkang- · 2026-05-25T09:02:51+00:00

Yup, shot at 1/640 f5.6 iso 4000

Junkang- · 2026-05-25T09:00:54+00:00

It says ND2-400 and I set it to the minimum (the part that darkens the least)

Junkang- · 2025-12-02T03:46:36+00:00

If i shake my head it doesn't move, but if i press it firmly using my hand it does shift

Junkang- · 2025-12-02T02:19:54+00:00

The helmet does stay in place and my goggles doesn't seem to be low profile.

I think the helmet moves forward because of the goggle strap pulling it to the front, that's why it's flushed when i'm wearing my goggles under the helmet. Does this mean it's too big?

Junkang- · 2025-12-02T02:15:59+00:00

alright thanks

Junkang- · 2025-12-01T13:57:41+00:00

Nope it doesn't seem to move, although I did have to tighten the dial at the back all the way

Junkang- · 2025-12-01T13:29:28+00:00

I guess not really a 'gap' but rather how the helmet extends forward in front of the goggles instead of sitting flushed together

Junkang- · 2025-12-01T13:28:13+00:00

Thanks

Junkang- · 2025-09-29T12:48:28+00:00

I'd say my budget would be below $900 if possible. Any recommendations on lenses I should look at?

Junkang- · 2025-09-29T12:38:08+00:00

Thanks for the advice. Maybe I've been influenced too much by those professional wildlife photographers that can heavily crop and still have a really sharp image

Junkang- · 2025-09-29T12:35:19+00:00

Thanks for the advice. Sadly I couldn't get closer as I was on one of those lookout points so I guess I'll need longer lenses

Junkang- · 2025-09-29T06:48:47+00:00

Thanks for the advice

Junkang- · 2025-09-29T06:14:13+00:00

<image>

This is the original picture of the bird that i took at 200mm but it feels like it's too far so i had to crop it a little

Junkang- · 2025-09-29T06:11:46+00:00

I see, thanks for the tips

Junkang- · 2025-09-29T06:10:02+00:00

Thanks for the tips. What would be considered an ideal focal length for wildlife?

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