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Slow motion creates a zoom
159 5 5-23 23:38
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Weev
lvl.1
Switzerland
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Hi all,
I had the last update of my osmo pocket yesterday just before using it in slow motion mode.
I didn't use this mode a lot before, but it creates a zoom effect and the video is not as smooth as it should be, with some noise.
ok for the noise maybe I was using a little too strong filter with auto iso, but for the very noticeable zoom... is this normal?
I don't remember noticing such a zoom the previous times I used slow-motion.
Cheers,
Yves
5-23 23:38
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CemAygun
Second Officer
Turkey
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Hi Yves,

Slow motion cannot use the full sensor (at least so far), so it gets a 1080 crop from the center of the sensor, which is roughly 4 times the resolution causing the "zoom" effect. It has always been like that.

When it comes to the noise; bear in mind that slow motion mode at 120fps needs to expose every frame 4 times faster compared to a 30fps video, so it needs all the light it can get. Even natural, outside light might not be enough to push the ISO (and the noise) down at those speeds some times.

Hope this helps,
Cheers,
5-24 00:27
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Weev
lvl.1
Switzerland
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thank you for this clear explanation, is makes perfect sense.
Cheers,
Yves
5-24 02:06
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DJI Gamora
Super Moderator

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Weev Posted at 5-24 02:06
thank you for this clear explanation, is makes perfect sense.
Cheers,
Yves

Hi, there Weev. I'm sorry that I was unable to help you with your problem and we're glad to know that you already manage to sort out the issue using the suggestion of our beloved DJI member. Should you have any other concerns please don't hesitate to reach us. Thank you and have a wonderful day.
5-24 10:17
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STRIDE8
Captain
Flight distance : 515331 ft
United States
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CemAygun Posted at 5-24 00:27
Hi Yves,

Slow motion cannot use the full sensor (at least so far), so it gets a 1080 crop from the center of the sensor, which is roughly 4 times the resolution causing the "zoom" effect. It has always been like that.

That's a great explanation.  so should the slow motion mode be used at the lowest ISO possible?
5-24 12:19
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CemAygun
Second Officer
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Well, as a rule of thumb any and all modes should be used at the lowest ISO possible. The digital ISO is a signal amplification in it's simplest description; which basically multiplies the low sensor readout ( = low light input) but along with it any noise that exits in the system also gets amplified (hence the grainy videos at high ISOs).

Ideally we always aim for "double the frame rate" shutter speeds, which produce the most perceptually pleasant videos. This puts the perfect shutter speed for the 120fps OP slow motion video at 1/240th of a second (pretty close to 1/250th of a second shutter speed in the full stop chart). It is not very easy to attain proper exposure at those speeds with low ISOs unless there is a lot of light. This is why one might end up increasing the ISO, just to make sure the videos are properly exposed (not too dark) albeit grainy.

I personally look at the ISO setting as a workaround, a "band aid" solution to a problem (not having enough light for the required exposure time) rather than a preference; and try to keep it as low as I can get away with...

Hope this also helps,

Cheers,
5-24 20:31
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