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Partial Focus Issue (After Firmware Update)

oJFw

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Hi all,

Hoping someone here will be able to shed a light on what’s happening to some elements of my footage.

Yesterday I installed the new firmware and the DJI GO 4 app and took my Mavic out for a spin.

Once I got my video footage back to the editing suite I noticed some really awful looking background/ details in a bunch of my shots. Please have a look at the screen grabs I took from the video file attached. (You might have to fullscreen them to notice.) If you look at the background, especially the trees, you’ll notice how they’re completely void of details…and really just look like a splash of green.

Wondering if this has something to do with how I focus. I tend to hit the C1 button for infinity focusing before starting any recording. Up until recently I got well-focused wide shots out of this, however suddenly this seems limited.

I was shooting at the highest resolution in D-log and at -2 -1 -1.

I doubt there’s an issue with my Mavic, but can’t quite put my finger on where the issue is coming from.
Any help would be hugely appreciated. Thanks in advance!


Oliver
 

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Sisyphus

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Are those the full frames, or are they cropped?

I think the softness/blurring you are seeing is due to JPG compression. I have compared JPG and raw (DNG) images of the same scene and found that the raw frames have MUCH more detail. Of course, the files are much larger and take much longer to record because they are lossless, uncompressed formats.

There are other benefits to shooting raw, such as being able to non-destructively edit the image, change the white balance, contrast, saturation, and sharpness, and recover blown highlights or shadows (in some cases). DNG is the "digital negative" format developed by Adobe, and is similar to other raw formats from Canon, Nikon, etc.

Try this: in your camera settings, set to record JPG + RAW. Then compare your images at 100% magnification. You'll be convinced.

There are various free and paid apps and programs that can read, view and edit DNG files. For Windows or Mac computers, I recommend Raw Therapee. For Android devices, try Snapseed. These options are free. You can also download and install the codec for DNG files from Adobe's website (also free). Installing the codec on your Windows computer will allow your machine to display the image thumbnails and allow you to preview the images. Different OSs may have the DNG codec built in. Adobe Lightroom and Photoshop will read and edit DNG natively.

Working with any of these raw editors entails a learning curve similar to learning video editing/grading software like Resolve. But it will make a huge difference in your images.
 

Sisyphus

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Oh, wait. Are these screengrabs from video? What I said above applies to still frames. Video shot by Mavics and Phantoms is always (very) compressed. DJI does offer an expensive raw video camera for some of their high-end drones.
 

oJFw

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Oh, wait. Are these screengrabs from video? What I said above applies to still frames. Video shot by Mavics and Phantoms is always (very) compressed. DJI does offer an expensive raw video camera for some of their high-end drones.
Thanks for your tips and yes, I was referring to video footage. Sorry my original post didn't make that entirely obvious...

Totally get what you're saying re compression. But it is odd how terrible those elements now look in my footage. I exported it to screen at very high res on my 4k TV and those trees and some of the background made the overall image just really appalling.

Plus other elements aren't as compressed, so I wonder whether I'm doing something wrong with my camera set up/ focus.

Thanks anyway matey.
 

Sisyphus

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And you exported from the micro SD card, not your mobile phone, right? The cached version on your phone is always terrible. I'm sure you know this, but just in case...

I'm not convinced that D-Log is the best mode to use in most situations. Others have pointed out that D-Log footage seems to knock the contrast down so much that often only half the histogram is used. Of course, you can stretch it back out in postprocessing, but that is not the same as recording the full range of contrast in as many steps as possible in the first place. In those cases, D-Log may actually record less useful data than None, -2,-1,-1.

I wish DJI would offer an option to completely eliminate sharpening in the recorded video. Even at the minimum setting, the sharpening is way overdone...and there's no way to reduce it in post.

Overdone sharpening and egregious compression are the main reasons that I mostly shoot stills with my Mavic. At least with RAW stills, I can avoid both.

The Mavic camera is reasonably decent. It's the compression and sharpening that messes up the recorded JPGs and video.
 
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halley

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So I'm confused. You set -2 to sharpness, then wonder why sharpness is so poor that the compressor turns your images to watercolor?
 

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So I'm confused. You set -2 to sharpness, then wonder why sharpness is so poor that the compressor turns your images to watercolor?
The problem is that the sharpness is WAY overdone. It is an electronic digital manipulation that is done to create the perception that the image is sharper than the optics actually provide. In simple sharpening algorithms, like the one used in DJI phantoms and the MP, this is done primarily by overboosting contrast at edges of objects. In other words, if you look at the edge of a dark object on a light background, the background is actually lighter in the first pixels adjacent to the dark object. If you look closely at the video images from your MP, you'll see this.

More sophisticated sharpening algorithms (which require more processing power) are able to eliminate the "halo" effect, while still increasing the perceived sharpness.

The problem with oversharpening in the video and JPG images is that, once "baked in" to the image, there's no way to remove it in postprocessing.

I'm not saying that DJI shouldn't include sharpening in the processjng of the videos and JPGs. Rather, I'd just like to be able to turn it off so that we can decide for ourselves if/how much we want, and can apply more sophisticated algorithms in post processing if desired.

Make sense?
 
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Sisyphus

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Put another way, sharpness at -2 doesn't soften your image, it just applies less of a quick and dirty (and to my eye, unappealing) sharpening algorithm - which I cannot undo.

And nothing cures an unfocused image.
 

oJFw

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And you exported from the micro SD card, not your mobile phone, right? The cached version on your phone is always terrible. I'm sure you know this, but just in case...

I'm not convinced that D-Log is the best mode to use in most situations. Others have pointed out that D-Log footage seems to knock the contrast down so much that often only half the histogram is used. Of course, you can stretch it back out in postprocessing, but that is not the same as recording the full range of contrast in as many steps as possible in the first place. In those cases, D-Log may actually record less useful data than None, -2,-1,-1.

I wish DJI would offer an option to completely eliminate sharpening in the recorded video. Even at the minimum setting, the sharpening is way overdone...and there's no way to reduce it in post.

Overdone sharpening and egregious compression are the main reasons that I mostly shoot stills with my Mavic. At least with RAW stills, I can avoid both.

The Mavic camera is reasonably decent. It's the compression and sharpening that messes up the recorded JPGs and video.

Yup, exported from the SD card. (My iPhone doesn't support 4k footage.)

The new D-Log seems vastly improved, so will have to have a play with different settings re sharpness, contrast, saturation and see what comes of it.

Still wondering if I'd achieve better results by going with 'tap to focus', rather than infinity focus via c1 on the controller.

Agree, the camera is reasonably good. Stills (in RAW format) tend to turn out really nicely. And I do have a bunch of 4k footage I'm very happy with. Suppose it's just some particular set ups I need to grow aware of.
 

Sisyphus

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Yup, exported from the SD card. (My iPhone doesn't support 4k footage.)
...
Still wondering if I'd achieve better results by going with 'tap to focus', rather than infinity focus via c1 on the controller.

Agree, the camera is reasonably good. Stills (in RAW format) tend to turn out really nicely. And I do have a bunch of 4k footage I'm very happy with. Suppose it's just some particular set ups I need to grow aware of.
The video that's streamed over the air and cavhed in your phone is 1080 HD max, even if your phone supports 4K.

In general, I recommend tap to focus each time the distance to your closest subject changes. However, the distance to the closest subject in the images you posted appears to be far enough away that infinity focus should do a good job if you're actually getting infinity focus. But you may not be getting that. There are some recent YouTube videos that claim (with recent firmware) the MP autofocuses at center frame each time the MP stops moving. I haven't confirmed this myself, but it seems like a bad idea. If your closest subject is at a different distance than whatever is at center frame (particularly if it is closer) when this autofocus adjustment occurs, it will be out of focus. Unfortunately, DJI's documentation of the focusing behavior is scant, so trial and error is needed.

I don't think focus issues are the reason for what you're seeing in your video screengrabs, though. I think it's just compression artifacts. Some objects just really seem to get crushed by the compression - trees, especially.

Recording 4K video on a SD card in real time is a tall order, requiring huge bandwidth. By compressing the video, DJI is able to achieve it, but with significant and irrecoverable loss of quality. In some cases, we might be better off recording in 1080 or 2.7K, especially if we are going to sample down to lower resolution in post processing anyway. I intend to do some testing of this, but haven't yet.

If anyone out there can explain exactly how autofocus behaves in the latest firmware, please jump in here.