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Camera scaling oddities

I have been experimenting with the Nokia 8 camera this weekend. When videoing at 1080p it seems to be using nearest neighbour interpolation. I recorded a hockey match and the almost horizontal distant poles of the goal cross bars appeared and disappeared rapidly as the camera moved. I wonder if internally 2160 lines are being sampled and every other one is being discarded to make the recording. The photos have similar odd issues. If you compare the field of view left to right of a landscape shot in 4:3 and 16:9 at maximum resolutions (4160 v 3840 pixels) you'd expect the 16:9 shot to have slightly less in (take two photos and compare objects at the far left and right to see this). However the 16:9 image has slightly more in but spread over fewer pixels left to right. This means there can't be a 1:1 correspondence between camera sensor pixels and final image pixels. Whatever interpolation scheme is being used will be artificially softening the image.

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 I've taken some photos and made a composite image that is 4160 pixels wide which shows the above effects.


image


There are 4 slices taken from four photos. From top to bottom: 4:3 in camera app, then again in the Open Camera app, then 16:9 in the camera app, then again in the Open Camera app. In both cases the Open Camera app seems to have a slightly wider field of view than the inbuilt app, even though the final image pixels are the same. I've right aligned everything so the bench is on the right. If you look at the bush on the far left of each strip you can gauge how much is showing.


There can't be a 1:1 correspondence between the output of the camera and the final file that makes it to storage. The two apps have different fields of view too. I'd expect the 16:9 image to be slightly wider in pixels than 4160.


Another example, use the front camera and take a photo of your face at arm's length. Do this for 16:9 and 4:3 sizes. Then look at the images 1:1 on your screen or computer. Surely your face (in the central portion of the image) should be the same size? It isn't! the 16:9 image is smaller! Why? Why through away detail by selection 16:9? Has someone typed the wrong numbers/aspect ratios into the driver files?

 This is a link to the example photo.

I've done some more controlled tests! I am now wondering if leaned back a little with the Open Camera test as when I repeat this with the camera fixed the fields of view do match. However there does appear to be more in the 16:9 shots than the 4:3 ones, slightly, but over far fewer pixels, so something odd is going on the the scaling. I took four photographs of a tape measure. I'll post links when I get a minute...

Here are some photos of a tape measure. The 16:9 shots seem to have an extra millimetre visible on the scale, but this wider real life image is imaged over 3840 pixels, whereas the 4:3 images have a slightly smaller field of view horizontally but spread over 4160 pixels. Why is quality reduced on the 16:9 shot?


4:3 Nokia Camera

https://photos.app.goo.gl/oxbI8iqLYJwkyKgF3


4:3 Open Camera

https://photos.app.goo.gl/vWCJE4mcEp03LFIF2


16:9 Nokia Camera

https://photos.app.goo.gl/2yzXRvXeStiBNEiW2


16:9 Open Camera

https://photos.app.goo.gl/sOOO4zFjbODnKoUw1

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