One month ago, one Digital Foundry article showed us an anormal "soft blur" on the PS4 version of BF4. As I am really sensitive (allergic) to blur in games, I spend a lot of time during this last month into elucidating this interesting mystery.
After the new definitive DF face-off article in which things were kinda inversed. Now the PS4 look is normal (there is not anymore any anomaly) and even slightly sharper than the X1 version because the sharpen filter on X1 has been removed. We now have 2 perfectly corresponding versions of BF4 upscaled from 720p to 900p into 1080p.
Indeed on the new Face-off we can see, even if it is very hard to notice, that the PS4 version if finally a tad sharper than the X1. Well perfectly normal because of the different upscaled from resolutions. Because those 2 screenshots are really similar, you'll see a very more slightly sharper textures if you look at the left (the building wall and the near rock "wall") or the crane center-right. My point is not to critizise the X1. Those images are almost similar (because of same assets). you'll need to look very closely with a native screen but the textures and assets on the PS4 are a tad sharper. It is normal, the (again, very slight) blur on the X1 is created by the stronger upscaling.
But where did this "soft blur" comes from in the Digital Foundry preview article? here the PS4 "soft blurred" screenshot of the preview DF article:
At first you'll think that the brightness is different, it is, and it has maybe caused the anomaly. But now compare the 3 screenshots during long minutes if necessary. If you mainly compare the left close textures of the walls (or the crane at the center-right too) you notice that, in fact, the textures of the old PS4 from the botched preview appears to have exactly the same relative "soft blur" of the X1 compared to the new PS4 capture.
Again. For an untrained eye. Those 3 images, except for the brightness, will look the same. But for sensitive to blur eyes like mine. It is obvious.
The capture of the PS4 version in the preview has the perfect same upscaled blurriness of the 720p X1 new face-off screenshot.
As I read in some interviews that if you set your PS4 output to 720p it will downsample any existing resolution produced by the game to 720p but let the game produce its higher resolution internally, the mystery is maybe solved.
Richard Leadbetter has (unintentionally?) captured 720p downsampled image of BF4 (then upsampled to 1080p) from the 900p PS4 version.
Remember that's it is just a theory. But this theory just explains everything we saw in the infamous botched DF preview.
If the theory is true it doesn't explain how it could have been possible. Maybe it was done internally in the game. I don't know. But this 900p to 720p to 1080p upscaling madness explains perfectly the "soft blur" noticed in the Digital Foundry preview article.