IIRC on an old camera increasing the apature size would do that, how to achieve on my phone camera?
It’s not possible to blur the background on a smartphone by opening the aperture because the sensor size in a phone is actually somewhat less than the size of a fingernail.
This small sensor means that to produce a ‘normal’ looking focal length image like the one above – a 4mm focal length lens is actually used. On a ‘full frame’ 35mm camera, this would be insanely wide-angle. The very small sensor in a phone, however, renders an image that is in effect a very extreme crop of the ultra-wide-angle image you would obtain using a 4mm lens on an 35mm ‘old camera’ with a 24×36 mm sensor plane. Here, it looks ‘normal’ on the tiny fingernail phone sensor.
Sadly, it is virtually impossible to blur out the background in a shot like this made with a 4mm lens – unless you somehow could make a lens with an aperture width many times greater than the focal length itself.
Hence, selective blurring software is now used to implement this effect quite successfully in phone – albeit artificially.
*Probably too much detail here than anyone needed 😂 *