[Q : Picture resolution taken built-in Instagram mode on camera is low and fixed. Why is this?]
A : New ‘Instagram mode’ on Samsung Galaxy S10 allows users to directly upload pictures from the camera app to their Instagram story.
Based on internal policy of Instagram, high resolution photo is automatically compressed to limited resolution(2020x1080) when you want to upload the picture on Instagram story. Therefore user cannot select picture resolution using not only built-in Instagram mode on camera app but also Instagram app.