Printable slids have the effect of a blurred background comparable with capturing a portrait or a macro photography. This effect intensifies the depth effect by sharply separating the foreground and the background from the captured object.
Under the condition that the captured object did not move around during capturing, it should be sharp.
The farther any image point from the axis that you are moving around, the blurrier it will be.
This needs to be taken into account during capturing and it must be checked that the object being captured is sharp in the draft preview that you see when placing on filters after capturing or while viewing the printable slid on the device’s screen.
Remember that it is a draft preview created for quick operation; meanwhile, the final image that will be printed will be much higher quality (the maximum quality that the resolution on your device’s camera permits) and will have a very smooth blur unlike what you see in the preview.