You have options through a robot job or through the ladder.
To convert 8 bit to 16 bit:
DIN B000 IG#(1) this is the LSB.
DIN B001 IG#(2) this is the MSB.
SET D000 B001 copies value is B001 to D000.
MUL D000 256
ADD D000 B000
The MUL and ADD could be combined with the SET by using the EXPRESS tag.
SET D000 B001x256+B000
You may also need another MUL to shift the decimal point since a P-Var goes 4 decimal places.
Also another bit to denote positive or negative, MUL by -1.
Through the ladder you would write logic to trigger the camera and place the value into a M-register. The register data could be retrieved into a robot job and converted using the GETREG instruction.