For this production, many photos would have had to be taken, costing money in materials, a photographer and actors waiting around doing nothing for hours. The time would be taken up by trying to firstly get a good pose of the 5 actors, then having to waiting for each photo to develop, and only then knowing if it developed well enough to make out all the actors clearly enough. It probably saved them a lot of time and money to edit and appropriately age a modern photograph digitally, then reproduce it onto glass. For filming you need at least half a dozen identical copies of any graphic prop that might get significant screen time like this, incise one gets scratched, broken or lost. Continuity is vital and as stated above, ambrotypes are hard to reproduce from the original.
This is however, a beautifully designed, and period appropriate, graphic prop that did its job well, capturing a significant moment in time for the character of Wonder Woman, played by Gal Gadot, and hit all the right emotions when she sees it after so many years. We really feel Wonder Woman’s nostalgia and love for the characters depicted in this ambrotype photograph.