Which national flag did the Australian Flying Corps use in World War I? The Australian national flag wasn't formalised until 1953 with the Flag Act and up until then a mixture of the British Union Flag, the defaced Blue Ensign and the defaced Red Ensign was used. Early photography allows us to pick which ensigns were blue and which were red despite being black and white because of the orthochromatic technology used in making photos.
Note the dark flag in the bottom right. It is a red ensign. Orthochromatic film makes warm colours appear black and cool colours appear pale. The top flag looks to be a blue ensign. This is pretty normal for World War I as the blue flag represented government and the red flag was the civil flag. Formal military functions often mixed all three.
A good example of the orthochromatic effect is the Belgian roundel which is black, yellow and red. On film it appears as a black disc.
