An army corporal accused of secretly filming a woman while she showered at an Adelaide Hills barracks has been acquitted in the Adelaide Magistrates Court.

Nathan William Freeman was alleged to have planted a tiny camera in the women's shower block at the Woodside army barracks in December 2009.

The victim handed in the device to lost property, not realising it was a camera.

Freeman was charged with engaging in indecent filming of a person other than a minor.

During the trial, the court heard the footage in the device shows a man wearing a military identification card and military uniform placing it in the shower and adjusting it.

Magistrate Kym Boxall rejected claims by the defence that the card may have been stolen and worn to disguise the identity of the perpetrator.

"I find that rather the actual perpetrator inadvertently filmed himself, including the identification card, and thereby almost gave himself away," he said.

Mr Boxall described the filming as a "serious and disgusting act" of "great concern to everyone at the base."

"There is no doubt that a crime of indecently filming a female person was committed at Woodside Army Base using a small filming device that looked like a vehicle remote control unit," he said.

However, he said he was not satisfied beyond reasonable doubt that Freeman was the person who planted the device.

Freeman was found not guilty and the charge was dismissed.

The matter will return to court next month to determine whether police should pay Freeman's legal costs.