Dress code for a passport photo

This morning I left my apartment early with a mission -- to get passport photos taken for my visa application. Luckily there's a photo shop in the ABS-CBN building. (A person could actually live quite well without leaving the ABS-CBN compound, which includes multiple restaurants, a cafeteria, Starbucks, a bank with an ATM, a gym, a flower shop and a place to get a foot massage).

I walked in and asked the clerk if it was too early to get a passport photo taken.

Clerk: Come back in an hour.
Me: OK
Clerk: And with a collar.
Me: What? The photo is in color?
Clerk: A collar.
Me: A collar? I have to wear a collar?
Clerk: Yes.
Me: A shirt with a collar? Really? Why?
(I was wearing a tasteful, sleeveless shirt with no collar.)
Clerk: You need a collar.
Me: Can you show me an example?
(The clerk pulls out a passport photo of someone wearing a shirt with a collar.)
Me: OK. Thanks.

I was more upset about walking back home in the heat to change my clothes than the fact that I had to change my clothes for this man to take what is essentially a mugshot.