You should ask the person if you can take some pictures out of common courtesy especially when they are sitting right there......if it was me and you just waltzed up and started taking pictures I would be like WTF????
in this day and age, it could be argued that when you go to a car show people will take pictures of your car
and if you leave the hood up, they may take picture of under your hood
would it be proper etiquette to ask permission?
sure
would permission be implied by the open hood?
sure