The indefinite and definite articles are often omitted in signs, newspaper articles, and advertisements. This is also the case for the advertisement featured above. The indefinite article could have been used:
Shot with an iPhone 6
The definite article would have sufficed as well:
Shot with the iPhone 6
Use the indefinite article (a or an) or the definite article ( the) when it is possible to generalize about an invention ; or the name of a manufactured product, as an entire group or by each individual case. (Rule 6.6)