Good to see him again! It's always tricky to get focus on energetic dogs. It's not possibile with an iPhone to set the f-stop but remember to leave a little bit more open than you would need with a human due to their big noses :) I'd start at f5.6 with your main camera if you plan on doing something similar and make sure you have a lot of light.
I look forward to seeing you in future challenges! |