If he's going out for the sole purpose of photography, then yes it would be an issue legally.

However, the catchily named Health Protection (Coronavirus, Restrictions) (All Tiers) Regulations 2020 don't define "local" nor "exercise". As long as he is "exercising" and/or "food shopping" in England then there isn't a problem by law.*

I'm not exactly impressed that people are still going out to take photos, perhaps it's morally wrong, but there's certainly nothing wrong legally - as long as he's doing what's allowed in the regulations too.

*GOV.UK shows heavily worded (optional) guidance mixed with law. If you're wanting to check the actual law, visit legislation.gov.uk.