The TV series, first of all, has low production values. Higher, surprisingly, than Rumpole of the Bailey, but low nonetheless. Each episode felt like a filmed play. That said, the acting, aside from Father Brown himself and a few side characters, is over the top and not very good. But I'm not sure how much of that is the acting and how much is the writing.
The show does a decent job of adapting the stories for the screen, if by "decent" I mean that it tries to lift from one medium and place almost unfiltered in another medium. For Father Brown, at least, I don't think this works.
The Father Brown stories, at least in my reading, are not very realistic, and I'm not sure Chesterton intended them to be. I should define what I mean when I say the stories are not very realistic. I mean that the characters are more caricatures than anything. Many of them are one dimensional and stand in as "types" of attitudes and worldviews that Chesterton wanted to comment on. This works on paper, but transferring these caricatures to another medium is a bit more difficult.
The ready example from Tuesday night's viewing is the Chesterton story "The Three Tools of Death." In this story there is a character who is always cheerful but not always happy, and Father Brown comments that this is a dangerous mixture. The character is always railing against strong drink (something near and dear to GKC--an early tip-off that everything is not as it seems) and religion (red flag! red flag!), though he is a very charitable man. This character is purposely over the top in the story; Chesterton isn't making a comment on this particular philanthropist, but is commenting on the greater danger of hypocrisy in general. He has purposely drawn an overblown caricature because...I'll get to this in a moment.
But this works in a written story because we can better understand the stark figures of archetypes when we read. In a sense it's more mythological. On screen, however, such bombastic disregard for the complexity of human beings smacks of laziness or, worse, ignorance. It is nearly impossible to suspend disbelief, and it's grating to watch. It rings false. In a written story (at least for me), I can recognize that a character represents something else--almost a metaphor. This is harder to do when the character isn't starkly drawn--it's so-and-so the actor, and the character is before my eyes. (Kurt Vonnegut called movies the most bullying form of entertainment. He said that while there were thousands of versions of Anthony Burgess's A Clockwork Orange floating around in people's imaginations, there was only one Stanley Kubrick's A Clockwork Orange. I tend to agree.)
This archetypal way to tell a story may seem didactic, and in many of the Father Brown stories it is. But there is another writer (Catholic as well) who does the same thing, but to greater effect: Flannery O'Connor. In fact, she even admits to doing so in her essay "The Fiction Writer and His Country" (in Mystery and Manners):
Flannery O'Connor's stories are brilliant, but they are also "unrealistic" in the sense that many of her characters are caricatures, though they are more like the caricatures you see drawn at the fair. Her characters still have depth, but O'Connor's gift, in my opinion, comes in taking a character flaw and putting it under a magnifying glass, like the caricaturist who draws someone with a big nose with a gigantic nose. She draws attention to something that might otherwise be missed: to the "almost-blind" she "draw[s] large and startling figures."
Redemption is meaningless unless there is cause for it in the actual life we live, and for the last few centuries there has been operating in our culture the secular belief that there is no such cause. The novelist with Christian concerns will find in modern life distortions which are repugnant to him, and his problem will be to make these appear as distortions to an audience which is used to seeing them as natural; and he may well be forced to take ever more violent means to get his vision across to this hostile audience. When you can assume that your audience holds the same beliefs you do, you can relax a little and use more normal means of talking to it; when you have to assume that it does not, then you have to make your vision apparent by shock—to the hard of hearing you shout, and for the almost-blind you draw large and startling figures.
I think Chesterton's Father Brown stories are much the same way. If you read Heretics and a collection of Father Brown stories back-to-back, you can see many of the Heretics reappear as victims or, more likely, perpetrators in Father Brown. The stories are unrealistic in that the characters are overblown, but they are hyperrealistic in the picture they paint of sin. I never understood why the villains in Captain Planet seemed to pollute for pollution's sake. Now I understand that CP was trying to teach children that pollution is wrong, and the producers went out of their way to make that point. Chesterton and O'Connor seem to be doing the same thing, drawing "large and startling figures," "shouting" to make the case that we are sinners (something that Chesterton said in Orthodoxy is perhaps the only Christian doctrine for which there is measurable proof). As I said, this works on paper, but not on screen--or at least not in this form. In order to translate the Father Brown stories to the screen, it may take a different approach, like the one Andrew Davies claims to have taken with his BBC production of Bleak House.
(For the record, my favorite Father Brown stories are the first several in The Innocence of Father Brown, especially those featuring Flambeau and especially "The Blue Cross," and "The Chief Mourner of Marne"--one of my favorite stories, period--in The Secret of Father Brown. The Innocence of Father Brown is in the public domain, and is thus available for free download. FYI.)