I've come up with a different scoring approach to most. My rules are:

1. I need to have seen at least three films by a director for them to be eligible.

2. For each director I take the average of their best seven films that I've seen and rated.

3. If I have seen fewer than seven films, then I give them a notional score of ★★½ for each phantom film they are missing. In this way each director is assessed on the basis of seven films, including up to four phantoms.

For example, I've seen six films* by Asghar Farhadi, so he gets one phantom film notionally scored at ★★½. His top seven then becomes:

A Separation ★★★★★
About Elly ★★★★½
Fireworks Wednesday ★★★★
The Past ★★★½
Everybody Knows ★★★½
The Salesman ★★★½
Phantom Film 1 ★★½
Seven film average score = 3.79.

I’ve sorted the list using the best seven films average. In the case of ties, the first tie-breaker is based on which director has the most ★★★★★ films, and it there is still a tie then the all films watched average determines the order.

If you’re curious to know my reasoning for this approach:

1. Many directors with a large filmography will have some duds. For example, Hitchcock was prolific, but his quality was variable. My view is that his lesser films shouldn’t detract from his standing as a great director. Hence my rule to judge each director on only their top seven. 

2. Seven films is my subjective yardstick for what constitutes a substantial body of work. It could be more, it could be less, but I've drawn a line in the sand at seven. I figure that if a director can deliver seven masterpieces then they are a cinematic deity of the highest order. I am yet to award any director with seven ★★★★★ films (Kubrick is close). If one day I do, then I might shift the yardstick out to eight films. 

3. Not every top director has made seven films, or if they have, I may not have seen enough of them yet. But if what I have seen of theirs is fantastic, then I want them to play in my league. 

4. A notional score of ★★½ for each phantom film is a way of handicapping these directors. Their overall seven-film average score will be below the average score of the films of theirs I have seen, but they’ve still got something to prove and I don't want to give them the benefit of the doubt and assume they’ll maintain their form. If Farhadi comes up with a masterpiece for his seventh film, then this will replace his notional ★★½ rated phantom film with a higher score and he will deservedly climb up the league. But if, instead, he turns away from film-making to try his luck at golf, or hands in his auteur’s badge and becomes a by-the-numbers action director, then sorry Asghar, you’ll have reached your peak in my league and you will gradually slip down the league and into oblivion as other directors overtake you. 

5. I do have to draw a starting line somewhere, so a minimum of three films is the entry criterion. Three good films is enough for me to think they're a real contender and deserve to enter the fray. Time will tell if they can shine on, or whether I’ll look back at them as a briefly glorious shooting star in the pitiless firmament. 

6. I played about with a bunch of different rules, but I felt that this method was the best at mirroring my subjective preferences. In other words, I feel fairly comfortable with this list.

Thanks for reading.

* Update, I’ve now seen 7 films by Asghar Farhadi - he didn’t throw it all in for golf and he continues to move up my league.