Keeper rate math: 24 eight-second Seedance 2.5 clips at 25% to 80%

Sume bills every generation, kept or not, so the cost of 24 usable 8-second Seedance 2.5 clips at 720p depends on your keeper rate. At 40 percent keepers you need 2.5 takes per keeper, 60 takes in all: 60 x $4.6224 = $277.34, against $110.94 for 24 takes. A 480p draft pass followed by one final at 720p is cheaper only when the keeper rate is below about 53.5 percent.

The formula

Expected takes per keeper = 1 / k, where k is the keeper rate. A 720p take is 8 x $0.5778 = $4.6224; a 480p draft is 8 x $0.268677 = $2.1494. Direct cost per keeper = 4.6224 / k. Draft route = 2.1494 / k + 4.6224, assuming a draft you approve always gives an acceptable final.

The break-even

Set 4.6224 / k = 2.1494 / k + 4.6224. Then 2.4730 / k = 4.6224, so k = 0.535. Below a 53.5 percent keeper rate, drafts at 480p save money; above it, go straight to 720p. At 25 percent the draft route saves 24 x ($18.4896 - $13.2201) = $126.47.

The assumption is the weak point. If a good draft does not guarantee a good final, add the final's own retake risk, and the draft route loses its edge.

The same test at 1080p

At 1080p the numbers are larger and the break-even moves. A take is 8 x $1.42155 = $11.3724, and a 720p draft is $4.6224. At a 50 percent keeper rate, going straight to 1080p costs $22.7448 per keeper. Drafting at 720p and finishing once at 1080p costs $4.6224 / 0.5 + $11.3724 = $20.6172, a saving of $2.13 per keeper.

The break-even is (11.3724 - 4.6224) / 11.3724 = 0.594, so with a keeper rate under 59.4 percent the 720p draft pays. The wider the price gap between draft and final, the more often the draft pays.

The rule of thumb: the draft pays when its price is a small fraction of the final and your keeper rate is below the fraction (final - draft) / final.

Measure your own rate

Count takes and keepers over your last 20 clips and plug the ratio in. A rate from five clips is noise. Keep the arithmetic in a spreadsheet, not a guess; at 24 clips the difference between a 40 percent and an 80 percent keeper rate is $277.34 - $138.67 = $138.67.

A worked log

Here is what a log should show after a real run of 24 clips.

• Takes made: 60. Keepers: 24. Keeper rate: 24 / 60 = 40 percent.
• Direct 720p cost: 60 x $4.6224 = $277.34.
• If the run had used 480p drafts: 60 drafts x $2.1494 = $128.96, plus 24 finals x $4.6224 = $110.94, for $239.90, a saving of $37.44 over direct.
• Update the rate after every campaign; it changes with the prompt style and the model.