The recipe calls for 1.25Lbs of fresh plum tomatoes. They are to be simmered with hydrated whole dried chiles and other seasonings for 20 minutes, then pureed and strained.
This time of year it's nearly impossible to find fresh tomatoes (plum or otherwise) that have any flavor at all and I can't see any reason not to use what I already have on hand – all the Hunts Diced Tomatoes I could possibly need before spring. As most diced tomatoes do, these contain calcium chloride to preserve the shape of the dice, but it won't matter since the sauce/marinade is to be simmered, pureed and strained anyway. What concerns me is the second ingredient after tomatoes – tomato juice.
EDIT: The core of the question is how much "extra" liquid is typically used to can tomatoes? It would seem that lightly (as in no "pushing" on the solids) strained tomatoes would have approximately the same liquid to solid ratio as fresh, is that right?
Best Answer
Most savory cooking simply isn't exact enough to worry about this in any level of detail. Tomatoes are extremely high in water to start with, even whole, about 94%.
Savory recipes can be adjusted easily by adding liquid or reducing in most cases, if it does matter.
Simply use the entire weight of the can content in substitution for the weight of fresh tomatoes, and adjust the recipe as needed based on the outcome.
This is educated speculation, but note that while tomato packers may pack the diced tomatoes in juice, that juice almost certainly comes from the core of the very same tomatoes whose flesh was diced. Otherwise it would be less economical to pack them that way, and they would pack them in water.