A method of operating a furnace having a plurality of burners, each of the plurality of burners having flow rates associated therewith, the furnace containing a plurality of process tubes, the method comprising: (a) selecting target temperature criterion for the plurality of process tubes; (b) measuring first temperature information comprising data for each of the plurality of process tubes at a first operating condition wherein the first temperature information for the plurality of process tubes is measured by: capturing a first plurality of images of an interior area of the furnace, at least some images of the first plurality of images being associated with different portions of the interior area of the furnace, wherein each image of the first plurality of images comprises first pixel data associated with a portion of the plurality of process tubes; and processing a portion of the first pixel data to obtain the first temperature information for the plurality of process tubes; (c) providing an estimate of a mathematical function characterizing a relationship between burner flow rate changes for two or more of the plurality of burners and individual temperature changes for at least a portion of the plurality of process tubes; (d) calculating a first target flow rate solution set having solutions for the two or more of the plurality of burners consistent with conforming temperatures of the plurality of process tubes to the target temperature criterion for the plurality of process tubes using the estimate of the mathematical function and the first temperature information for the plurality of process tubes; and (e) adjusting a first valve upstream of at least one of the two or more of the plurality of burners to change at least one of the flow rates of the two or more of the plurality of burners in accordance with the first target flow rate solution set wherein the first valve is not upstream of all burners of the furnace. (a) selecting target temperature criterion for the plurality of process tubes; (b) measuring first temperature information comprising data for each of the plurality of process tubes at a first operating condition wherein the first temperature information for the plurality of process tubes is measured by: capturing a first plurality of images of an interior area of the furnace, at least some images of the first plurality of images being associated with different portions of the interior area of the furnace, wherein each image of the first plurality of images comprises first pixel data associated with a portion of the plurality of process tubes; and processing a portion of the first pixel data to obtain the first temperature information for the plurality of process tubes; capturing a first plurality of images of an interior area of the furnace, at least some images of the first plurality of images being associated with different portions of the interior area of the furnace, wherein each image of the first plurality of images comprises first pixel data associated with a portion of the plurality of process tubes; and processing a portion of the first pixel data to obtain the first temperature information for the plurality of process tubes; (c) providing an estimate of a mathematical function characterizing a relationship between burner flow rate changes for two or more of the plurality of burners and individual temperature changes for at least a portion of the plurality of process tubes; (d) calculating a first target flow rate solution set having solutions for the two or more of the plurality of burners consistent with conforming temperatures of the plurality of process tubes to the target temperature criterion for the plurality of process tubes using the estimate of the mathematical function and the first temperature information for the plurality of process tubes; and (e) adjusting a first valve upstream of at least one of the two or more of the plurality of burners to change at least one of the flow rates of the two or more of the plurality of burners in accordance with the first target flow rate solution set wherein the first valve is not upstream of all burners of the furnace.