There are some generally recommended guidelines for how much light intensity cannabis plants should have for optimal growth in different stages of their life (you will see some variation between these recommendations depending on the source, but they are generally very similar.)
IN SEEDLING, 100 TO 300 PPFD (6 TO 19 DLI)
IN CUTTINGS (CLONES,) 75-150 PPFD (5 TO 10 DLI)
IN VEGETATIVE, 300-600 PPFD (19 DLI TO 39 DLI)
IN FLOWER, 600+ PPFD (26+ DLI MINIMUM)
Cannabis is different from typical greenhouse plants in how it thrives under high-intensity light. It's one of the few plants which flourishes growth in full bloom with more than 900 to 1200 PPFD (38 to 52 DLI.)
However, as light intensity (PPFD) increases, photosynthetic rates also increase until a saturation point is reached. Every plant species has a light saturation point where photosynthetic levels plateau. Light saturation normally occurs when some other factor (normally CO2) is limited.
Here's a chart that was produced by the engineers from Fluence Bioengineering, a very reputable lighting company in the cannabis industry, from their guide on Photobiology showing the percentage of relative photosynthesis based on average atmospheric CO2 levels in the air (around 400 ppm.) According to their rhetoric, photosynthesis plateaus in efficiency around 500 PPFD.
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So without augmenting the CO2 levels in your grow environment, photosynthesis reaches a plateau at a certain light intensity threshold. This gives us a guideline for determining how much light is simply "too much light" based on the environment, as well as "how much is not enough." There is literally a point where you're just pushing photons against a plant that can withstand them, but not utilize them.
It's important to note that if temperature, humidity, CO2, nutrients, or even the moisture level of the grow medium are outside the optimum range for cannabis, these attribute to the limitations of photosynthesis.
