Thanks @Alexi_Maschas for taking the time to share this info. Agree that the parameter to consider implications of variations would be the exposure time.
Same here. The design with the current mirror first came about from the difficulty to source the common switching regulators around the pandemic. I was not familiar with these particular ones either.
The ones used in the popular boards however (fentobuck for example AL8805, and some other boards/ICs) had the particular inability to regulate below 20% of max current. A second deal breaker (part availability was first).
It hasn’t been hard, but maybe so. The LM3409 (as other buck regulators) have the similar limitations on deal with the low current segment of the voltage control (see datasheet Figure 12. Amplitude Dimming Using IADJ Pin, between 0 and 0.3), and that will not work well with mid/low current LEDs (100 mA Absolute Max in my case). Essentially the lower portion of the DAC 16 bit, which are required by the exponential nature of light perception, are truncated by the buck.
Undoubtedly the current mirror is -for me- a well known and tested topology. (first design round in this post around the pandemic).
In the context of mid-power LEDs with a rolling shutter stop-motion application, linear is as good as it gets, and is working well.
For other applications (continuous motion, global shutter, large current LEDs), the LM3409 and similar may be simpler, providing the issues (sawtooth and low current regulation) do not affect requirements, are managed, and/or mitigated in the context of the application.