The problem with current controlling LEDs is that there is a very non linear relationship between current and light output.
You will get much better results by keeping the current constant, set at the maximum desired brightness level, and switching that full current on and off with PWM.
This is particularly effective with seven segment displays and where you need good matching of brightness between segments that may have very poor brightness matching at very low current.
Nothing looks worse than a mosaic of multiple LEDs that are run on much reduced current, where the whole thing looks very uneven and patchy.
The same mosaic run at full current, but very small duty cycle will dim down wonderfully even right down to completely off, even with poorly matched LEDs.