Pentax Q 01 8.5/1.9 Standard Prime: Built-in ND filter

Although I didn't perform detailed tests, regular use shows that the built-in ND filter of the Pentax Q 01 8.5/1.9 Standard Prime lens is not strictly ND 4 (2 EV) or ND 2 (1 EV).  I would estimate it to be around 1.4 EV, ND 2.6.

Additionally, this ND (neutral density) filter is not truly neutral. However, the white balance compensates for this.

See also related notes:

• Pentax Q 01 8.5/1.9 Standard Prime (2025-09-23)