文中还对锐聚焦系统给出了最佳归一化离焦量的表达式和相应的ETF近似公式。
For sharp-focusing system, the expressions for the position of optimum image plane and its corresponding ETF are also given.
它拥有无可比拟的锐度，焦外，整体色彩还原，以及宾得特有的动力变焦。
It boasts unmatched sharpness, bokeh, and overall color rendition, as well as the Pentax-exclusive power zoom function.
同样的锐度下降问题也出现在镜头的长焦段（包括中央的锐度也下降得厉害）。
The same applies to the sharpness in general (including the image center) at the lens' tele setting.
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