<P> If w / w = ff, the linear fill factor of the lens, then the condition becomes </P> <Dl> <Dd> (f / #) m i c r o l e n s ≤ (f / #) o b j e c t i v e × f f (\ displaystyle ((f / \ #)) _ (\ mathrm (microlens)) \ leq ((f / \ #)) _ (\ mathrm (objective)) \ times (\ mathit (ff))) </Dd> </Dl> <Dd> (f / #) m i c r o l e n s ≤ (f / #) o b j e c t i v e × f f (\ displaystyle ((f / \ #)) _ (\ mathrm (microlens)) \ leq ((f / \ #)) _ (\ mathrm (objective)) \ times (\ mathit (ff))) </Dd> <P> Thus if shading is to be avoided the f - number of the microlens must be smaller than the f - number of the taking lens by at least a factor equal to the linear fill factor of the pixel . The f - number of the microlens is determined ultimately by the width of the pixel and its height above the silicon, which determines its focal length . In turn, this is determined by the height of the metallisation layers, also known as the' stack height' . For a given stack height, the f - number of the microlenses will increase as pixel size reduces, and thus the objective lens f - number at which shading occurs will tend to increase . This effect has been observed in practice, as recorded in the DxOmark article' F - stop blues' </P>

Aps-c type (23.5 x 15.6 mm) exmor® cmos sensor