The Rodenstock / ALPA HR ALPAGON 6.5/138 mm Float is an exceptional sharp long focal length lens for adjustable technical cameras intended for a wide distance range from infinity up to an image scale 1:5 (β' = -0,2).The optical design with eleven lens elements in ten groups is very complex fora prime lens. It has the highest possible resolving power extremely close to the diffraction limit. This is not only achieved across the entire field of the largest digital sensors – but also to the edge of the large 110mm image circle to allow for lens shifts and tilts. The rotation of the focusing ring automatically controls the floating elements group and all aberrations are therefore minimized throughout the whole focusing range. Even with extreme camera movements (shift and tilt) this lens provides an unprecedented sharpness to the corners as proven by the MTF curves given up to 80 lp/mm. It provides negligible distortion (almost always below 1‰)and a total suppression of the chromatic aberration for perfect freedom from color fringing.

HR ALPAGON 138毫米的图像圆在其整个图像比例范围内具有110毫米的恒定直径。对于专业技术相机来说，即使是最大的传感器格式，这也为透视校正的平行移动提供了充足的空间（避免或减少汇聚的垂直线）。这也允许摆动和倾斜以扩大景深，而不需要根据Scheimpflug规则过度缩小光圈。

螺旋支架的宽大对焦环可以实现敏感而精确的对焦，并自动控制上述浮动元件组的调整。

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