Hockney and falco explain this shift as follows : van eyck traced part of the image projected in an epidiascope , then accidentally bumped the silverpoint , the oil or the mirror , and finally traced the remaining , now shifted , image 霍克尼与法柯对此位移的解释如下：范艾克用幻灯机描了部份的影像后，不小心碰到银尖笔、油画、或者镜子，然后继续描完剩下已经位移的影像。
2.
I copied a reproduction of the silverpoint using a homemade epidiascope based on a small circular concave mirror and direct solar illumination , and when i deliberately “ bumped ” my own epidiascope , i found such a mismatch to be very conspicuous 我用小型的圆凹透镜与阳光组成的自制幻灯机，从银尖笔画复制了一张画，而当我蓄意碰撞自己的设备后，我发现位移结果是非常醒目的。
