Note that it is very important to set the camera film back size correctly if focallength measurements in any units other than pixels are being entered.
请注意，这是非常重要的设置相机的胶片回来大小正确如果焦距测量在任何单位除了像素被进入。
2
Then, image surface position was kept steady during a zooming process by controlling the spherical aberration of front fixed group and the focallength of back fixed group.