When viewing extended objects, the apparent brightness seen in the eyepiece is a function only of aperture and magnification, it is not related to focal ratio.
当观察扩展光源时，目镜中所看到的亮度只跟孔径和放大率有关，它跟焦比并没有关系。
2
At high magnification, the dark red thrombus is apparent in the lumen of the coronary. The yellow tan plaques of atheroma narrow this coronary significantly, and the thrombus occludes it completely.