I take SLR photos with a bird-watching mirror. Why is the effect gray? But it's clear to the naked eye?

The lens of the mobile phone is small and the eyepiece is large. It doesn't matter if the lens is misaligned, and the off-axis effect is not significant. SLR is different, the optical axis of bird mirror is not aligned with the main axis of SLR, which has a great influence. So usually the bird mirror needs a special connector to connect the SLR. In addition, the optical effect of the bird mirror is poor, and there may be deviation between the objective lens and the eyepiece spindle, which can be adjusted by the human eye during visual inspection, but the camera at this price is not good. Ordinary achromatic, the sharpness is not good, and then through an eyepiece and a camera lens, the light of the object image must penetrate at least 12 lenses. The mechanical vibration of the SLR is already very large, and the hand is unstable again, and the picture quality can be imagined. Moreover, photography behind the mirror is equivalent to further improving the magnification of the bird's-eye mirror, and cheap goods often match the limit, thus forming an invalid magnification. Bird's-eye lens photography should at least be a domestic ed bird's-eye lens, which will be significantly improved at around 4,000 yuan. Regular bird's eye lens photography is Swarovski, Leica, Zeiss, Kova and Nikon ED, all of which cost more than 10,000 yuan. Domestic bird killing mirrors can only be visually observed.