But the study also showed that, while less effective, simply painting crude cross marks on the cows deterred predators better than leaving them au naturel.

但研究还表明，虽然效果不太好，但仅在牛身上画上粗糙的十字记号也比让它们保持自然状态更能制止捕食者。

He did it by putting a glass panel in front of the camera and painting black marks over specific sections to block the light.

他通过在相机前放置一块玻璃面板并在特定部分涂上黑色标记来阻挡光线来做到这一点。