Why is the picture darker than the naked eye when taking pictures in a small studio with a card machine?

Cameras are different from human eyes, and automatic cameras can't keep up with the adjustment of human eyes, unless the light is too dim to see clearly, which is beyond the adjustment range of human eyes.

How to solve your problem depends on your experience: evaluate the background brightness when metering to decide whether to make exposure compensation, and increase the exposure when the background is bright, otherwise even if the ambient light is sufficient, the exposure will be insufficient; Reduce exposure when the background is dark, otherwise it will easily lead to overexposure. Backlight photography is more prone to underexposure, and the solution is forced flash compensation.

You said that the lens has different orientation and brightness because it is influenced by the background. You can guess carefully and try again.

In addition, spot metering may be better, but appropriate exposure compensation adjustment is still needed.

Special reminder: exposure compensation is not allowed in automatic gear. Please shoot in aperture priority mode to compensate.

for reference only