SLR photography problem, how to take pictures of curtains indoors during the day, always backlighting.

As far as this photo is concerned, there is no fill light in the room. The indoor light mainly comes from the reflection of the back wall (not far from the later stage, it is a white wall). The window light is overexposed, and the theme curtain is exposed normally.

Even an ordinary SLR can be set to measure the light of the curtain when shooting by spot metering, or to measure the light of the curtain locally to avoid the window light, and then shoot with the exposure parameters of the M file just now.