how do I take good photos of curtains when they are up against windows

Hi there, the problem lies with the very high contrast. The bright daylight is confusing the camera and it is exposing for this and as a result the curtains come out really dark. As we move our eyes around our iris's open and close and therefore we can see a greater range of tones.

There are a few solutions:
Ideally studio lights are needed to balance the huge range of tones but I will assume you dont have these.

Flash is a possible solution, try that as the flash will reach the curtains but not outside. The results might not always be to your taste as flash on camera can render the patterns differently. Ie a bright hot spot in the centre and flat and lifeless around the edges.

The other way is to put the camera on a tripod or balance on a table. Set the camera to manual where you should be able to independantly adjust the aperture and the shutter speed. Set the aperture to around f5.6 and the shutter speed to around 1/15th, take a few shots while setting the self timer to around 2 seconds so that you dont shift the camera with your finger. Try various exposures according to the ambient light in the room and I'm sure you will get better results than having the camera on auto or program. You can always do the shots in the evening when it is less bright outside or get a few household lamps nearby but dont forget to adjust the white balance setting to 'tungsten' light - auto may not do it correctly.

Hope this helps.