A: The standard iCloud Photo Stream feature uploads your original photos as-is, in their original resolution with all metadata intact. This means that your photos as transferred to your Mac or Windows PC will be the original photos from your device.
However, where this gets confusing is that iOS stores a downscaled version of your photo in the Photo Stream section on your devices. This is true even on the device where the photo originated. The specific resolution of the Photo Stream stored photos varies slightly between devices as it is optimized for the screen resolution, but the maximum is between 3.1 and 3.5 megapixels, depending on the photo’s aspect ratio—2048 x 1536 for standard 4:3 images, a slightly higher 2304 x 1536 for “pro” camera 3:2 images.
This basically means that even on the iPhone 4 the images stored in your Camera Roll will be significantly higher in resolution than those stored in the Photo Stream. If you’re planning to work with original, full-resolution images in another app on your iOS device you should keep the photos in your Camera Roll even after they’ve been uploaded to your Photo Stream so that you can use these instead of pulling them from the Photo Stream. However, the resolution of photos stored within the Photo Stream should be more than adequate for viewing on the device or uploading to most social networks—many of which will resize the photos to even lower resolutions anyway.[/quote]