This is the first step in Photoshop when processing a linear image. It is necessary to be able to visualize the image, but undesirable to alter the range of the image data at this point.

Using the Levels tool in Photoshop on the RGB channel, just move the middle slider to the left until you begin to see recognizable image data, then click OK. The middle slider, called the gamma slider, does not clip any data, it simply adjusts the mid-point of the dynamic range. After this adjustment, the image is no longer "linear", but no pixel data has been lost.

Don't worry about the blotchy appearance of the preview image while making this adjustment. Photoshop is using a low resolution preview, but your adjustment will be applied to the full resolution image. Don't make any adjustments to the black point (left) or white point (right) sliders at this stage!