Photometry includes several methods of analyzing image data. For example, one might look at several different images of the same object to see changes between them. Photometry as a supplement to the transit method may involve cross checking the drops in brightness with color images to see if the color of the star appeared to change. Color changes can be caused by either a change in temperature or by a different object passing in front of the star - in which case the observed color of the star is a mix of the color of the star and the color of the object. Another photometric method, used for finding planets, involves attempting to block out the light from the parent star to isolate the light from the planet.
Photometry tries to even the field to help one see the planet directly.
This can be aided by taking images in wavelengths other than those of visible light. Planets emit in the infrared portion of the spectrum and putout no visible light. Stars put out a vast amount of light in the visible bands, and a lot in infrared, but not nearly as much. If one looks in the infrared, the relative amount of starlight that must be blocked out is considerably less. Indeed, they should be, since observations must be long-duration to increase chances of seeing multiple transits of the same planet.