Methods and apparatus for analysis of nano-objects using wide-field bright field transmission techniques are described. Such methods may comprise acquiring a plurality of images of a sample comprising a plurality of nano-objects using bright field illumination via a continuously variable spectral filter, and identifying a nano-object within the sample in the plurality of images, wherein the position of the nano-object changes between images. Using data extracted from the plurality of images, an extinction cross-section of the identified nano-object may be quantitatively determined.