Instruction: Using the product's title, description, features, price, and brand, identify and retrieve the values associated with a specified set of target attributes. Output the extracted values along with their respective sources (e.g., title or feature) indicating where each value was found.

Input:
Product title: Canon EF 14mm f/2.8L USM Wide Angle Lens
Product description: This ultra-wide-angle lens has the shortest focal length in the L-series. Element 2 is an Aspherical lens to correct distortion. Other aberrations such as astigmatism are also corrected, resulting in ideal image quality. The lens has a fixed, petal-type hood and a gelatin filter holder at the rear., This ultra-wide-angle lens has the shortest focal length in the L-series. Element 2 is an Aspherical lens to correct distortion. Other aberrations such as astigmatism are also corrected, resulting in ideal image quality. The lens has a fixed, petal-type hood and a gelatin filter holder at the rear., This is a true rectilinear ultra-wide-angle lens thats absolutely corrected for linear distortion--straight lines remain straight. Its outstanding for shooting in confined areas and interiors, and is often used by professionals because of the unique "look" its extreme wide angle perspective provides. The optics are superb, highlighted by a ground and polished aspherical element. It has a gel filter holder in the rear that allows up to three gel filters to be used for color correction., Wide and Fast If you need an ultra-wide angle and a large aperture, one of the following lenses will fit the bill. Ultra-wide-angle lenses can capture scenes beyond your natural field of vision. The EF 15mm f/2.8 Fisheye, the widest of them all, has a 180 angle of view. For more normal-looking wide-angle shots, there are longer wide-angle lenses up to 35mm with the maximum aperture you need.
Product feature: Filter Size - Rear Gel Holder, Unit Dimensions - Maximum Diameter x Length, Weight - 3.0 x 3.5, 1.2 lbs. / 77.0 x 89.0mm, 560g
Product price: $699.99
Product brand: Canon
Target attributes: Mount
Answer: attribute: mount
value: canon ef
source: product title