Zoom lens Calibration

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Maybe, this is a silly question, currently I have a len (AF-S DX NIKKOR 18-55mm f/3.5-5.6G) with this features:

• 18-55mm lens with f3.5-5.6 maximum aperture for Nikon DSLR cameras .
• Focal length equivalent to 27 to 82.5mm in 35mm photograph

My question is, to get intrinsic calibration, and then correct len distort, Do I have to do it for each focal length of the len? For example:

# images = images_with_18mm_focalLength
# calibrationMatrix18mm = Do_Calibration(images)

# images = images_with_24mm_focalLength
# calibrationMatrix24mm = Do_Calibration(images)

Our does is enough with a global calibration?:

# images = images_from_18mm_to_55mm_focalLength
# calibrationMatrix = Do_Calibration(images)

I think I should go with first option, but I want to clear out my doubts. Also, how could I get an image that maps with colors the less and more distorted regions of the image?

Thanks, in advance