Comparison of Canon EF 400mm f/2.8L IS USM and Pentax SMC P-FA 600mm f/4 ED IF

Attribute	Pentax SMC P-FA 600mm f/4 ED IF ×	Canon EF 400mm f/2.8L IS USM ×
Notes	Included Accessories: Case	Image Stabilization
Magnification Ratio (x)	-	0.15
Filter Size (mm)	43	52
Focus Details	Internal	Inner focusing; full-time manual focus and USM
Closest Focus (m)	5	3
Lens Construction	9 elements in 7 groups	17 elements in 13 groups, including 1 flourite and 2 UD elements
Length (mm)	457	349
Focal Length (mm)	600.00	400.00
APS Equivalent	900mm	640mm
Brand	Pentax	Canon
Image Circle	35mm	35mm
Name	Pentax SMC P-FA 600mm f/4 ED IF	Canon EF 400mm f/2.8L IS USM
Weight (g)	6450	5370
Type	Telephoto Prime	Telephoto Prime
Aperture (f)	4.00 - 32.00	2.80 - 32.00
Diaphragm Blades	-	8
Diagonal Angle of View (degree)	4.10	6.20
Diameter (mm)	175	163