Comparison of Pentax SMC P-FA 600mm f/4 ED IF and Tamron SP AF 300mm f/2.8 LD IF

Attribute	Pentax SMC P-FA 600mm f/4 ED IF ×	Tamron SP AF 300mm f/2.8 LD IF ×
Diameter (mm)	175	120
Aperture (f)	4.00 - 32.00	2.80 - 32.00
Diagonal Angle of View (degree)	4.10	8.00
Filter Size (mm)	43	43
Notes	Included Accessories: Case	Available AF Mounts: Canon, Minolta, Nikon; Included Accessories: Lens Hood, Case
Type	Telephoto Prime	Telephoto Prime
Closest Focus (m)	5	2.5
APS Equivalent	900mm	1.5x: 450mm; 1.6x: 480mm
Lens Construction	9 elements in 7 groups	10 elements in 7 groups, including 2 LD elements
Image Circle	35mm	35mm
Focal Length (mm)	600.00	300.00
Brand	Pentax	Tamron
Name	Pentax SMC P-FA 600mm f/4 ED IF	Tamron SP AF 300mm f/2.8 LD IF
Weight (g)	6450	2800
Diaphragm Blades	-	9
Length (mm)	457	215.9
Magnification Ratio (x)	-	0.141
Focus Details	Internal	Internal; Focus ring slides back and forth to switch between AF and MF