IQ: Canon 70-200mm f2.8 IS vs f4.0 (5D2 x1.0 FF)

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Having owned the f/2.8 IS for about 2 weeks on the 40D I switched to the f4 IS for cost and weight issues. I also remember that the f4 was sharper wide open and across the range on the 40D then the f2.8.

But since purchasing a FF 5D2 i wanted to test for myself if this still holds true on the FF.


Test set up

• Canon 5D2
• Canon 70-200mmL F2.8 IS
• Canon 70-200mmL F4.0 IS
• Tripod in same position
• Tested at 70mm and 200mm @ ISO200
• The neighbors high contrast wall

The test images.


5D2

@ 70mm



Center Crops
Left Image = 2.8 Lens- Right Image = 4.0 Lens

f/2.8


f/4.0


f/5.6


f/8.0


f/11.0



Corner Crops

Left Image = 2.8 Lens- Right Image = 4.0 Lens

f/2.8


f/4.0


f/5.6


f/8.0


f/11.0





@ 200mm



Center Crops
Left Image = 2.8 Lens- Right Image = 4.0 Lens

f/2.8


f/4.0


f/5.6


f/8.0


f/11.0



Corner Crops

Left Image = 2.8 Lens- Right Image = 4.0 Lens

f/2.8


f/4.0


f/5.6


f/8.0


f/11.0




Observations:

@ 70mm end - Center
The 2.8 lens is soft wide open. But as both lenses are at f4.0. Things look better and they are almost identical in terms of sharpness.
If you look really really closely. the F4 lens has very very slightly better contrast

@ 70mm end - Corners
The 2.8 lens is soft wide open.
The 2.8 lens gets better at around f/5.6 but the f4 lens is sharper throughout the range.

@ 200mm end - Center
The 2.8 lens is soft wide open as expected.
Both lenses look sharp @ f/5.6 till f8.0.
Then the F4 lens looks to have slightly better sharpness

@ 200mm end - Corners
Very surprised at the results. At first i thought i switched the images but i triple checked.
The 2.8 lens is sharper in the corners then the f4 lens.
There is also noticeable red shift in the f4 lens.


Conclusion:

Well. both lenses are quite good in terms of IQ. We are looking at mega 400%+ crops here so in real life it wouldn't effect IQ that much.

When choosing a 2.8 or 4.0 version i would suggest.
Consider

• Cost (Significant 30-40% difference in price )
• Weight (the 2.8 is a heavy lens x2 the weight of the f4)
• If you really need f/2.8 for sports?