In this video I’ll be testing the auto focus capabilities of the Sony Alpha 77 vs the Canon 5D mark II. The lighting is extremely poor in this auto focus test which is by design. I wanted both cameras to be struggling with the focus, and the results are going definitely going to surprise you!!
Here’s what you need to know about the auto focus systems and aperture in order for this test to make sense. When slr’s or slt’s like the a77 are trying to focus, the aperture of the lens is always open to widest aperture until the shutter button is pressed. Then the camera then adjusts the aperture to whatever setting you have, and takes the picture. This all happens in a micro-second as you would imagine. You may have noticed this about the aperture on some cameras when using the DOF (depth of field) preview button. What that button does is set the aperture to the actual value you have set, hence giving you an accurate depth of field preview.
In addition to this Sony a77 has a bright AF Assist beam that shoots out to “assist” the af system in focusing. The issue when in close range however, is the AF Beam doesn’t hit the subject where you need it. So it’s basically focusing with no assist lamp, just like the canon.
Firmware Update fixed this issue considerable on the Sony A77!! Get it here >>
For the Canon 5D mark II I purposely used the 24-105mm f/4 L Lens.
Here is a closer look at the cardboard box used in the test so you can see the pencil lines.
Interesting results right? Now if you a regular follower on SonyAlphaLab.com you will remember me complaining about the af system on the a77. I actually put the Sony A77 AF in the Cons section on my full review, because I thought it a bit weak in low light. This test proves it to me. At least against the Canon 5d Mark II much older af system.
Notice how well the Sony a77 worked when it had the f/1.4 lens mounted, but when the lens changed to f/2.8 it could no longer focus on just the cardboard.
The Canon was using a f/4 lens the entire time which also means it did not use it’s single cross type sensor. That only works with f/2.8 and faster lenses.
The Canon locked onto just the cardboard instantly with no problem at all.
I don’t know exactly how the sensors are orientated in relation to the light, but I believe the Canon’s sensors are getting a lot more light. I could be wrong though. Perhaps the sensors themselves are just better technology?
To be fair I do not know the physical differences between the actual focus sensors themselves, but looking at the Specs, the Sony a77 appears to have the advantage over the Canon in both sensor points and sensitivity. In the real world low light scenario however, the Canon out performs the A77 when not using the AF Assist lamp.
Why does this matter?
At close range like macro photography or product photography you may have questionable AF performance when shooting low contrast subjects.
The A77 needs the AF assist lamp in order to deliver the -1 ev sensitivity, and at close range that is not possible. The Assist beam doesn’t hit the subject where you need in close range due to the off-set placement on the camera. I ran into this issue when trying to take close-up pictures of the a580 using just the center af point on the a77. The low contrast smooth black body of the camera in low light was just to hard to focus on with no beam. I ended up manually focusing which is usually easier in these situations anyway.
Sony A77 Auto Focus System:
- TTL phase detection AF (CCD line sensors)
- 19 points (11 points cross type)
- EV -1 to 18 EV (at ISO100 equivalent, with F2.8 lens attached)
Canon 5D mark II Auto Focus System:
- TTL-CT-SIR AF-dedicated CMOS sensor
- 9 AF Points (1 Cross Type) + 6 AF Assist Points
- EV -0.5-18 (at 73°F/23°C, ISO 100)
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