Sony Alpha cameras (and NEX as well) have two very nice features that make manual focusing a pretty effortless exercise. The first one is focus peeking, where the areas in focus are highlighted in a selected colour, and the other one is MF assist.
The way MF assist works is that when the camera is in MF mode, the preview screen on the LCD display or EVF is magnified, making it very easy to see when the subject is in focus. Once the MF assist is enabled, all you need to do is to turn the manual focus ring on your lens and the magnification kicks in.
However, if you are using third party lenses with the lens adapter in manual focus mode, the screen magnification doesn’t work. You can turn the focusing ring all day long, you will only have the benefit of focus peeking but not the MF assist.
I was really disappointed with this when I got my Fotodiox EF-NEX Pro adapter. I tried it on my Sony A7 II with Canon EF 85mm f/1.8, Tamron SP 24-70mm, Tamron 70-200MM F/2.8 and Sigma 50mm f/1.4, and the MF assist magnification didn’t work with either.
I dug into the menu system to look for an answer and I have found one that works just fine. First, you have to enable the MF assist and specify the Focus magnification time to No Limit. Both settings are available under the 2nd menu tab (General settings) on the page 1. Then you need to go to page 6 of the same tab and select Custom Key Settings. Select which Custom Button you’d like to configure (in my case it’s the C2) and choose Focus Settings. Exit the menu and you’re set.
What happens now is that I set the lens in MF and press the C2 button twice. The first press allows me to specify which area of the view is magnified and the second press enables the 5x magnification. If I press the same button one more time I get the 10x magnification. These value can be changed somewhere in the settings but I still haven’t figured out how. Post a comment if you know how to do it.
Be careful not to select the Focus Magnifier when mapping the Custom button and this is why. The Focus settings lets you do two things; when in MF mode, the button works as explained above, but when in AF mode, the button lets you select where your flexible spot focus point is. If you select the Focus Magnifier, it will work fine in MF, but the AF mode will give you a message “The operation or settings not operational”
So, there you go, it’s as simple as that. Happy focusing!