Sony 500mm F8 continuous AF

The Sony 500mm F8 autofocus mirror reflex lens is a very interesting lens. It is the only mirror reflex lens which can autofocus, is reasonably light (665g) and compact . Hence it will not be taxing on your back to bring this lens along. Now one of the things I wanted to test was whether this lens could do continuous autofocus with a moving subject using my Sony A6000 and LA-EA4 adapter.

As this lens does not have a built-in focusing motor, it will not work with the Sony A7RII with the LA-EA3. It will only work with the LA-EA4 which has a built-in focusing motor. Now the big question is whether the focusing motor of the LA-EA4 can drive this lens fast enough to maintain focus on a moving subject.

Sony 500/8 mirror AF lens with LA-EA4
Sony 500/8 mirror AF lens with LA-EA4

When at Florence Park, Oxford UK, I had a chance to photograph a few animals moving about. Now one of the things I noticed after shooting for a while was that the lens was front focusing a little (i.e. the subject in front was in focus rather than the subject being photographed), because the firmware update of the A6000 had removed all AF microadjust I had done previously. Once this was adjusted by +4, things were looking much better.

First subject Рa squirrel moving under the trees about 20 metres from  where I was sitting. This lens was shot handheld, which I would not be able to do with any other 500mm lens.

Squirrel - from over 20m away using Sony 500/8 + A6000
Squirrel – from over 20m away using Sony 500/8 + A6000

These are three continuous shots cropped slightly into the image to show the movement of the squirrel.

Center crop
Center crop
Center crop
Center crop
Center crop
Center crop

Next subject was a magpie in the field. These images were not cropped in, which just shows the reach of this lens.

Magpie with Sony 500/8 AFC
Magpie with Sony 500/8 AFC
Magpie with Sony 500/8 AFC
Magpie with Sony 500/8 AFC
Magpie with Sony 500/8 AFC
Magpie with Sony 500/8 AFC
Magpie with Sony 500/8 AFC
Magpie from far away with Sony 500/8 AFC

From my brief experience, it looks possible for the Sony 500mm F8 mirror reflex lens to do continuous autofocus with the Sony A6000 and LA-EA4.

There are a few great features of this lens, which has to do with its relatively small size and weight, which makes handholding and bringing it about less energy-sapping. It also costs considerably less than the other 500mm autofocus lenses out there available for Sony. I am more likely to bring this lens around than most other 500mm lens, as the weight of this lens, the LA-EA4 adapter and the Sony A6000 together weight less than any of the other 500mm lenses out there (the Tamron 200-500mm lens, one of the lightest 500mm lenses available, weighs over 1.2kg by itself).

But there are some negatives to this lens:

  1. It is a relatively slow lens fixed F8 which requires the use of higher ISO to capture the images.
  2. It does not have a built-in focusing motor which means you cannot use the mirrorless LA-EA3 adapter and make full use of the accuracy of the on-sensor phase detection sensor of the Sony A7RII, where there is no need for micro AF adjustment.
  3. The bokeh of this lens is a little chaotic due to the lens design, which can be seen in the images above.
  4. Autofocus only works with the center autofocus point, which means it cannot do subject tracking and in practice, it can be difficult to keep this point on a small or fast moving subject.

I am aware that there are many very good Sony lenses which do not have a built-in focusing motor, and hence requires the mirrored Sony LA-EA4 adapter to work with the Sony E-mount cameras. These include the Sony 85mm F1.4 Zeiss, 135mm F1.8 Zeiss and this lens. It would be great if Sony could come out with a new LA-EA adapter (perhaps LA-EA5) with a built-in lens motor but no translucent mirror, so these lenses can benefit from the on-sensor phase detection autofocus points as well as the in-body image stabilisation of the A7RII. This is the one big point (other than the price) that is preventing me from getting the Sony A7RII, as I own both the Sony 85mm F1.4 and this lens.

So my big plea to Sony, whom I’m told does read reviews, is please bring out a Sony LA-EA adapter which has an in-built focusing motor but no translucent mirror to allow for the use of some of their great lenses on the newest members of the E-mount cameras and get the most benefit from the new technology. How hard can it be?

Boon