Customisation Mode Settings

Sigma Optimization Pro also allows you to configure further settings when using the latest version of the 120-300mm F2.8 telezoom. This has two custom memories, C1 and C2, which are accessed by a switch on the barrel. Using the USB dock, combinations of focus distance limits, AF speed, and OS mode behaviour can be configured to suit specific shooting scenarios.

The 120-300mm has a switch on the barrel that lets you choose between its standard setup, and one of two custom configurations These settings memories are configured from Sigma Optimization Pro

AF speed options

You can choose between three AF speed settings - 'Drive Speed Priority' for the fastest response, or 'Focus Accuracy Priority' for slower, but more accurate focus.

There are three AF speed options, which we can see being genuinely useful for sports work. For example if you shoot fast-moving action, then setting the lens to the fastest drive speed may well give best results, although not all might be in absolutely perfect focus. However if you shoot slower action, selecting accuracy priority might deliver the most 'keepers'.

Focus distance limiter

The focus distance limiter lets you define the near and far limits over which the lens will search for focus.

Most sports telephotos have focus distance limiter switches, to stop the camera racking the lens through its full range looking for focus when the subject is always going to be in the distance (for example). Sigma has taken this concept further - you can freely define the distance range the lens will use for autofocus. This will override the 120-300mm's own distance limiter switch when shooting in a 'C' mode. 

Again it's a good idea with a slightly 'version 1' implementation. The distance scale isn't exactly detailed (essentially it matches the one on the lens itself), and in particular, with the 120-300mm there's a vast swathe between 2.5m and 10m with no markings at all. So if the limit you want to apply doesn't coincide with one of the marked distances, you more-or-less have to guess where to put the slider and then see if it works. You can estimate this by focusing on the closest or furthest subject and looking at the lens's scale, but having more distances marked would be a huge help.  

OS Setting

The OS mode setting lets you change the degree of viewfinder stabilisation, from a 'Dynamic View Mode' that quickly 'locks' the image, to a 'Moderate View Mode' that allows it to drift more.

The OS setting relates purely to the viewfinder stabilisation - Sigma doesn't suggest it has any affect on either image quality or the effectiveness of the OS system. Instead it lets you choose between a decidedly Tamron-esque 'Dynamic View' that quickly 'locks down' the viewfinder image, and 'Moderate View' which lets the image drift around more smoothly. The latter is probably going to give a more natural and less jerky effect when panning.


What we like

  • Uniquely fine control over lens's autofocus calibration
  • Relatively inexpensive
  • Simple and generally intuitive software

What we don't like

  • Several aspects of Sigma Optimization Pro software still feel rather 'version 1'

Sigma's USB dock may not look like much on its own, but in concert with the Optimization Pro software it should be interesting to photographers who like to tinker with their equipment to get the best possible results. You can update the lens's firmware (although as far as we can tell, Sigma hasn't actually released any updates yet) and fine-tune the autofocusing for all supported lenses. With the 120-300mm F2.8 telezoom you get further control over focusing and image stabilisation behaviour too.

Most SLR owners have never had the facility to update lens firmware before (probably because it was never built into the design of film-era lens mounts), so might question its usefulness. But we've seen lens updates for mirrorless systems that demonstrably improve focusing speeds, for example, so it's not to be dismissed lightly. Also, if future cameras require the lens's firmware to be updated to work properly (which has happened in the past), users will be able to do this at home, rather than take the lens to a service centre or send it away for a few days. 

The dock also provides the ability to set autofocus microadjustment for four focal lengths at each of four different focus distances, which is beyond what any SLR body offers. So if your lens has a specific front- or back-focus problem at the telephoto end, for example, then in principle you can fix it without any risk of throwing out the focus at wideangle. But we do wonder how many users will genuinely take the time and trouble to program in and verify a full set of AF microadjust settings. 

For users of Sigma's 120-300mm F2.8 telezoom, there's a range of other settings that can be changed, and which are likely to be helpful to serious sports shooters. The ability to set custom focus distance limits makes a lot of sense, for example, even though its current implementation leaves something to be desired. 

This is all very clever, but does it work?

The USB dock and Sigma Optimisation Pro certainly offers lots of really interesting-looking options, but of course the big question is simple; does it all work? The basic answer, in terms of whether the functions work as advertised, appears to be yes. Microadjust settings clearly change the focus position bias, the AF speed options are visibly different, the focus distance limiter genuinely limits the focus distance, and the OS view modes are clearly different too. So far, so good.

The bigger question, of course, is whether this all works in a practical fashion. Our biggest reservation about the USB dock lies in the process of changing and verifying settings. Because you have to repeatedly swap the lens between the camera and the dock attached to a computer, it's not easily done in the field - we can't see how you'd easily program near and far focus limits when setting up to shoot a game, for example. (A Bluetooth-equipped dock and a smartphone app might be nice...)

The Final Word

Sigma's USB dock provides lots of interesting options for photographers who like to tinker with their equipment to get best results. Its current implementation still feels somewhat basic, and we think Sigma Optimisation Pro would definitely benefit from some refinements (but to be fair, we're literally using version 1.0.0 at the moment). However we're really impressed by the idea, and applaud Sigma for having the imagination to bring it to market. It's perhaps not yet a 'must have' accessory - it only works with a few lenses, after all - but we can easily see advanced photographers finding it hugely useful.