A closer look at Sony’s FE 70-200mm F2.8 GM OSS II

Sony has just announced the FE 70-200mm F2.8 GM OSS II, an update to one of its first ‘G Master’ lenses. While the original was certainly well-built, handled well and was fast to autofocus, we weren’t so fond of some of its optical characteristics, and it looks like Sony has really gone all out to make sure this latest 70-200 is up to snuff.

The outside of the lens comes with a few updates, but it’s what’s on the inside that really counts. All-new optics, coatings, focus motors and more add up to an impressive offering. Let’s dig in and check out not only how the new lens looks, but how it compares to the previous model.

Size and weight

Next to the previous 70-200mm F2.8 GM (top), the new model is exactly the same in terms of overall exterior dimensions, but weight has been reduced by 435g (15.3 oz): almost 30%. The result is a much more comfortable shooting experience with Sony’s full-frame bodies, particularly if you’re not using an optional battery grip.

It’s worth noting that Sony is touting this as the ‘world’s lightest’ constant large-aperture telephoto zoom, and it is indeed a bit lighter than Canon’s collapsible 70-200mm F2.8 for RF mount. If every last gram matters to you, though, Tamron’s 70-180mm F2.8 is 230g (8.1 oz) lighter, though it doesn’t have a built-in image stabilizer like the other two, and it doesn’t quite reach 200mm.

Aside from that, you can see that the new lens has a few additional control points, as well as a slightly slimmer manual focus ring to make room for them. Let’s take a closer look.

External controls – aperture ring

The FE 70-200mm F2.8 GM II’s most significant exterior change is the addition of a dedicated aperture ring, shown here. It ranges from F2.8 to F22 with 1/3 stop markings, and there is an ‘A’ option for those users that want to carry on using the camera’s command dials to control aperture.

The ring can be ‘clicked’ for stills photography or ‘de-clicked’ to allow silent use while shooting video using a switch on the right side of the lens…

External controls – aperture ring

…and there’s a unique application to the click-less aperture dial for video shooters.

On Sony’s FX-series cinema cameras equipped with variable ND filters, the aperture ring can be operated in a click-less fashion such that as the iris is smoothly adjusted, the variable ND automatically adjusts in smooth increments between 1/4 and 1/128 EV to compensate for the change in light gathering. This allows for a smooth transition of depth-of-field while maintaining exposure.

Traditionally one might rack focus from afar to your subject to bring attention to it but, instead, you might imagine starting off with extensive depth-of-field, then smoothly opening up the aperture to isolate your subject utilizing shallow depth-of-field.

It can make for an interesting creative effect.

External controls – additional switches

On the left side of the lens, opposite the aperture ring click / de-click switch, is the usual array of controls, including a standard AF/MF (autofocus / manual focus) switch. Below that is a ‘Full Time DMF’ (with DMF meaning Direct Manual Focus) switch. When set to ‘on’, photographers can rotate the manual focus ring at any time, even while focus tracking is engaged, to fine-tune things.

There’s also a focus limiter, the ‘OSS’ switch for the optical stabilizer and a mode switch for controlling the behavior of the stabilizer. Finally, there’s an ‘Iris Lock’ switch, which will lock the aperture ring into the ‘A’ position for users that opt for command dial control.

Front element

Around the front of the lens is a 77mm filter thread, and the front element comes with a fluorine coating to combat dust, oil and fingerprints. The bayonet mount for the hood is also visible here, with the hood offering a locking mechanism that requires a button-press for removal. Sony notes that dust and moisture resistance are notably improved compared to the previous model. All seams are sealed, and buttons and switches have silicone rubber gaskets, while a rubber ring seals the lens mount.

Optical design

The lens comprises 17 elements in 14 groups. One extreme aspherical (XA) element, pictured in orange, helps to control variations in distance-related aberrations, while an extra-low dispersion (ED) aspherical element, pictured centrally in dark blue, suppresses both chromatic and spherical aberration.

Controlling spherical aberration (SA) ensures that marginal light rays entering at the edge of the lens focus at the same plane as paraxial light rays entering centrally. And to state the (perhaps) obvious: if light rays emanating from an object focus at different planes behind the lens (instead of all at the sensor plane), it risks appearing blurry. See this slide for ray diagrams of a lens with and without SA, and note how the ray bundle at the point of ‘Best Focus’ is tighter for the ‘perfect’ lens with no SA. The end result is a sharper image.

There’s another aspheric, pictured in purple, and these three more exotic elements we’ve discussed in this slide work together to suppress aberrations and achieve high resolving power across the frame wide open, particularly on the long end where, arguably, it matters more for a lens of this type.

Lateral chromatic aberration

Two Super ED (pictured in grey, at the front of the lens, in the previous slide) and two conventional ED glass elements (in green) help to reduce both lateral and longitudinal chromatic aberration, and in our initial shooting, there’s very little of either. There’s a bit more lateral green / magenta fringing in the corners on the wide end (3 pixels worth at worst, on a 50MP sensor) compared to the tele end (1-2 pixels worth), and in both cases this CA is easily removable with the included profile (or automatically in camera JPEGs).

Here it is at 200mm (click on the fullscreen icon at upper right, then click on ‘100% zoom’). And for some perspective, 1 to 2 pixels of fringing in a 50MP file translates to 0.2 to 0.4 mm in a 40 x 60″ print.

Photo: Chris Niccolls / Jordan Drake

Longitudinal chromatic aberration

Longitudinal CA, typically seen as magenta and green fringing in front of, and behind, the focus plane, respectively, is nearly completely absent. That’s great, because it’s the type of CA that’s hard to remove. Peek closely at the white features curling outward in front of, and behind, the vertical in-focus rod. And note the slightly out-of focus metal features in the background. There are no colored fringes around any of these.

Photo: Chris Niccolls

Flare and ghosting

The Mark II version of the lens includes the Mark II version of Sony’s ‘Nano AR (anti-reflective)’ coating to prevent (veiling) flare, or loss of contrast, and ghosting, the appearance of distracting, repeating ‘ghosts’ of a bright point light source. Both are caused by reflections off of internal elements, so generally tend to worsen with an increasing number of elements. Nano AR II was developed specifically for application to large optical elements with highly curved surfaces, such as the extreme aspherics increasingly found in Sony’s lenses.

Our initial samples indicate that while you can certainly see ghosting, it’s more of an issue when you stop the lens down, as in the F9 shot above. That’s because the ghosts aren’t very prominent wide open, instead appearing rather low contrast and diffuse. The wide end is where you’ll see the most number of ghosts, and this is the worst example of it we could find over at Lenstip. There are fewer ghosts on the tele- end, and given how low contrast they are to begin with, you really have to stop down to see them. We don’t consider ghosting to be much of an issue at 200mm wide open.

The opposite is true for veiling flare. Lenstip’s results show there can be a significant loss of contrast when shooting into the sun on the telephoto end, but contrast holds up fairly well in a similar situation on the wide end. This is also confirmed in our shooting.

Photo: Chris Niccolls

Bokeh

Bokeh was not the forte of early copies of the original 70-200mm F2.8 GM. Despite Sony’s claims at the launch of the G-Master brand that it could control XA element surface precision to within 1/100th of a micron for smooth bokeh free of onion rings, some copies of the 70-200mm F2.8 GM (and the 24-70mm F2.8 GM, launched at the same time) suffered from rather severe onion rings and what I can only best describe as ‘donut bokeh’.

Sony makes the same claims of surface precision control, but in recent years has churned out premium lens after lens with pristine bokeh, and this one is no exception. Defocused specular highlights are free of onion rings and bright edges, yielding smooth foreground and background bokeh. An 11-bladed aperture ensures bokeh discs remain circular, even as you stop down. This also helps maintain a smooth look to bokeh at smaller apertures. There is however a prominent cat’s eye effect wide open, visible in this image, but it’s mostly gone by F4.

Photo: Chris Niccolls

Bokeh

In some images we noted a bit of a frenetic look in the transition zone where things are just starting to fall out of focus. If you zoom in to 100% on the left edge of this image (just above the water), you’ll note some ‘double image bokeh’, where slightly out-of-focus objects appear repeated. It’s not always an issue, but where it is, transition zones can appear busy. This is something we’re starting to see with increased frequency in recent lenses featuring complex aspherics, including Nikon’s Z 14-24mm F2.8, and Sony’s own 14mm F1.8 GM and 24mm F1.4 GM.

Photo: Chris Niccolls

Autofocus

The original 70-200mm F2.8 GM was relatively fast to focus compared to its ring-type USM peers. It had two independent focus groups, one powered by a ring-type motor and the other a linear motor. But since the launch of the original GM lenses, we’ve seen Sony make strides in autofocus speeds with its development of XD (‘extreme dynamic’) linear motors.

So it’s great to see the new version powered solely by linear motors. Four XD linear motors drive two independent ‘floating’ focus groups (two motors per group), as pictured above. The improvements to autofocus speeds appear to be significant in our initial testing. Sony claims this is the first large aperture tele-zoom to use four linear AF actuators (Fujifilm’s 50-140mm F2.8 uses three to move a single focus group, while Canon’s RF telephoto uses two nano USM motors to move two independent floating groups).

Sony claims focus acquisition times have decreased 4x compared to the original model. The ability to focus while zooming has also improved 30% compared to its predecessor, possibly due to the lens being more parfocal (remaining more in focus when changing zoom ratio).

Video oriented features

There are a number of features on this lens aimed at video shooters. Focus is silent thanks to those linear motors we were discussing, and manual focus response is linear, making focus pulls easy and repeatable (a set number of degrees of focus ring rotation always changes the focus the same distance). Sony has also reduced focus breathing, to a point where it’s barely an issue at the telephoto end. There’s still some on the wide end, but it’s subtle and greatly reduced compared to the Mark I version. See for yourself in our DPReview TV episode here.

Beyond this, there’s also greater axial consistency as you zoom, as well as less focus shift when zooming (that is, the lens is more parfocal). Both of these attributes make the video footage more stable and consistent during zooms, while also aiding in autofocus performance.

Conclusion

All in all, the FE 70-200mm F2.8 GM OSS II looks to be a nice, rather significant update to its predecessor, and our images so far appear to support the super-sharp modeled MTF figures Sony has published. It’s not a cheap lens but it appears to address some of the shortcomings that had become apparent in its predecessor, particularly image sharpness and consistency, as well as bokeh (early copies of the Mark I suffered from onion ring and other bokeh issues).

Lighter weight, faster AF and better optics means there are tangible benefits for stills shooters on top of those for videographers. The lens lists at $2799 and units start shipping in mid-December. The Mark I continues in the lineup, but we’d highly recommend those in the market for this type of lens to save up for this much improved version.

Author: Go to Source
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