#647. Sony GM 24-70 : Extreme aspheric bokeh master?

#647. Sony GM 24-70 : Extreme aspheric bokeh master?

Around a year ago, Philippe wrote this review of the then new Sony “G Master” (GM) 24-70mm f2.8 zoom for their full frame E mount cameras. In his review he talked about the excellence of the lens, it’s resolution, it’s sharpness, it’s contrast, but also it’s lack of “magic”. His conclusion was that many modern lenses such as the 24-70 GM can be technically excellent, but that the last drop of something “special” that raises a picture from soulless perfection to having “magic” eluded them.

 

I’ve been photographing with Sony’s A7 and A7s cameras since 2014, and my most used lens has probably been the Sony FE 24-70mm F4 ZA OSS Zeiss Vario-Tessar. My experience with that lens could probably be a review of it’s own, as I always felt it is much maligned in many online reviews, and basically offered solid performance on 12-24Mp cameras.

 

 

Lone flower (Sony FE 24-70mm f4 OSS Zeiss Vario-Tessar)

 

 

I recently purchased a Sony A7R2 body, and it was then that the greater demands of a higher resolution sensor (42Mp) started to reveal some weakness in the 24-70mm f4 Vario-Tessar. It wasn’t that the photos were terrible, but whilst it made good quality photographs at lower pixel counts, the very finest detail and “bite” was simply missing with such a high resolution sensor.

 

I think that there is a philosophical issue with the “zoom vs. prime” debate about focal length and composition, the one side favouring the flexibility of a lens that fits the scene, the other favouring finding scenes that fit the focal length.  Since many of my photographs fall broadly into “travel”, the flexibility of a standard zoom that covers wide angle to short tele focal lengths often trumps the potentially better image quality of prime lenses and the need to constantly change lenses.  For travel, I believe it’s important to have a lens that can capture the scene you want, not force you to find compositions that suit it, a subject I hope to return to in a future article.

 

 

Offering (Sony FE 24-70mm f4 OSS Zeiss Vario-Tessar)

 

 

So it was that I decided to upgrade my “standard” zoom to the Sony 24-70mm f2.8 G Master to take full advantage of the A7R2 sensor.

 

After using it for a couple of days it was obvious that my copy of the lens had some issues. Part of the frame towards one corner would often show smearing, and closer inspection of images at different focal lengths and apertures revealed some apparent centring issues that made corners on one side look rather soft at any aperture. More worryingly the plane of focus appeared to be diagonal through the frame, so depth of field on one side of the frame was different to the other.  Fortunately the dealer where it was purchased was very understanding, and after discussing the problem with Sony, Sony offered to replace it instead of taking it in for service, which could have taken several weeks. The second copy had notably better, more consistent image quality across the frame.

 

 

River View, taken at 66mm with an aperture of f11, shows excellent corner to corner detail

 

 

Many opportunities to show the lens at it’s best had been missed, as at the time the replacement was only used for some physique portraits, a test it passed with flying colours.  I was interested to find opportunities to see it’s “bokeh” rendering. “Bokeh”, a Japanese term, refers to the way a lens renders out of focus detail.  The general goal is to produce very smooth out of focus details with good blending of luminance and tone, with no bright hard edges. Philippe also wrote an article about “Why am I such a bokeh slut?” . Further background to the term can be found in this article written in 1997 In Photo Techniques magazine, which was thought to be the first time the term was discussed in western media.

 

Sony made great claims about the bokeh quality of the G Master lens series, which the company stated required new “extreme aspheric” elements which had surfaces ground with extreme precision. Aspheric elements, which have irregularly curved surfaces, can be made more cheaply by bonding components together (“bonded aspheric”), but where the elements meet the bonding creates imperfections which can result in optical imperfections visible in out of focus highlights (sometimes called “dirty bokeh”). Sony claimed to have improved bokeh quality by using a new manufacturing technique which required a new lens polishing machine to create very smooth extremely perfect lens surfaces.

 

One of my particular dislikes about out of focus rendering is what is sometimes referred to as “wiry bokeh”, where out of focus details take on a rather nervous wire-like quality rather than being smooth and blended. This is often combined with out of focus edges of contrast that have double edges, and “Nissen rings” can also occur, where out of focus discs of light are formed with a hard bright edge.  In my experience, some lenses with very high contrast which are often also optimised to produce very “sharp” results, particularly suffer from these effects.  It seems that very high contrast and excessive “sharpness” work against blending of out of focus areas and tend to accentuate brighter tones and highlights as discs where the goal of “good” bokeh is smooth tone.  Samples from my Zeiss Batis 85mm f1.8 show some of these traits.

 

 

Wiry bokeh, showing poor blending in out of focus detail (Zeiss Batis 85mm f1.8 OSS at minimum focus distance)

 

 

Nissen rings from tiny highlights on wet foliage (Zeiss Batis 85mm f1.8 OSS at minimum focus distance)

 

 

Even with my first defective copy of the 24-70mm G Master lens, my initial impression seemed to show a pleasant smoothness to out of focus areas, although it’s a common mistake to judge lens bokeh with plain low contrast backgrounds, since they offer little challenge and rarely reveal true character.

 

 

Chinese statues

 

 

I wrote recently about my “short breaks” of a few hours where I have been able to spend a few hours indulging in some photography as an antidote to some of life’s stress.

 

During one of these breaks, I took a walk in a narrow park beside the river Severn, and came across some beds of meadow flowers in the afternoon sun. There is always something quite satisfying photographing flowers, because nature does all the hard creative work for you, and the photographic process is often little more than the act of recording it: as Steffen asked, is photography creation or just depicting creation?  Philippe and others often take beautifully minimalist photos of flowers, shallow depth of field and plain backgrounds showing them off in all their delicate beauty.

 

 

Distant cathedral

 

 

My meadow flower photos weren’t like that, as bright directional sunshine created flowers half in backlight showing their translucent petals and half in their own hard shadow. The sunshine and the busyness of the backgrounds made photos that screamed out to be brightly coloured and cheerful, an antidote to recent pressures on my mood.

 

 

Distant sky 1 : Handling of back lighting shows good resistance to flare

 

 

Distant Sky 2 :  Again, with strong sunlight in front of the camera, resistance to flare and colour fringing is good

 

Busy : probably one of the “worst” samples I could produce, with some slight nervousness to the background, although certainly not “bad”, although I find the result quite “painterly”

 

Smooth : at minimum focus with low contrast backgrounds, the bokeh can be very smooth

 

It was one of the first opportunities to use the lens at open aperture, and I was immediately struck by the quality of the bokeh behind the plane of focus. Even with bright sunshine creating high contrast backgrounds with bright specular highlights and hard shadows, the effect was painterly, almost impressionistic. No hard edges, no nissen rings, no double edges and only the slightest nervousness.

 

Sunflower

 

Meadow field

 

Close up : minimum focus is around 38cm from the film plane, so as the lens telescopes when zoomed to 70mm, the subject can be only a few cm from the front element

 

Close up 2 : At minimum focus distance, the lens has slight softness towards the long end of it’s focal length range, which probably aids bokeh

 

Pretty in pink

 

Painterly meadow : a surprisingly “painterly” rendering with fairly gentle fall off to out of focus

 

 

Although the needs of high resolution digital imaging has made the design of all lenses more complex, prime lenses are generally still simpler than zoom lenses that cover “standard” focal lengths, and require fewer aspheric elements and esoteric types of glass.  Their faster apertures offer greater control over shallow depth of field, and their simpler designs can offer cleaner more attractive bokeh.  I don’t really expect magic from a zoom lens, even a fancily manufactured high end one.  The value of a good quality zoom is the ability to be consistent: you want a lens that you can use at different focal lengths and apertures that will produce good photographs.

 

 

Bloom : highlights behind the plane of focus can show some slight lack of blending

 

 

This article was never meant as a detailed technical review of the lens – there are several good places on the internet that can provide very detailed bench tests of resolution, vignetting and other technical measurements.  Since I haven’t yet had much opportunity to grow accustomed to my second copy, it would be premature to make too many statements on it’s character and performance.  With modern lenses, resolution can mostly be taken as a given, and even when used with a 42Mp sensor the results seem excellent.  At minimum focus there is some obvious softness, although it’s not extreme, and detail becomes crisper with focus even a few inches away from minimum.  Contrast is enough to give good detail without becoming excessive and screaming “sharp”.

 

 

Death and Decay

 

 

The fall off from in focus to out of focus seems quite soft and gradual, which works against very obvious “3D” effects, but I suspect contributes to it’s general drawing style and bokeh, which for a zoom I would regard as mostly very good and occasionally excellent.  So far I have seen no significant issues such as nissen rings, double edges or “hardness”, although there can be a slight nervousness behind the plane of focus.  I didn’t think a mere lens could turn my photographs into Monet’s water lilies or Van Gogh’s sunflowers, but based on some of these photographs and their quite gentle almost painterly style,  I  think I’m going to have to politely disagree with Philippe and say this lens can have magic – it just needs the right challenge.

 

Photographs in this article were taken with the Sony 24-70mm f2.8 G Master lens using an F2.8 unless otherwise stated, using a Sony A7R2  E mount full frame camera, and were post processed to taste using SilkyPix Developer Studio Pro v8.

 


Email: subscribed: 4

7 Comments

  1. Avatar
    philberphoto September 23, 2017

    Adrian, your pictures definitely incorporate magic, so I stand corrected. However, you will let me say that this magic has more to do with the delicate skills of the photographer than of the lens itself…:-) You have clearly found the right way in which to let that magic shine through. But, as you point out, it is a matter of finding the right challenge for it. For your type of shooting, the results are a delight, such as the “painterly background”. For mine, less so. Kudos to you for not letting my opinion stop you!

    • Avatar
      Adrian September 23, 2017

      I don’t think there is very much that is “delicate” about these photographs Philippe – bright, brash, and saturated as they are! However, the lens did a lovely job with many of them. Physique portraits taken with it at f2.8 were technically very good, with a pleasant fall off from focus, but definitely didn’t have “magic” in my opinion. Stopped down, it has great clarity and detail, and in fairness to it, I feel the black and white river scene has a certain “classic” look to it. That may be a result of the post processing used, although it helps that the lens doesn’t have excessive contrast to accentuate it’s resolution – older Minolta G lenses certainly had resolution but often weren’t optimised for “sharpness”, and Sony seem to have continued that tradition with some of the newer models. “Sharpness” in a lens is somewhat over-rated by those who like to pixel peep, perhaps without an understanding of the relationship between resolution, contrast (at a spatial frequency), and apparent “sharpness”. I was somewhat surprised how “special” some of the flower photographs looked even on the back of the camera, and I do feel some of Sony’s claims about it’s bokeh and drawing style appear to be true in the right circumstances. I don’t choose a zoom to be “special”, rather for versatility combined with “enough” image quality, and in that respect my second copy passes with flying colours.

  2. Avatar
    jean pierre (pete) guaron September 24, 2017

    Adrian, everything has its purpose in our lives. Some people say appalling stuff about zooms, others – the ones whose opinions I have more respect for – draw attention to the fact that zooms have improved over the years and these days, a good zoom isn’t much different in performance from a collection of primes covering the same range.
    IMHO (laughter off-stage: I have to say it that way, I’m a Leo!) – well IMO, anyway – it boils down to personal choice, these days. I do use a zoom from time to time (the main lens on my D7200 is the kit zoom that came with the cam, and the PowerShot ONLY has a zoom).
    One thing I find the zoom is useful for is when planning a shot. Using either zoom, I can stalk a shot I want, plan it properly, take a few test images, come home and see what sort of haul I have and – from the meta data – see exactly what focal length prime I require for the actual shot. This is quite different from the despised practice of not shooting from the right location, but – instead- using the zoom to avoid walking to the right spot. You have to do it FROM the right spot – then use the zoom to plan the composition of the shot – and, in the process, measure the required focal length.
    Then when the time is right, I can take exactly the right gear, tripod, remote, filters, exposure meter, a book to read while I wait for the exact right lighting, and everything else.
    Meanwhile, I thank the good Lord for allowing me to do all the planning with just one cam/lens combo

    • Avatar
      Adrian September 24, 2017

      Pete, thanks for your comments – very insightful and interesting.
      To be honest, I have the biggest problem with the “prime vs. zoom” debate with wide angle lenses. Personally, I regard ultra wide lenses as fairly specialist tools, and so the idea of having only one focal length just seems to limiting. What suits a 12mm won’t suit an 18mm, and with such extreme angle of view, the idea of “zooming with your feet” is often impossible nonsense. When I photographed the Singapore skyline at dusk I used a 16-35mm zoom, because I couldn’t zoom with my feet without being able to walk on water (a skill not yet mastered!) – and Singapore wasn’t going to move for me. What would have resulted would not have been the image I wanted to make – hence my comments about zooms for travel. The other instance where fixed focal length can be an issue is surprisingly portraiture, as I often work indoors in quite confined spaces. Of course, it’s nice to use an 85mm lens or other similar internet-mandated “portrait” lens, but often space and composition don’t allow, and a zoom can be an effective way of dealing with the unknown – I know the view I want, and need to get a focal length to fit.
      In the past, I often used a 17-35mm zoom with 50mm and 85/100mm primes as a daily “travel” kit. Now, with vastly improved high ISO performance, and much better zoom lenses, something like a 24-70mm zoom and perhaps a 50mm prime is a good alternative. I feel slightly “dirty” admitting this, but zoom lenses seem to have become so good – not “magic”, but with more than enough quality – that they remove the need to carry every lens for every possible occasion, and then constantly change them in the field and get a sensor covered in endless dirt.

      • Avatar
        jean pierre {pete} guaron September 25, 2017

        Thanks for your response, Adrian. Actually I was trying to be gentle about it – but really, I’m fed up with “opinionitis”. If you listen to the “purists”, it would stultify all creativity, development, growth, experimentation, progress, whatever.
        The reason I ventured the comment that “good” zooms are now comparable is quite simple. Everyone [?] in the group knows I shoot Otus on the FF. With the exception – for the moment – of the Sigma 85mm ART, the Otus’s are the “world’s best”, for FF’s. So what? – sensors don’t keep up with them. It’s no earthly use claiming that the next sensor or the one after that is going to outperform those lenses. That’s twaddle. They can put a zillion pixels on a sensor, for all I know or care – I’m prepared to wager that it will NEVER outgun top quality lenses. Or, for that matter, the next level down.
        SO what’s the solution?
        Well for one thing – stop making silly dogmatic claims that primes are somehow “better” than zooms, when in fact some of the best zooms actually perform just as well as most of the better primes – and when that doesn’t matter anyway, because image quality falls away ages before the quality of EITHER type of lens does.
        And if you really want to persist with such arguments – well (a) please leave me out of it, I can’t be bothered with it and (b) to win, what you must do is trade in all your FF & HF gear, buy any half decent MF or larger, and any half decent lenses for the MF. That’s guaranteed to widdle all over ANYTHING you can produce with smaller format cams, and it doesn’t matter a stuff if you use a zoom or a prime to lose the argument. The MF will win hands down.
        So – bring on the angry horses, and let the war games begin. 🙂 🙂 🙂
        Meantime, I’m more interested in photography than that line of argument. I fully intend to withdraw from the debate, and enjoy the gear I’ve got, taking the photos I want to, and put a stopper in my mouth, to prevent any repetition of these views from my direction in future postings.

        • Avatar
          Adrian September 25, 2017

          Pete, I would regard my attitude as mostly “pragmatic”, in that I use whatever gets the job done with “enough” quality. I know some may dismiss this and say they (want to) use the very best equipment possible for the very best image quality. Towards the end of my time using 35mm film, I “chased rainbows” looking for elusive image quality from esoteric lenses in my chosen mount because of all the words like “micro-contrast”, “tone”, “colour” etc. In the end I came out the other side and realised that the (male?) obsession with equipment and the like had little relevance to the quality of the pictures taken. Nobody (except some photographers) looks at a photograph and thinks “nice micro-contrast and tone”, most people judge the content. It’s not that I don’t care about quality – let’s be honest, the Sony 24-70mm f2.8 GM is hardly “inexpensive” – but it’s only important that it’s “enough” for the final purpose and to get the job done, not a pursuit in itself. It is why I am intrigued by the potential of the RX10 mk4 – yes, the sensor is small and it’s not as good as larger formats and the dynamic range isn’t as good blah blah blah – but it shoots at 24fps with a lens that’s f4 from 200mm to 600mm. A Sony A9 shoots at 20fps, but it costs 3 times as much, and a lens of the nearest similar specification would cost a few thousand more, and weigh a few kilos. For what I mostly need, web presentation and some A4 prints, the RX10 would probably be just fine. It’s “enough” quality for the intended use. The Sony FE 24-70mm F4 Zeiss Vario-Tessar that I used is mostly derided on the internet, I think because it doesn’t work very well with the Sony A7R 36mp sensor, which was rather difficult with some lenses, but on my cameras as 12Mp or 24Mp in the middle of it’s focal length range and stopped down, it was near to prime quality as far as I could tell, and it became my most used lens for sheer convenience, versatility, and overall image quality. Knowing when equipment is at it’s best or worst is important to be able to play to it’s strengths and get good results. I’m not really interested in “chasing rainbows” any more, because I think it becomes a pursuit by itself that is nothing to do with taking photographs. I still use prime lenses, mostly for available light work when I need their faster apertures, or when I want more control over depth of field. The Sony FE 24-70mm f2.8 G Master appears to be a very capable lens that I think will become an often used tool in my bag, because in the situations that matter to me, it will offer more than enough image quality (“prime like”?) and greater versatility than carrying primes. My most used lenses when travelling have become a 16-35mm and a 24-70mm simply because of their versatility, and no Otus or Milvus or Summilux will change that.

          • Avatar
            jean pierre (pete) guaron September 26, 2017

            I couldn’t agree more, Adrian – that’s much the same as my explanation for using the Canon PowerShot to photograph people’s dogs – they never want anything larger than A4 anyway, and that cam is so easy to use for that purpose.
            When I want to chase rainbows, I’ll get all the help I need from passing showers.

Leave a Reply

Your email address will not be published. Required fields are marked *