There are several fast-normal options available today for Micro 4/3 users – the Panasonic 20/1.7, the Panasonic-Leica 25/1.4 DG Summilux, and the fastest of them all, the Voigtlander 25/0.95. There are also a whole host of modified CCTV and C-mount lenses, some of which cover the whole M4/3 frame, some of which don’t. None of them have enough resolving power to match the resolution of the sensor at full aperture, either.
Given the limited high-ISO capabilities of the earlier M4/3 sensors, there was an obvious gap left for a hyperspeed lens of any sort; being one of the M4/3 consortium members, Voigtlander stepped in to fill the gap. However, not having AF technology, Cosina had to make do with a manual-focus only design, but with a native M4/3 mount. The lens feels nothing like the M4/3 lenses from Panasonic, Olympus or Sigma; it’s a hefty lump of metal, built with the same solid feel as the more premium modern manual focus lenses. It’s not a small lens, especially once you attach the supplied hood – it’s actually about the same size (and much heavier) than the Voigtlander 75/1.8 for M mount. This lens rates very highly on the tactility scale; the focus ring is well-damped but turns smoothly without much effort; there’s no backlash and this makes focusing a very pleasing experience. The aperture ring has neat half-click detents, but I would prefer the stops to be a bit more decisive and less easy to turn.
Let’s talk a bit about focusing – because one of the most frequently asked questions I’ve had with this lens. I would say it’s easier than expected, but not as easy as I would like – especially when using the lens stopped down. Since there’s no electronic linkage between the lens and camera, aperture is entirely mechanical; this means that you’re always seeing the stopped down view through the finder or on the LCD. The trick is to shoot raw, and turn focusing on your jpeg settings up to the maximum – this actually creates a little bit of a shimmery halo in the finder. (These settings of course do not affect the raw file). It also accentuates sharpness of the image, which makes it easier to tell when things are in focus – as you turn the focusing ring past then point of focus and back again, there’s a slight shimmer in the live preview. The focusing ring is also well-spaced – the normal range from about ~0.4m to infinity is easily covered by a turn of the wrist without having to reposition your hand; the near range – down to just 0.17cm – is more widely spaced, and allows for precise placement of the focal plane.
One doesn’t buy this lens with the intention to use it at any other aperture than wide open, at least most of the time. There’s simply no point in paying so much (it’s considerably more expensive than the Panasonic-Leica, which of course has autofocus and is about one stop slower) and carrying around so much extra weight if you’re going to use it at f2. In fact, you might as well get the Panasonic 20/1.7 – it’s cheaper, much smaller and focuses itself. The good news is that the center produces acceptable sharpness, even wide open – providing you focus it accurately. (The shallow depth of field transition profile of a 25mm focal length lens means that that finding the optimum plane isn’t always easy, either.)
There’s a considerable improvement in acuity at f1.4 in the center, and again at f2; however, the corners don’t reach anywhere near central levels of sharpness until f2.8 and beyond. Note that I use the term ‘acceptable’: it’s not great at f0.95, and there’s a distinct softness that’s probably caused by internal flare; I suspect that if the internal surfaces of the barrel were better coated against reflection, we’d see a corresponding improvement in contrast and sharpness. Microcontrast is simply nonexistent until f2, and macro contrast is generally quite flat, too – making it good for retaining dynamic range under extreme lighting situations, but poor for fine texture reproduction.
What about the other common lens shortcomings, like vignetting, chromatic aberration, flare and distortion? The 25 has all of them, and in quite generous amounts, too. It will vignette wide open, but this is easily corrected and gone by f2.8. Chromatic aberration is a bit more problematic; we see that and purple fringing against high-contrast backgrounds, especially when subjects are backlit. If you get a bright point light source in the wrong part of the frame, you’re going to have fun with flare, lowering already low contrast even further – and the hood isn’t going to help you much. I didn’t actively look for distortion, so I can’t comment on it; the types of subjects this lens is suited to probably wouldn’t show it anyway.
After all of that, you might have come to the conclusion that this lens is pretty bad – optically, it’s definitely not the best I’ve used. But, what other lens offers a true f0.95 aperture (and T stop that’s not far off, either) at US$1200? I can see some uses for the 25 – portraiture, mostly – but it just doesn’t suit what I do. Even though the optics at f4-5.6 are excellent, and the 17cm near focus distance makes it quite useful for food photography, there just isn’t enough reason for me to keep the lens around since it replicates the performance of the Panasonic 20/1.7.
As much as I love using the lens simply because it feels like a real lens, not a plastic shell – I just can’t recommend it for the kind of photography I do; it’s not sharp enough wide open to be used as an available-light lens, and is further hampered by the difficulty of focusing it under low light conditions; it’s big enough to defeat the point of the compact M4/3 system, and expensive enough that I think having the 20/1.7 and 45/1.8 lenses instead makes much more sense.
If you’re an object shooter, as tempting as the close focus capability is, you can’t really use it wide open without dealing with rendering that’s best described as ‘impressionist’; you’re better served by the Panasonic-Leica 45/2.8 Macro, or the forthcoming Olympus 60/2.8. If you’re an available light shooter, and don’t mind the occasional softness due to focusing misses, then go ahead; if sharpness bothers you, then go for the Panasonic Leica 25/1.4 Summilux. However, I can see a very narrow niche of portrait photographers for whom pictorial style takes precedence over sharpness; this is your lens, and it offers a look previously limited to larger format systems.
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