Sunday, 20 October 2013

Lumix Leica DG Summilux 25mm f/1.4 Review Part 1

Back in the 1960's, when SLR cameras started to become available to the general public, one could essentially only buy prime (non-zoom) lenses. The cheapest lenses were the ones which were short, but still long enough, in terms of focal length, to be constructed without a complicated retrofocal design.

The cameras generally had a register distance of around 45mm, which means that any lens shorter than this will be more expensive to make. Hence, a popular segment became lenses around 50mm. These could be made fast, i.e., with a large maximum aperture, fairly inexpensively. For this reason, many bought their camera with a 50mm lens lens, which became known as the normal lens. It was the kit lens half a decade ago.

Wide angle lenses would require a retrofocal design, which was expensive. And longer lenses would require larger lens elements, again keeping the price high. So the 50mm lens was the most common (normal) lens to use on SLR cameras, simply because it was inexpensive.

At that time, to have a zoom lens which covers a range of focal lengths would be an unbelievable luxury. Today, it is the other way around. It is the zoom lens which has become the normal lens, the lens people buy in kits with their camera. While the 50mm (equivalent) prime lens has become the luxury item.

That is the case with Panasonic Lumix G Micro 4/3 LEICA DG SUMMILUX 25mm f/1.4 Leica Aspherical Lens. With the 2x crop factor of the Four Thirds sensor size, this lens corresponds to 50mm on a traditional film SLR camera, in terms of field of view. It has been co-branded with Leica, to underline the luxury, premium value of the lens.



Lumix 20mm f/1.7, Lumix Leica 25mm f/1.4, and Sigma 30mm f/2.8 DN



If you read internet forums, you will often see people saying that a fast 50mm equivalent lens, like the Leica 25mm f/1.4 is all you need. If you feel the need for zooming, just zoom with your feet, they would say.

It doesn't take much reasoning to see that this does not always hold. And there is nothing wrong about using a zoom lens at all. There are many good zoom lenses, e.g., the Lumix X 12-35mm f/2.8.

That, said, a fast prime lens like the Leica 25mm f/1.4 is also a good lens to have. The focal length is versatile, between a wide angle lens and a portrait lens.

Why this lens?


Most people who buy into the Micro Four Thirds format have a kit zoom lens, which came with the camera. This zoom lens includes 25mm, so why buy this lens in addition? What's the extra value?

The answer is of course the aperture. A kit zoom lens typically has a maximum aperture of f/4.5-5 at 25mm. This lens opens up to f/1.4, which is about 3.5 stops faster. This translates into 10-12x more light coming through the lens.

This can make a big impact when it comes to light gathering capability. Let's say you are limited to a shutter speed of 1/5s using the kit zoom lens, given a dark scene. Using the Leica 25mm f/1.4 wide open means that you can use a shutter speed of 1/60s and get the same exposure.

Another important factor is selective focus. The larger the aperture, the more narrow the depth of focus becomes. Read about it here. Essentially, this means that with a big aperture (small f-number) you can better isolate what you are focusing on. What's in front of the subject, or behind it, becomes blurred.

The selective focus can be used as an effect, as part of your composition. This way, it can be a positive thing. For people who like to use selective focus as an effect, a lens with an aperture of f/1.4 would be a "holy grail", something to crave for.

On the other hand, there are times when you need a deeper focus. Then, the selective focus can be a limitation. At larger apertures (small f-numbers), only a smaller part of your image will be in focus, which may not be what you want. To illustrate this, look at the pictures below.

Leica 25mm @ f/1.4Leica 25mm @ f/5
With a kit zoom lens, you are limited to a maximum aperture of around f/5 at 25mm. This gives a fairly deep depth of focus (the right image above). To be able to take pictures with a shallow depth of focus, you need a fast lens, with a large maximum aperture, e.g., the Leica 25mm f/1.4.

For this to work, there are two important factors to consider: Is the lens sufficiently sharp at large apertures? This is far from obvious. Many fast lenses are only sharp when stopping down the aperture by some stops. If this is the case, then you may find the lens useless, despite the large aperture. What use is it to have f/1.4, if you need to stop it down to f/2.8 for the image to become sufficiently sharp?

The other factor to consider is the bokeh. If the out of focus rendering is busy, not effectively blurring the background or foreground, then you may find the lens useless at big apertures, and, again, why buy the lens in the first place? In this article, I look at the bokeh of the Pentax 50mm f/1.4, finding that it is not very good at f/2 and below. Hence, people may find the Pentax 50mm f/1.4 to be less useful.

For these reasons, I am testing both the sharpness and the bokeh in this article. If the sharpness is poor at large apertures, or if the background is rendered in a distracting way, then why get the lens in the first place? If you have to stop down to f/2.8 anyway, then you could rather get the Sigma 30mm f/2.8 DN, which does have a good sharpness and a nice bokeh already from f/2.8. It would be much less expensive.

Physical


The lens is very similar to the Leica 45mm f/2.8 1:1 macro lens. The exterior is matte black plastic, apparently of high quality. Beyond the focus ring, it has no moving elements at all. This makes the lens feel very solid.

Just like the 45mm lens, the focus ring is quite wide and rubberized. Rotating it feels very smooth and well dampened. It has a high quality feeling. Those two lenses have the best focus rings, out of the lenses I have tried for Micro Four Thirds.

Contrary to what you might guess, the lens is actually fairly large. Compared with the Lumix 20mm f/1.7 pancake lens, it is massive. While it is smaller than legacy 50mm lenses for SLR cameras, it is not a lot smaller.

The exit pupil is a bit recessed into the mount, and has a quite large diameter. This is usually a sign of a quality lens, but there is of course not any automatic correlation:



As you can see from the picture above, the mount has a good polished finish, a nice touch.

Hood


Just like many of the Panasonic lenses, it comes with a hood. It goes into the front bayonet mount. To put it bluntly, I don't like the hood. It is large enough to be annoying, but not large enough to reverse on the lens for storage. I think the lens was designed to look nostalgic, and not to be practical.

Like with many of the smaller prime lenses, rather than use the original hood, I prefer to use a 46mm to 37mm step down ring as hood. This gives some basic protection of the front lens element, while keeping the overall package compact. If you go down this route, you also need a 37mm front lens cap. See below for an illustration:



With original hoodUsing a 46mm to 37mm step down ring as hood

Focus speed


To test the focus spees, I set up the three lenses (Lumix 20mm f/1.7, Leica 25mm f/1.4, and Sigma 30mm f/2.8 DN) on the Panasonic GH3 camera, with a figure about 0.3m from the tip of the lens. Then I started the camera, bringing the lenses into "around infinity focus" position, and saw how much time it took for them to reach the correct focus and snap the picture. Here is the test:



The results can be seen below:

LensLumix 20mm f/1.7Leica 25mm f/1.4Sigma 30mm f/2.8 DN
Focus delay0.56s0.38s0.52s

In this overview, the most surprising result is how fast the Lumix 20mm f/1.7 lens focuses. This has always been referred to as a slow focusing lens. However, it is important to keep in mind that this result is mostly due to the focus improvements of the GH3 camera. In this test, I show that when paired with the GH3, the lens focuses impressively good. So if you are unhappy with the focus performance of this lens, perhaps a solution could be to upgrade your camera to a newer model. Panasonic have made big improvements over the last year.

Regarding the Leica 25mm f/1.4, it focuses the fastest of the three. Still, the focus speed is not impressive, when compared with the zoom lenses. One explanation is that this is a lens with a very large aperture, hence, the focus must be a lot more precise than with zoom lenses that have a smaller aperture. This focus precision takes some more time, it means that the lens groups must move in smaller steps to avoid overshooting. I'd say the Leica 25mm f/1.4 does well for a fast prime lens.

Image quality


To test the image quality, I have taken example images with the Lumix 20mm f/1.7 and the Leica 25mm f/1.4 at various apertures, for comparison. I used the GH3 camera, had the camera on a tripod, used 2s delay to avoid camera shake, and set the base ISO (200) for the best image quality. The shutter speeds were generally very fast, faster than around 1/500s. I focused on the tree in the right half of the frame.

Lumix 20mm f/1.7 @ f/1.7Leica 25mm f/1.4 @ f/1.4

To better assess the image quality, here are 100% crops from the centre:



And from the top of the frame:



And finally from the extreme top right part of the frame:



We see that the sharpness is not optimal at f/1.4, but improves until reaching f/2.8. The performance of the Leica 25mm lens is especially impressive in the extreme corner. Here, the Lumix 20mm lens falls short, but the 25mm lens is very good.

There are some chromatic aberration (CA) artefacts even in the centre when wide open. You can see this as the purple fringing around the twigs. These artefacts are typically seen when you have high contrasts in the image frame. In this example, they are caused by having the sun just behind the trees, which causes the large contrast between the sky and the branches.

If I had chosen an example image without this high contrast, then I would not have had any CA artefacts. That's the reason for finding an example scene with the contrasts in the first place, to make the test more challenging for the lenses. The CA issue is gone when stopping down to f/2.8.

Despite this, I think both lenses are impressively good, even wide open.

Bokeh


I have previously looked at the bokeh of this lens, compared with a host of other lenses. The Leica 25mm f/1.4 did not get perfect scores here. I noted that out of focus highlights were non-round outside of the image centre. Further, objects in the background were rendered a bit busy at f/1.4, and with moderate focus distances.

I have another comparison image here. I focused on the leaves in the foreground, with a distance of about 0.5m.

Lumix 20mm f/1.7 @ f/1.7Leica 25mm f/1.4 @ f/1.4

Here are 100% crops from the centre. Note that you should not use this to assess the sharpness of the lenses, as this part of the leaf is not in focus:



And from the extreme left part of the frame:



We see that the Lumix 20mm lens has somewhat more jagged edges when stopping down. So the aperture blades of the Leica 25mm lens appear more rounded. Apart from that, both lenses appear to blur the background quite effectively, even at maximum aperture. The background could have been more evenly blurred, but it is no significant problem.

Example images


This picture was taken at f/1.4, 1/60s, ISO 1250. I panned the GH3 camera while taking the picture, to blur the background:



In this picture, I focused on the postcard in the foreground. I used f/1.4, 1/800s, ISO 200. I focused using the touch function, setting the focus area by pressing on the lower, centre part of the LCD display:



An example 100% crop from the foreground, where I focused:



Example video


In this concert video, I set the exposure manually, due to the changing stage light. I set f/1.4, 1/40s, ISO 3200. The autofocus was left on, in the auto everything mode, where the camera tries to find faces to focus on. This works quite well. Some times, when the stage is busy, the camera focuses in the background, which is more stable.



The lightning on the stage is very challenging. There is very dim light on the artists, corresponding to an EV value of only 1.5. On the other hand, there is very strong backlight. This usually causes heavy flaring with most lenses. It seems like the Leica 25mm handles it quite well, though.

Conclusion (so far)


I plan to investigate the Lumix Leica 25mm f/1.4 further in a second part of this review. In the mean time, it is safe to say that this lens is very good. The build quality is pleasing, it focuses quickly, even during video recording. Further, the sharpness is impressive. And the quality of the out of focus rendering (bokeh) is good, albeit not perfect.

With the large maximum aperture of f/1.4, this lens is very good to have for the dark season which has just started, at least for those living on the northern hemisphere.

In the next instalment, I will be looking at the focus breathing, the clicking sounds the lens makes, comparing with other lenses, and more.

At this time of writing, this is this is the autofocus capable Micro Four Thirds lens with the largest aperture. However, it is expected to be beaten by another Leica branded lens soon. Panasonic will be releasing the Lumix Leica DG Nocticron 42.5mm f/1.2, expected to be available late 2013 or early 2014. It will feature OIS, and will probably be very expensive.

There are even faster lenses available today, but they are manual focus only. There is a series of Cosina Voigtländer lenses: 17.5mm f/0.95, 25mm f/0.95, and a 42.5mm f/0.95 is in the pipeline. There is also an SLR Magic 50mm f/0.95.

Here is part 2 of the review.

10 comments:

  1. I'm not seeing evidence to support the "sharpness is impressive" comment in the conclusion. In particular the image focused on the postcard with a man on the left and a woman on the right in the background. The other examples are difficult to tell but don't exactly scream "impressive" when it comes to sharpness.

    ReplyDelete
    Replies
    1. I think the sharpness is impressive, given that this is an f/1.4 lens. Very fast lenses are typically not very sharp wide open, but this one is. I will be making more comparisons with other lenses in the next instalment which demonstrates this.

      Delete
  2. thank for your review. I sold my 20mm for 25mm last month, it's an impressive lens.

    ReplyDelete
  3. A lens you should try is the Olympus 45mm f1.8. Inexpensive and very good image quality. Thanks for this review. Hilsen Jon Arne.

    ReplyDelete
  4. Good writeup Fredrik.

    On your leaf bokeh test you say that you are taking a picture at 0.5m for both the 25mm and 20mm lenses.

    Realistically and "in general use" the point of having a larger aperture is so that you can obtain out of focus effects at a further distance. Taking aside all the internet reviewer comments about "rendering" which are subjective it is much easier to get out of focus effects without getting close to people and subjects using this lens due to its larger physical size and aperture, which is the purpose of this lens from the start.

    To judge the bokeh fairly you would need to stand further back with the 1.4lens at a distance which offsets it's larger aperture and focal length) difficult in practice I know!) What constitutes "busy" would surely depend on what is in scene the background, I find it too subjective. If we were looking at 2 lights 1m apart then the scene would not be busy at all, we would all say it's beautiful rendering.

    The companies who make these lenses generally have a specific customer in mind. I would say if you are shooting landscapes, backgrounds just stick with the 20mm. However if you like portraits, people pictures and street photography the 25mm is a better choice. It depends on what you want to do with the lens, we should not forget that for a photographer a lens is a tool.

    I did not get the 25mm in 2011 on release as it was expensive. It has actually dropped in price now, it is perhaps 30% more than the 20mm 1.7. At this price I think the 25mm overall is a better choice.

    In my opinion I think this lens is excellent and is very cheap at its current price it is very sharp wide open relative to it's peers (in price and system) and anything other than super expensive FF primes.

    f you remember Panasonic/ Leica collaborated to make a 1.4 for the old 4/3rds system. Nowadays that lens costs anywhere between £700-1000 UK so there is a case to be made for buying the 25mm as an investment.

    ReplyDelete
  5. I enjoyed this comparison. I have the 20mm and look forward to the 25mm for its colour rendering and clarity.

    My first question is about how well your 46 to 37mm step-down works with a 20mm. How does the movement of the lens focusing affect this? I am slightly confused about this issue.

    My second question is how effective the small step down works as a hood on the 20mm, 25mm, 45 2.8mm etc.

    FrankS009

    ReplyDelete
    Replies
    1. 1. The Lumix G 20mm f/1.7 lens has a traditional focus method, in which the whole array of lenses move back and forth. The focusing could be hampered in two ways by attaching various stuff to the front end of the lens: (A) The attachments could strain the focus motor simply by sheer weight. (B) The attachments could physically stop the movement of the lens elements.

      The step down ring is not really heavy enough for (A) to be a factor. People often put filters on the lens, which weight much more than this step down ring.

      (B) could be a problem if the attachment extends wider than the moving lens elements. This can happen if you put a step up ring on the lens. As the step up ring is wider, it can jam as the lens powers up or down, when it jogs the focus back and forth for testing. This has happened to me, and other people as well. So don't put step up rings on the lens.

      But the 46-37mm step down ring is not too wide, and neither (A) nor (B) is an issue

      2. I don't think a 46-37mm step down ring is very effective as a hood. It my keep out some stray light, but not a lot. I use them mostly as physical protection, to avoid putting my finger on the front lens element, for example. And for this purpose, they work well.

      Delete
    2. Thank you.

      Smaller, reversible lens hoods like those of the Sigma 60 for example seem practical. But they are still a bit obtrusive for street shooting. I have no desire to show off with my big square lens PL hood so am looking for alternatives for the PL25mm and the PL45mm.

      Incidentally I like the idea of a 37mm step down ring as protection, especially since my GF1 fell off a shelf and jammed the UV filter into the lens. A 37step down ring might have only jammed onto the UV filter. As it happens the 20mm lens was fine afterwards - the UV filter not so much so.

      F.

      Delete
    3. On this subject, you could also see my article on lens Hoods for prime lenses. It includes some related thoughs.

      Delete