Fans have been puzzled over the large number of kit zoom lenses released by Panasonic. Why reiterate this formula so many times, when the original Lumix G 14-45mm f/3.5-5.6 was so good, many will ask.
The answer is probably three-fold: To cut costs, to make the lens smaller, and to improve the quality. Here are the lenses sold in kits after the original zoom lens:
In the front, I have the Lumix G 14mm f/2.5 and the Sigma 30mm f/2.8 DN, which I will use as reference lenses. After all there are plenty of those who think that a prime lens is always better than a zoom lens, and we shall see if it is true.
Most of the Micro Four Thirds lenses need geometric distortion correction applied for the output images to become rectilinear. This is done totally seamlessly by the camera and software, both for JPEG and RAW images. So the user never notices that the image, as seen by the camera through the lens, is not rectilinear in the first place.
This is in contrast to older DSLR systems. In these systems, there is an optical viewfinder, in which the users sees exactly what the sensor sees, through the lens. With a DSLR system, the lens must be rectilinear, otherwise, the user will be appalled by the geometric distortion when using the camera.
Here is an illustration of two basic kinds of distortion: Pincushion distortion (left) and barrel distortion (right):
In reality, the geometric distortion might very well be more complicated than what is illustrated by these simple models.
Again, I have done the tests by taking a pictures of a tiled wall. The images look like this:
Since I am only interested in the geometric distortion, I have increased the contrast so that the images become monochrome. I also superimposed the corrected out of camera JPEG images (black) onto the original RAW uncorrected images (red).
I included the appropriate adjustment needed. The adjustment numbers in percent refer to the "Lens Distortion" filter in The Gimp, an image processing software. Of course, to become rectilinear, some lenses might require more complicated adjustment than the simple model given by the "Lens Distortion" filter. So these figures are just intended to be approximate relative indicators of the degree of distortion. A positive figure indicated barrel distortion, while a negative figure indicates pincushion distortion.
Here is a comparison of the uncorrected and corrected images for some lenses.
There is a significant barrel distortion, which is corrected in the in-camera JPEG image. However, there is some residual barrel distortion even in the corrected image. I have noticed this previously. In fact, the lens is rectilinear (after correction) at long focus distances, but has some barrel distortion at close focus distances. In this example, we see the barrel distortion at close focus distance. This is not an uncommon behavior for lenses that feature internal focus.
No distortion correction at all. It looks like there is a small amount of pincushion distortion, though, so perhaps there should have been some in-camera correction done by the camera.
We see that wide angle lenses and zooms typically feature barrel distortion (negative figure) in the wide end. On the other hand, longer lenses are often not corrected, or are corrected for a small amount of pincushion distortion (positive figure). The in-camera distortion correction is some times insufficient, for example we've seen that the Olympus M.ZD 45mm f/1.8 and Lumix G 14mm f/2.5 pancake lenses feature some geometric distortion in the short focus range, while behaving better at infinity focus.
There are some who have speculated that Leica-branded lenses are not subject to any software corrections. I have looked at the Panasonic Leica 45mm f/2.8 1:1 macro lens, and found no indications of software adjustments to the images. However, I still don't believe that statement. One of the first cameras for which the software corrections were widely discussed online, was the Panasonic Lumix LX3 high end pocked camera from 2008. And it does feature a Leica-branded lens, and quite clearly, there is a significant barrel distortion in the wide end of the zoom, which is corrected by software.
There are many ways to achieve macro possibilities. The simplest is of course to buy a dedicated macro lens, like the Leica-Lumix 45mm f/2.8 1:1 macro. This lens does macro very good, and is easy and fun to use. The only negative side is that it is rather expensive, probably in part because of the premium Leica branding.
Another way is to get a cheap legacy lens, and some macro extension rings. If the lens has a mechanical aperture ring and focus ring, then it is quite easy to use with macro. Of course, you must control the focus and aperture manually on the ring, and there is no EXIF information to the camera. For even better control, you could buy some macro bellows, for stepless extension distance.
A third method would be to buy a macro lens to put into the filter threads of the lens. There are a number of third party macro filters to buy, and Panasonic has even launched their own, which can be used with the Lumix G 14mm f/2.5 pancake, and the Lumix G X PZ 14-42mm powerzoom pancake kit lens. I have not tried any of these.
A fourth method is to buy a macro reverser ring. A reverser ring is quite simply an attachment which allows mounting a lens reversed on the camera. I have tried one such ring, easily available on various auction sites for around US$10. It is a simple thing. On one side, it has a Micro Four Thirds lens mount. The red dot makes mounting easy:
On the other side, it has a 52mm lens thread:
The 52mm threads is a good choice, since it fits a number of lenses.
Here is the adapter mounted to the Panasonic GH2. It will of course fit any Micro Four Thirds camera.
Mounting a Nikkor 24mm f/2 AIS lens
I have got an old, rather banged up Nikkor 24mm f/2 AIS lens. It has got a 52mm front lens thread, and hence fits well onto the adapter. Here is a video showing how to mount it:
After mounting the lens, you can still control the aperture with the mechanical aperture ring, which is a good thing. When used like this, the lens has a very short focus distance, good for macro, but it also has a very thin depth of focus. Hence, you will normally want to stop down the aperture to at least f/5.6 to get more in focus. Normally, you will focus at f/2 (for the best focus accuracy), and stop down to f/5.6 (or more) before taking the picture.
I took this test picture of a ruler (in millimeter) to test the magnification:
The test picture shows that the magnification is 17.3:13 (with 17.3mm being the horizontal width of the Four Thirds sensor, and 13mm being the width of the object depicted). This corresponds to 1:0.75 magnification, also written as 1.33x. This is slightly more magnification than what is possible with the Leica-Lumix 45mm f/2.8 1:1 macro. On the other hand, no focus is possible at all with this solution. You can only take pictures at 1.33x magnification.
Mounting a Lumix G 14-42mm f/3.5-5.6 kit zoom lens
The Lumix G 14-42mm kit zoom lens also has a 52mm front thread. Hence, you can mount it to this adapter. Here is a video showing how to mount it:
Using this is quite different from the manual Nikkor 24mm f/2. First of all, the negative sides: The Lumix G 14-42mm lens does not have an aperture ring. Hence, you cannot easily adjust the aperture. This makes macro use difficult, since you will normally need to stop down the aperture for more depth of focus (DOF).
The positive side is that you can use the zoom ring for changing the magnification rate. The focus distance is also changed at the same time, but at this enlargement, it makes more sense to use the word "magnification" than "focus". At 14mm, you get the maximum magnification, and the minimum at 42mm. Let's take a look at this.
@14mm
Again, I photograph the ruler to find the magnification:
The ruler shows 7mm, hence the magnification is 1:0.4, or 2.5x:
The working distance is 2cm, which is quite short. I try to photograph a LEGO figure here, and as you can see, the subject is almost touching the rear end of the lens:
Here is the result, at 14mm f/3.5. I focused on the eye, but due to the very thin DOF, only one eye is in focus:
@42mm
Here is the photo of the ruler, showing a 1:0.87 or 1.15x magnification ratio:
At 42mm, the working distance is 4cm:
And here is the result, at 42mm f/5.6:
Example image
This is a picture a tooth brush, and was taken at 14mm, f/14. I could probably have stopped down the lens even more for more depth of focus.
Also note the dots throughout the image. They are probably dust particles on the sensor, and come into focus when using extremely small apertures, like in this case. Otherwise, they don't cause any negative effects.
Mounting a Lumix G 45-200mm f/4-5.6 tele zoom lens
However, when mounted reversed, it focuses near infinity at 45mm, and nowhere at longer focal lengths. Hence, it is useless for reverse macro use.
Mounting other lenses
Both these lenses have a front thread of 52mm, making them easy to mount. But let's say you have the Lumix G 20mm f/1.7, with a front thread of 46mm. What to do?
You can get a step up ring. Mount a 46mm-52mm step up ring to the front of the lens, and then mount the front of the step up ring to the adapter. A step up ring is very cheap to get on various auction sites.
Take care that mounting a wide attachment to the Lumix G 20mm f/1.7 lens can cause the focus mechanism to jam. So don't power the lens with the step up ring attached.
Conclusion
Using the reverser ring adapter, the Lumix G 14-42mm lens can be mounted reversed, and the zoom ring can be used for focusing. The magnification rate is 1.15x-2.5x, which is not a very large range. For comparison, Canon has a specialized macro lens called Canon 65mm MP-E, with a macro focus range of 1x-5x.
Changing the aperture is not very easy with this lens, but it is needed. You cannot photograph macro images using the lens wide open, since the DOF is too thin. To stop down the lens, you can mount it to a camera, and start a long exposure at f/8, 4s, for example. As the camera is exposing, remove the lens. That way, the lens is stopped down to f/8 when you remove it. Do this at your own risk.
This is a cheap way to achieve macro possibilities with the kit lens, a lens that quite many users probably have already. But is is not very easy to use. First of all, the working distance is very short, so you cannot photograph live insects. They will be scared off.
Second, changing the aperture is awkward. And third, the macro range is limited, at 1.15x to 2.5x.
But if you want to experiment with macro images of static objects, than this is a very inexpensive way to do so.
However, when evaluating the bokeh characteristics of the lens, I noticed that the out of focus highlights were non-round. This is found for some lenses, for example the Lumix Leica 45mm f/2.8 1:1 macro lens has elliptical out of focus highlight rendering outside of the centre of the frame. But I found that the Lumix G 14-42mm lens had more like potato shaped highlights.
The store keeper has some problem verifying that his off the shelf lens did not exhibit the same non-round aperture. I helped him by taking a photo with the lens mounted to the Panasonic GF2 camera at f/9, 2 seconds, and removed the lens during the exposure. Looking towards the light through the lens showed that his copy had a round aperture.
So he accepted my lens as defective, and sent it for repair.
After one month, I started enquiring about the lens. I always got the same answer: "The lens is just around the corner, should be in our store the beginning of the next week."
It was not until after three months that the lens finally did arrive in the store. When I went to pick it up, I was told that they simply replaced the lens with a new one. Why let me wait for three months when they would just give me a new copy?
Coming home, I once again checked if the aperture was rounded. See for yourself, this image was taken with the Lumix Leica 45mm f/2.8 1:1 macro lens:
In fact, my new lens exhibits exactly the same problem as the one I returned in the first place. I did check that the new lens has a different serial number, so it is not the same lens that I returned.
Letting me wait three months for a new lens is bad. But giving me a new lens which has the same problem as the one I returned is simply appalling.
Epilogue
I took the lens back to the retailer again. This time, they offered to change my lens directly from their stock. We tested two lenses, and neither had completely round apertures. One was as bad as my own lens, and the other was pretty rounded. So I took the best one.
I don't expect perfectness from a lens this cheap. So I am happy with the near round aperture opening.
First, I took a picture in which I set the lens to tele (42mm), focused as close as possible, and placed a flashlight in the background. The flashlight renders out of focus. Here is the full image at f/5.6, the maximum aperture. The flashlight is placed in the centre of the image:
To see how the roundness changes when stopping down, I have made 100% crops from the centre at various apertures:
This verifies the problems I saw when studying the bokeh. The out of focus highlights are definitively not circular. It looks like the aperture diaphragm blades are misaligned.
Micro Four Thirds lenses are always wide open when powering the camera down. This means that normally, you cannot look at the diaphragm blades from the inside, since the aperture is wide open.
However, a trick is to stop down the lens, and then remove the camera battery. That way, you can remove the lens while stopped down. This procedure is not exactly recommended by the manual, so use with caution.
Using this trick, I could photograph the back side of the lens when stopped down:
Here it is clear that some of the blades are misaligned. Thus, the resulting image has non-round out of focus rendering.
I've made a video showing the stopping down of the aperture blades. The apertures goes from f/3.5 down to a full close in 1/3 stops.
Here's a photo of the setup for capturing the video:
Conclusion
My lens most certainly has a bad aperture mechanism. Whether this is a one-off bad copy, or a systematic problem with the lens line is hard to say. I would guess it's an example of poor quality checking, and that most lenses are ok.
This problem annoys me a bit. I've previously found the basic kit lens to be a good one, despite the mixed reception it generally gets online.
Now, this is not really a big issue. Generally, you don't get much bokeh with kit zoom lenses anyway. So the problem is not very likely to show in images. If using the camera at full auto, it generally chooses the maximum aperture anyway, in which case the aperture opening is round.
This problem might affect the exposure correctness. The defective aperture blades could cause slight exposure irregularities. But again, this is not likely to be a big problem
Epilogue
If found the aperture to be so bad, that I took the lens back to the shop where I bought it in the first place.
The store keeper has some problem verifying that his off the shelf lens did not exhibit the same non-round aperture. I helped him by taking a photo with the lens mounted to the Panasonic GF2 camera at f/9, 2 seconds, and removed the lens during the exposure. Looking towards the light through the lens showed that his copy had a round aperture.
So he accepted my lens as defective, and sent it for repair.
After one month, I started enquiring about the lens. I always got the same answer: "The lens is just around the corner, should be in our store the beginning of the next week."
It was not until after three months that the lens finally did arrive in the store. When I went to pick it up, I was told that they simply replaced the lens with a new one. Why let me wait for three months when they would just give me a new copy?
Many people are looking for camera systems that can give a thin depth of focus (DOF). With a thin depth of focus, objects that are beyond the focus distance, or closer, are out of focus.
The Micro Four Thirds system is not ideal for getting thin DOF. To get a thin DOF, you are better off buying a camera with a large sensor, for example full frame DSLR cameras.
I took the same picture using the three lenses at various apertures. Here are the full images at maximum aperture:
Lumix G 14mm @ f/2.5
Lumix G 20mm @ f/1.7
Lumix G 14-42mm @ 14mm f/3.5
Lumix G 14-42mm @ 20mm f/4.1
The focus was set on the emblem on the bell in the middle left part of the image. I used the Panasonic GH2 at base ISO, and the shutter speed was around 1-6 seconds. I used a tripod, and also two second shutter delay, to avoid camera shake.
The images above are taken using the maximum aperture available with the given lens. Hence, the DOF is as thin as possible, given the focal length and focus distance.
To better evaluate the bokeh, I have made 100% crops from two parts of the image (click to enlarge):
The first crops are from the focus area. From these images, it could look like the 14mm pancake lens is unsharp. However, these images were taken primarily to evaluate the bokeh, not the sharpness, and the focus point might be slightly different between the lenses. In my experience, the sharpness of the 14mm pancake lens is rather good.
In the seconds image, we see the out of focus highlights. I suppose one could say that neither of the lenses give a very nice bokeh. They have various problems. They all exhibit some ringing, but it seems to be worst at 14mm. Also, the bokeh is uneven, and "dirty", "swirly".
The 20mm pancake lens shows the most non-circular highlights, both wide open and closed down.
The 14-42mm lens shows some strange irregularity at f/5.6, at both 14mm and 20mm. This could look like a construction error of the aperture diaphragm. However, it is not likely to pose much of a problem, since only at very close focus distance would you see much out of focus rendering at f/5.6
In terms of roundness, the 14mm pancake has the most consistent appearance.
Many Micro Four Thirds lenses feature in-camera geometric distortion correction. Two examples are the Panasonic pancakes, Lumix G 14mm f/2.5 and Lumix G 20mm f/1.7. Both have pretty similar distortion correction needs. When converting the sensor output to the out of camera JPEG image, around 10% of the pixels in the border area are lost.
This is somewhat controversial. Some feel that a quality lens should not require further software correction. In fact, the lack of geometric distortion is a traditional sign of a high quality lens.
I think that this is mostly a non-issue. By allowing some aspects of the image to be adjusted in software, the lens designers can focus on issues which cannot be corrected in post processing. This has the potential of making the lenses better, at a smaller size, and potentially a smaller cost. Panasonic Micro Four Thirds lenses are adjusted for geometric distortion and some chromatic aberrations. The geometric distortion is also corrected in Olympus Micro Four Thirds cameras. At this time, though, Olympus does not correct chromatic aberrations.
To illustrate the geometric distortion done with various lenses, I have photographed a tiled wall with them, and shown the sensor output compared with the corrected JPEG output.
Note that this is in no way a criticism of using RAW images. There are many RAW image converters which will do the distortion correction automatically and seamlessly, and you will never notice that there was any geometric adjustment done at all. I am using the RAW images to visualize the initial image captured by the sensor, as it is the only way to access it.
Here is a comparison of the uncorrected and corrected images for some lenses. Since I am only interested in the geometric distortion, I have increased the contrast so that the images become monochrome. I also superimposed the corrected out of camera images (black) onto the original uncorrected images (red).
I have also included the appropriate adjustment needed. The adjustment numbers in percent refers to the "Lens Distortion" filter in The Gimp.
Normal zoom lenses pretty consistently feature barrel distortion in the wide end. The tele zoom Lumix G 45-200mm appears to have some very small pincushion distortion, but very minor.
The focus was set on the post to the left, which is around 30cm from the camera, close to the minimum focus distance for these lenses. I used the A (aperture) exposure mode.
To evaluate the bokeh, let's enlarge some of the areas from the image.
From the centre of the image:
And from the top of the image:
(Click for larger images.)
I think the bokeh from both lenses is a bit "dirty" and "swirly". The 14mm pancake lens has the most ringing in the out of focus rendering.
Conclusion
My conclusion, which is a bit unexpected, is that the zoom lens has the best bokeh. Or perhaps it is better to say it has the least displeasing bokeh, since neither are very good. But the difference is small.
The 14mm pancake lens has non-circular bokeh even at the largest aperture, which is not so usual. The Lumix 20mm f/1.7 pancake lens also exhibits non-round bokeh. So perhaps it is related to the pancake design?
Keep in mind that these enlarged images are 100% views from the 16 megapixel GH2 sensor. most people will probably downscale the image some, in which case the dirtiness and ringing of the bokeh becomes a smaller issue.
Also, bokeh and wide angle is not that much of an issue anyway. To get some out of focus rendering at 14mm focal length, I had to focus close to the minimum distance, and look at objects in the far background. It is not so likely that you'll find the same situation in real life.
So even if the bokeh for these lenses at 14mm could have been better, you should not see it as a fatal problem. It is, at worst, a minor annoyance for some types of images.
The Lumix G 14mm f/2.5 pancake and Lumix G 14-42mm f/3.5-5.6 are both rather new lenses. What they also have in common, is that they have received a mixed reception online.
The new kit zoom lens is said to be worse than the lens it replaces, the Lumix G 14-45mm f/3.5-5.6. While it is probably true that the old kit lens was better, I have found the new one to be good, too.
In this article, I have taken a look at how the lenses render out of focus parts of the image, the bokeh. I did this by taking the same image with both lenses. The lenses were focused on the checkered pattern in the lower right part of the image, which is about 30cm from the camera. (click for larger images):
Lumix G 14mm @ f/2.5
Lumix G 14-42mm @ 14mm f/3.5
The pictures were taken with ISO160, base ISO for the Panasonic GH2.
To better evaluate the images, here are 100% crops from the left, centre and top parts of the images, respectively. The images were taken with apertures ranging from f/2.5 to f/8:
(Click for larger images.)
Due to diffraction, one should avoid using apertures smaller than f/8, i.e., avoid larger aperture numbers. This is especially true if you are going to be studying enlargements from the images. If you plan on publishing the images in web size only, go ahead and use apertures as small as f/22. The diffraction will not be a problem if you are going to downscale the images that much.
Conclusion
I think this test does not reveal any bokeh problems with any of the lenses. Perhaps the test could have been made more challenging by having some strong highlights in the background.
The patterned textile in the first compilation image is in focus. We can see that it very sharp already from the smallest aperture. This appears to verify my initial claim that both lenses are in fact quite good, despite their rather bland reception.
The Lumix G 14mm f/2.5 pancake lens appears to be sharpest. This was to be expected, I think, since it is not a zoom, and hence has fewer optical compromises. Further, it also lacks an OIS lens group, and has a simpler construction with only six lens elements. The 14-42mm zoom lens has twice as many lens elements. Generally, more lens elements can lead to worse optical performance, for example reduced contrast. However, modern quality zoom lenses can retain superior optical performance with 15-20 lens elements.
