Sunday, 28 November 2010

Lumix 14mm, insufficient distortion correction

Just like a host of other Micro Four Thirds lenses, the Lumix G 14mm f/2.5 pancake lens utilizes in camera distortion correction.

However, when using the lens on the Panasonic GH1 camera, I've noticed that the distortion correction is not sufficient. There is still some residual barrel distortion after the in camera correction.

Here are a couple of examples. First, let's look at an example at a close focus distance, close to the minimum focus distance of the lens:

Corrected JPEG
Uncorrected RAW

In this example, even when looking at the small image (above, left), it is easy to see that there is still some barrel distortion in the upper, horizontal line. The line is not straight. You can click on the image to view a larger version of it.  The corrected image to the left is the JPEG output from the camera.

The right image shows the image as captured by the sensor, without any distortion correction at all.  I used the UFRaw RAW processing software.  But any software that allows for disabling the distortion correction could be used for this purpose.

And one example with a longer focus distance:

Corrected JPEG
Uncorrected RAW

In this latest example with a longer focus distance, it appears that the remaining distortion is not so significant. I added a red, straight guideline to the left in the JPEG image, above left. You can see that there is some barrel distortion still, but not much.

Conclusion

It appears that when using the Lumix G 14mm f/2.5 pancake lens on a Panasonic GH1 camera, there is some residual barrel distortion. This is most apparent at shorter focus distances.

One could speculate why this is so. I don't think it is a firmware issue, since I have the newest firmware available for my camera.

Another speculation is that Panasonic chose to not correct all the barrel distortion, since that would have decreased the diagonal angle of view. The diagonal angle of view for this lens is specified to 75°. Further correction of the barrel distortion would reduce this figure, albeit with a small margin.

The Lumix G 14mm f/2.5 pancake lens uses internal focusing, and it is not uncommon that these designs lead to changes to the distortion properties, and field of view, at closer focus distances.

Saturday, 27 November 2010

Camera sales statistics from Japan

Update: There is newer sales data from the end of December 2010 here.

BCN Ranking provides monthly sales statistics for various items in Japan. One of them is system cameras, which includes DSLRs and mirrorless systems.

Here is the most recent sales statistics for Micro Four Thirds camera systems. The number in the graph is the ranking the given month. So a "4" means that the specific model was the fourth most sold model during that month. In the first two places you typically find the basic kit models from Nikon and Canon.


There are a lot of interesting findings here.  For example, two Panasonic models have had a second birth: Both the GF1 and GH1 have seen an increase of sales, probably due to the discounted prices awaiting the arrival of the newer models GF2 and GH2.  This also applies to the Olympus E-P1 camera, which saw a significant sales increase in the third quarter of 2010.

Another finding is that while the Panasonic Lumix G1 sold pretty stably, it was the Olympus E-P1 which made a big difference in the Japanese market.  This is consistent with what I saw in the Nordic market.  Even though the G1 has, in my opinion, better photographic functionality, it was the E-P1, with the retro styling, and somewhat slimmer body, which got the landslide sales.  The E-P2 never was a big seller, it seems.

In the mean time, some competitors have also launched systems. I was not able to find statistics for the Samsung NX system, but the Sony NEX was easy to find.  In the diagram below, it is apparent that the Sony NEX was a big hit in Japan.


The top model Sony NEX 5 got an impressive second place in June 2010, and retained the third place in July and August.

Saturday, 20 November 2010

Using the 8mm fisheye lens as a macro lens

Using a fisheye lens as a macro lens is probably a very strange idea. But the Panasonic Lumix G 8mm Fisheye lens has a remarkably short minimum focus distance, so it actually makes some sense.

The closest focus distance is specified as 0.1m. However, this is measured from the sensor plane. So the distance from the front element is about 0.02m, or 20mm.

This corresponds to a magnification of 0.20x, or 1:5, which is not very impressive. We should keep in mind, though, that the field of view is more compressed in the corners, hence this magnification measure doesn't make much sense for the fisheye lens.

Here's my setup for photographing a LEGO figure at the closest focus distance:


The camera is on a tripod, and the figure is about 2cm from the front lens element. At this close distance, it is inevitable that the lens casts some shadow on the subject.

And here is the resulting image, taken at ISO 100, f/5.6, 1.3 second exposure:


The very close focus distance possible with the Lumix 8mm lens can be used to make interesting compositions. Especially when combined with the deep depth of field associated with a wide angle lens.

Friday, 19 November 2010

Measuring the field of view of the Lumix 14mm f/2.5 pancake lens

There has been some uncertainty as to the actual field of view of the Lumix 14mm f/2.5 pancake lens. While I personally don't doubt Panasonic's specifications, I decided to make my own measurement.

I placed the camera level, facing 90° towards a window. On the window, I placed a measuring band. The distance from the camera's mount to the measuring band is 870mm. This means that the distance to the sensor is 890mm, since the register distance of Micro Four Thirds is 20mm.

Here is the setup:


And this is the resulting image, after in-camera distortion correction:


It's easier to measure the width when looking at 100% crops of the endpoints:


We can see that the total horizontal distance is 1039mm.

Doing the basic trigonometrical calculation, we get the horizontal angle of view to be: 2*arctan((1039mm/2)/890mm)° = 60.5°.

Now, we want to find the diagonal angle of view. The diagonal width is sqrt(10392+(1039*3/4)2) = 1298.75. Hence, the diagonal angle of view is 2*arctan((1298.75mm/2)/890mm)° = 72.2°.

Panasonic's specifications state that the diagonal angle of view is 75°. However, we know that the angle is specified at infinity focus. And in my case, the focus is just below 1m. It is also a fact that the angle of view can change with the focus, especially with internal or rear focusing mechanisms. So this is probably the explanation for the difference.

Thursday, 18 November 2010

Lumix 14mm distortion correction

Just like most other Micro Four Thirds lenses, the Panasonic Lumix G 14mm f/2.5 pancake lens is corrected for barrel distortion in camera. This is applied when looking through the viewfinder, when producing JPEG images or videos, and when using some RAW converter programs. So many users are probably not aware of this at all.

It is easy to see the effect of the distortion correction when opening the RAW image file in a converter program that allows for not applying distortion correction. One such example is UFRaw.

Here is an example image. It was taken at f/2.5, ISO 400, 1/13 second exposure. Both the out of camera corrected JPEG, and the non-corrected RAW image are shown below:

Corrected JPEG
Uncorrected RAW

It is apparent that there is some barrel distortion in the RAW image. To correct this requires about -14.5 adjustment in the Lens Distortion filter within The Gimp image processing software. This is slightly more than for the Lumix 20mm lens, for which I found that -13.5 was an appropriate adjustment.

This picture shows what sensor area is lost during this conversion: The area outside the white frame is unused when applying the distortion correction.



This corresponds to around 12% of the sensor area, and hence you lose around one megapixel of resolution with the normal 12 megapixel sensor. This is nothing to worry about.

The upside is that if you need a wider field of view, you can use the whole sensor output from the RAW file. The normal diagonal field of view for this lens is 75°. Using the extra sensor area output to the RAW file gives you around 80° field of view. Of course, this will not be distortion corrected, but as long as you don't photograph any straight objects, this shouldn't be any problem. For nature and people, this might not be an issue.

Framing your picture will be difficult, though, since the viewfinder only shows the image after the distortion correction. And you might experience more vignetting in the extreme corners.

Insufficient distortion correction

To my surprise, I noted that the distortion correction is in fact not fully sufficient. After the in camera distortion correction, there is still some residual barrel distortion, especially at shorter focus distances. You can note this in the top left image: The pillar to the left is not entirely straight. Also, the ceiling is slightly distorted.

It could be that newer cameras do a better job of correcting the distortion.

Saturday, 13 November 2010

Panasonic Lumix G 14mm f/2.5

The Panasonic Lumix G 14mm pancake lens is the long awaited miniature standard wide prime. Some people have been disappointed by the aperture: The max aperture is f/2.5, which is a tad slow for primes. On the other hand, it is clear that size was important when designing this lens, and a moderate max aperture is needed to design a small lens.

To further reduce the overall size, it comes with new slim line, low profile front and rear lens caps:


Here you see the lens without the front cap:


Hood

No hood is supplied with the box. I like to have a hood on my lenses, for protection against objects touching the front lens element, as much as protection against stray light. To get some basic protection, while retaining the compact size, I have put a 46mm stand off ring on the lens.

A 46mm stand off ring is a bit uncommon, and might even be expensive to buy. So to avoid this, I simply ordered one of the cheapest UV filters from an auction site, and removed the glass. I did this by unscrewing the inner ring which holds the glass:



The filter cost less than US$5, so it is not a huge investment. If you're unable to unscrew the ring that holds the glass, you can just break it. But be careful, so you don't harm yourself.

Here you have the lens with the stand off ring mounted:


Mounting this ring does not add any extra vignetting to your images.

You could also put the 46-37mm step down ring on the lens, and use it as a hood. It does not cause vignetting on the 14mm wide angle lens. But you'll need to buy a 37mm front lens cap as well. They are usually not as slim as the supplied 46mm hood, hence the lens will take up more space in your bag in this configuration. It is still very tiny, so I don't think this would be an issue.

Here is the lens with the 46mm-37mm step-down ring added:





On the camera

When mounted on the GH1 camera, the lens looks hideously small. Not that I mind, though. I much prefer compact lenses to large ones, as long as the image quality is good enough.


Autofocus

This lens uses a different focus mechanism compared with the Lumix 20mm. Whereas the Lumix 20mm lens uses a traditional focus method, in which the whole lens assembly moves back and forth, the newer Lumix 14mm lens has internal focusing.

The advantages with internal focusing are apparent: The elements that need to be moved are smaller, hence, they can be moved faster, more quietly, and using less energy. Also, the front of the lens does not move at all, which makes the lens more rigid, and less prone to water contamination.

In use, it is immediately apparent that the autofocus is faster than the Lumix 20mm. My examination reveals that it is about twice as fast. Still, it is not as fast as the HD rated Lumix G HD 14-140mm superzoom lens.

The aperture still makes some noise when it changes. But it's not a problem in most cases. As long as the shutter makes even more noise, you don't notice it much. But when shutterless cameras become common, you might recognize the aperture noise to a larger degree.

Sharpness

The Lumix 20mm is known for it's good sharpness even wide open. So I'm sure a lot of people are curious if the 14mm is as sharp.

My experiment shows that the 14mm lens is as sharp in the centre, but could be slightly less sharp in the corners. However, both lenses are very capable.

Here's the common "foliage against the sky" test of the sharpness (click for larger images):

f/2.5, 1/125, ISO 160
f/5.6, 1/25, ISO 200

I left the camera at auto exposure, which appears to have given slightly different exposures.

To better evaluate the sharpness, let's look at 100% crops from the images (click for larger image):



The sharpness appears to be good from the largest aperture. There is some purple fringing in the centre at f/2.5, but not much. In the corners, there is still purple fringing when stopping down to f/5.6, but this is not really a big problem.

We can also see that there is some vignetting in the corners at f/2.5, but it is completely gone at f/5.6. This is not the best comparison for vignetting, since the exposure appears slightly different in the two pictures. But you can see that the sky is darker in the corners, compared with the centre, in the picture taken at f/2.5. I'd say this vignetting is to be expected with such a small lens and small front element. I wouldn't worry too much about it.

Here's another look at the sharpness and bokeh of the lens.

Bokeh

I have made this study of the bokeh during daytime (low contrast), and this during nighttime (out of focus highlight in the background).

The first study does not reveal any problems with the bokeh. The second test, during nighttime, and with high intensity lights in the background, reveals that the bokeh is somewhat "dirty" and "swirly", and has some ringing. Put another way, the bokeh is not optimal.

On the other hand, you are not very likely to experience the unpleasing bokeh during normal real life use of the lens. Say you take a picture of people. To avoid distortion of the faces, you'll want to keep a distance of about 1 meter or more. At this focus distance, the out of focus rendering is hardly noticeable, even at f/2.5, due to the wide angle property of the lens. So don't worry about the bokeh.

Chromatic aberrations

I have made a study of the chromatic aberration (CA) artifacts of this lens, and some other prime lenses. It shows that there are some quite small red/green fringing artifacts in the corners of the frame, but it is effectively corrected by software.

All the example images on this page are from the out of camera JPEG images, which have been adjusted for CA artifacts. Panasonic Lumix G cameras automatically apply this correction when it produces JPEG images, and it is also done by some RAW conversion programs.

Even before this correction, the artifacts are not very annoying. So users of Olympus cameras, which to date do not apply this correction, should not find this a big problem.

Example image

The image was taken using f/4, 1/8s, ISO 640. I held the camera against a hand rail for some support during the long exposure.


And here is a 100% crop from the centre of the image. It has not been sharpened:


And here is a 100% crop from the top left corner area:


Example videos

Low light video with some action using the Lumix G 14mm f/2.5 pancake lens on a GH2:



More information about the video parameters used in the movie above. You'll notice that the audio quality is poor in the video. However, this is due to the sound system, which clips the sound at high levels.


This video showing the ice breaking up in Stockholm was recorded using a Lumix G 14mm f/2.5 pancake lens on a GH2, at 1080p, 24fps:




More information about the video and the image parameters here.

Distortion correction

Just like a host of other Micro Four Thirds lenses, the Lumix 14mm pancake lens utilizes in-camera distortion correction. Without this correction, it gives a pronounced barrel distribution.

Compared with the Lumix 20mm f/1.7

It is natural to compare the lens with the other slim pancake from Panasonic: The Lumix G 20mm f/1.7. In the picture below, in which I am using a step down ring as a simple hood on the 20mm, it is very clear that the newer 14mm lens is significantly smaller. However, note that the 14mm lens has the slimmer rear lens cap mounted, which makes it even smaller.


The lens designs are rather different. The 20mm lens features 7 lens elements in 5 groups (2 aspherical), while the 14mm lens has 6 elements in 5 groups (3 aspherical).


Obviously, the 14mm lens has a wider field of view than the 20mm lens. The 14mm lens is a wide angle lens, while the 20mm lens is what people would normally call a "normal" lens. Normal lens have a focal length which correspond roughly to the diameter of the sensor. The Four Thirds sensor diagonal measures 21.6mm, so the 20mm lens is in fact a slightly wide normal lens.

Based on the field of view difference, which is quite significant, which lens would you want to buy? Experienced photographers will probably not ponder long about this. They are already well aware of the concepts "wide angle" and "normal lens", and know their preferences. What about the rest of us?

If you have used the kit zoom lens for some time, you could take a look at your favourite photos and see what focal length they were taken with. Did you typically use the wide end of the zoom lens? Or the longer end? The answer here might determine your focal length preference.

There is a philosophy which goes like this: You can always get closer to an object, but you cannot always get further away from it. So to be able to photograph what you want, choose the widest lens. In this case, this philosophy dictates that you choose the Lumix G 14mm f/2.5 lens over the Lumix G 20mm f/1.7 lens, since the former is wider.

However, it doesn't take much thinking to see that the premises are not always right. Let's say you want to photograph people. Then, you should not get closer to them than around 1 meter. Going closer will give you perspective distortion, which can make the photo unflattering.

Hence, if you intend to photograph a person, and want to have their face as the main part of the image, you will want to choose the longer lens. At a 1 meter distance, their face will be just a small spot in the frame with the 14mm wide angle lens. Even the 20mm lens is not long enough to be a portrait lens, but it is still the better choice. For a portrait headshot, you will generally want a focal length of around 40mm or higher. But the 20mm lens can be used to take an environmental portrait.

On the other hand, if you intend to photograph a group of people, you will want to choose the wide angle lens. You cannot always back up more, so the widest lens is best to cover a group of people.

Compared with the kit lens

The focal length 14mm is covered by the kit lens. So why get the 14mm pancake if you've already got the kit lens?

In addition to the kit lens, there are also other zoom lenses that include the 14mm focal length. In fact, there are eight zoom lenses available for the Micro Four Thirds format that cover 14mm: Two basic Olympus kit lens variants and two basic Panasonic kit lenses (14-45mm and 14-42mm). Then there are the two superzooms, and two wide angle zooms.

We've already discussed the size. The Lumix 14mm f/2.5 pancake lens is very, very small. This has a lot of advantages. You're more likely to bring the camera and lens if it is small and compact. Also, a small lens looks less obtrusive. It doesn't scare people the same way as a large lens does.

The 14mm pancake lens has also got a larger max aperture than the zoom lenses. The brightest zoom lenses are specified at f/3.5 at 14mm, which is about one stop slower than f/2.5. However, one stop difference isn't that significant. It means that you can use twice the shutter speed, roughly. While the Lumix 20mm f/1.7 pancake lens is a true low light lens, the 14mm pancake isn't overly fast. So if you buy it for the low light properties, you're bound to be unhappy.

Compared with the kit lenses, the pancake lens has a much simpler construction, with only six lens elements. This has the potential of making the image quality better, in terms of sharpness and contrast. However, how the image quality actually compares is unknown to me, since I haven't studied them head to head.

Conclusion

This is a very capable, fast focusing, sharp and compact lens. What's not to like?

Example video capture, GH1+Lumix 45-200mm

This recording was done in Union Square Park using a Panasonic GH1 and a Panasonic Lumix G 45-200mm f/4-5.6 zoom lens.





In this example capture, you can see that the camera jogs the focus back and forth now and then, probably to verify the correctness of the focus. Also, while zooming, the focus is lost for a short period. The newer Lumix G 100-300mm f/4-5.6 lens is said to have some technology to prevent the loss of focus during zooming.

The recording was done in 720p, and converted/edited using HandBrake and Kdenlive.

Of course, one should be very careful with zooming during video recording. It is almost impossible to get the zooming smooth and undistracting. When zooming is done by professional videographers, the usually use a dedicated zoom motor, which attaches to the zoom ring and rotates it smoothly.

This video example illustrates how you can achieve a nice background blur using one of the cheapest lenses available. The possibility to blur the background to enhance the foreground subject is one of the reasons why some people like using Micro Four Thirds for filming.

Here is another example video capture:





This was filmed using 720p, 50 fps. I set the focal length to 120mm, which corresponds to 240mm on a traditional 35mm film camera.

The camera was not on a tripod, but I rested it against a fence for extra stability. Still, it was difficult to keep it entirely stable. You can see that there is some camera shake.

Tuesday, 9 November 2010

Lumix G 8mm f/3.5 Fisheye

The 8mm fisheye lens is a specialized lens, meaning that it is not a lens that most people would use a lot. One can imagine several reasons why Panasonic still chose to develop this lens, e.g.:

  • The short flange distance for the Micro Four Thirds system means that wide angle lenses can be made very compact, illustrating the strengths of the M4/3 concept.
  • Videographers commonly use fisheye lenses for skateboard, BMX and other types of sports events.
  • When panning with a rectilinear wide angle lens, the objects can appear as if they change size as they move across the frame. With a fisheye lens, this can look more natural. Hence, some videographers prefer fisheye for wide angle videos, as opposed to traditional wide angle lenses.
  • Fisheye lenses can be used to make "cute" images and videos, e.g., novelty images of animals where the nose appears very large.

Anyway, the user is of course free to choose what to use this lens for, and does not need to be restricted by the items above.

I have made a comparison of the sharpness and other aspects of the Lumix 8mm fisheye lens compared with the Olympus Zuiko 9-18mm f/4-5.6.

In 2011, the Samyang 7.5mm f/3.5 fisheye lens was announced. It is a fisheye lens with fairly similar specifications as the Lumix G 8mm f/3.5. The Samyang is a manual focus lens, with a manually operated aperture ring. My study has shown that it has remarkably good optics, in terms of sharpness and CAs. It also has somewhat less distortion than the Lumix G 8mm lens.




Type of fisheye lens

Most fisheye lenses fall into two categories: Circular fisheye lenses, and full frame fisheye lenses. Circular fisheye lenses cover the field of view of 180° in all directions, and only expose a disc in the centre of the frame. Full frame fisheye lenses, on the other hand, expose the whole sensor area, but only cover 180° in the diagonal.

The Lumix G 8mm fisheye lens is a full frame fisheye lens. A circular fisheye lens on the Four Thirds format sensor would probably have a focal length of around 3-4mm.


Physical appearance

The lens comes with a built in, non removable, hood. The hood also protects the front lens element against objects touching it accidentally. Due to the hood, you can place the lens upside down on a table without the glass touching anything.



The front lens cap is unusual. Rather than the pinch centre caps that we are used to, this one is more like a lid which slides onto the outside of the hood. It is held in place by friction. The outside of the hood is around 61mm wide. You better take good care of the lens cap, since replacing it can cost around US$40.

Comparing the fisheye lens with the Lumix 20mm f/1.7 Pancake lens, reveals that it's size is small:



The Lumix 20mm is seen here with a "home made" low profile hood.

Quality wise, the lens gives a very good impression. There are no moving parts on the outside (beyond the focus ring), due to the internal focus mechanism.

The aperture can be set from f/3.5 to f/22. Changing the aperture gives a small "click" sound. It is not as silent as the Lumix G HD 14-140mm superzoom lens, but still, I hardly think anyone will find this problematic.

There is no geometric distortion correction in software when using this lens.  As opposed to most Micro Four Thirds lenses, which utilize geometric correction in post processing, e.g., the Lumix G 20mm and Lumix G 14mm pancake lenses.

Autofocus

This lens has a very quick autofocus system. Except when photographing very close objects, you barely notice the focus at all: It appears to be in focus instantly when half pressing the shutter.

Here is a comparison of the focus speed for various lenses on a GH2. In this study, the 8mm fisheye lens has a very quick timing.

Moreover, the autofocus is virtually inaudible. It is barely noticeable in use.

I would recommend using multi point AF with this lens. The spot autofocus can be a bit awkward, with the very wide angle of view.

The closest focus distance possible is very short, specified to 0.1m. Keep in mind, though, that this is measured from the sensor, meaning that the minimum focus distance is very close to the front lens element. At this distance, it is ineviteable that the lens casts some shadow on the subject.

Here is an example use of the lens for macro purposes.

Manual focus is possible by using the focus ring. It is made of ribbed plastic, and for that reason it is not as easy to operate as a rubber ring would have been. On the other hand, the plastic ring is probably much more solid, and will not wear out any time soon. The ring feels fairly dampened and smooth, about the same as the Lumix 20mm focus ring.

Sharpness

My experience so far indicates that the sharpness is very good, even at f/3.5.

The typical way to evaluate the sharpness and artifacts of a wide angle lens, is to take a picture of foliage with the sky in the background. So here they are:

f/3.5, 1/13000, ISO 200
f/5.6, 1/500, ISO 200

To better evaluate the sharpness, let's look at some 100% crops from certain areas in the image (click for a larger image):



As we see from these crops, the image is very sharp from f/3.5, even in the corners. When stopping down the aperture to f/5.6, the corners sharpen up even more.

I have made a comparison of the sharpness and other aspects of the Lumix 8mm fisheye lens compared with the Olympus Zuiko 9-18mm f/4-5.6.

Here is another sharpness comparison with the Samyang 7.5mm f/3.5 fisheye lens.

My study of the chromatic aberrations (CA) artifacts reveals that the lens has around 2-3 pixels wide red/green fringing in the corners of the frame, caused by high contrast areas. This is corrected by post processing software in the camera, and by some RAW converters. There is still some residual purple fringing in the corners after this in camera image processing, but it's mostly not a problem.

Flare

The Lumix G 8mm fisheye lens covers a very wide field of view. For this reason, it can be difficult not to have a strong light source in the frame, e.g., the sun. Hence, it is important that the lens handles flare well. Otherwise, one strong light source could ruin your shot.

I have included an extreme example below. Here, the sun is in the centre of the frame, just behind the figures.


And here is an enlargement of the persons, who has the sun just behind them. This is a 100% crop, meaning that it has not been resized:


Here we see that the sun does indeed reduce the contrast. However, considering how difficult this scene is to render, given the very high contrast, I think the lens does a good job. So flare is not a big problem with this lens, I would say.

Example images

This specific fisheye lens is the full frame type, meaning that the image fills the entire rectangular frame. The diagonal coverage is stated to be 180°.

A fisheye lens generates images that are not rectilinear, as we are used to, but rather hemispherical. This looks like an excessive amount of barrel distortion.

This distortion is very apparent when photographing rectangular shapes, like, for example, the Apple store in New York:



However, when photographing organic forms, the distortion might not be a huge problem. Here is the sled dog Balto, the only one to get a statue in Central Park while still being alive:



It is easy to see that the head is too large, and that the hind part of the dog is too small. This is due to the fisheye distortion. But on first glance, the shapes do not look very wrong. Only when the intention is an anatomically correct image, would the distortion be a problem.

Fisheye lenses can be defished, i.e., transformed to a rectilinear projection. In this example, I used the program Hugin to do the transformation. The original picture of the Tourneau store was taken with a 16:9 aspect ratio:


The diagonal field of view is 180°. In the 16:9 aspect ratio, the ratio of field of view becomes even more narrow, due to the curvature of the projection. The field of view is 136° horizontally, and 76° vertically. Here's how the defished image looks:


You'll note that there is some residual barrel distortion even after the defishing process. This is because the Lumix G 8mm f/3.5 fisheye lens gives somewhat more distortion than what is common for a fisheye lens. Here is a distortion comparison with the Samyang 7.5mm f/3.5 fisheye lens.

Example video

Here's an example video, filmed at 720p with the Panasonic Lumix GH1. It was filmed while holding the camera above my head at arms length, so it is a tad shaky. Doubleclick on the video to go to the YouTube view, which may work better than this embedded view.



Compared with the Lumix G 7-14mm f/4

It is natural to compare this fisheye lens with the Panasonic Lumix G 7-14mm f/4 ultra wide zoom lens. They are both extremely wide lenses, and their pricing are fairly similar.

When it comes to the lens construction, the 8mm fisheye lens is a much simpler design. It features 10 lens elements in 9 groups, while the 7-14mm zoom has 16 lens elements in 12 groups. In terms of exotic elements, it is also simpler: 1 ED glass element (4 in the 7-14mm), and no aspherical elements (2 in the 7-14mm).


There's no significant difference in the speed. The wide angle zoom has a maximum aperture of f/4, which is only slightly smaller than f/3.5. While the fisheye wins in this respect, the difference is hardly significant.

The fisheye lens has a close focusing distance of 0.1 meter, which is very, very close. The corresponding distance is 0.25 meter for the 7-14mm zoom, which is also close, but still not comparable. While you may not use this close focusing distance a lot with the fisheye, the front lens element is less than an inch from the subject at this distance, it can still be used for some interesting effects.

In terms of overall usefulness, the 7-14mm zoom wins, no question about it. In the longer end, it becomes a "normal" wide angle lens, useful for a lot of shooting situations. The fisheye lens, on the other hand, remains an exotic, specialized lens all the time.

The 8mm fisheye lens is still attractive due to it's very wide angle of view, and the small size (37% shorter and 45% lighter).

Conclusion

This is a very good and compact lens. But it's usefulness is a bit limited for most people, and it is expensive.

Due to its lower cost and good optics, the Samyang 7.5mm f/3.5 fisheye lens can be a good alternative to the Lumix G 8mm f/3.5 fisheye lens.

The Samyang lens also has a more common fisheye projection model, and is easier defished, in my experience. If you plan on doing that, then the Samyang may be a better choice.



Lensbaby Tilt Transformer and Composer: First impressions

For Photokina 2010, Lensbaby introduced their newest product: The Tilt Transformer. It can be had for Micro Four Thirds cameras, and for Sony NEX E-mount. It can be bought stand alone, or with a Composer lens element.

Below are both products: The Composer (left) and the Tilt Transformer (right):



The Tilt Transformer (right) can be mounted to a Micro Four Thirds camera. This device acts as an adapter for Nikon F lenses, and also as a tilting platform.

The Composer (left) is a very simple lens. Turning the black ring around the lens pushes the lens elements back and forth, thus giving manual focus capability. To change the aperture, you need to disassemble the lens, and change the aperture plate. The lens comes with round plates with curcular holes, corresponding to apertures from f/1.8 to f/22.

One would perhaps think that the Composer can also be used as a lens on Nikon cameras, since the Tilt Transformer accepts Nikon lenses. However, this does not appear to be true. It is probably not a good idea to try to mount the Composer to a Nikon camera, since the lens element protrudes far into the camera, possibly interfering with the mirror.

The next picture shows the two devices mounted together:



In this configuration, it acts as a standalone lens for Micro Four Thirds cameras, with tilt capability built in. Loosening the ribbed metal ring allows you to rotate and tilt the adapter and Composer lens element. You can tighten the ring to fix the rotation and tilt in place.

Build quality

Unlike most native Micro Four Thirds lenses, the chassis of this lens is composed largely of metal. Still, it does not have a very good quality feeling: For example, the finish of extruded parts is somewhat rough. Also, what annoyed me, was that when mounted on a camera, the connection is a bit loose. Even the cheapest adapters fit the camera well, in my experience, but when mounting the Tilt Transformer on the camera, there is some play in the connection. It can be jerked a bit back and forth, unlike any other lenses I have tried on a Micro Four Thirds camera.

In use

When loosening the ribbed metal ring, you can adjust the amount of tilt. This adjustment is not dampened well. The tilting adapter moves quite jerkily. Again, I think this is a bit disappointing. Tightening the locking ring fixes the position of the adapter, and this functions well.

Manual focusing is pretty easy. The focus ring is very light to operate, and there is a lot of rotation, meaning that fine tuning is easy.

Changing the aperture is, of course, a bit of a hassle. You must unscrew the front section of the lens, remove the aperture disc with the supplied magnet tool, and then insert a new disc with the aperture of your choice, before putting back the front lens section.

Example image

This is the very first image I took using this adapter/lens combination. I used the f/4 aperture plate, and tilted the lens a bit to the side. Then I rotated the focus ring so that the middle part of the image was in focus, and pushed the shutter release. That's it. The picture was taken with a Panasonic Lumix GH1. (Click for a larger image.)



So is this image interesting? Well, it does have a "miniature" look to it, due to the selective focus. With some practice, the effect can be made much better.

Saturday, 6 November 2010

Index of lens related articles

Here is an index of lens related articles on this blog, sorted by lens:

Panasonic Lumix X 12-35mm f/2.8



Review

Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro



Review

A study of the bokeh at various apertures

Bokeh comparison with Lumix G HD 14-140mm and Lumix G 45-200mm, all at 45mm

Bokeh comparison with the Olympus Zuiko 50mm f/2 1:2 Macro

A study of the diffraction effects when using smaller apertures

A verification that the enlargement is actually 1:1

Example use of the touch screen AF with Panasonic GH2

A sharpness comparison with the Olympus Zuiko 50mm f/2 1:2 Macro at a long focus distance

A very simple sharpness comparison with the Olympus Zuiko 50mm f/2 1:2 Macro at a close focus distance

Autofocus speed

Olymus M.Zuiko Digital 45mm f/1.8



Review

Optical performance comparison with the Panasonic Leica 45mm f/2.8 macro

Panasonic Lumix G 20mm f/1.7 Pancake



Review

Autofocus speed comparison

Using a third party screw in 46mm metal hood, Leica Summicron type

Using a 46mm to 37mm step down ring as an alternative, low profile hood

An example video capture with the Panasonic Lumix GH1

Bokeh comparison with the Lumix G HD 14-140mm

Using the Lumix 20mm as a portrait lens

Distortion correction

Compared with the Lumix G 14mm f/2.5 pancake lens

A comparison with the Sigma 30mm f/1.4 lens on an APS-C camera. This is a lens that, in my opinion, does more or less the same job, and has around the same price point.

Panasonic Lumix G 14mm f/2.5 Pancake



Review

Compared with the Lumix G 20mm f/1.7 pancake lens

Comparison with the Lumix G 14-42mm and Lumix G HD 14-140mm zoom lenses at 14mm focal length

Autofocus speed comparison

Distortion correction

Measuring the field of view

Lumix G 100-300mm f/4-5.6



Review

Sharpness comparison with the Lumix G 45-200mm and the Lumix G HD 14-140mm

Lumix G 45-200mm f/4-5.6



Review

Bokeh comparison with Lumix G HD 14-140mm and Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro, all at 45mm

A bokeh comparison with the Nikkor 200mm f/4 AIS, not conclusive

Autofocus speed comparison

A look at the relation between the focus distance and field of view

An example video capture

Lumix G X PZ 45-175mm f/4-5.6



Review

Sharpness comparison with Lumix G 45-200mm

Lumix G HD 14-140mm f/4-5.8



Review

Autofocus speed comparison

Bokeh comparison with Lumix G 45-200mm and Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro, all at 45mm

Bokeh comparison with the Lumix 20mm f/1.7, both at 20mm

Example use of the touch screen AF using Panasonic GH2

Lumix G 8mm f/3.5 Fisheye



Review

Autofocus speed

Using the fisheye lens as a macro lens

Sigma 19mm f/2.8 EX DN



Autofocus speed comparison with the Lumix G 20mm f/1.7.

Sharpness comparison with the Lumix G 20mm f/1.7.

Sigma 30mm f/2.8 EX DN



Review

Samyang 7.5mm f/3.5 Fisheye



Review

Field of view comparison with the Lumix G 7-14mm f/4 wide angle zoom

Projection comparison with the Lumix G 8mm f/3.5 fisheye lens

Olympus Zuiko Digital 50mm f/2 1:2 Macro (Four Thirds lens)



Review

Manual focus with the Panasonic Lumix GH1

Bokeh comparison with the Panasonic Leica Lumix 45mm f/2.8 Macro

A simple sharpness comparison with the Panasonic Leica Lumix 45mm f/2.8 Macro

Using a cheap and simple macro soft box

Lumix G 7-14mm f/4 wide angle zoom lens



Short review

Field of view comparison with the Samyang 7.5mm f/3.5 fisheye lens