Fisheye sharpness

When I reviewed the Samyang 7.5mm f/3.5 fisheye, it was natural to compare it against the native Lumix G 8mm f/3.5 fisheye lens. Since the Lumix lens costs about 2-3 times the price of the Samyang lens, I would expect that the Lumix lens comes out as the winner.

However, what I found was that the Samyang lens was sharper, even in the extreme corners, and without the in camera CA correction which is done with the Lumix lens when using it on a Panasonic camera.

Some have doubted this result, and I have also been a bit unsure now and then. So I decided to do another test.

This time, I photographed a couple of trees against the bright sky, a useful test for lens sharpness. The focus was set on the centre of the image. With the Lumix lens, I used autofocus, and set a centre spot. With the Samyang lens, I used the 10x focus assist magnification available with the Panasonic GH2 camera. Here are the two images, both at f/3.5:

Samyang 7.5mm f/3.5	Lumix G 8mm f/3.5

To better evaluate the sharpness performance, I have compiled some 100% crops. From the centre of the image:

And from the top right corner:

Based on this study, it is perhaps not correct to say that the Samyang lens is much better. I think the Samyang lens appears to have slightly better sharpness in the corner, but the differences are fairly subtle.

Keep in mind that the Lumix lensis automatically corrected for CA artifacts, though. By looking at the RAW image files, and converting them to JPEG with third party software, we can see how the images were before the software CA corrections. These 100% crops are from the top left corner:

I used the free program UFRaw to convert the RAW images, but any program could have been used here, as long as it allows for doing the conversion without applying CA correction.

Here we see that without the in camera software CA correction, there are some significant red/green fringing artifacts. These are largely removed in the out of camera JPEG image. In the light of this, the Samyang lens's performance is even more impressive, as no in camera CA correction was done.

Conclusion

I wouldn't say that the Samyang 7.5mm f/3.5 fisheye lens is significantly better than the Lumix G 8mm f/3.5 fisheye lens, even if it appears to perform better in this test. So the image quality should not be an important factor when deciding between the two.

You could also consider the fact that they have slightly different projections. The Samyang lens gives images that are slightly less barrel distorted, and may be easier to defish.

The Samyang lens also handles flare better, see a direct comparison between the two in my review. Flare handling is very important for a fisheye lens, since you are quite likely to find the sun or a strong light source inside the image frame, due to the wide field of view.

When focusing manually with the Samyang lens, it is important to keep in mind that you shouldn't blindly trust the focus distance scale. On my lens, it is slightly off, and I reach infinity focus slightly before the infinity mark. This is not uncommon with manual focus lenses. Exact calibration would be very expensive, and the producers usually leave some slack for themselves by allowing the lens to focus beyond infinity.

The autofocus of the Lumix G 8mm f/3.5 fisheye isn't really needed for landscape pictures, as you easily get infinity into focus manually. But when taking closeup images, the autofocus can come rather handy.

Samyang 7.5mm f/3.5 fisheye lens review

The Samyang 7.5mm f/3.5 fisheye lens, also marketed as Rokinon and Bower, is special in that it is one of the first third party lens designs made specially for Micro Four Thirds. Some other manual focus lenses for Micro Four Thirds are older designs with a new mount.

The Samyang fisheye lens is an alternative to the native Panasonic Lumix G 8mm f/3.5 fisheye lens, so it makes sense to compare them. Here they are, with lens caps:

They have different type caps. The Samyang, on the left, has a cap held in place with clips, operated by pressing the side tabs. The Lumix's cap is held in place with friction only. I prefer the latter, since the Samyang cap must be inserted correctly rotated, which is somewhat more awkward.

Sharpness of Lumix G 45-200mm and Lumix X 45-175mm

I have previously tested the sharpness of the Lumix G 45-200mm and Lumix X PZ 45-175mm lenses. My test images then were fairly low contrast, and not too challenging for the lenses. To put them to a more difficult test, I've tried to test them head to head with a backlit subject. This is taken at approximately infinity focus, which is perhaps not the most realistic usage of these lenses.

Lumix G 45-200mm (left) and Lumix X PZ 45-175mm (right)

@ 45mm

The first set of images are taken at 45mm with both lenses. I used the Panasonic GH2 at ISO 160, and a tripod. The shutter speeds were fast. This is what the whole frame looks like:

Lumix G 45-200mm @ 45mm f/4	Lumix X 45-175mm @ 45mm f/4

Here are 100% crops from the centre:

And from the left corner:

I've also made a similar comparison at maximum zoom extension. First, the full images:

@ 175mm and 200mm

Lumix G 45-200mm @ 200mm f/5.6	Lumix X 45-175mm @ 175mm f/5.6

Here are 100% crops from the centre:

And from the left corner:

Conclusion

While my first test indicated that the lenses were fairly similar in terms of sharpness, these tests, taken at more challenging lightning, show a consistently better performance from the newer Lumix X PX 45-175mm f/4-5.6. The newer lens shows less Chromatic Aberration (CA) artifacts, and a better sharpness in the corner, especially in the longest zoom reach.

Olympus vs Panasonic @ 45mm

The long awaited portrait prime lens for Micro Four Thirds is finally here. Olympus has launched their M.Zuiko Digital 45mm f/1.8 lens. It is compact, fairly light, relatively cheap, and focuses quickly and noiselessly.

Before this lens was available, the closest we had to a portrait lens for the Micro Four Thirds format was the Panasonic Leica 45mm f/2.8 macro lens. While this lens is a good macro lens, it has not been very well received as a portrait lens because of the not so impressive f/2.8 maximum aperture.

Panasonic 45mm f/2.8 macro (left), Olympus 45mm f/1.8 (right)

How do these lenses compare when it comes to sharpness? I have made some tests to find out. The images were shot using the Panasonic GH2 camera, at base ISO 160, on a sturdy tripod, and with OIS turned off for the Panasonic lens. The Olympus lens does not feature any OIS.


Infinity focus

These images were taken at a focus distance of around infinity. The sun is in the upper left corner of the image frame, which makes for a challenging situation for any lens. A strong light source in the image frame can easily lead to flare, loss of contrast and chromatic aberration (CA) artifacts.

PL45 @ f/2.8	Olympus 45 @ f/1.8

Let's take a closer look at some 100% crops from various parts of the image frame. Here's from the centre:

And from the upper left corner, where the contrast is the largest:

And finally from the top right corner:

10m focus

These next set of images were taken at a focus distance of about 10m. These images were rescaled and sharpened. You can click on the images to see them in a larger size.

PL45 @ f/2.8	Olympus 45 @ f/1.8

For better evaluation of the sharpness, I have made crops from the centre of the image. These crops are taken at 100% magnification, meaning that one pixel in the image corresponds to one pixel from the camera. Click for an enlargement:

And here are similar crops from the extreme top right corner:

0.7m focus

And to complete the review, I have also compared the sharpness at a closer focus distance. In this case, the focus is placed on the centre of the ball, which is at approximately 0.7m distance (about two feet). A portrait distance is typically at 1m or more.

PL45 @ f/2.8	Olympus 45 @ f/1.8

And the crops from the centre:

To evaluate the sharpness based on these is probably not so easy. But the image series can be used to look at the out of focus rendering (bokeh):

Just to satisfy my curiosity, I also took these images at f/16. Due to diffraction, you would normally not use such a small aperture, since it will lead to some dullness at pixel level. But if you need a deep depth of focus, and are planning to publish the image on the web, I would say that it could be a reasonable balance between DOF and image quality to use f/16.

Night scene

Here is a night scene. The focus is set on the middle of the branch:

PL45 @ f/2.8	Olympus 45 @ f/1.8

Some closeups of the out of focus rendering of highlight on the top, right corner:

And from the left side:

Conclusion

So, which lens is best in terms of sharpness? I think that the Panasonic lens generally does better. The Panasonic lens appears to render a bit better at f/2.8, in my opinion. At larger apertures, there is no comparison, of course, since the Panasonic lens cannot be opened further.

The Olympus lens does exhibit quite a bit of dullness at f/1.8 and f/2. On the other hand, it could be that the DOF is too thin for this comparison, even at a focus distance of 10m. So the subject for this comparison was perhaps not entirely perfect.

At the largest apertures, the Olympus lens does show some chromatic aberration (CA) artifacts, both in the centre and in the corner. You can see that near objects have a purple outline, while far objects have a green outline. This is quite common, and can be seen also for the older Olympus Zuiko Digital 50mm f/2 macro lens. When stopped down to f/2.8, CA artifacts are no longer a problem.

The Panasonic lens does not exhibit any significant CA artifacts. Perhaps this is because the CA artifacts are removed in software post processing? I have tried to examine this by looking at uncorrected RAW images and JPEG images, and concluded that there are probably no software correction with the PL45.

I think it looks like flare affects the Panasonic lens the most. This is not surprising, since flare is generally a larger problem the more lens surfaces the light passes through. And the Panasonic lens has the most complicated optical design, with 14 lens elements in ten groups, while the Olympus lens has nine lens elements in eight groups.

The Olympus lens does not exhibit much vignetting. The Panasonic lens, on the other hand, has a bit of vignetting wide open, which goes away at f/4. Again, this could be due to software correction to the Olympus lens, I don't know.

The bokeh appears to be effective smoothing the background, but my daylight example image was not very challenging for the lenses. With higher contrast, at night, the out of focus rendering is not perfect for either lens. The discs are non round off-center for the Panasonic lens: They are elliptical when the lens is wide open. The Olympus lens gives pretty round discs wide open, but they have a tad bit more tacky edges when stopped down, due to the aperture blades not being as rounded.

The Olympus lens is cheaper and faster than the Panasonic lens. But the larger aperture comes at the expense of worse image quality wide open. At f/2.8, they are pretty comparable, but the Panasonic lens perhaps has the upper hand by a small margin. Despite these findings, the Olympus lens does appear to give a good value for money. For users looking for a portrait lens, or a moderately long and fast prime, this is the only choice at the moment.

I have also compared the PL45 with the Nikon Z 105mm f/2.8 for the Nikon Z system. It very apparent in this review that the Nikon lens is way better.

Software correction to the PL45?

One important aspect of the Micro Four Thirds system is the software correction to the images. Traditionally, lenses need to correct the images optically, so that the medium capturing the images sees the correct image. With the advent of digital imaging, though, the camera can do software based corrections to the image, adjusting for aspects that the lens does not correct.

This has the potential of making the lenses smaller and cheaper. Also, by allowing some aspects of the lens output to be adjusted with image processing, other aspects not possible to correct with software can be given more weight in the design process. This has the potential to give a better image quality. I think that software correction of lens output is a good thing, however, it remains a controversial issue.

One aspect which is corrected with a number of Micro Four Thirds lenses is geometrical distortion. I have explored this in a number of articles, here is one summarizing the effect for a number of lenses.

The other aspect corrected with some lenses, is some chromatic abberations. In my study, some chromatic abberations are corrected for lenses like the Lumix 8mm fisheye, the Lumix 20mm pancake and so on. Currently, this correction is only done when using Panasonic Micro Four Thirds cameras. At the time of writing, Olympus cameras do not perform the CA corrections.

Panasonic Leica 45mm f/2.8 macro

There is some rumor on the internet that Leica branded lenses are not corrected using software. This is clearly not true, since a number of Panasonic compact cameras feature Leica branded lenses that are corrected for geometric distortion. Examples include the Lumix LX3, and Lumix LX5, as well as the Leica branded counterparts.

But what about Leica branded interchangeable lenses? The Panasonic Leica 45mm f/2.8 macro lens (PL45) is the first Leica branded Micro Four Thirds lens. Are there any software based adjustments to the image output? Let's try to find out.

Geometric distortion correction

Here is an example image taken with the Panasonic Leica 45mm f/2.8 at f/2.8:

By looking at the uncorrected RAW, and comparing with the out of camera JPEG, we can easily see if there was any geometric distortion correction. Here are 100% crops from the lower left corner:

As we can see, they are identical in terms of geometric distortion. The RAW image contains about eight more pixels along the borders, which is why a bit more detail is visible from the wall and the leaves. I have previously written about this: Using RAW gives you approximately 1% more megapixels.

Corrections of Chromatic Abberations

So we conclude that there is no geometric distortions correction when using the PL45 lens. What about CA corrections? Usually, we see the CA artifacts most easily in the corners of the image frame, and where there is a huge contrast between light and dark elements. A typical place where this is visible, is where foliage meets the sky. So let's try to see in the upper right corner:

The exposure and white balance is not entirely the same in both crops, so it's not straight forward to compare them. But I think it is safe to conclude that there is no more or less CA artifacts in either image, thus indicating that there is no in camera CA correction performed for this lens.

In my previous study of some Panasonic lenses, it was easy to see that there was a correction of some CA artifacts.

Conclusion

Based on my study, I conclude that there is no software correction of the image when using the Panasonic Leica 45mm f/2.8 lens on Panasonic cameras.

This does not necessarily mean that no Leica branded Micro Four Thirds lenses will feature in camera adjustments to the output image. There is a newer Leica branded Panasonic Lumix 25mm f/1.4 lens. I have not tried it, and so I cannot say if it features this kind of image processing or not.

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.

Chromatic Aberration and lens correction

Chromatic Aberration (CA) is a type of lens distortion. It is caused by light of different colours being refracted differently by the glass lens elements.

This is one reason why lenses often consist of pairs of lenses grouped together: The two lens elements in the pair are made of different glass types, and have different optical properties. The aim of the construction is to neutralize the effect of chromatic aberrations, so that all visible colours focus in the same place.

Here is an example image illustrating CA. The image was taken with a Panasonic GH1, using the Olympus Zuiko 9-18mm f/4-5.6 wide angle zoom lens at 9mm f/4:

An enlargement of the lower left corner reveals the CA artifacts:

You'll see that there is red and green fringing off the high contrast areas, where the white and black paint meet. These artifacts are typically seen in the corner of the frame, while the centre of the image is generally free from them.

In the extreme corner, the artifacts take up about 2-3 pixels, which is a moderate effect.

CA artifacts are generally found in the corner, especially when using wide angle lenses.  The lack of CA artifacts indicate a high quality lens design.

Automatic lens correction

Panasonic Lumix G lenses are automatically corrected for CA artifacts by the camera. In the JPEG output files, the camera has adjusted the images with the intention to remove these distortions.

When using Panasonic Micro Four Thirds lenses on Olympus cameras, the CA corrections are not done with current camera models. Future cameras from Olympus may employ the same technology as Panasonic uses, and adjust for these effects.

We can still see the original exposures by opening the RAW image files in a converter which allows for not implementing the CA adjustments. One such RAW converter is UFRAW. By using this converter, we can compare the original exposure with the out of camera JPEG output, to see what kind of adjustments were done.

I am fully aware that there are RAW converters which will do the CA corrections as well.  So this is not a test of the RAW converter, but rather a look at the image before the CA correction, to see what kind of CA artifacts the lenses generate.

I have done these comparisons for three lenses. The images were taken with the Panasonic GH1 at ISO 100:

Lumix G 8mm f/3.5 fisheye

Here is the full image, take with a wide open aperture at f/3.5:

And the upper right corner at f/3.5 and f/5.6:

In this example, we can see that the fisheye lens is very sharp in the corner, even wide open at f/3.5.

In the extreme corner, there is some red and green fringing where white meets black.  Perhaps around 2-3 pixels of colour artifacts.  They are corrected well in the JPEG output, though.

Lumix G 14mm f/2.5 pancake

Here is the full image, take with a wide open aperture at f/2.5:

And the lower right corner at f/2.5 and f/5.6:

We see here that when using the lens wide open, there is some vignetting in the corner, and also, the sharpness is not optimal. This is quite common for any lens, really, and I wouldn't say it is a problem.

Looking at the CAs, it looks like there is about 1-2 pixels of red and green fringing in high contrast areas in the original RAW image. In the adjusted JPEG image, there is still some purple fringing.

Lumix G 20mm f/1.7 pancake

Here is the full image, wide open at f/1.7:

And the lower right corner at f/1.7 and f/5.6:

My comments here are mostly the same as for the Lumix G 14mm lens: There is vignetting, and there is dullness in the corner at f/1.7. Again, this is not uncommon, and especially so for a low light lens with a large aperture.

Before conversion to JPEG, there is some small amount of green and red fringing. In the converted JPEG image, the green fringing is gone, but there is still some purple fringing.

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

This lens is rather well known for it's CA artifacts. Here is a video showing the lens being used on a Panasonic GH1 camera (with an adapter). When focusing manually close to the minimum focus distance, you can see clearly black text on white background is black only when in perfect focus. Focusing a bit longer gives a green outline. And focusing closer gives a red outline. Doubleclick on the video to get a larger view, up to 720p is possible.



Here is a 100% view of a photo taken using the Olympus 50mm f/2 macro at 1:2 magnification, and f/2 aperture. As you see, text which is beyond the focus point has green fringing, while text nearer has red fringing.

The Panasonic-Leica 45mm f/2.8 macro lens for Micro Four Thirds does not exhibit these kinds of artifacts.

Conclusions

When using Panasonic lenses on Panasonic cameras, some CA artifacts are corrected automatically. However, there are still some purple fringing left in the corners.  It is generally restricted to around one pixel width, which is not much.

Even before the CA correction, the CA artifacts are very moderate on the Lumix G 20mm f/1.7 and the Lumix G 14mm f/2.5 pancake lenses. The Lumix G 8mm f/3.5 fisheye lens has somewhat more CA effects in the extreme corner, but it is well corrected by software.

All in all, I think that CA artifacts are nothing to worry about with these lenses. Even when using the lenses on Olympus cameras, without in camera CA correction, this should not bother you much.

Wide angle: 8mm vs 9mm

The Micro Four Thirds format is blessed with a number of compatible very wide angle lenses. There are:

Lumix G 8mm f/3.5 Fisheye

Lumix G 7-14mm f/4

Olympus M.Zuiko 9-18mm f/4-5.6

The Olympus Zuiko 9-18mm f/4-5.6 Four Thirds lens can also be used on Micro Four Thirds cameras, given that you have the appropriate adapter, e.g., Panasonic DMW-MA1, Olympus MMF1 or Olympus MMF2. These are all functionally similar. This lens will autofocus on Micro Four Thirds cameras, but the focus can be a bit slow.

In this article, I am comparing the first and the last on this list. Here's a picture of them both:

The Olympus Zuiko 9-18mm f/4-5.6 (left) is shown without the appropriate adapter. Mounting the adapter will add 18.67mm length, since that is the difference between the register distance of the two formats.

The Panasonic Lumix G 8mm f/3.5 fisheye is a truly compact lens. Olympus has a similar lens on their 2011 roadmap, and it remains to see how compact it will become.

Field of view

At 9mm focal length, the Olympus lens has a diagonal field of view of 100º. The 8mm fisheye lens, on the other hand, has a diagonal field of view of a whopping 180º! How can one mm difference in focal length make up such a massive difference in field of view?

The answer is that the projection is different in the two lenses. Projection in this case refers to the mapping of the real world objects in three dimensional space, down to the image sensor and two dimensions.

Most photographic lenses feature a rectilinear projection. This is what we have become used to. A rectilinear lens will produce an image where straight lines in the real world object are straight also in the resulting image.

Fisheye lenses are fundamentally different. With a fisheye lens, only straight lines the pass through the image centre are straight. All other lines will be bent. There is a significant amount of barrel distortion.

Within fisheye lenses, there can also be variations. Circular fisheye lenses will give a disc of exposure. A 180º view in all directions is mapped into a single disc, and the rest of the sensor frame is left black.

Full frame fisheyes are perhaps more common. They feature a 180º only in the diagonal, and otherwise fill out the entire sensor area. The Lumix G 8mm f/3.5 is a full frame fisheye lens.  To most users, these are more useful, as they give a rectangular image, as we are used to.

Example images

To further illustrate the difference between a rectilinear wide angle lens and a fisheye lens, let's look at an example. The images below were taken at base ISO, and on a tripod.

Olympus 9-18mm @ 9mm f/4	Lumix G 8mm Fisheye @ f/3.5
Olympus 9-18mm @ 9mm f/8	Lumix G 8mm Fisheye @ f/8

As you can see, the fisheye image is wider, and also features significant barrel distortion. Straight lines in the real objects are bent in the depiction.

This is not really the right type of image to evaluate the vignetting, but it seems that the 8mm fisheye lens vignettes a bit more at f/3.5. However, with such a wide angle of view, it is unlikely that you have the same tone across the field anyway, so I cannot see that vignetting will be a significant issue with this lens.

Note that the light source, the setting sun, is in the middle of the frame.  Both lenses handle this fairly well. There is not a big amount of flare or lack of contrast caused by the light source in the centre of the frame.

Sharpness

To evaluate the sharpness, let's look at 100% crops from various parts of the image. These images have not been sharpened. Click for a larger version.

Here are crops from the centre of the frame:

We see quite clearly that the Lumix 8mm Fisheye is the sharpest lens, straight from wide open at f/3.5.

Corners and Chromatic Aberration

From these border crops, we see basically the same thing. We can see some softness in the 8mm Fisheye image at f/3.5, but it sharpens up well at f/5.6.

Also, we see some Chromatic Aberration lens distortion artifacts in the Olympus images.  There's the red and green fringing off high contrast areas.  These artifacts typically appear near the borders, and become more significant the further away from the image centre you get.  This can be corrected pretty well by software, so it's not a big issue.

Panasonic lenses are automatically corrected for Chromatic Aberration (CA) distortion during the in-camera image processing, when using Panasonic cameras. So the JPEG out of camera images I have used could have been corrected for these effects, which may be why we don't see any CA in the Fisheye images.

To examine the effects of the automatic CA correction in the 8mm fisheye lens, let's look at one example. This picture of the Morris Jumel Mansion was taken with the GH1 and the Lumix G 8mm f/3.5 Fisheye:

Here are 100% crops from the extreme top right corner, and from the middle right border:

We see that the corrected image still shows some colour fringing artifacts in the extreme corner, but they are mostly gone in the border crop. From the rest of the frame, i.e., not the extreme borders, you will be hard pressed to find any CA artifacts in the out of camera JPEG image.

From the RAW images which have not been corrected for CA distortion, we see that there are some CA artifacts. These fringes are about 1-2 pixels wide in the extreme corner, which is not very significant. For comparison, the colour fringes are about 2-3 pixels wide in the images from the Olympus Zuiko 9-18mm f/4-5.6 wide zoom lens.

It's also fair to comment that the image from the Lumix 8mm fisheye is remarkably sharp in the extreme corner. Keep in mind that the corner is at a 90º angle from the optical axis.

Defishing

It is possible to convert the fisheye image to a normal image. This process is usually refered to as defishing the image.

Many different programs allow this kind of transformations. I have used a program called Hugin for this purpose.

Below is a comparison of the original images taken with the rectilinear lens at 9mm, the fisheye, and, in the bottom row, the fisheye image converted to rectilinear.

Olympus 9-18mm @ 9mm f/8	Lumix G 8mm Fisheye @ f/8
Fisheye image converted to rectilinear	Fisheye image converted to rectilinear and cropped

The original fisheye image can be stretched to look fairly similar to the rectilinear image. But it has an even wider field of view. I would say the difference in field of view is significant.

This defishing process is hardly optimal, though. The corners have been stretched, and hence lack some resolution compared with the centre of the image. Also, it is difficult to frame the image correctly if you intend to defish it later. But having the option to defish the image makes the fisheye lens more useful.

Here is another example of defishing. The original image is from the Apple Center in New York, Manhattan:

After defishing, it looks like this. There is still a bit of barrel distortion, which could have been removed with some tweaking of the parameters. You can see that the image is less sharp in the corners, due to the stretching needed in the defishing process.

Another note is that the aspect ratio changes when defishing the image. The original fisheye images were taken with a 4:3 aspect ratio, while the defished image has a much wider aspect ratio, closer to 16:9.

On first inspection, this might look like a mistake. However, it does actually make sense. A fisheye lens creates an image where the field of view is not constant across the frame. What I mean is that the field of view is more compressed in the corners than in the centre. Hence, the ratio of horizontal to vertical field of view becomes larger than that of the original image.

When using the 4:3 aspect ratio, the output image of course has a 4:3 ratio in terms of pixels.  However, due to the compressed field of view in the corners, the horizontal to vertical field of view ratio is 124º:92º. 

Conclusion

In concluding, it is clear that the Lumix G 8mm f/3.5 Fisheye lens is better optically than the Olympus 9-18mm zoom. The Lumix 8mm fisheye appears to vignette a bit with wide open aperture, but I can't see that being a big problem.

On the other hand, the 9-18mm zoom is more versatile. In the longer end, it gives a pretty normal field of view, and can be used for general photography. In the wide end, it is an extreme wide angle lens. It can be used to make stunning and interesting wide angle images, as well as pictures with a more normal perspective.

The fisheye lens is an exotic lens, and is not always easy to use. When you nail an interesting image with the fisheye lens, it can be very rewarding. But many pictures end up looking just hideous, or like clichés. It is a lens with a required taste. Given the high price, I would not recommend buying it unless you know what you are doing.

Finally, the 8mm fisheye lens focuses much faster and more silently on Micro Four Thirds cameras.

Of course, nobody with a Micro Four Thirds camera should buy the Olympus Zuiko 9-18mm f/4-5.6 Four Thirds lens, since it requires and adapter, and is much larger than the M.Zuiko Micro Four Thirds version of the lens.  From what I have read, the M4/3 version has comparable optical qualities, and focuses much faster.  It is also collapsible, and much lighter and more compact.