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.



5 comments:

  1. Thank you for the test - it is a little disapointing, that the lens is a bit prone to flare/ghosting (but I am still interested in this lens, very much in fact), but Nikon 10,5 fisheye, here you shall "work hard" to get it, it is very resistent to this.

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  2. ...but it is very fine, thank you, that you test for this flare/ghosting, a lot of testers do not, and I can add about the NIkon 10,5, that it makes a lot of CA in high contrast scenes, so perhaps this here is better in this area ?

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    Replies
    1. You could take a look at the Samyang 7.5mm f/3.5 fisheye lens. It is much better in terms of flare/ghosting.

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  3. Don't forget Underwater photographers.
    This lens is one 4/3 best for us underwater nuts.
    A good underwater photo is when you're nearly sticking to your subject (less water between you & it is always better).
    Thanks for your review.

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  4. I am developing a defishing software now:
    http://anglerfish.ajotte.com/
    and I am asking people to make profile photos of their lenses.
    You wrote that this Lumix lens is hard to defish, so I'd like to add its profile asap. Anyone could help?

    ReplyDelete