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|Dec 20, 2003, 3:01 AM||#1|
Join Date: Oct 2002
Poor Man's Circular Fisheye Lens
This is the second installment of my "Poor Man's Lens" series. The first one is about wide angle and is available here:
This installment is about circular fisheye lenses. There are not many SLR circular fisheye lenses available. Currently, we can find a Sigma 8mm F4, and a Russian Peleng 8mm F3.5. The Peleng is cheap ($225) and becomes a 12mm on a D100. See http://www.kievcamera.com/camera.php?ID=14 for the details.
Nikon also made a Fisheye FC-E9 for Coolpix 5400 and 5700. This FC-E9 has a coverage slightly larger than 180 degree and has a rear thread size of 46mm. See below:
The following shows the FC-E9 mounted on a AFD 24mm F2.8. Since the 24mm and FC-E9 have thread sizes 52mm and 46mm, respectively, the combo uses a 52-62mm step-up, 62-49mm step-down, and a 49-46mm step-down rings.
The following is an image taken with this combo with F8, 1/5 sec, and hand-held. The image was recorded in the JPEG FINE mode without sharpening. Note that the image circle is clipped near the top and bottom. A focal length slightly wider than the 24mm is needed to see a full image circle.
The following shows four 100% crops of the above image, far left, center left, center right, and far right, with the far left and far right crops at the edge of the circular image. Obviously, chromatic aberration is visible, especially the green fringes in the left and center left crops, and both purple and green fringes in the far right crops. However, the center sharpness appears to be good.
The following shows the result after a sharpening for web using all default parameters of Nik Sharpener is applied.
Next, we try this FC-E9 fisheye on a cheap Tamron 19-35. The Tamron has a thread size of 77mm, and step-down rings 77-72mm, 72-62mm, 62-49mm and 49mm-46mm are needed. Although this combo looks strange, it does work!
The following image shows the result when the Tamron is at 19mm. As you can see the image circle is smaller than the height of the image frame.
If the Tamron is zoomed to somewhere between 22mm and 24mm, the image circle will be brought "closer" and becomes larger.
The following image shows 100% crops from the left edge, center left, center right and right edge portions. The image characteristics are very similar to those obtained by the AFD 24mm, although this image seems to be softer than that of the 24mm.
The following is the sharpened version. Other than the edge portions, the result still looks very promising.
The following shot shows that the FC-E9 indeed covers more than 180 degree. The camera is placed at the middle and above the bar in the lower edge of the image circle. As you can see, the bar becomes a semi-circle. Moreover, the left portion still has space, which means the FC-E9 covers more than 180 degree.
Given the fact that currently all SLR circular fisheye lenses on the market are for full frame SLR cameras, which means using them on a APS DSLR the image circle will be clipped, the use of front-mounting fisheye lenses may be a very viable approach before one can find a circular fisheye lens for the APS size DSLR cameras. The Nikon FC-E9 has a price tag of about $260 and may be cheaper on eBay. Thus, in less than $500 (i.e., FC-E9 and Tamron 19-35 or similar lens), one will have a circular fisheye lens to use with acceptable image quality. Note that many cheap "super fisheye" or "fisheye" lenses are actually uncorrected ultra-wide angle lenses. See the image below for an example. In other word, they are wide angle lenses with angle of view significantly less than 180 degree and allow straight lines to become curvilinear. In general, the quality of these cheap fake fisheye lenses are poor or unacceptable.
Before we conclude, one thing must be mentioned. It appears to me that none of the wide angle lenses I tried can produce diagonal fisheye images because the D100 cannot focus. It may be due to many step rings were used pushing the FC-E9 farther away from the lens (i.e., 24mm or Tamron 19-35). However, this is only my speculation and cannot be supported by any scientific evidence. Consider this problem as a single incident.
Nikon Coolpix 950/990/995/2500/4500 User Guide
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