| review: Zenitar 16mm f/2.8 Fish Eye Lens M42 thread (appr. € 200,- ) |
The Zenitar is a 16mm fish eye lens made in Russia.
It is designed to fill the whole frame of a 35mm camera.
The speed of 2.8 is quite fast.
It can be stopped down manually to 22.
All lenses are multicoated.
But the huge number of lenses (11 elements in 7 groups) causes some danger for internal reflections.
It weighs about 310 grams and is 55mm long and 63mm in diameter.
The center resolution is claimed to be 60 lines per mm dropping to 23 at the edge.
It comes with 4 filters in red, green, yellow and pale.
The filters are placed at the rear (towards the camera).
One of them should always be in place because they are part of the optical design.
I have chosen the pale one which might be something like a daylight filter and seemed to have the best transmission (the manual is telling nothing about that).
This one is the version with 42mm screw and hence I can easily adopt it to my CCD camera.
Unfortunately the filter is blocking the thread of my filter wheel.
So I was not able to use it for RGB photos.
I will give it a try later without a filter in place.
The M42x1 thread is also known as 'universal screw mount' and was used on Pentax, Praktica, Mamiya/Sekor, Yashika and many other brands.
The flange-to-film distance is 45.5mm and hence too long to screw it directly to a CCD camera.
The Starlight Xpress cameras come with a tube adaptor for that.
I used it and focus for iternity was reached at 3.5 meters on the scale of the Zenitar.
Example Photo of the Orion Constellation
The Zenitar was stopped down to f4.0 to increase overall sharpness and improve the ability to reach good focus.
Image was taken with Starlight XPress HX916 without IR-blocking filter.
The pixel size in that picture is about 12 mym and is giving a field of about 32 degrees.
It covers a diameter of about 12mm of the focal plane.
The sky was a bit hazy with thin high clouds which show up as stripes in that 30 seconds shot.
The unsharp disk in the lower right is a reflection of a street lamp.
Example Photo of the Pleiades
The Zenitar was fully open at f2.8 to show the maximum of aberration.
At that speed it was very hard to reach good focus.
But I finally succeeded quite well.
When judging the sharpness please keep in mind that 35mm camera lenses are normally designed to have spot diameters if about 0.03mm.
That is fine for reasonable fast 35mm film.
The HX916 CCD camera can go down to 6.7 mym which is 4.5 times higher resolution!
On the other hand the CCD frame with a diameter of 12mm is much smaller than 35mm film.
And aberrations tend to grow with radius further away from the optical axis.
The pixel size in the big picture is again about 12 mym and is giving a field of about 32 degrees.
Look how small the Pleiades are appearing in the center of that photo!
The smaller pictures below show parts of the picture at full resolution with pixels of 6.7 mym.
The left one is at the optical axis, while the right one is at the maximum diameter of 12 mm.
I would guess the aberration at the edge is dominated by coma.
But near the center the optical performance is very good with a slight indication of astigmatism.
Conclusion
The Zenitar is a great wide angle lens for CCD cameras.
It should be stopped down to about f4.0 to improve the ability to reach perfect focus and to reduce aberrations and internal reflections.
Comparing the resolution of the HX916 of 150 lines per mm to the resolution of the Zenitar to 60 lines per mm I think the Zenitar is even better than claimed.
Use the search tool on this site to find more astro photos taken with it:
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