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Sunex 5.6mm f/5.6 185° SuperFisheye

Lens
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#1 UlfW

    Ulf W

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Posted 19 December 2020 - 11:42

Finished: 04 Jan 2021
Last Update:

Sunex 5.6mm f/5.6 185° SuperFisheye

Manufacturer: Sunex, Inc., 5963 La Place Court, Suite #309, Carlsbad, CA 92008
Manufacturer's lens designation: Sunex, 185° SuperFisheye 5.6mm F/5.6
Note that Sunex includes defishing software with new purchase of this lens.

Introduction year: 2008?
Currently manufactured: Yes
Lens type: Fixed focus, Circular fisheye
Focal length: 5.6mm
Aperture range: f/5.6, fixed, circular
Intended Focus range: 0.5m - Infinity, fixed.
Sensor format/coverage: APS-C, image circle 14.5mm.
Available mounts: Canon EF, Nikon F, other via adapters.
Front filter: None
S/N of test object: C-2L05AG219

Lens review (VIS), on the web: https://www.kenrockw...per-fisheye.htm

Transmittance Summary
Definitions of the parameters below
  • UV Range: The Sunex lens transmits 0-65% in an increasing slope between 345-400nm.
  • TVISmax (%) = 85%
  • T400nm (%) = 64%
  • T365nm (%) = 16%
    This low percentage is an indicator for a longer exposure time under typical UV-pass filtration peaking around 365 nm.
  • λUV HMvis(nm) = 382nm
  • λUV HM400 (nm) = 375nm
  • λUV Zero (nm) = 350nm
  • These three values indicate that the lens is best in the near-UVA range.

Spectral transmission graphs

The transmission measurement accuracy into the NIR range is less good due to limitations in the light source and spectrometer configuration.
UV-NIR, Sunex, 185° SuperFisheye 5.6mm F/5.6
Attached Image: Sunex Full.png

UV, Sunex, 185° SuperFisheye 5.6mm F/5.6
Attached Image: Sunex UV.png

UV Log, Sunex, 185° SuperFisheye 5.6mm F/5.6
Attached Image: Sunex UV Log.png
Numerical Spectra Data available: Pending


General comments about the UV-reach:
Wide angle lenses from 28mm and shorter normally have a poor UV-transmission.
They also give problems with filters and filter stacks due to vignetting and in some cases flare and colour shift at the corners when using dichroic filters.
Wide angle lenses normally do not need a very deep cutoff for the typical usage in landscape photography as sunlight contains little UV below 330nm.
Even some transmission closer to 400nm might be enough for that.
For such a wide lens as the Sunex the transmission is unusually good and still useable, after a proper white-balancing.

Filters and how to use them on this lens:
Fisheye lenses cannot be used with front-mounted filters and this lens has no holder for rear mounted gelatin-type filters.

It is possible to use rear mounted filters, either in lens mount adapters for mirrorless cameras like Sony A-series etc., or placed directly in the camera.

An alternative, if space in the camera allows, is to putty-mount a filter directly against the lens's rear element mount ring.
The rear lens element is recessed and thus safe and the ring provides a good reference plane for orienting the filter normal to the optical axis.

Here a filter glass from a B+W 550nm long-pass filter is putty mounted.
The rear element's diameter is small enough that it is possible to mount 25mm filters.
My Omega 330W80 Improved, used for the UV-image below, is mounted in a 27mm-filter ring and works well to mount as it is.
Posted Image


When using rear mounted filters, it is important to realise that they shift the focusing towards infinity as the filter-glass gives a shorter optical path length mimicking a forward shift of the lens.

For wide-angle lenses even a short shift is very critical and can destroy sharpness at infinity.

The Sunex lens has a factory set critical focus point which can be readjusted.
That has to be done if introducing rear mounted filters.

The massive lens-block is mated to the lens-mount parts with an external M42 x 1mm thread.
The lens-block is then locked with four grub screws placed in its cylindrical side.
The screws can be loosened with a 1.5mm hexagonal (Allen) screwdriver or bit.
When these screws are loosened, the lens-block can be rotated in the mount and thus shifted back and forth to set a proper sharp infinity.

When using different filters, there is an optimal setting for each filter so it is convenient to make a scale to quickly set the proper focus-point when changing filters.

Here is my scale for the filters for which I have so far found the settings.
Posted Image


Canon EF mount mechanical quirks:
The mount does not have any coloured indication dot for guiding the rotation angle when mounting the lens.
When mounting the lens by turning it correctly, it distinctively clicks into place at the end point as any normal lens.
The mount also lacks the feature that normally stops the reverse rotation beyond the engage/release-point when removing the lens from the camera.
These are not big problems when you get used to them, but at first they can cause confusion.
Aside from these quirks, the mount is made with a very good precision.

Handling and focusing:
As the aperture is fixed, then either Aperture priority or manual mode is the only way to use the lens.
If a scale with focus settings is used, it is easy to reset to infinity focus.
If a closer focus is desired, loosening the locking screws and turning the lens to a closer focus is easy. However, then do not expect any flat field as the lens is not being used as intended.

The main difficulty when using this lens is to avoid getting your feet or shadow in the picture.
You also have to look for different compositions than with a normal lens as everything is shrunk and distorted.
This effect is shared with all super-wide-angle lenses.

Flare and sun-stars:
The lens design and coatings are very good so there are seldom big problems with flare even with the sun in the image.
There are no sun-stars as the fixed aperture is circular.

Sharpness:
I have found the lens impressively sharp.
My main usage has been for IR and VIS+NIR photography.

Fisheye projection:
The lens deviates a bit from the ideal fisheye projection, pronouncing the central parts and squishing the edges.
This can be corrected almost completely by software like Hugin or LensFun by mapping the error and generating correction coefficients.
Darktable might be used to make the projection more pleasant by applying the lens-correction for another fisheye lens.
I prefer the correction made for Sigma 8mm 3.5 FX for that, but often no processing or correction is needed.

Chromatic Aberration / fringing in UV:
In extreme situations in UV, the lens has a distinct fringing near the edges of the circle.
That can often be more or less cured by software in the postprocess.
The second UV sample below shows such a situation with dark beams in silhouette against the UV-rich sky.
The third image shows a partial section at 100%.


IMAGE SAMPLES

Reflected Ultraviolet. Filter: Omega 330W80 Improved UV-Pass
Posted Image


Fringing in Reflected UV. Filter: Omega 330W80 Improved UV-Pass.
Posted Image


Fringing in Reflected UV at 100%. Filter: Omega 330W80 Improved UV-Pass.
Posted Image


Reflected Visible and Near-Infrared. Filter: ZWB3 Dual Bandpass.
Posted Image


Reflected Near-Infrared. Filter: 800 nm Longpass.
Posted Image


Full Resolution Reflected Near-Infrared. Filter: 800 nm Longpass.
Double-click to see the full resolution image.
Posted Image
Find the second bird against the sky!

Edited by UlfW, 15 April 2021 - 16:19.

Ulf Wilhelmson
Curious and trying to see the invisible.

#2 Andrea B.

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Posted 04 January 2021 - 20:19

Ulf, you will need to copyright your chart pngs.

Example ----

Attached Image: sunex.png
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 Andy Perrin

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Posted 04 January 2021 - 20:50

At least under US law, it’s not actually necessary to write copyright on there to have rights under the law. But it’s probably a good idea to remind people that data comes from someone’s work.

#4 Andrea B.

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Posted 04 January 2021 - 21:20

Yeah, I know it isn't really necessary. And I know it really doesn't prevent all image theft.
But still.......I think it is more about not making it easy for image thieves.
Andrea G. Blum
Often found hanging out with flowers & bees.

#5 UlfW

    Ulf W

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Posted 15 January 2021 - 12:04

Updated the transmission graphs and revised the Transmittance Summary.
Reason: New improved measurements with less offset from crosstalk and extended NIR-range.

Edited by UlfW, 15 January 2021 - 12:05.

Ulf Wilhelmson
Curious and trying to see the invisible.

#6 OlDoinyo

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Posted 15 April 2021 - 02:18

I wonder if rear-mounting filters is exacerbating the chromatic aberration in a lens such as this. Not that I have any better idea--it is a tough challenge.

#7 nfoto

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Posted 15 April 2021 - 07:35

I would expect the opposite. Several Fisheye-Nikkors, for example 10.5mm f/2.8 and 16mm f/2.8 (AiS and AF models) have slots to rear-mount filters. However, the basic issue is that the optical design of the Sunex is not intended to perform in UV alone.