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06-14-2018, 08:18 AM   #1
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Rokinon 8mm lens with K-1

Has anyone used the Rokinon 8mm fisheye lens with removable hood
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on the K-1? Does the sensor capture the entire circle? Sample pics? Thanks.

06-14-2018, 09:00 AM   #2
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QuoteOriginally posted by tomcook Quote
Has anyone used the Rokinon 8mm fisheye lens with removable hood
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on the K-1? Does the sensor capture the entire circle? Sample pics? Thanks.
AFAIK it's a crop lens, you'd get a circle in the frame.

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06-14-2018, 09:56 AM   #3
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Christopher Frost did a review on FF and cropped Cannon, in 2016. It shows the image on both--you get quite a bit more on FF. Correction it was 2014. (Sorry I don't seem to know how to copy the link.)

Last edited by dms; 06-14-2018 at 10:04 AM.
06-14-2018, 11:00 AM   #4
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I have a Samyang 8mm with non removable hood, and a K-1, but I have never combined them. I did some research about the Samyang before I bought the K-1. The hood on the Samyang limits the image circle to a rectangle slightly larger then APS-C. When the hood is removed the image becomes almost circular with a diameter about 1,2-1,3x the diagonal of APS-C, depending on how much vignetting you feel are acceptable and what aperture you use. In other words somewhere in between APS-C and FF. If you prefer square crops it will be almost 1,5x a square crop from APS-C.

Anyway, I decides to buy a Zenitar 16mm f/2,8 to replace the Samyang, I just havent got my self to sell the Samyang yet.

06-14-2018, 01:01 PM   #5
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I would not recommend it, after trying it out, I noticed that the hood creates a serious rectangular vignette which negates the wide angle of the Fisheye.
06-14-2018, 01:07 PM   #6
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I trimmed the hood of my Rokinon 8mm fisheye a few years ago in order to mount it on a Canon T3i with adapter. The adapter shifted the lens to some angle which ended up causing shading, even though the T3i was an APS-C body too.
I tried it on my K-1 II recently and just got a circle in FF mode. No point. I sold the lens to a friend who owns a K-30.
06-14-2018, 01:08 PM   #7
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QuoteOriginally posted by tomcook Quote
Does the sensor capture the entire circle? Sample pics? Thanks.
QuoteOriginally posted by Adam Quote
AFAIK it's a crop lens, you'd get a circle in the frame.
There are quite a few examples online and the Samyang 8mm's image circle (removable hood version) does not quite fit in the 24x36mm frame. There is a cut off at top and bottom. The fixed hood version projects a vaguely rectangular image to FF.


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06-14-2018, 01:20 PM   #8
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The 8mm FE will leave a definite circle, however if you couple with a 1.4 TC it is very useable in FF.
Mine is the Bower with out detachable hood.
Here is an example to show how little vignette there is with the TC attached.
8mm APS FE + 1.4TC + K1 - PentaxForums.com

06-30-2018, 03:42 AM   #9
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Thanks everyone. I am looking for a full circle, 180 degree image on FF (K-1) like a legacy fish-eye lens. It appears that the Samyang/Rokinon 8mm will _not_ quite do the job.
06-30-2018, 07:07 PM   #10
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If you're looking for full circular the only one I know of new is from Lensbaby. They say it is optimized for APS-C but compatible with FF and they do make quality lenses. You might give them a call.
Other options would be vintage. I seem to remember Sigma had both a diagonal and circular in k mount at one time and then there are the Taks. Have fun, though I don't use a fisheye but once every few years they can be very creative.
07-01-2018, 06:13 PM   #11
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If you want a full circle for the image** (while not the most elegant solution):
-- you can crop to a circle in pp
-- or possibly (?) mount a circular cutout in front of the lens (that vignettes to a circle).***
-- Also it may be some pp software allows you to do a mathematical mapping from the actual image to a circle (one would likely expect if anyone does it, it would be photoshop, but I did not investigate further/try it) .
_____
** Finding a lens that shows the image as a circle does not ensure that the actual FOV will be as large as what you get from this 8 mm FE.

*** You probably would do better mounting a circular cutout to the rear of the lens. The rear of this lens is reasonably flat and the rear most glass does not protrude. With photo tape it should be pretty easy, just need to experiment with the diameter of the hole.

Also you could look for a older lens attachment that converts the FOV to a circle--Spiratone for example. This will do it, and will be inexpensive, but the image quality will suffer. Older Pentax Takumars apparently have a 24mmx36mm rectangle image. Older Nikon's had it--especially for atmosphere/sky photos for cloud cover studies--and they may be usable on K mount, but it may require the mirror be manually raised, and in any event they are likely very rare and costly.

Thinking more about it--I should have realized my Pentax fisheye the SMC-A 16 mm f/2.8 (or the earlier K 17 mm f/4) had a gel holder on the rear of the lens, so you could make a circular cutout and in complete safety mount it on the lens. The 17 mm f/4 also was available as a Takumar--but I don't recall if it had a gel holder (BTW there is currently one [or was anyway] listed at KEH).

Last edited by dms; 07-01-2018 at 06:48 PM. Reason: Added paragraph covering Pentax lenses w/ gel holder.
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