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Defishing experiement with the Samyang 8mm F/3.5


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#1 M4cr0s

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Posted 18 November 2011 - 15:59

I recently acquired the Samyang (also sells under the names Bower, Rokinon, Vivitar and several others, but Samyang is the manufacturer). This lens offers a FOV of 180 degrees on a cropped sensor. It's built-in lens-hood can also be shaved for using the lens with relative success on FX.

I've owned a few rectilinear wide-angles, my favorite being the Sigma 8-16 which offers a FOV of a little bit less than 120 degrees at the wide end. I've sold the Sigma to fund other things and got this Samyang as a cheap 200$ substitute for a couple projects I have in mind and to have that extreme wide-angle option in my bag. I was hoping to get acceptable "defished" results out of the Samyang using Photoshop trickery. I found the results are so interesting I thought I'd post them.

I tried three different solutions for defishing. DXO Optics, PTlens and Fisheye Hemi, the later two being Photoshop plugins. I did not include the sample from DXO Optics as it is very similar to the results from PTlens. Note that none of these applications/plugins have specific profiles for the Samyang. The Fisheye Hemi-plugin do not however operate with specific camera/lens profiles, rather with generic ones whose result can be further tweaked by increasing canvas size. The test image is not at all interesting or good in any technical or artsy meaning of the word (just a quick one out the window), but I think it shows what is possible. The "test" was conducted on a D7000 body.

The original image is of course distorted with bent lines, but it's really not that bad for a fisheye, there's somewhat less bulging than I expected. It might be down to the slight controversy over this lens' projection, some claim it's more or less stereographic. Lenstip attempts to explain it in their review of the lens. The image modified with PTlens offers a classic rectilinear kind of projection where the corners are stretched but lines straight. This is similar to how for instance the Sigma 8-16 would draw, although not quite as extreme. Also quite a bit of FOV is lost due to cropping. The last sample is from the Fisheye Hemi-plugin that uses mapping algorithms.

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I'd say that the results achieved with the Fisheye Hemi-plugin are impressive and interesting and shows that a fisheye lens can be more "practical" than you'd think. An important thing to notice though, that the Hemi-plugin only seem to straighten vertical lines unlike other solutions that attempt to straighten them all. Of course there's a lot of fake pixels, and resolution in the corners isn't the best, but with careful post processing large prints can definitely be made and you who have experience with wide angle lenses know that corners will inevitably suffer from field curvature, vignetting and distortion while the center portion of the frame often remains extremely sharp. I do not however find the Hemi'd results from the Samyang any worse than the rectilinear wide-angles I've worked with!

Generally speaking the overall IQ of the Samyang is exceptional considering the price and I've started to think it actually rivals the comparable offerings from Nikon and Sigma. It is also a small, light yet very, very well built lens (as good as classic MF Nikkors) and although it has no chip, thus not super accurate exposure even on the bodies that can meter with it, it works well. Achieving what one deem an acceptable exposure is always a challenge with extreme wide-angles due to the tendency to capture scenes with a large dynamic range. Color and contrast is not extremely punchy, but it's no slouch and so far I can't see any heavy color casts. Manual focus is a moot point on a lens this wide and the extreme DOF achieved even at largest aperture. The best results seem to be around F/5.6-8.0 (as expected).

Mac

Edited by M4cr0s, 18 November 2011 - 16:01 .

"I cannot and will not cut my conscience to fit this years fashions."

Lillian Hellman


#2 DougB

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Posted 18 November 2011 - 16:31

Mac
Thanks for posting this. The result is impressive!

I have the Rokinon\Samyang etc 85 f1.4 - another impressive $250.00 purchase.
Regards
Doug

-------------------------------------------------------------------------------------------------------
D700, D300; D200; F2, Lumix FZ30; and a bunch of Nikon MF & AF glass (& a Rokinon 85mm f1.4)

#3 Coreopsis

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Posted 18 November 2011 - 17:08

Thanks for posting.
John

#4 RKPhotog

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Posted 18 November 2011 - 17:34

Interesting results. Have you tested it yet for flare?
Bob
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#5 M4cr0s

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Posted 18 November 2011 - 17:41

Mac
Thanks for posting this. The result is impressive!

I have the Rokinon\Samyang etc 85 f1.4 - another impressive $250.00 purchase.


The Samyangs are getting quite a reputation. I think many of us with 2000$ brand-name lenses, Zeiss-o-holics and so forth are a bit stumped that those guys in Korea are churning out surprisingly good lenses at ridiculously low prices. They may not be better, but certainly very competitive in the IQ-department. If they'd ad some some kind of half-way decent AF motors and double the prices, they'd still be competitive.

Mac

"I cannot and will not cut my conscience to fit this years fashions."

Lillian Hellman


#6 M4cr0s

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Posted 18 November 2011 - 17:44

Interesting results. Have you tested it yet for flare?
Bob


Haven't had a chance yet. Mostly gray skies. It seems to behave ok indoors though. Flare tests in several reviews indicate that it should be pretty decent, but I won't know before we get some sunny days.

Mac

Edited by M4cr0s, 18 November 2011 - 17:44 .

"I cannot and will not cut my conscience to fit this years fashions."

Lillian Hellman


#7 Thor Lidasan

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Posted 18 November 2011 - 19:00

Thank you for the very informative post! :) I have never been happy with the de-fishing methods available for Samyang but your post made me take a second look at Hemi.

I have been using Samyang for visible and IR shots. Flaring is not an issue for me however allow me to post several images of "against the sun" shots using the Samyang 8mm.

with D200:

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with D7000:

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with D40 IR 830nm filter

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#8 M4cr0s

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Posted 18 November 2011 - 22:12

@ Thor
If you try out the Hem-plugin, try to extend the canvas to about 135 % wide (ctrl + alt + c in PS) before using setting number one of the three in the Hemi plugin. That seems to give the best results for me.

Your samples look good to my eye, thank you for posting! I've gone through Flickr looking for shots with the Samyang, a lot of decent stuff but also a lot of heavily processed images too which makes it kind of hard to judge. Looking forward to getting to know it, but it will probably take some time considering the weather we've had lately.

Mac

"I cannot and will not cut my conscience to fit this years fashions."

Lillian Hellman





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