Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-25-2012, 06:20 PM   #1
Veteran Member
madbrain's Avatar

Join Date: May 2008
Location: San Jose, CA
Posts: 807
Samyang 8mm fisheye vs Sigma 10-20mm super-wide angle

I already own a Sigma 10-20mm f4-5.6 which is a rectilinear super-wide angle lens. I bought it 4 years ago. It is a great lens which I will definitely keep.

I have had a severe case of LBA lately - I bought 7 lenses in the past month, almost all used on craigslist. A couple of them went to my mother with my K200D, a few went to ebay and were resold for a nice profit (thanks Pentax for raising your lens prices!). The only 2 lenses I actually added were a mint used DA 55-300 and a new Rokinon 800m mirror lens. But I digress ...

I have never owned a Fisheye lens before . Recently, I noticed the Samyang 8mm Fisheye which sells for $299 new under various brand names, such as Rokinon.

I am intrigued about the possibilities of this lens, and wondering if it is worth adding considering I already own the Sigma 10-20.

The Samyang fisheye has the following advantages over the Sigma 10-20 :
1) obviously, it is wider by 2mm
2) it is faster - f3.5 at 8mm, which is better than the Sigma's f4 at 10mm
3) it has an aperture ring. For me, that means I could also use it on my Canon DSLR with the help of a PK-EOS adapter. I cannot use the Sigma due to the lack of aperture ring.

The sigma has the following advantages over the Samyang :
1) auto-exposure. Unfortunately, this is the only way, no aperture ring. But the Samyang is the opposite, no A setting on the aperture ring. Edit: actually, looks like I am wrong on this one, reading a few threads here, the Pentax version does have an A setting on the ring. Great news !
2) auto-focus . Not that much of an advantage. In my experience, manual focus is really easy for wide lenses.
3) can use filters such as UV and polarizer.
4) of course it is a zoom up to 20mm. But in practice when I put the lens on, I only ever use it at 10mm.

What I am wondering is about the distortion effect on the Samyang fisheye .
1) If I forego buying the Samyang and the extra 2mm of focal length, and just shoot at 10mm with the Sigma, is the fisheye effect something that can completely be replicated in software ? Or is it that distortion actually unique to the fisheye ?
2) if I shoot with the Samyang 8mm, can the distortion be completely removed in software if I wish to do so occasionally ? Is there specific software that knows the optical characteristics of this lens to be able to compensate for this ?

I think I am leaning towards buying this lens, but the questions still bother me, as I probably wouldn't want to carry both in my bag on the same day.


Last edited by madbrain; 05-25-2012 at 06:28 PM. Reason: error about A setting
05-25-2012, 06:53 PM   #2
Loyal Site Supporter
WPRESTO's Avatar

Join Date: Aug 2010
Location: Massachusetts
Photos: Gallery | Albums
Posts: 26,082
10-20 vs. fisheye

I have both a Sigma 10-20 and the Rokinon labeled 8mm fisheye. I've never tried putting fisheye style distortion into a image taken by the 10-20mm Sigma, so I cannot tell you if it's possible to obtain that "look," obviously without the full 180 degree diagonal capture. Using PP, some but not all of the 8mm fisheye distortion can be removed, but at the expense of losing some of the super-wide frame, specifically the corners. The correction basically involves converting the rectangular image into something that looks like extreme pincushion distortion, then cropping out a rectangular frame by eliminating the protruding corners. I find very limited use for the fisheye, primarily interiors, but the distortion is obvious and annoying, and works better sometimes than others. I posted an 8mm image taken of the interior of a tavern in the "I spy" challenge just today, and I would rank it as a "very good" outcome using the fisheye. You might want the fisheye look for artistic reasons, but in my opinion, that look will wear thin very quickly = after being used for relative few images. I would classify it with the automatic power-zoom effect of the PZ series Pentaxes, where for a long night shot the lens would automatically zoom for 1/2 the exposure to streak any point-source lights toward a central vanishing point. After showing maybe 3 images, it's "OK, there it is again. Seen that, let's see something else."
SO--- In my opinion, don't replace the 10-20 with a fisheye. Don't expect to convert an 8mm fisheye image to an 8mm rectilinear image (get the Sigma 8-16). Expect the "fisheye look" to have limited artistic impact unless you're awfully clever with your subjects. Interiors done with a fisheye sometimes work, sometimes just look distorted.

Will try to gather a couple images and post them here for your consideration.
Hope these observations are of some use.
WPRESTO
05-25-2012, 06:59 PM   #3
Veteran Member
kaiserz's Avatar

Join Date: Nov 2011
Location: NoVa The "burg"
Photos: Gallery
Posts: 899
If I'm not mistaken the siggy's always on "A" settings
05-25-2012, 07:34 PM   #4
Loyal Site Supporter
WPRESTO's Avatar

Join Date: Aug 2010
Location: Massachusetts
Photos: Gallery | Albums
Posts: 26,082
Here are two pairs of comparison slides.
1) A cathedral interior done with the Sigma 10-20 (@17mm) and the same region, but not from the same spot, taken with the 8mm. This gives you an idea of how annoying the fisheye distortion can be, at least in my opinion.
2) two views of the interior of a tavern taken from essentially the same spot, this time with the Sigma @ 10mm. This pair gives a better idea of how much more the fisheye encompasses, and in my opinion is a much more successful application of the lens

These are all hand-held, and as I do not have especially steady hands, the IQ in any/all may suffer from shake so do not evaluate on the basis of "sharpness."


Last edited by WPRESTO; 07-31-2012 at 01:50 PM.
05-25-2012, 08:03 PM   #5
Veteran Member
madbrain's Avatar

Join Date: May 2008
Location: San Jose, CA
Posts: 807
Original Poster
Hi,

QuoteOriginally posted by WPRESTO Quote
I have both a Sigma 10-20 and the Rokinon labeled 8mm fisheye. I've never tried putting fisheye style distortion into a image taken by the 10-20mm Sigma, so I cannot tell you if it's possible to obtain that "look," obviously without the full 180 degree diagonal capture. Using PP, some but not all of the 8mm fisheye distortion can be removed, but at the expense of losing some of the super-wide frame, specifically the corners. The correction basically involves converting the rectangular image into something that looks like extreme pincushion distortion, then cropping out a rectangular frame by eliminating the protruding corners. I find very limited use for the fisheye, primarily interiors, but the distortion is obvious and annoying, and works better sometimes than others. I posted an 8mm image taken of the interior of a tavern in the "I spy" challenge just today, and I would rank it as a "very good" outcome using the fisheye. You might want the fisheye look for artistic reasons, but in my opinion, that look will wear thin very quickly = after being used for relative few images. I would classify it with the automatic power-zoom effect of the PZ series Pentaxes, where for a long night shot the lens would automatically zoom for 1/2 the exposure to streak any point-source lights toward a central vanishing point. After showing maybe 3 images, it's "OK, there it is again. Seen that, let's see something else."
SO--- In my opinion, don't replace the 10-20 with a fisheye. Don't expect to convert an 8mm fisheye image to an 8mm rectilinear image (get the Sigma 8-16). Expect the "fisheye look" to have limited artistic impact unless you're awfully clever with your subjects. Interiors done with a fisheye sometimes work, sometimes just look distorted.

Will try to gather a couple images and post them here for your consideration.
Hope these observations are of some use.
WPRESTO
Thanks, yes, that is very helpful. I am not considering getting rid of the 10-20. Only whether adding the 8mm to my lens bag would provide benefits. It sounds like the 10-20 is more versatile and likely to be used more often, and the extra weight wouldn't be worth it.

There is still the benefit of being able to use the lens with my Canon t3i. That may be the main reason to buy it. I only own one Canon mount lens , the 18-55 IS 2. I am not really looking to buy any other Canon mount lens, since they cannot be used on the Pentax bodies with adapters. The other way around works with an adapter, as long as the lens has an aperture ring, which the Sigma does not unfortunately.
The Canon version of the Samyang lens doesn't even have an "A" setting on the aperture ring apparently, it is manual only, unlike the Pentax version. Seems like that Canon mount version shouldn't even exist, it should just come bundled with the PK-EOS adapter and the manufacturer wouldn't have to make 2 models
05-25-2012, 08:05 PM   #6
Veteran Member
madbrain's Avatar

Join Date: May 2008
Location: San Jose, CA
Posts: 807
Original Poster
QuoteOriginally posted by kaiserz Quote
If I'm not mistaken the siggy's always on "A" settings
Right. And that is why it can't be used with a PK-EOS adapter. I tried one, and the Sigma aperture actually was stopped down all the way, with no way to open it Same thing happened with my DA 18-250 lens.
05-25-2012, 08:17 PM   #7
Veteran Member
madbrain's Avatar

Join Date: May 2008
Location: San Jose, CA
Posts: 807
Original Poster
Hi,

QuoteOriginally posted by WPRESTO Quote
Here are two pairs of comparison slides.
1) A cathedral interior done with the Sigma 10-20 (@17mm) and the same region, but not from the same spot, taken with the 8mm. This gives you an idea of how annoying the fisheye distortion can be, at least in my opinion.
It's not that bad actually IMO, but very difficult to compare since they are from different locations.
I think in such a big space, I probably wouldn't use either the 8 or 10-20 lens, I would just keep the DA 18-250 that I have on most of the time anyway.

QuoteQuote:
2) two views of the interior of a tavern taken from essentially the same spot, this time with the Sigma @ 10mm. This pair gives a better idea of how much more the fisheye encompasses, and in my opinion is a much more successful application of the lens

These are all hand-held, and as I do not have especially steady hands, the IQ in any/all may suffer from shake so do not evaluate on the basis of "sharpness."
Thanks for those images.
Agree that the second example in the tavern is a much better usage . The 8mm really does capture much more, I am really impressed by the difference.
05-25-2012, 08:35 PM   #8
Pentaxian
Bob from Aus's Avatar

Join Date: Jul 2011
Location: Australia
Photos: Gallery
Posts: 1,085
Love my Sigma 10mm fisheye and pentax 15 Ltd combo. My sigma 10-20 has been gathering dust even though it's a nice lens.

05-25-2012, 08:52 PM   #9
Site Supporter
jimr-pdx's Avatar

Join Date: May 2010
Location: 1hr north of PDX
Photos: Gallery | Albums
Posts: 3,550
I had made plans to buy a fisheye 8.. then along came a 'make offer' at auction on a Sigma 15/2.8 fisheye. Other than filters it does well in both your lists: faster than the 8mm and the 10-20, aperture ring, AF and auto-aperture. Full-frame friendly too. Last I looked it rang up a perfect 10 here with owners (how can I evaluate honestly with that hanging over me?). Not as wide as the 10-20 as far as focal length, but by field of view I cannot say - until someone loans me a 10-20 for a bit

If you see one of these they are mighty nice. I really hoped to find a DA15 some day, but the Sigma beat the going rate for DA15s by over $100. More food for thought.
05-25-2012, 08:59 PM   #10
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by WPRESTO Quote
SO--- In my opinion, don't replace the 10-20 with a fisheye. Don't expect to convert an 8mm fisheye image to an 8mm rectilinear image (get the Sigma 8-16). Expect the "fisheye look" to have limited artistic impact unless you're awfully clever with your subjects. Interiors done with a fisheye sometimes work, sometimes just look distorted.
Quite right. A FE and UWA complement each other. They have different coverages and purposes. My set are the DA10-17/3.5-4.5 (the lens that drove me to Pentax) and the Tamron 10-24/3.5-4.5 (the lens that completes my walkabout set). For coverage, the FE starts where the UWA leaves off. They can't be compared by focal length. Here are AOVs on my K20D (I'll include your Sigma and the Samyang for comparison):

Pentax 10-17 FE: ~110-175 degrees
Tamron 10-24 UWA: ~60-110 degrees

Samyang 8mm FE: ~180 degrees
Sigma 10-20 UWA: ~70-110 degrees

Note: These are numbers for the actual K20D sensor (diagonal= 28.1mm) not a nominal APS-C sensor (diagonal= 30.1mm). I'm not sure of the exact size of your K200D sensor, but you'll be somewhere in the neighborhood.
________________________________

The speed differences are hard to judge at AOVs of 100 degrees and more. My fishy Zenitar 16/2.8 has an AOV of ~100 degrees, comparable to a UWA @12mm, and it's notably faster than the DA10-17 @16mm (f/4.5) and the Sigma UWA @12mm (~f/4), and a bit faster than the Tamron UWA @12mm (~f/3.5). But we don't usually use FEs and UWAs for their speed, but for their projection effects. DOFs are immensely thick from 100 degrees on up. I like the Zenitar in darker active interiors. I like the Pentax and Tamron everywhere else.

Ah, projection effects. Cartographers have grappled for around 650 years with the problem of projecting a curved universe onto a flat plane. Rectilinear UWAs stretch the edges, FEs bend them. An FE projection is actually more accurate but our brains don't like to see that bending. I can't use an FE in my forest -- all the trees are falling on me! So as with mapmakers, we choose the projections that best serve our purposes.

There's a nifty trick that's cheaply done: Take a DA18-55 or -135 or -250. Mount on it a cheap 0.25x FE adapter -- mine (new) cost US$20 (shipped) a few months ago. The zoom @18mm gives a 180-degree full-circle fisheye; by ~30mm it's a frame-filling FE, and it becomes less fishy (with a narrower AOV) as we zoom onwards. It's easy to dial-up a projection for almost any purpose. No, don't expect the greatest optical clarity at the edges. But it's fun and educational.
________________________________

With your Sigma UWA at the wide end, you know how a slight shift in lens angle can have a dramatic effect on perspective distortion, how rectangles become acute parallelograms. FE distortion gets bendy instead. No, we usually don't want straight lines to curve too much. So, just as we use a UWA carefully, we use a FE even more carefully.

Where I use the 10-17 FE @10mm (similar to the Samyang 8mm FE):

* Inside a curved space
* Where 3 or more lines intersect
* Shooting straight up or straight down
* With centered rounded subjects where edges don't matter
* With land- and sea-scapes with the horizon centered
* For stitching 360-degree full-world panoramas
* Where I really *want* perspective distortion

That last is popular in some action sports (like surf- or skate-boarding) and fashion (really s-t-r-e-t-c-h those legs!) and 'psychedelic' shots (everything's bent!) and so on. The frame-filling FE works inside wells and tunnels and caves. Stuff like that.

There are fairly few straight-line interiors where only a FE will do. Case in point: The Venetian Casino in Las Vegas has a reproduction of the Sistine Chapel ceiling where its entry lobby merges up to a gaming level. Tis a darkened space, and the 10-24 UWA just won't capture it all. But the FE @10mm grabs it very nicely -- and those slot-machine lights at the image edges just become a necklace of shining gems.
________________________________

The Samyang is the least expensive high-quality frame-filling FE. The DA10-17 costs rather more but is much more flexible. The Zenitar is the fastest of the lot and not super-fishy. There's also a super-fishy and pretty cheap Sigma-made 12/8 fixed-focus FE; but the less said about that, the better. An 0.25x FE adapter (mine is branded Precision Design Super AF Fisheye) on an 18-whatever would be a cheap way to find if you like super-fishiness enough to spend US$200-500 on a better lens.

My recommendation: Get the cheap adapter. Test your comfort level for distortion before you spend more money.

Last edited by RioRico; 05-25-2012 at 10:06 PM.
05-26-2012, 05:58 AM   #11
Veteran Member
Louicio's Avatar

Join Date: Mar 2012
Location: Melbourne
Posts: 432
Embrace the distortion =) It's not a lens you use for architecture it is supposed to distort the perspective (or retain the true perspective however you look at it) and the samyang fisheye is pretty good choice for a low price.

And as a side note on distortion, a fisheye actually retains the perspective of the image better than a rectilinear and does not attempt to flatten the image as in the bar photo. But don't replace an ultra wide with a fisheye and try to flatten it, too much effort for an average reward esp if you already have a sigma 10-20. =)
05-26-2012, 11:40 AM   #12
Veteran Member
liukaitc's Avatar

Join Date: Jul 2010
Location: New York
Photos: Albums
Posts: 1,008
fisheye is a very cool lens for portrait as well.
I am inspired by the video host by B&H
that guy's favourate wedding lens are 10mm fisheye and 15mm fisheye (he uses APS-C camera)
so honestly, I think pentax 10-17 fisheye is a lot versatile than samyang 8mm fisheye.
05-26-2012, 02:16 PM   #13
Site Supporter
jimr-pdx's Avatar

Join Date: May 2010
Location: 1hr north of PDX
Photos: Gallery | Albums
Posts: 3,550
Following up on RioRico's stats:
Checking the field values at this website, it seems the 10-20 at 10mm has a diagonal FOV of 110, and the 15 fisheye is listed 114 diagonally. This is for a rather generic 1.5x crop, sensors do vary a bit as noted elsewhere. So for overall field the 15 fish is close to a flat 10, but oh boy those edges..

I realize this is strictly for academic purposes, as the OP never brought up the 15.. yes, that's Sigma kool-aid coloring my lips.
05-26-2012, 03:39 PM   #14
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by jimr-pdx Quote
Following up on RioRico's stats:
Checking the field values at this website, it seems the 10-20 at 10mm has a diagonal FOV of 110, and the 15 fisheye is listed 114 diagonally. This is for a rather generic 1.5x crop, sensors do vary a bit as noted elsewhere. So for overall field the 15 fish is close to a flat 10, but oh boy those edges..
I forget whether it was with PaintShopPro9 or PentaxPhotoLab3 -- but I was defishing shots from my Zenitar 16/2.8 (180-degree fishy on 135/FF cameras) and determined that its AOV was equivalent to about 12.5mm rectilinear. Assuming that lensmakers were honest about the focal length (*) then a true 15mm FE would have AOV close to 11mm rectilinear. But numbers are a bit tricky in this realm, especially when makers use different geometric projections. In this vicinity, 1mm can make a noticeable difference, much more than just 1 degree. I pessimistically expect about 5% tolerance on any lens numbers.
___________________________________

(*) Honest focal lengths: I've read that the FA50/1.4 is actually about 52.5/1.5 -- that's about 5% off the specification. I've seen other lenses under different badges but otherwise identical labeled as f/3.8-3.9-4.0 (small difference), or f/1.8-1.9-2.0 (MUCH greater difference). I've had some Jupiters and Industars and Kodak copy lenses marked as 52mm or 53mm. Are they being honest, or hopeful?
05-27-2012, 11:54 AM   #15
Veteran Member
madbrain's Avatar

Join Date: May 2008
Location: San Jose, CA
Posts: 807
Original Poster
Riorico,

Thanks for the long writeup. I'm replying on my phone and can't respond to your individual points at the moment.
I will say however that I'm not fond at all of the cheap adapters. I tried some before for wide angle with the da 18 55, and there was terrible vignetting. When I did some PP to remove vignetting, the FOV was almost the same as without the adapter. It was basically useless. That was a big reason why I got the sigma 10 20 in the first place.

The DA 10 17 is not in my price range, and also lacks an aperture ring, therefore I would not consider it.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
10mm, 8mm, aperture, distortion, fisheye, k-mount, lens, pentax lens, ring, samyang, sigma, slr lens, software
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Sigma Zoom Super Wide Angle 10-20mm f/4-5.6 (US) jgredline Sold Items 3 10-19-2010 12:39 PM
For Sale - Sold: Sigma 10-20mm Super Wide Angle Lens TomInJax Sold Items 5 08-06-2008 04:47 AM
Sigma Super Wide Angle 10-20mm or Pentax Fisheye? azcavalier Pentax SLR Lens Discussion 11 10-13-2007 01:40 AM



All times are GMT -7. The time now is 01:45 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top