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05-08-2016, 01:00 PM - 3 Likes   #16
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QuoteOriginally posted by CarlJF Quote
Both have their use. You just don't want a fisheye if you need a rectlinear, and the other way around too. Only you can tell what you need depending on the effect you want to achieve.
Nicely put. That being said, which make sense is not always clear when dealing with ultra-wides. Here are a few talking points:
  • Anything 16mm and under is very wide on APS-C, though a fisheye will have somewhat wider FOV at a particular focal length
  • A proper rectilinear lens will provide straight/parallel lines
  • Most rectilinear ultra-wide lenses are not proper and have mild to moderate barrel distortion. This is easily addressed in post processing using available tools (I favor PTLens).
  • All rectilinear ultra-wide lenses will distort "volume" at the edges of the frame. This shows itself in the form of bent heads (people), smearing (many natural forms), or stretching (architectural). Probably the most familiar example of volumetric distortion in a rectilinear design is the Mercator projection commonly used for wall maps. No, Greenland is not the same size as the contiguous U.S..
  • For many purposes, a stitched image using a longer focal length lens is preferable to an ultra-wide. Doing so avoids issues such as the point above.
  • Both fisheye and rectilinear lenses may be used for novelty effect, though the flavor of that novelty will depend on angle, distance, and orientation to the subject.
  • Fisheye lenses differ from rectilinear in that they are designed using some form of circular projection. In a circular projection, relative volumes within the frame remain true, though at the cost of some lines not appearing straight.
  • The curved lines from a proper fisheye are not due to barrel distortion. The two present differently and with the fisheye is actually a factor of a design.
  • How and whether a line within the fisheye frame is bent depends on the angle of the lens axis to the line. How this works is best learned by experience or by viewing examples. Here are search results from my Flickr account for fisheye shots showing a variety of orientations:
    https://www.flickr.com/search/?user_id=28796087%40N02&sort=date-taken-desc&t...eye&view_all=1
    Some are more fishy than others and it is not always a matter of crop.
  • There are different types of fisheyes, defined loosely on field of view. Most provide 180 degrees across the frame diagonal. Others are 180 degrees across the horizontal axis. Still others are a full 180 on both x and y axes and project a circular image to the frame representing a hemisphere.
  • Fisheye lenses originally designed for FF 35mm format are often deemed "not fishy" on APS-C due to the frame being cropped. Yes, the field of view is no longer 180 degrees, 120 degree is more typical. No, cropping the margins does not make the lens rectilinear. It is still a fisheye.
  • There is nothing about fisheye design that dictates the lens be less sharp in the corners/edges than a rectilinear design
  • Ironically some subjects look more natural when photographed with a fisheye as opposed to rectilinear. This is particularly true for landscapes and some event photography where people having normal looking heads and faces is important. Many wedding photographers shoot at least part of the reception with some sort of fisheye.
  • While it is possible to "defish" a fisheye shot, doing so comes at the cost of throwing part of the image away. How much depends on how much straightening is desired. If routine "defishing" is anticipated, a rectilinear lens or stitching might be the best option for the ultra wide view.


Steve


Last edited by stevebrot; 05-08-2016 at 01:12 PM.
05-08-2016, 01:10 PM   #17
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QuoteOriginally posted by CarlJF Quote
You just don't want a fisheye if you need a rectlinear, and the other way around too. Only you can tell what you need depending on the effect you want to achieve.
This. If you want to experiment with the fisheye effect, get the fisheye. But if you want it to use a ultra wide angle lens...that's not what it's for. If that's what you want, get the rectilinear UWA.
05-08-2016, 02:25 PM   #18
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QuoteOriginally posted by MadMathMind Quote
This. If you want to experiment with the fisheye effect, get the fisheye. But if you want it to use a ultra wide angle lens...that's not what it's for. If that's what you want, get the rectilinear UWA.
The thing is that I kind of want both xD
I'm going to Victoria BC on wed, so I'd mostly be shooting in the forests, ocean, and city. I'm also going to be going to a few trestle, so legs hanging over the edge pics obviously going to be taken lol.
With this information, which would you prefer? This is really going to be my first "new" lens so that's why I'm having a really hard time deciding. Or do you have any other lens recommendations that are in my price range?
05-08-2016, 02:31 PM   #19
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if it were me, it would be my DA18-135mm and the DA10-17mm in the kit... but I'd also have a Tamron 72B along for the fun of it....

05-08-2016, 02:53 PM   #20
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I have the 10-17 f3.5 and say that Carl is right about this being the best for landscapes. The distortion is minimized.
05-08-2016, 02:54 PM   #21
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I meant say sigma 10-20 f3.5.
05-08-2016, 02:59 PM   #22
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QuoteOriginally posted by stuarrt Quote
At what focal length does the pentax stops being a fish eye?
It never really stops being a fisheye. At 17 mm, the effect is minimal as long as you frame your shot with the horizon line in the right place within the frame but the effect is still noticeable in most shots. I'm not going to say it's going to ruin the shot. Often, shots from the 10-17 look really good, even landscapes once you learn how to use it.
05-08-2016, 03:26 PM   #23
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Has anyone tried the samyang 16mm?

05-08-2016, 04:24 PM - 3 Likes   #24
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For me, Sigma 10-20 if you want a wide normal easeyish lens to document things..... such as



Pentax 10-17 lends itself to more creative "how do I get this to work" stuff


Goolwa morning.jpg
by Noel Leahy, on Flickr




Come on down spinner
by Noel Leahy, on Flickr

The Pentax is a fair bit smaller and gives me more "Kapow images" ... so its the one I kept

Last edited by noelpolar; 05-08-2016 at 04:30 PM.
05-08-2016, 05:42 PM   #25
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QuoteOriginally posted by stuarrt Quote
Hey guys! Just joined today, so sorry if this is in the wrong section.
Anyways, I need to pick a lens today if I want it to arrive before I go.
I've been stressing like mad trying to pick a decent wide angle lens.
I've narrowed it down to either the Sigma 10-20mm or the Pentax 10-17mm.
From the reviews I've read, both of their corners are soft and not very sharp.
I like the fact that the Pentax get's a less fish-eye effect as you zoom, but I'd really like that extra 2mm that the sigma has
So, please weigh in on this. If you have either lens please post some of the pictures you've taken with it, and share your experience.
If you also have any suggestions please feel free to comment. Don't really want to spend more than $450 CAD
I'd mainly be using the lens for landscapes.
Thanks!
I have the 10-20 f4-5.6. It has been my go to lens for all my wide work. I did consider the Pentax 10-17, however the Sigma won the battle because of being a rectilinear lens. Is it as sharp as my FA or other more expensive lenses? The answer is no. But it is more than adequate for my paid projects. I have never had a complain from a client about my pictures not being sharp. I use it on my K3 and K5IIs. I am getting ready to sell it because I am upgrading to the K1 and need a FF wide lens. I wish Sigma had something in the range of 10-20 costing less than the Pentax 15-30 which is a little out of my reach right now.

---------- Post added 05-08-16 at 05:43 PM ----------

QuoteOriginally posted by noelpolar Quote
For me, Sigma 10-20 if you want a wide normal easeyish lens to document things..... such as



Pentax 10-17 lends itself to more creative "how do I get this to work" stuff


Goolwa morning.jpg
by Noel Leahy, on Flickr




Come on down spinner
by Noel Leahy, on Flickr

The Pentax is a fair bit smaller and gives me more "Kapow images" ... so its the one I kept
Nice pics. Good examples.
05-14-2016, 05:07 AM - 3 Likes   #26
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I have the 10-17 and the Sigma 8-16, they are completely different lenses. I had a Sigma 10-20 but I really didn't care for it so I returned it. As Noel said the 10-17 really is for the creative photographer who likes to experiment with different techniques. It really is a fun lens to use. It is small enough to always fit in a bag. The corners can be soft unless you really stop it down, f8-f11. This essentially going to be the case with any ultra wide angel lens. My 8-16 is not much different. As for defishing, from 13mm on the 10-17 can be defished if the shot is composed correctly. With the 10-20 or 10-16 the same applies for composition. You must be careful when holding the camera and keep the lens level. The Lightroom lens profile does a pretty decent job with the 10-17. I usually end up doing some manual adjustments to finish up. DXO Viewpoint does a better job in my opinion. By the you correct for distortion the corners are usually gone away and you have to remember this when taking the shot. For architectural shots the 8-16 is the goto lens.

10-17 @10mm


8-16 @8mm


10-17 @17mm


10-17@ 13mm


10-11mm the distortion never totally goes away.
05-14-2016, 09:58 PM   #27
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What about the 16-45? There's one on sale for about $125 USD so I was thinking about getting it.
In all honesty as long as it's better than my kit lens I'll be okay lol
05-15-2016, 05:07 AM   #28
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QuoteOriginally posted by stuarrt Quote
What about the 16-45? There's one on sale for about $125 USD so I was thinking about getting it.
In all honesty as long as it's better than my kit lens I'll be okay lol
The 16-45 is a nice lens. It was one of the first DA lenses. There is a huge difference between 16 and 18mm. It is a lot bigger than the kit lens. I found that below 18mm you really have to stop the lens down to keep the corners sharp, around f8-f11. The constant f4 aperture is nice but f2.8 is better for indoors. My DA*16-50 is one my most used lenses.
05-15-2016, 09:18 AM   #29
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QuoteOriginally posted by Scorpio71GR Quote
The 16-45 is a nice lens. It was one of the first DA lenses. There is a huge difference between 16 and 18mm. It is a lot bigger than the kit lens. I found that below 18mm you really have to stop the lens down to keep the corners sharp, around f8-f11. The constant f4 aperture is nice but f2.8 is better for indoors. My DA*16-50 is one my most used lenses.
Well, I think I'm going to go for the 16-45 then. It's a lot cheaper than any of the other lenses I've been looking at. Is the IQ any better than the 18-55?
05-15-2016, 01:57 PM   #30
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QuoteOriginally posted by stuarrt Quote
Well, I think I'm going to go for the 16-45 then. It's a lot cheaper than any of the other lenses I've been looking at. Is the IQ any better than the 18-55?
I think so, a constant apeture always helps, especially for video. My 18-55 has been sitting in a drawer for years. It has never been on any camera other than my K10D. I have a lot older lenses I should really sell. I have an older Sigma 18-50 f2.8 that really should be getting used.
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