[sany]

Till which focal length is a fish eye and from which FL it becomes an extreme wide angle (without the baloon look of a fish eye effect) in a DSLR.

Any cheaper lens in these category please. I haven't seen any cheaper wide angles or maybe there are?

[adpo]

difference between fisheye and a wideangle is the amount of barrel distortion inherent in the lens design. for example, there is a 17-28mm fisheye that used to be produced by pentax, but there is also a 12-24mm wide angle. There's no magical focal length where things become fisheye, since each lens applies a varying amount of correction for distortion.

as for cheaper wideangles, define cheap

[RioRico]

Both fisheye (FE) and ultrawide (UW) lenses distort reality, because they attempt to project a 3D world onto a 2D frame. This is exactly the same problem that has plagued mapmakers for many centuries. Many different geometric models can be (and are) used for such cartographic or optical projections. None are perfect for all uses. An FE preserves lengths but distorts angles; an UW preserves angles but distorts lengths. Something like that. There is no cut-off between those based on focal length. We can build a 100mm FE lens and an 8mm UW lens for an APS-C camera. Many many cine cameras use lenses in the 2-8mm range that are not FE, because the image is projected onto a very small frame from a very short distance. Those are the determining factors: frame size, register distance, and projection geometry. An FE projection is actually LESS distorting than a rectilinear UW projection -- we just don't see it that way!

[hcc]

I am interested by the thread and it would be useful if experienced Pentaxians could share below their opinion of the better fisheye (FE) and ultra-wide-angle (UW) lenses for K-mount.

Which fisheye (FE) lens(es) do you recommend strongly?

Which ultra-wide-angle (UW) lens(es) do you recommend strongly?

Thank you in advance for the inputs and advice.:ugh:

[RioRico]

I can strongly recommend what I have and know: DA10-17 (FE), Tamron 10-24 (UW), Zenitar-K2 16/2.8 (FE). Some don't like these, but I do. The DA10-17 is the lens that drove me to Pentax. I got the Zenitar a few months later and it has been a mainstay, even since I got the Tamron, because of the Zen's speed and size. The Zen sees less use now but is still invaluable for inside shooting. These three lenses are among my most-used.

I can strongly recommend AGAINST the 12/8 (FE) (variously branded as Vemar, Spiratone, Vivitar, etc) and the Kenko (or Hoya or Spiratone etc) 180 Degree fisheye adapter. Neither of these has acceptable optics IMHO. I can't comment on any other fisheye primes or adapters.

Many people like either version of the Sigma 10-20 (UW), but I have also read may reports of buyers returning 2 or 3 of them before getting a good copy. I have talked to pros who despise Sigma's flaky QC, but I have had no problems with Sigma lenses. I also hear of frustration over copy quality of the Tamron 10-24, but mine is just fine. You pays your money, you takes your chances. Be sure to buy from a firm with a good return policy.

[hcc]

I can strongly recommend what I have and know: DA10-17 (FE), Tamron 10-24 (UW), Zenitar-K2 16/2.8 (FE). Some don't like these, but I do. The DA10-17 is the lens that drove me to Pentax. I got the Zenitar a few months later and it has been a mainstay, even since I got the Tamron, because of the Zen's speed and size. The Zen sees less use now but is still invaluable for inside shooting. These three lenses are among my most-used.

I can strongly recommend AGAINST the 12/8 (FE) (variously branded as Vemar, Spiratone, Vivitar, etc) and the Kenko (or Hoya or Spiratone etc) 180 Degree fisheye adapter. Neither of these has acceptable optics IMHO. I can't comment on any other fisheye primes or adapters.

Many people like either version of the Sigma 10-20 (UW), but I have also read may reports of buyers returning 2 or 3 of them before getting a good copy. I have talked to pros who despise Sigma's flaky QC, but I have had no problems with Sigma lenses. I also hear of frustration over copy quality of the Tamron 10-24, but mine is just fine. You pays your money, you takes your chances. Be sure to buy from a firm with a good return policy.

Riorico
Many thanks for the input and valuable advice. That is greatly appreciated.

[SpecialK]

I am interested by the thread and it would be useful if experienced Pentaxians could share below their opinion of the better fisheye (FE) and ultra-wide-angle (UW) lenses for K-mount.

Which fisheye (FE) lens(es) do you recommend strongly?

Which ultra-wide-angle (UW) lens(es) do you recommend strongly?

Thank you in advance for the inputs and advice.:ugh:

Allow me to post (again) a focal length comparison of two lenses I own and use a lot, the 10-17 fisheye and 12-24. I regret I did not do the fisheye at 10mm...

[interested_observer]

I use a set of 3 lenses, and they each complement each other. In my opinion, especially here at the ultra wide end, focal lengths break down and do not tell the entire story. A better way to describe things here is in Angle of View (AoV). Here are the specifics:

• Pentax DA 10-17 - This is a fisheye, and the 10-17mm focal length really does not accurately describe what it does. Its AoV is 180 degrees at 10mm and goes to 100 degrees at 17mm. The fisheye effect is very pronounced at 10mm and dissipates greatly by 17mm. Within its entire focal length range, you are able to place the "bend" where you want it by slightly tipping the lens either up or down. You are able to keep the horizon very level while having the bend effect be at the bottom of the frame.
• Pentax DA 12-24/f4 - This is a rectilinear or "normal" lens. Its AoV ranges from 100 degrees at 12mm to 60 degrees at 24mm. The distortion is well controlled. The resolution is at its peak at about 18mm and then trails off from there.
• Pentax DA 16-45/f4 - This is again a rectilinear or "normal" lens. Its AoV ranges from 83 degrees at 16mm to 35 degrees at 45mm. The distortion is very well controlled. The resolution of this lens, is picking up as the resolution of the 12-24 starts to trail off.

Now just for the sake of argument, lets say you have all three of these lenses, and use them on the same camera. The camera sensor's size is a constant X by Y pixels. So as you mount each one of these lenses, they are each going to take their Angle of view and project it on to the fixed size sensor. So the amount of area represented by each pixel is going to vary dramatically as you move from the fisheye to the other lenses. The image quality of the fish eye is excellent, given the amount of information its providing to the sensor. So as you talk about sharpness of the lenses, you need to keep in mind the range of views each of the lenses is supporting.

hope that helps......

[RioRico]

Pentax DA 10-17 - This is a fisheye, and the 10-17mm focal length really does not accurately describe what it does. Its AoV is 180 degrees at 10mm and goes to 100 degrees at 17mm. The fisheye effect is very pronounced at 10mm and dissipates greatly by 17mm. Within its entire focal length range, you are able to place the "bend" where you want it by slightly tipping the lens either up or down. You are able to keep the horizon very level while having the bend effect be at the bottom of the frame.

Just don't use the this at 10mm in an evergreen forest. All the trees are falling on me! HELP!!!

Very good synopsis on those 3 lenses, i_o. I'll just add that images shot with the 10-17 at 17mm will defish to a rectilinear equivalent of 13mm. But defishing in software s-t-r-e-t-c-h-e-s the edge pixels, so to keep good resolution, it's necessary to downsize the image by about half. And if I'm shooting in that focal region, I'll more likely use the Zenitar, which is 2.3 f-stops faster there. But as you mention, the fishiness there (rather slight) is easily controlled by careful camera handling -- just tilt and shift a little.

[northcoastgreg]

I am interested by the thread and it would be useful if experienced Pentaxians could share below their opinion of the better fisheye (FE) and ultra-wide-angle (UW) lenses for K-mount.

I can only comment on the DA 10-17 and DA 12-24. Both are excellent lenses, but neither is perfect. The DA 12-24 is quite sharp, has excellent contrast and color rendition. It has an FOV of about 60º to 99º. I find it almost perfect for landscape shooting, both in terms of FOV and IQ. I'm especially pleased with how it renders greens and blues. It will give you a deep rich blue sky without a polarizer filter (which is important as polarizers won't work terribly well on UWA) and it will render forests a deep, rich, verdurous green. The DA 10-17 has similar color rendition and contrast to the DA 12-24 without its sharpness. It's FOV begins at 100º, where the DA 12-24 leaves off, and goes all the way to 180º; so the two lens make a good tandem for capturing the wide end of things. They also share something else in common: CA issues. The DA 10-17 is particularly prone to CA problems: under particularly harsh light, I can see the bluish-purple fringing in the viewfinder. Some people are rather uptight about such defects. But the real issue is how easily such fringing can be removed in post. I've had little trouble removing the fringing from the DA 12-24 in Lightroom. Images from the 10-17 can sometimes be more difficult to clean up; traces of fringing may remain. But that's the trade-off for having a fisheye that zooms, something I find quite useful.

[RioRico]

Just a note: We have another fisheye discussion going on now, here: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/152731-fisheyes.html

[Nick Siebers]

For some input on others - I have an A 16mm f/2.8 fisheye, and really like it. Although manual focus is a bit difficult, when spot on the lens is quite sharp even wide open, in the center. Edges are prone to CA and distortion, naturally. I just got a K 17mm f/4 fisheye, for reasons I cannot explain. That seems similar but less convenient and perhaps a little less sharp (too soon to tell for certain. It is amazingly small though. I also have the Spiratone 180 degree fisheye adapter, and in certain conditions I have got decent pictures with it, but I wouldn't recommend it except at a bargain price.

I don't have a rectilinear ultrawide beyond 18mm, although I have used 20mm on film. I find with the ability to de-fish the 16mm on digital I do not need to go wider, personally. If I was starting with a clean slate, I would just buy the DA 10-17 and be done with it. Or maybe the Zenitar 16/2.8 with which to play around, as mentioned above.

[interested_observer]

In using a fisheye, I have found several approaches that may be useful...

• Man made vs natural shapes - things that are linear or square tend to be "bent" more than natural shapes. You eye knows what man made shapes look like and tends to be more sensitive to them being misshapen. I have found very square or rectangular architectures tend to be the big offenders. Natural items like trees and rocks come away reasonably well formed - for the most part.
  
• Big things - up close - Extremely large things up close are handled very well - in fact so well that it just does not seem possible.
  
• De-fished images - Again for the most part, defishing works pretty well. However, you need to be careful. Some items - due to their shape or their aspect within the image, will just not defish well, regardless of what you do.

[Ron Kruger]

I may look at this differently than most, because I shoot for publication and am possibly more critical of IQ. To me the best compromise I've found between distortion and dramatic POV is the DA 15mm Limited, and the IQ of this lens is unsurpassed by any lens I've used in almost four decades. From what I've seen, the Pentax 12-24 and the Sigma 10-20 run a close second, although I think the colors from the 12-24 are generaly better and richer than with the Sigma. As SpecialK's post clearly shows, the FOV of a rectilinear is not as wide as a standard WA at the same mm. It's not just that the rectilinear lens is flatter--it doesn't take in as much, especially at the wider end.
A fisheye lens is designed to have distortion for effect, and it seems silly to buy one and then try to correct the distortion in PP. I don't have much market for fisheye shots, but I am very interested in the creative aspects of the effect, so I have been researching them. I borrowed and tested the 10-17 for a couple of months, and at first was impressed with it, because the first thing I did was test it at 10mm. It does a fine job at the wide end. But gradually I became very dissapointed in this lens' performance under difficult lighting conditions and angles and larger mms. I can't see buying a zoom for only the wide end (plus I'd never use this lens on the narrower end, since I already have the 15mm), so I began looking at primes, and from the samples I've seen and the reviews I've read, I've settled upon the Samyang/Bower/etc., though I haven't decided upon the 8mm or 10mm yet. (The wider you go, the bigger the difference with each mm.) A plus is that the Samyang is less than half the cost of the Pentax/Sigma zooms. I look at IQ first, price second, but price counts, because my purchases are from a business perspective.
Anyway, that's my thinking on all this so far.

[interested_observer]

There are large differences between the three lenses that seem to be in play here - the 10-17, 12-24 and the 15, along with some of the other FE primes that are out there. Each lens has it's place and provides somewhat a specialized functionality.

As I wrote in another thread - I received an all expense paid 14 day luxury cruise to Hawaii, courtesy of the US Navy a couple of years ago (the Cruise ship was painted grey). Actually, I made the best of it and had a good time - as I was supporting a couple of new systems they were evaluating. Anyway, I had the opportunity to take a shot while we were performing an underway replenishment (UNREP), from on one of the flight elevators - about 30 feet out over open water, at sunset. One of my most favorite images I have taken.



The image to be effective really needed to be that wide, and stitching was not an option since everything was in motion. So the 180 degree wide shot is very effective. The 12-24 would have only covered - at best a but less than 2/3 of the shot in width.

CA on this lens has never been a problem, and this is a perfect opportunity for CA, a direct shot into the sun, through the lattice work of the mast.

The "narrower" end of the 10-17, although not as pronounced in terms of fisheye effect is still very useful, even though its limited to just 100 degrees of view. When you compare this to the DA 15 which is "only" 83 degrees wide you have a significant 17 degrees of difference between the two lenses. That's a difference of 20% over the 15mm lens.

Also, as an aside, I have tried to defish this as an interesting exercise. The result has the destroyer's stern and fantail, pulled out of proportion. Maybe it was just my eye, knowing what to expect, but it would up looking better just as it was taken with the fisheye distortion and all....

Just don't use the this at 10mm in an evergreen forest. All the trees are falling on me! HELP!!!
.

.... and Rico - Yes, you can see the mast of the BHR falling in on you!!