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07-30-2011, 03:29 PM   #16
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I bought Rokinon 8mm f3.5 fisheye and I'm very happy with it. It has aperture control but focus is manual. With 180 degree FOV it's not a problem, just stop down to f5.6-8.0 and adjust it to about half a meter distance and you get great pics. It does not have typical fish eye effect, but much more "natural" look if you shoot horizontally.
I naturally still have the DA 12-24, but as the Rokinon is so cheap it doesn't matter...


Last edited by reytor; 07-30-2011 at 03:42 PM.
07-30-2011, 05:35 PM   #17
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QuoteOriginally posted by Pentaxor Quote
that is 180 degrees before the defish and salvagable corners before distortion correction, not to mention corner IQ as well. if the OP wants to utilize fish-eye as is, then that would be fine. but since the OP consider some corrections, it may take a lot of effort on doing such, not to mention losing some as well.
I'd already said (2nd post) that defishing reduces IQ, and that fisheyes and recitilinears are quite different; and I recommended the Tamron 10-24 because I know it. In the post you're critiquing, I mere pointed out that the 8-16's AOV is much less than a 180-degree fisheye's. What's *done* with that AOV is up to the users.

You seem grumpy today. Everything OK?
07-30-2011, 07:37 PM   #18
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Really wish Pentax had a wider high-quality ultra-zoom. So far, I'm stuck too with only 12-24mm F/4

I tried several third-party ones starting at 10mm and none of them cut-it, period. The Sigma 8-16mm is gaining a lot of praise and the sharpness I've seen in tests is actually quite good. Vignetting is not... only one review seems to have gotten different results, but everyone else shows over 1.5-2 EV drop-off around 8mm. That is simply unacceptable. Even stopping down to F/8, there is still more than 1 EV, meaning you're going to have to crop your images out of a dark tunnel!

Fisheye I also tried but its not for me. Perspective distortion is one thing but when lines become curves it gives a look that gets tiresome, event though the first few shots are neat.

- Itai
07-30-2011, 09:00 PM   #19
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QuoteOriginally posted by RioRico Quote
I'd already said (2nd post) that defishing reduces IQ, and that fisheyes and recitilinears are quite different; and I recommended the Tamron 10-24 because I know it. In the post you're critiquing, I mere pointed out that the 8-16's AOV is much less than a 180-degree fisheye's. What's *done* with that AOV is up to the users.

You seem grumpy today. Everything OK?
I'm not grumpy. you just misunderstood my post. I was only stating the cons of using a fisheye when you try to correct it, it would give less FOV than it's initial 180 degree capacity. given the circumstances and the troubles of further corrections, it would be much easy to use an 8-16 instead.

07-31-2011, 09:16 AM   #20
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QuoteOriginally posted by The Kurly One Quote
Which lens is going to give me "Comparable" IQ, but give me more range? Sigma 8-16? Sigma 10-20? or just f it and get the Pentax 10-17 fisheye and use the lens correction in LR3? What are your suggestions? I can get the Pentax for less than $500 brand new... or I have to hunt for the others... lmk your opinions!
Wide angle lenses are a bit different than the rest of optics. Other areas of optics, are pretty much all about managing magnification. Wide angle is about bending light from ever wider angles of view on to the sensor. This "bending" causes distortion. There are two types of wide angle lenses. "Rectlinear" or normal lenses, where by the design attempts to pull in additional angle of view in such a way as to minimize the distortion and try to keep things linear. The other approach is to use distortion, e.g., a Fisheye lens.

There are 2 types of lenses, prime (single focal length) and zoom. Prime lenses are easier to design and manufacturer since you are only dealing with a single focal length, you can concentrate on the quality of everything. Zoom on the other hand you are dealing with a range of focal lengths, and that complicates the design.

In terms of zoom lenses, a normal rule of thumb is 4x, in order to maintain good IQ, sharpness, contrast, etc. the design attempts to keep the zoom factor to around 4 (ratio of the low end to the high end). In wide angle lenses, due to the large amount of distortion in pulling in the extra angle of view, the rule of thumb is about 2x in order to maintain some semblance of balance across sharpness, IQ, distortion, etc.

It stands to reason that if the lens is difficult to design and manufacturer, then its going to cost more.

The other aspect that you need to understand is the sensor. The sensor is not gaining in size or dimension. The sensor is still X by Y pixels in size - regardless of the lens sitting in front of it. So as you widen the angle of view, each pixel on the sensor is going to need to represent a larger area that you are viewing. With more information to represent accurately, sharpness and IQ are bound to suffer to a degree. Think of a paperbag - you can only cram so much into it before it tears apart.

So, you as the consumer, need to understand what you want to do with the lens, and work within the limitations of optics. If you want sharpness and excellent IQ with little or no distortion - then you angle of view is going to be limited. If you are willing to accept greater distortion with its accompanying effects on sharpness and IQ, they you can go wider.

Then there is the Pentax Tax and we are talking price here - since you are asking about new. Very simply stated, the Tokina and Pentax 12-24 lenses are essentially the same. Tokina builds them in a number of different mounts.
  • Tokina Nikon $525 and up
  • Tokina Canon $450 and up
  • Tokina Sony $660 and up
  • Pentax $625 and up
Now, I have and shoot with both the 10-17 and the 12-24. The respective focal lengths tell a very distorted story. It appears that there is a large amount of overlap here in terms of FL. That is not the case. There is actually no overlap. A better more accurate way of looking at and comparing these lenses is through Angle of view.
  • DA 10-17 - 180 degrees to 100 degrees
  • DA 12-24 - 100 degrees to 60 degrees
So in essence these lenses are not competing against each other, but instead they complement each other. This tells a much more compete story in terms of what the respective lenses are able to provide you. Now with the angle of view, comes the respective distortion accompanying the enlarged angle of view and how it is accomplished.

You were asking about maintaining a "Comparable" IQ. Well, in order to maintain IQ you need to go not to the extremes of ultra wide angle. 12-24 with its reasonable capability of managing distortion and good IQ, however use the lens in a stitching environment. Rather than shoot "landscape" mode, put the camera body up into "portrait" mode, for the bulk of the angle of view in the vertical axis and stitch horizontally. This gets you away from the "long skinny" picture. In this way, you the photographer are in control of how wide you shoot - 2, 3, 4, 5, ..... 11, 12 frames wide. It also gives you the ability to shoot say 12-15 frames wide and then only stitch the 2. 3 or 4 that are really the compelling shots.

Stitching is a way to add pixels. Rather than being stuck at say 3000 x 2000 pixels, you can go to 10000 x 3000 pixels. Or going to multiple rows, 15000 x 6000 pixels (neglecting overlap). Of course this presents additional problems or challenges - mechanical support and stitching software, but that is a different set of threads.


Last edited by interested_observer; 07-31-2011 at 09:13 PM.
07-31-2011, 06:19 PM   #21
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Wonderful post, interested observer. Agree with it. I also have Pentax 10-17 and 12-24. Rarely use them at the same time. As you say, they compliment each other. My Sigma 8-16 has shipped and will arrive soon. Should be interesting .

thanks for sharing
barondla
07-31-2011, 06:21 PM   #22
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I really enjoy the Sigma 8-16mm. its color rendition may not quite be up to par with the da* 16-50 but it is so amazingly wide it makes up for it.
07-31-2011, 06:22 PM   #23
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QuoteOriginally posted by RioRico Quote
The Sigma's maximum AOV is about 115 degrees. The DA10-17's is about 180 degrees. These are totally different fish. Also, while the Sigma has good optics, they're in a questionable package: Sigma 8-16mm
Nothing questionable about the package of my 8-16. Good focus - solid build. Any lens with the same FOV will have great depth of field, making dust on the lens more visible.

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