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02-02-2011, 05:42 PM   #31
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I wish there were more options around 10mm. It seems like the cheapest to get below 12mm is the 10-17mm Pentax and the 10-24 Tamron. (The 10-20 or 8-16 Sigma are expensive.) And if I "settle" for 12mm, the options don't improve much, they are expensive too (the 12-24mm). I would love to have the Tamron, and will probably wait until it can fit in my budget. I wish there was a good cheap manual zoom that covered 10mm, or even a prime 10mm.

02-02-2011, 09:24 PM   #32
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QuoteOriginally posted by Kitty Quote
I wish there were more options around 10mm. It seems like the cheapest to get below 12mm is the 10-17mm Pentax and the 10-24 Tamron.
I have both. The 10-17 is what drove me to Pentax, and the 10-24 is my latest buy. They are quite different -- the 10-17 is MUCH wider, and also tricky if you're trying to keep angles rational. I used the 10-24 in bleak COLD mountains today, in situations where I wouldn't have even considered the 10-17.

QuoteQuote:
I would love to have the Tamron, and will probably wait until it can fit in my budget.
Shall I bum you out? Tammy had a steep discount into early January 2011, US$100 off (my rebate check arrived a couple days ago). That brought the cost down to US$275 shipped. I don't know when the next deal will come along.

QuoteQuote:
I wish there was a good cheap manual zoom that covered 10mm, or even a prime 10mm.
T'ain't none. Most of our old manual lenses were made for 135/FF cameras, where 21mm was ultrawide, and anything wider was an expensive specialty item. The widest+cheapest glass I've grabbed are my Lentar-Tokina 21/3.8 (also badged as Vivitar, Soligor, et al), and my fishy Zenitar 16/2.8. For anything wider, you'll just have to rob a minimart or something.
02-02-2011, 09:45 PM   #33
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I posted this earlier... didn't get much attention, but maybe it'll help you?

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/130711-compari...ctilinear.html
02-03-2011, 06:27 AM   #34
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QuoteOriginally posted by Kitty Quote
I wish there were more options around 10mm. It seems like the cheapest to get below 12mm is the 10-17mm Pentax and the 10-24 Tamron. (The 10-20 or 8-16 Sigma are expensive.) And if I "settle" for 12mm, the options don't improve much, they are expensive too (the 12-24mm). I would love to have the Tamron, and will probably wait until it can fit in my budget. I wish there was a good cheap manual zoom that covered 10mm, or even a prime 10mm.
Check out the Samyang/Bower/etc. 10mm and 8mm primes. After considerable testing and research, I think that is the way I'm going.

02-03-2011, 08:08 AM   #35
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QuoteOriginally posted by Kitty Quote
I wish there were more options around 10mm. It seems like the cheapest to get below 12mm is the 10-17mm Pentax and the 10-24 Tamron. (The 10-20 or 8-16 Sigma are expensive.) And if I "settle" for 12mm, the options don't improve much, they are expensive too (the 12-24mm). I would love to have the Tamron, and will probably wait until it can fit in my budget. I wish there was a good cheap manual zoom that covered 10mm, or even a prime 10mm.
I'm not sure I saw the real explanation in any answers so far...

Fisheye versus rectilinear (aka non-fish-eye) has to do with the lens construction, not the focal-length.

A fisheye, regardless of focal-length will straight turn lines into curves unless they do not pass with through the center.

The curving effect is inversely proportional to the focal-length, so a 10mm fisheye is noticeably more curved than a 17mm one. They rarely do fisheyes with longer focals because the effect would be very minor. These kinds of things, in photography, tend to work better when done more fully.

A rectilinear lens is designed to render straight lines straight, although you may see some curvature called 'barrel' or 'pincushion' which are actually defects.

A 16mm rectilinear lens when mounted on an 1.5X crop camera gives you a field of view equivalent to 24mm on a 35mm or full-frame camera. This is the beginning of 'ultra-wide'. Images like that have an unnatural perspective but not extremely so. Depending the different depths shown in your image, it may be more or less noticeable.

When you go down from there to 12, 10 and 8, things start to look distorted because of the great discrepancy between the perspective we see with our eyes. Straight lines should remain straight but angles are not preserved.

Hope this clears things up for you!

- Itai
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