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Author Topic: 15mm/2.8 fish eye as normal wide angle  (Read 1404 times)

paul

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15mm/2.8 fish eye as normal wide angle
« on: January 27, 2013, 10:16:23 AM »
why does a 15 mm fisheye , corrected in ACR,so that the lines are straight,still have a wider angle than a normal 14 mm?
I've made a comparison with 16/35 (II) ,15 mm fisheye, en samyang 14 mm,and I think the fisheye,lens-corrected,is the sharpest.(all shot at 2.8,same white balance)

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15mm/2.8 fish eye as normal wide angle
« on: January 27, 2013, 10:16:23 AM »

Plamen

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Re: 15mm/2.8 fish eye as normal wide angle
« Reply #1 on: January 27, 2013, 12:14:10 PM »
In case of fisheyes, the FL does not tell you all. The projection is different and the same FL (15mm) can create a wider AOV. See the diagram at the bottom of this page, for example:
http://en.wikipedia.org/wiki/Fisheye_lens

RS2021

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Re: 15mm/2.8 fish eye as normal wide angle
« Reply #2 on: January 27, 2013, 02:04:12 PM »
Rectilinear UWA lens designs are fundamentally different from the fisheye designs and include specific glass elements to render the focal plane more flat, reduce CA, and overcome a slew of other nifty optical challanges. 

The usual trade-off in super wide rectilinear lenses is "stretching out" especially at the corners and edges which shows up as corner/border "softness".

Some of this falls well beyond post processing fixes.
« Last Edit: January 27, 2013, 02:06:16 PM by Ray2021 »
“Sharpness is a bourgeois concept” - Henri Cartier-Bresson

paul

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Re: 15mm/2.8 fish eye as normal wide angle
« Reply #3 on: January 27, 2013, 05:19:51 PM »
thanks for your reaction.So should I sell the Samyang and use the 15 mm fisheye instead(lens corrected)?
It's much smaller and lighter.As far as I can see the quality is quite good,and the only disadvantage is you have to guess how much will loose of the frame after software correction.

By the way,what I would like most is Canon making a small fixed 16 mm/f4  lens...

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Re: 15mm/2.8 fish eye as normal wide angle
« Reply #3 on: January 27, 2013, 05:19:51 PM »