10mm vs 10mm?

So I want to get an ultra wide and I have become confused by the searches i've done on the forum regarding the sigma 10-20 and the pentax 10-17. My reading of the past threads indicated that the sigma's 10mm is somehow not as "wide" as the pentax 10mm because one is fisheye and the other not?

I always thought 10mm was 10mm in terms of angle of view and that the term fisheye loosely translated to major pincushion? Someone please set me straight.

Thanks, Tim

--
eyeballistic.blogspot.com

tacotim said:

So I want to get an ultra wide and I have become confused by the
searches i've done on the forum regarding the sigma 10-20 and the
pentax 10-17. My reading of the past threads indicated that the
sigma's 10mm is somehow not as "wide" as the pentax 10mm because one
is fisheye and the other not?

Click to expand...

Right, the 10-17 has about 180° field of view and the Sigma is about 100°, a huge difference.

tacotim said:

I always thought 10mm was 10mm in terms of angle of view and that the
term fisheye loosely translated to major pincushion? Someone please
set me straight.

Click to expand...

I think it's barrel distortion on the fish-eye, not pincushion.

Now I'd also like to hear more technical explanations about this difference in FOV between a fish-eye and a rectilinear UWA.

--
Manu



http://flickr.com/photos/ensh/
Pentax forums: http://tr.im/grmh

My PPG: http://www.pentaxphotogallery.com/home#section=ARTIST&subSection=1312871&subSubSection=3929608

ManuH said:

tacotim said:

So I want to get an ultra wide and I have become confused by the
searches i've done on the forum regarding the sigma 10-20 and the
pentax 10-17. My reading of the past threads indicated that the
sigma's 10mm is somehow not as "wide" as the pentax 10mm because one
is fisheye and the other not?

Click to expand...

Right, the 10-17 has about 180° field of view and the Sigma is about
100°, a huge difference.

ManuH said:

I always thought 10mm was 10mm in terms of angle of view and that the
term fisheye loosely translated to major pincushion? Someone please
set me straight.

Click to expand...

I think it's barrel distortion on the fish-eye, not pincushion.

Now I'd also like to hear more technical explanations about this
difference in FOV between a fish-eye and a rectilinear UWA.

Click to expand...

Roughly:

10mm = focal-length (distance from lens plane), not FOV.

FOV should only apply if comparing similar lenses (rectilinear vs. rectilinear or fisheye vs. fisheye).

Rectilinear lenses have an increasing magnification going from the center to the corners....so a "10mm" rectilinear lens must be > 10mm at the corners. Once you realize that the rectilinear lens has a increased FL at the corners, then you can intuitively understand that the FOV will be less than FE at same nominal FL.

--
-Dave

tacotim said:

So I want to get an ultra wide and I have become confused by the
searches i've done on the forum regarding the sigma 10-20 and the
pentax 10-17. My reading of the past threads indicated that the
sigma's 10mm is somehow not as "wide" as the pentax 10mm because one
is fisheye and the other not?

Click to expand...

Correct.

tacotim said:

I always thought 10mm was 10mm in terms of angle of view and that the
term fisheye loosely translated to major pincushion? Someone please
set me straight.

Click to expand...

A lens projects an image of what it sees onto the sensor. There is more than one kind of projection possible. The most desireable for most photographic lenses is rectilinear. Projecting a flat plane of the world onto the flat image sensor. This produces the least distortion (although all lenses have some distortion since they aren't perfect). This is like a pane of glass for a window. It is flat. If you took a picture of a flat brick wall straight on, all the bricks would appear the same size.

A curvilinear lens, or fisheye, projects a spherical (or curved field) onto the flat sensor. This causes the center to be relatively "normal", but the edges will be heavily curved and distorted. These distortions can be minimized by keeping straight lines through the center of the lens on the horizontal and vertical axises or diagonal (corner to corner). Pointing a fisheye at a brick wall straight on would give you bricks curving in an arch near the edges.

Google curvilinear or rectilinear lens to learn more. I know very little about the projections, but there are more than one type of fisheye, circular is a full hemisphere projection and produces a circular image, where as most fisheyes are not quite that extreme (having a 180 diagonal field of view, but differing horizontal and vertical fields of view that are less than 180 degrees).

Eric

--

I never saw an ugly thing in my life: for let the form of an object be what it may - light, shade, and perspective will always make it beautiful. - John Constable

See my Blog at: http://viking79.blogspot.com/
See my Flickr Photostream: http://www.flickr.com/photos/28177041@N03/
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad

Ahhh, ok, thisis all extremely helpful info, thank you. So the pentax is definitely
The one I want then as I need a very wide field of view.

Also, I was digging through bh's website and came across a yet unreleased sigma 10mm

Prime. Does this lens have a release date and is it the rectilinear or curvilinear type?

Many thanks, tim
--
eyeballistic.blogspot.com

tacotim said:

Also, I was digging through bh's website and came across a yet
unreleased sigma 10mm
Prime. Does this lens have a release date and is it the rectilinear
or curvilinear type?

Click to expand...

It is a fish-eye and as far as I can see, it is released, at least in Germany.

http://www.sigma-foto.de/cms/front_content.php?client=1&lang=1&idcat=53&idart=274

The widest lens for APS-C is the Sigma 4.5mm Fish-Eye, which is a "circular fisheye", meaning that it creates an image circle fitting into the APS-C frame with black corners.

This lens, too, should already be available for Pentax - at least the onlines shops I just browsed to said they have them in stock.

There is also the Russian Peleng, an M42 manual-focus 8mm fisheye, which is a circular fisheye on film (24x36) so does not cover the APS-C completely (black corners).

Cheers
Jens

--

'Well, 'Zooming with your feet' is usually a stupid thing as zoom rings are designed for hands.' (Me, 2006)
My Homepage: http://www.JensRoesner.de

tacotim said:

Ahhh, ok, thisis all extremely helpful info, thank you. So the
pentax is definitely
The one I want then as I need a very wide field of view.
Also, I was digging through bh's website and came across a yet
unreleased sigma 10mm
Prime. Does this lens have a release date and is it the rectilinear
or curvilinear type?

Many thanks, tim
--
eyeballistic.blogspot.com

Click to expand...

Here are some sample shots from a Nikon 10.5mm fisheye used on a crop sensor (similar to what you would be using if you used the 10-17 at 10mm). I took these quite a while ago, but useful for field of view and distortions you will see, in a couple of them I tried to compose to minimize distortions.
http://homepage.mac.com/atastad/LightroomGalleries/Fishy/index.html

And some more with a Zenitar 16mm used on a film Pentax (Same field of view as a 10.5mm used on digital crop)
http://homepage.mac.com/atastad/LightroomGalleries/SacFoxSf1/index.html

And here are some from a rectilinear Sigma 10-20mm:
http://www.flickr.com/photos/28177041@N03/tags/sigma1020f4f56/

Eric

--

I never saw an ugly thing in my life: for let the form of an object be what it may - light, shade, and perspective will always make it beautiful. - John Constable

See my Blog at: http://viking79.blogspot.com/
See my Flickr Photostream: http://www.flickr.com/photos/28177041@N03/
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad

I have both lenses. The DA at 10mm offers an 180 degree view, the Sigma 113 degrees. Remember it's the angle of view that's important. Now if you were only looking at rectilinear lenses (ie. Sigma 10-20) then you can compare all by their mm but you can't do that when comparing different types of lenses.

I use the Sigma 10-20 far more often than the DA fisheye though that lens still has it's place and it's getting a little neglected now that I have the Sigma 10-20. What lens you want depends on what you're going to use it for. The Sigma is the widest rectilinear lens available for APS-C at 113 degree view. If you want a wide lens for architecture, landscapes, etc. the Sigma 10-20 is better (unless you always frame landscapes smartly or in a certain manner to avoid the fisheye barrelling). If you just want wide, can work with the fisheye for landscapes and want a cool effect then the DA is what you want.

Cheers,
--
Sinan
http://sinantarlan.zenfolio.com/

tacotim said:

So I want to get an ultra wide and I have become confused by the
searches i've done on the forum regarding the sigma 10-20 and the
pentax 10-17. My reading of the past threads indicated that the
sigma's 10mm is somehow not as "wide" as the pentax 10mm because one
is fisheye and the other not?

Click to expand...

Other posters have mentioned types of "projection". This link explains that quite well:
http://www.bobatkins.com/photography/technical/field_of_view.html

It also shows how a fisheye view "de-fished" looks wider than a rectilinear view of the same scene.

If you want a really wide FOV then a de-fished fisheye is probably best but you should do some research of what focal length is best - don't pick 10mm just because Pentax does one.

Note too that fisheye lenses are usually softer than rectilinear, although you may be happy to accept some softness to get the FOV.

--
Gerry


First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

Gerry Winterbourne said:

Note too that fisheye lenses are usually softer than rectilinear,

Click to expand...

That's a bit tricky to test sharpness with fish-eye because the edges are so curved but in my subjective test of the DA 10-17 this lens is extremely sharp in the center but it's bit more difficult to be as assertive for the borders.

--
Manu



http://flickr.com/photos/ensh/
Pentax forums: http://tr.im/grmh

My PPG: http://www.pentaxphotogallery.com/home#section=ARTIST&subSection=1312871&subSubSection=3929608

Hi Tim -
I posted this a few weeks ago, it might help you:

http://forums.dpreview.com/forums/readflat.asp?forum=1036&message=31282667&q=sigma+fisheye&qf=m
Here are the photos at 10mm from the Sigma and DA Fisheye, respectively:



SIGMA AF EX DC 10-20 @ 10mm



DA FISH-EYE 10-17 @ 10mm

Mike

WOW, every one, thanks so much for all the info. particularly for the photo comparisons, that was very helpful. I plan on shooting mostly action sports with the lens. I shoot video of skateboarding, bmx, surfing, snowboarding etc for a living and i've toodled in photography for years. So I wanna shoot some stills of the same with this lens. Looks like the pentax is the one for me. Unless anyone has any experience with that sigma 10mm prime? I suppose if that's actually available in the US then that is still a contender for me as well.

-Tim

--
eyeballistic.blogspot.com

Yeah you shoulda mentioned you were going to be shooting skating and stuff, the fisheye is used lots in skating shots and videos (I used to skate back in the day) though ultra wides have their place too. I'd get the DA fisheye first then see if you also want an ultra wide retilinear lens.

Cheers,
--
Sinan
http://sinantarlan.zenfolio.com/

Hi guys!

Even though I've not yet shot skate or BMX action from upclose, I support Sinan's suggestion: For this application, the FE seems better suited: People's faces at the edge/corner of close-ups will look more natural: A rectilinear lens will "stretch" their faces/arms/bodies. This can be used to an effect, too, but a fisheye seems better suited. (You could apply artificial fisheye distortion to a rectilinear shot, too...)

Cheers
Jens

--

'Well, 'Zooming with your feet' is usually a stupid thing as zoom rings are designed for hands.' (Me, 2006)
My Homepage: http://www.JensRoesner.de