Digital (R) fisheyes

Does anyone know what happens when a fisheye lens is used on a (any)

digital camera, which has a lens magnification factor?

 

I assume the lens still gives a 'fisheye' view but no longer 180degs.,

and thus removing the extremes of fisheye distortion?

 

What is left? a less distorted very wide angle, that could be

corrected by software? If so it could be a viable alternative to the

expensive 15mm R lenses.

 

Thanks for any help/advice given.

 

Regards

 

 

Bruno

yes to all of the above. do a google search - there is a page out there the describes exactly what your're talking about.

People were trying to do that to avoid paying $1400 for the Canon 14/2.8 rectilinear or even $600-1000 for a Sigma or Tamron. It involves software manipulation after the fact, so if you shoot a lot with the fisheye you've got to figure your time in the equation. I found a Sigma 14/3.5 for the same as a Canon 15 fisheye, so I went that way. However I think it's really pretty hilarious to hear someone griping about the cost of the Leica 15 considering the only reason a sane person would be in the R system in the first place is for the glass, and it's no secret that it's expensive as all hell. Why pay $2000 for an R9, $5000 for the Digital Back, and then slap a run-of-the-mill Minolta-made fisheye on it and resort to software to square up the image?

Jay

 

The answer is that I already have the camera and use it with a range of lenses, all of which could be used with the digital back . The proposed use of the fisheye would be for very occasional use and therefore it would be sensible to investigate the 16mm fisheye, that may be Minolta designed etc, but is still extremely good , and is available used, for MUCH less [i know that maths are not such a hot point in Florida ,( especially at election times) , but check the figures and you'll see what I mean] than a 15mm Elmarit/Elmar

 

The fact that Leica users know Leica equipment is expensive, doesn't mean they have to throw money away!

 

Regards

 

Bruno

Would a 17mm do it for you? (22.1mm equivalent with the 1.3x crop factor). If so you can pick up a Tamron 17/3.5SP adaptall with an R adaptor for less than the Minoltaleica fisheye and not have to bother d*cking around with de-fisheyeing software. Especially with the smaller image circle the Tamron's a pretty decent lens, I've got one.

Jay

 

Good point! But I have the 21 - 35 zoom and wonder if ,in real life and in pictorial effect, a 17 is 'that' much wider than a 21? (104dgs v 92dgs)

What's the colour rendering like, compared to Leica?

 

 

Regards

 

Bruno

http://www.photo.net/learn/fisheye/

Stephen

 

Thanks for the info.

 

Regards

 

Bruno

<<wonder if ,in real life and in pictorial effect, a 17 is 'that' much wider than a 21? (104dgs v 92dgs) What's the colour rendering like, compared to Leica?>>

 

The difference is greater pictorially than between a 21 and a 24, if that helps you visualize it. The wider you go the more difference there is per mm of focal length. As to the color rendering, I can't really say, except that since you're intending to use it for digital you'll have ample opportunity to tweak the color into line with the Leica glass if it's a little off. The Minolta fisheye is straight Minolta, if the color matches Leica it's coincidental...the 28-70 Sigmaleica is a bit warmer than real Leica lenses too.

Here's an old page on Fisheye to Rectilinear conversion from Professor Dersch himself

(the gent who wrote Panotools):<P>

 

<A HREF="http://www.path.unimelb.edu.au/~dersch/architect/arch.html">

http://www.path.unimelb.edu.au/~dersch/architect/arch.html</A>

The 16mm fisheye will certainly work with a DSLR, you are just cropping out the center of the image circle. But you lose much of the "effect". That's why Nikon came out with the new, 10mm, full-frame fisheye for their digital cameras.

 

I'll second Jay's opinion of the Tamron SP 17/3.5. It's a darn nice lens for $100-200, plus the Adaptall mount. Just make sure to get the bit, 82mm petal hood with it.

Bruno: All that happens when you use a fisheye on a less-than-full-frame chip camera is that the image is cropped - you can simulate this easily by hand-cropping a scan of a shot with your 16 on film by 1.3x (or whatever).

 

You get an image about like a 18mm super-wide with significant barrel distortion. (Technically, a 1.3x crop factor makes it equivalent to a 20mm, but the barrel disortion sneaks in enough extra scenery around the edges that the field of view ends up more like an 18).

 

Incidentally, Nikon's most recent version of their RAW translation software includes an algorithm exactly tuned to the distortion "curve" of the new 10mm fisheye, allowing one to use it as either a fisheye or a rectilinear super-wide.

 

There is also the newly-announced DxO software (PMA 2004), with which you can analyse the distortion, and also the blur, color fringing and vignetting, of ANY lens used with ANY imaging chip, and build your own personal algorithm to perfectly correct the images from that lens. (Digital-M dreamers, take note).

 

You just shoot a digital picture of DxO's provided target sheet of precisely mapped points, and the software 'studies' each point for blur, vignetting, color fringes, and rectilinear mispositioning (distortion), and builds a permanent "profile" for that lens, which a Photoshop plug-in (or something similar) then uses to exactly correct all future images at the push of a button.

 

Sort of like using an IT8 target to profile your scanner, monitor, and printer's "errors" for color management - I guess you could call this "image defect management".

Andy

 

Thanks, I'll check into that!

 

Regards

 

Bruno

Bruno,

<p>

Sensor crop is a real headache for WA fans like myself. With standard 35mm lenses on a typical DSLR, you get to carry all the glass and enjoy less than all the image circle. Ultra-wide lens are expensive, bulky, and limited in their selection.

<p>

Fisheyes are my personal addiction, whether <a href=http://patternassociates.com/rico/d30/fisheye/>cropped 1.6x on a Canon D30</a> or used with film. My fling with defishing is over - I now prefer the images in their curvaceous glory. This is particularly important for <a href=http://patternassociates.com/rico/d30/misc/party3b.jpg>people pics</a>. Besides providing actual UWA coverage, a fisheye has better illumination, less CA, and a small size in comparison to a rectilinear prime.

<p>

Much as I hate the dichotomy, Nikon is addressing some of these digitally-induced traumas with their DX lenses. If I pick up a D2H, that DX fisheye is a no-brainer: can't go too wide, you know. :-)

Rico

 

Too right!

 

Regards

 

Bruno