Widest K-mount/M42 fisheye?

[stemked]

<p>Hi All.</p>

<p>A fellow prof in a neighboring lab has a special need for what he calls a hemisphere lens which I interpret to mean fisheye lens. He needs to get straight shots that goes from horizon to horizon. I am happy to let him use my equipment(K7, K5iis, or K3), but my widest lens is the 12-24. There are reasonably inexpensive 8mm lenses, but even that with a cropped sensor is something like 122 degrees, which I interpret as not wide enough for his research. I might suggest to him to stitch together two images, but short of that are there wider K mount or M42 mount lenses than 8mm?<br>

Certainly in Canon EOS mount there are at least 6.5mm available and there is another Bio-prof with a Canon body, but I wanted to check on K mount/M42 mount options first.</p>

<p>Thanks.</p>

<p>Doug</p>

 

[john_shriver]

<p>For a full-frame camera, there's the Sigma Filtermatic 8mm fisheye.<br>

Sigma currently makes a 4.5mm circular fisheye in autofocus Pentax mount.</p>

[john_shriver]

<p>The 4.5mm Sigma is for APS-C sensors.</p>

[stemked]

<p>Thanks John. I'll look into this for him.</p>

<p> </p>

[MattB.Net]

<p>I think the <a href="http://www.bhphotovideo.com/bnh/controller/home?O=&sku=769499&gclid=CjwKEAiA7f-yBRDAgdv4jZ-78TwSJAA_WdMa8Pwz1sr4Txum-RMKla6SX2qaQ-xHPlt_H6R-sE_XDxoCKtTw_wcB&is=REG&ap=y&m=Y&A=details&Q=">Rokinon 8/2.5</a> (and all the clones) have a 180 degree FOV on APS-C. Cheap, decent, and available in many mounts. This one is under $200 at B&H.</p>

[andrewg_ny]

<p>For APS-C, Pentax has the unique 10-17 fisheye zoom, this gets you 180 degrees at 10mm. For film full-frame, Pentax has the similar-but-older-and-discontinued F17-28 fisheye zoom -- again, 180 degrees at 17mm. Both are autofocus on Pentax bodies.</p>

<p>These of course are frame-filling <em><strong>fisheye</strong> </em>lenses, with a significant characteristic distortion. These are NOT the type of fisheye that produce a circular image (like, I believe the Sigma 4.5) -- they do fill the frame from corner to corner. If the horizon or a vertical cuts across the middle of the frame, that line will be straight. However, lines will become increasingly curved the further from the center.</p>

<p>The 17mm end of the fisheye is wider than you think -- angle-of-view wise, it pretty much starts (wideness-wise) where the 12-24 leaves off at 12mm. It is much less fishy at the 17mm end, but still much more distorted than the 12-24. You probably don't want to think strictly about focal length but instead angle-of-view. The 10mm of this lens gets you 180 degrees, while the Sigma 4.5mm also gets you 180 degrees with an even shorter focal length.</p>

<p>Tokina made a version of Pentax's 10-17 zoom for Canon and Nikon APS-C as well though it's not priced quite as attractively as the Pentax. For Canon full-frame, it would be possible to adapt the F17-28 with an inexpensive adapter. That lens has an aperture ring (good for adapting). The 10-17 does not have an aperture ring, I don't know if they have aperture-control available for K => EOS adapters. Manual focus for these is pretty easy since they have tons of depth-of-field.</p>

<p>The Pentax 10-17 is a pretty good deal, relatively inexpensive and about the size of the 18-55 kit lens (a little better built & a smidge heavier). I find myself more likely to bring it along than the bulkier 12-24 -- for wide rectillinear often the tiny & good 15/4 limited or the wide end of 16-45 or 17-70 I'm likely to be carrying as well is enough ... then if I really want ultra-wide, I can really go there with the 10-17.</p>

<p>Whether this sort of view and distortion will satisfy your colleague's research is another story though -- perhaps find <a href=" on Flickr</a> and see if that kind of view would be of use to you or your colleague.</p>

[stemked]

<p>Actually what he needs for his research is a full circular image. Apparently he needs to digitize the relative amount of sky to tree canopy in his research sites. </p>

[john_narsuitus]

<blockquote>

<p>"Apparently he needs to digitize the relative amount of sky to tree canopy in his research sites."</p>

</blockquote>

<p>Out of curiosity, in addition to digitizing the relative amount of sky to tree canopy at his research sites, does he also need to quantify the relative amount of sky to tree canopy?</p>