Not exactly a Review. More like a Report.
But like all our reports, it gives you a lot.
Fish Story
Part II

8mm Sigma Optical Sushi

Sigma makes lenses for Nikon, Canon, Minolta, Olympus--the list goes on. As a third-party source of optics, they're competing for your lens dollar in a number of different ways.

One of the biggest factors is price. Third party lenses tend to cost 25-50% less than the camera brand optics.

Another way they compete is by looking for niches--areas of interesting optical performance that the camera brands have either overlooked or fulfilled in other ways.

Nikon's 10.5mm full frame DX fisheye lens covers their full digital frame. Canon's full frame fisheye covers a full 35mm film frame and doesn't give a powerful fisheye effect on their APS-C sensor size image chips for the 10D, 300D, 350D and 20D cameras that use this sensor dimension.

That spells opportunity. Sigma has produced a 180 degree 8mm f/4 fisheye lens that forms a 23mm circle, making a full-circle fisheye image on a 35mm film frame. So the question becomes, "What does that do for my DSLR?"

We took the Sigma out for a ride on the popular Canon Digital Rebel XT and found out some very interesting things. It doesn't cover the full APS-C size image chip, but it does fit the equator of the fisheye image just out to the sides when shooting horizontally.

Image quality is good overall, and the fisheye effect is superbly dramatic. This is definitely a fun lens to look through and capture unique points of view with.

We wondered if it would lend itself to the severe flattening technique we first employed with the Nikon 10.5 full frame fisheye. Roll your mouse over this image and see for yourself:

Holy cow. Or, as the Hawaiians say, Howlie Coe! Flat as a skate board. Oh, sure, the edges are a mess, since they represent a huge counter-distortional twist of the optical volume control (soda speak), but there it is, hyper wide-angle in extremis.

Notice that the central portion of the image is still a fun image with a super wide angle field of view. The ends of the image as seen here make the wide frame into a 1.94:1 aspect wide-o-ramic of sorts, but click on the image above and you'll see how much image survives inside the 3:2 original frame aspect.

It's now more than just a fisheye. It's two lenses in one.

The Photoshop iNovaFX Actions developed especially for this lens will show up in the DSLR: Canon Digital Rebel XT eBook in mere days from this essay's publication.

Final full-size images from the iBCxtSigma8.atn iNovaFX Photoshop Actions end up being 2142 x 1104 pixels. Versions are provided for horizontal and vertical originals. Extra Unsharp Mask image enhancement is delivered to the extreme sides of the images as a final step. A special double-size version delivers a larger 3:2 aspect image.

We've tested them in all versions of Photoshop since PS6. A small amount of chromatic aberration correction is built into the Actions. (We have never seen a fisheye image that did not have some degree of chromatic aberration.)

As with other super and ultra wide-angle lenses, filters are an "issue." Meaning "impossible" on the front, so a gelatin filter holder is on the back end of the lens. That's fine for colors, but what about polarizers? Are you squat out of luck? Read on...

Photo Editors and Fisheye Lenses
Photographers love fisheye images. Well, some do, but photo editors know that fisheye shots account for about 0.01% of published images. That's one in ten thousand for those of us who can't do small fraction math on my fingers.

So wouldn't it be cool to have some way of turning those fisheye pictures into the rectilinear perspective photo editors prefer and pay good money for?

It turns out that this is not only theoretically possible, but worth doing. You get two dramas with every shot; the first when you take the picture and the second when you flatten it. Here are some samples from a walkabout in downtown Los Angeles:

I used a polarizing iNovaFX Action with the above. Rollover for the original.

Ouch. Images like this make my brain hurt.

Price points
The Sigma 8mm f/4 fish sells typically for around $610. It would not be my first choice for a Nikon, since the Nikkor 10.5mm fisheye is more of a match to those cameras, but for a Canon 6 or 8 MP DSLR (10D, 20D, 300D and 350D) it delivers an image type that no other lens can touch.

The iNovaFX Connection
To get the straight line effect out of this lens, the option to use the iNovaFX Actions in the DSLR: Canon Digital Rebel eBook will be your first smooth choice.

You know my work. I'm sort of the Adrian Monk of Photoshop Actions. (USA cable-channel inside joke: Adrian Monk is an obsessive-compulsive private eye and funneee...)

Where Adobe in Photoshop CS2 says they're giving you a barrel distortion correction effect, it's only part of the story. Defects still show in their Lens Correction feature making it unsuitable for critical work like accurately stitching corrected shots together in a panoramic, but the iNovaFX Actions iron out the complex distortions that modern lenses produce with the design goal of making them absolutely stitchable.

If you missed Panoramic Class, images that can be stitched need to match exactly in the overlap area, so no residual aberration is allowed.

It's not just a spherical bulge, Mr. Adobe, and your CS2 Lens Distortion correction window is a mixture of good and merely lukewarm features. But tell me, how do I really feel about them?

The iNovaFX Actions take these corrections seriously, all the way to the point of turning a fisheye image into a straight-line wonder. They're necessarily image chip and lens specific because they allow no residual distortion to haunt the image. With the right setting on your Kit Lenses (Nikon and Canon versions exist) plus the right iNovaFX Action, all barrel distortion leaves the image down to the pixel. Straight lines that were barrel distorted even with the complex "M" distortion of today's aspheric optics and complex delineations pop out the other side of the iNovaFX Action with lines so straight, you'd swear they came out of a prime lens. But just for the record, prime 18mm lenses are a tad hard to find. Better to buy the Kit Lens and an eBook.



The eBook

Speaking of writing, at this hour the new eBook, "DSLR: Canon Digital Rebel XT EOS 350D" is out.

It contains over 120 pages of nitty gritty Rebel XT camera specific special techniques, problem solving procedures, operational short-cuts, headache prescriptions, shot achieving tips, smart camera tricks and hidden talents you've never seen anywhere else.

Then the book is rounded out with over 300 more pages on all the other things you need to print, make special effects, solve problems that come from all directions and get your digital photographic skills to the next level, and the next.

You'll see.



Photography and artwork on this site by Peter iNova. ©2005 Peter iNova, all rights reserved.






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