Rectilinear vs Fisheye?

[ishootRAW]

I'm contemplating getting ether a sigma/Tamron/Tokina Rectilinear lens, OR a fisheye. I do mostly landscapes. From what I'm reading, I will get more in the frame by using the fisheye and correcting distortion later. I also do a lot of panos, won't a fisheye make stitching easier?

Could someone shed some light on this for me?

[ravncat]

Fisheyes can be defished with software (made rectilinear) but you're squishing and stretching your pixels around, so you lose sharpness, especially on the edges (which are big) when you defish. Think of converting a circle to a square. The data is there and the math is known so it can look pretty good, but you're probably going to want to crop into it.

So you can go wider than a rectilinear lens, but you start to lose out on image quality. The choice is up to you - some people don't mind the loss in quality, others do. I'd use a fisheye to play to it's distorted strengths instead.

The moment you start stitching with one, you're going to have issues - you won't be able to just put them together as in a normal stitch, because the edges are not straight - you'd have to convert to rectilinear first - and when you do that it may not make the right edge of image A the same as the left edge of image B which makes stitching harder - you'll be throwing more of the edges away to effectively stitch. - You'd be better off stitching with a rectilinear lens.

(And alot of people who stitch would rather stitch with a longer lens than a wider one - because it allows you to get more detail into the final image. (pixel per angle)

[ishootRAW]

Thanx that does clear it up. Just out of curiosity, how do you like you Tokina? Im trying to decide between the Sigma 10-20, Tamron 10-24, Tokina 11-16 2.8, and the Tokina 12-24.

[ravncat]

Originally Posted by ishootRAW

Thanx that does clear it up. Just out of curiosity, how do you like you Tokina? Im trying to decide between the Sigma 10-20, Tamron 10-24, Tokina 11-16 2.8, and the Tokina 12-24.

Sorry, I was on the way to work and couldn't respond.

So, I like my Tokina, but it doesn't get much use anymore, (since I moved to full frame) I like it alot, it has it's good and bad points. I can tell you this, I spent a long time thinking about the different wide angle options, and price and quality narrowed it down to the Sigma or the Tokina for me.

So, Tokina

Pros
- Sharp (Excellent center sharpness throughout, reasonable corners at 2.8, but nice and sharp in the corners at f4)
contrasty
fast, nice for low light
build feeling
Clutch focus ring*
Low (barrel and pincushion) distortion and no complex distortion (unlike the sigma) - almost totally neutral at 14mm

Cons
- Chromatic Abberation (especially wide open)
- Heavy - (compared to the sigma)
- Short Zoom Range (feels like a prime)
- Not as wide, you will notice the difference between 10 and 11mm but it's not huge
- Clutch Focus ring*

Others (more neutral)
- Has a bluish colorcast (compared to the yellow/orange of the sigma)
- Works reasonably well at 16mm as a fast prime for full frame.
- no depth of field markings
- Larger size than the Sigma
- pinch type front cap
- There was a bad set that missed some lens spacers, which were recalled, but some made it out once, so be wary of decentering especially in used samples from some of the earlier batches - overall simmilar Quality Control to sigma, so there is some copy variation, but for the most part, it's well built.
- can see vingetting at 11mm on a crop sensor with a cokin type filter system, unless you "shave" some of the depth off the filter holder.

* The clutch is a cool idea and I like it for switching between manual and Auto, but manual focus is really hard to see in a viewfinder especially at that width and at 2.8 - the focus marks are nice though. The problem with it is when you go from AF to manual there's a slight bump that knocks the focus off of what you just had AF on, and as a result you can't switch without a very slight alteration.

Why I went with it, I do alot of available light shooting towards the edge of the day, and lots of handheld night shooting, 2.8 was worth it to me, for landscape work during the day, the 2.8 vs 4 or 3.5 of the sigma (depending on the model) is really not much difference. I find it easier to correct for CA than for Mustache distortion. I also knew it would work on full frame as a very wide prime (which has a field of view at 16mm about equal to the 11mm on a crop sensor).

I do sometimes with I had a longer zoom range, but I don't mind switching lenses so the gap between 16 and 18 was never an issue for me. There are times where I'd like it to be a tad wider, but you definitely feel the "short" zoom range. I'm happy with my choice, though I do wonder what it would be like to have purchased the sigma, I've used one - it's a slightly different lens. I suspect with DXO or a good way to correct for the mustache distortion I'd like the sigma better for landscapes. The Tokina is an integral part of my light dx backup travel kit - I won't sell it, and it still finds uses on my full frame camera, but it doesn't have a permanent place in my "go to" bag. I often take it with me when I know I can really use it. I'd have it with me all the time, if I didn't have a full frame camera.

[inkista]

Originally Posted by ishootRAW

From what I'm reading, I will get more in the frame by using the fisheye and correcting distortion later.

You will, but, as ravncat says, the distortion that you have to correct when "de-fishing" can severely compromise image quality, particularly at the corners where the stretching is biggest..

I also do a lot of panos, won't a fisheye make stitching easier?

Depends on the kind of pano. More on this below.

Originally Posted by ravncat

The moment you start stitching with [a fisheye], you're going to have issues - you won't be able to just put them together as in a normal stitch, because the edges are not straight - you'd have to convert to rectilinear first - and when you do that it may not make the right edge of image A the same as the left edge of image B which makes stitching harder - you'll be throwing more of the edges away to effectively stitch. - You'd be better off stitching with a rectilinear lens.

Well....

I'm in the opposite pano camp. There are generally two types of pano shooters: those who shoot for higher resolution as well as more coverage; the classic landscape look as it were. The folks who do the Max Lyons gigapixel infinite-zooming-in thang.

And then there are the weirdos like me who like to do full spherical-coverage panos. There are a number of names for this: cubic, virtual-reality, equirectangular, 360x180, etc. etc. I use equirectangular the most to refer to this. For us, fisheyes are the tool of choice, because it cuts down the number of images we have to shoot to cover an entire sphere, and with proper technique, we can even handhold for this type of pano.

We are the nuts who go bananas over rotating a lens around its no-parallax point. Landscape/gigapixel folks, not so much. They use a panohead's precise marking more for tracking coverage at smaller angles with a telephoto. We use panoheads to avoid moving the camera in space and to rotate around the no-parallax (aka nodal, aka entrance pupile, etc.) point in both pitch and yaw. We shoot zenith (straight up) and nadir (straight down) shots, too.

And when we stitch, we do so with specialized software based on Helmut Dersch's Panorama Tools. PT is a bunch of line command utilities, mostly sorta/kinda open-sourced, that can do a number of things aside from pano stitching, but they're the basis of a ton of different stitching software packages out there, like PTGui, PTLens, and Hugin (the Hugin project has replaced some of the older part-proprietary PT utilities with new completely open-source tools.)

You can feed fisheye images directly into Hugin or PTGui, and come out with an equirectangular (hell, with an HDR or enfused equirectangular if you want). No "de-fishing" before stitching required. Both packages can also do more traditional cylidrical high-res panos as well, obviously.

But yes, for me, a fisheye helps a lot with pano stitching, because instead of shooting four rows of images along with a zenith and nadir shot, and stitching together 30+ images, like I would have to do with my 18-55 kit lens set to 18mm; I can handhold four shots, and get complete coverage:



interactive view (requires Flash).

It's mostly a matter of usage and stitching software. And, of course, we can do strange and bizarre things with equirectangulars that the high-res guys can't with their cylindricals.

[ravncat]

Cool stuff Inkista,
My brain made the assumption that If he was going to stitch panos and talked about making a fisheye image rectilinear that he was going to do that just to get for the purpose of stitching. I definitely fit into the hey - I can make larger resolution images by stitching group.

Equirectangular images are definitely very cool, I'd not meant that fisheye stitching was impossible - so I hope it wasn't read that way. I assume Hugin is a paid program? Also one has to find the nodal point (though should be doing that with rectilinear lenses for panoramics as well) - so It probably has a bit more of a learning/price curve than rectangular stitching. (up until you consider alternate programs for the stitching)

I do need to get myself a fisheye some day - it's one of the few specialty lenses I've never really used. That's a cool shot Inkista. Still, I lack a pano head.

[inkista]

Originally Posted by ravncat

Cool stuff Inkista,

Thanks. It's my party trick.

My brain made the assumption that If he was going to stitch panos and talked about making a fisheye image rectilinear that he was going to do that just to get for the purpose of stitching. I definitely fit into the hey - I can make larger resolution images by stitching group.

I think it was a good assumption and I second your recommendation for a rectilinear. But you never know when somebody's gonna go nuts and do the equirectangular thing.

... I assume Hugin is a paid program?

Nope. Hugin is open source. Free as in free beer. PTGui is commercial software.

Also one has to find the nodal point (though should be doing that with rectilinear lenses for panoramics as well) - so It probably has a bit more of a learning/price curve than rectangular stitching. (up until you consider alternate programs for the stitching)

The nodal point thing gains importance as distances to the subject get smaller. With larger distances, you can handhold and it doesn't matter as much. Parallax error is minimal with shots to the horizon. I've done handhelds of 27-image landscape panos (3 rows x 9 columns). However, when you do panos indoors and the like, then the parallax error becomes a much larger issue at getting images to match when you're stitching.

I do need to get myself a fisheye some day - it's one of the few specialty lenses I've never really used. That's a cool shot Inkista. Still, I lack a pano head.

I use a Nodal Ninja 2. Unfortunately, as the years have gone by, Nick Fan seems to be making the NN more and more expensive...still less than going for an RRS pano head, though. And, as I mentioned, I actually took that shot under the Scripps Pier handheld, with only four shots, rotated in yaw at 90° intervals. Not that I wouldn't have preferred to use a panohead, but it's a pretty steep hike down to the beach and I didn't feel like hauling a tripod.

[sk66]

Inksta, you are such a geek! Those are pretty cool though.

However, I agree with the general consensus..rectilinear.
IMO 360* panos are more like trying to simulate video than photography, and the distorted images are "interesting" in an odd way....but not really what *I* think of as "photography"...(not that I wouldn't do it for the fun of it).

[inkista]

Yeah, whether VR photography is video or still imagery is one of those things you discuss over coffee or beer at 2am. To me, it's still imagery. And I've seem some amazing work in equirectangulars. But tastes differ. The distortion, imnsho, has a lot to do with how the pano is prepared and presented (particularly the initial FoV setting), and the viewer used.

Also, it's not like a rectilinear ultrawide is going to be distortion-free, either. But agreed, not nearly as bad as a fisheye in that regard.