Ultrawides & barrel distortion?

I know this is commonly said, Tony, but I have to say it is not in
keeping with my experience. If you look at the comments, they are mostly
quoting some supposed other person's views. The website that gives
visitors' opinions is statistically doubtful, as there is no attempt to
standardise the expectations. Clearly the purchaser of a ??1000 lens has
a higher expectation than the purchaser of a ??400, and may well
therefore make a harsher judgement.

I try to make most of my comments based on actual experience (otherwise
I say so), which means it is limited but direct. Having said that, I
appreciate there are also sample variations, so there are no
certainties.

It also is a very fine lens; I have one, but it is out of the country at
the moment and I cannot check it for distortion. I do not recall ever
finding it bothersome, and I am fairly fussy about curvilinear
distortion as I often photograph buildings. It is certainly much lighter
to carry round, and IMO much better value for most purposes than the
17-35 f/2.8L.
[snip]
--
David Littlewood

Sigma has just released a 15-30 f/3.5-4.5
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B&H is listing it for $549.00 (Out of Stock).
I don't have any idea how the new Sigma will perform,
just mentioning it to add to your confusion :)

Rumour has it that Canon _may_ be announcing a new ultrawide zoom this fall.
See "The new season will be hot ? [06/15/2001]" on this page:
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May the Light be with you.??

dan

Hi Lisa,

All wide angle zooms have barrel distortion at the wide and pincushion
distortion at the tele end. The very best wide angle zooms have much
less distortion, but it is still there.

I'm eagerly awaiting the first review of the 17-35mm f/2.8 lens for the
Contax N1, because the designers will cut no corners to provide the best
optical performance. The lens will probably be as good as, or better
than, any wide angle zooms ever made. However, it will probably cost
about as much as a sub-compact car or a timeshare in Hawaii. :-(

I'm not sure what options you have in the Canon range, but I do know
that the 17-35mm f/2.8 L lens is not especially good for the price. I
believe there is a consumer-grade 20-35mm at a price that offers good
value but it probably has distortion that's no different from your
current Tokina.

It's no use recommending the 17-35mm f/2.8 AF-S Nikkor as it won't fit
your Canon mount, but it is a fine lens. It's justly popular despite
its high price. For anyone wanting a cheaper Nikkor the 18-35mm
f/3.5-4.5 AF-D is good for the price but (IMHO) there is a better option
which also fits Canon:-

The Tokina 20-35mm f/2.8 is an excellent lens and has distortion figures
that are less than half of the 19-35mm f/3.5-4.5 (the AF 193). It's
optically superb with excellent sharpness. Contrast is slightly lower
than with the AF193. The focal length of the wide angle end is little
different from the AF-193 and the 18-35mm Nikkor; they are all between
19mm and 20mm despite what is says on the box.

The Tokina 20-35mm f/2.8 is a top quality "pro" lens for very little
money. It doesn't have a USM motor, so you should try before you buy.
But if you are happy with the focusing (and the manual focus action is
superb) you will find little fault with this lens. Do try one!
--

Best regards,

Tony Polson

Wide angle lenses are always prone to curvilinear distortion unless a
lot of effort is put into correcting it. This is particularly so if the
lens is highly asymmetric, as SLR wides generally have to be to keep
clear of the mirror. The position of the diaphragm in relation to the
optical elements is important.

With fixed focal length lenses, these problems can be solved reasonably
well, at least in high quality lenses, and these are mostly low on
distortion. With zooms, there is the additional problem of having
several groups of elements moving relative to each other through the
zooming range, plus the need to also keep other distortions down
(spherical aberration, coma, chromatic aberration etc.).

Thus most wide zooms have some curvilinear distortion, even good ones.
The better ones may have little or no distortion at some points in the
zoom range but a noticeable amount elsewhere. I checked my Canon 17-35L
recently and found it had very little distortion except between 30 and
35 mm, where barrel distortion became noticeable (I haven't measured it
precisely, but it looks to be around 1-2%). Reports on other examples of
this lens have shown significant pincushion at the wide end, which I did
not observe. It thus seems that there is a fair amount of sample
variation as well.

I guess you will just have to try to avoid placing any high vertical
walls or other straight lines near the edge of the picture if it offends
you. For the price of the Tokina, it's hard to expect perfection in
every aspect.
--
David Littlewood

That's a great little lens. I shot with one recently and I think I'm going
to buy it. I didn't see too much distortion in my pics. Well, not enought to
make me want to not buy the lens.

...

Lisa, a lot of the cost of a top quality ultrawide lens goes into correcting
spherical aberrations like the barrel distortion you mention. Even with a
better lens you'll get some elongation at the frame edges with close
subjects--this is a matter of perspective--but straight lines won't curve.
Here's a link to some test photos I took a couple weeks ago with a 21mm lens
I was trying out:

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The lens in question performs very well in terms of distortion. Most if not
all major lens makers should have ultrawides in their lineups that perform
equally as well.

-Dave-