Ultrawides & barrel distortion?
Lisa Horton
Tokina 193 19-35. It's pretty sharp and contrasty, but it seems to
have quite a bit of barrel distortion at the edges. Sometimes that's
useful compositionally, but more often it's not. My question is, is
this endemic to ultrawide zooms, or just inexpensive ones? If I
actually forked out for a better lens, would I see signifigantly less
of this distortion? TIA,
Lisa
David Kieltyka
> a better lens, would I see significantly less of this distortion?
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:
http://ourworld.compuserve.com/homepages/dkieltyka/Kobalux21.htm
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-
Dallas
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 Horton <Li...@lisahorton.net> wrote in message
news:3B90001A...@lisahorton.net...
David Littlewood
<Li...@lisahorton.net> writes
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
Tony Polson
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
dan
Sigma has just released a 15-30 f/3.5-4.5
http://www.sigmaphoto.com/html/pages/15_30_ex.htm
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:
http://eosseries.ifrance.com/eosseries/lenscanon/news_en.htm
May the Light be with you.©
-----
dan
David Littlewood
<no.e...@please.com> writes
>
>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 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.
> 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 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
Tony Polson
> In article <3ti1ptohu9hh2f4ni...@4ax.com>, Tony Polson
> <no.e...@please.com> writes
> >
> >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 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.
>
> 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.
Hi David,
I fully understand your point of view, and am aware of your careful
approach to making postings based on fact. I respect them both.
However it is clear that there is significant sample variation in all
wide angle zooms, of any brand.
Hopefully, in the case of the Canon the variation is not on the scale of
that found in the Cosina/Phoenix/Soligor/Vivitar Series 1 19-35mm lens,
which is truly appalling. If marketed as the world's first zoom
fisheye, which in effect it is, it would garner many more sales. <g>
But even the highly regarded Nikon 17-35mm f/2.8 AF-S Nikkor varies
significantly, as Bjørn Rørslett makes clear in his review.
Earlier this year, I participated in a long series of lens tests which
used a variety of bench testing, chart shooting and standardised 'real'
photographs to evaluate and compare over 140 lenses. I helped with
testing the Nikon and independent brands and was marginally involved
with Contax (Zeiss Japan) and Leica M tests. But several of my friends
who use Canon gear remarked on the variability of the 17-35mm f/2.8 and
deemed the overall results of its lens test to be disappointing. Sadly
I cannot disclose any of the results, so you will have to trust me.
Personally I have never used the lens, but I know the individuals very
well. I would trust implicitly their report of the tests. You yourself
posted on here about an unusual pattern barrel/pincushion distortion in
your example, and others replied describing a different pattern. I know
your style of writing enough to trust implicitly what you reported, and
the others who replied described a pattern that was present in two of
the three Canon 17-35mm lenses tested.
Let me make this clear: I am not in any way trying to criticise Canon;
I am a great admirer of Canon EOS gear and would have bought into that
system last year if I'd known more about it. As it is, my familiarity
with Nikon won the day. The point I am making is that the Canon has
production line variability just like every other manufacturer.
> 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 couldn't agree more.
Of course I assume you are talking about 'PhotographyBEWARE.com'; I am
fiercely critical of this site because of the lack of editorial control
and filtering. This allows almost any idiot to spout all kinds of crap
about almost any photographic item irrespective of whether he/she has
ever touched it, or used it, let alone owned it. It is probably the
most misleading photo site on the Web.
Of course it survives on advertising placed by "bait and switch"
merchants. You are encouraged to buy your camera, lens or what have you
by 'simply clicking on this link' or some suchlike.
Another misleading site is the authoritative-looking Photodo.com with
its narrow, subjective and surprisingly warped rating system. Although
I am very critical of Photodo I still reserve my deepest disdain for
'PhotographyBEWARE.com'. That's mainly because Photodo doesn't try to
tempt you towards any hyperlinks to suspect photo dealers.
Back to Canon. My recollection of the "Amateur Photographer" review of
wide angle zooms earlier this year is that the Canon 20-35mm did not
perform especially well. I no longer have that issue, and would be
grateful if anyone could supply more details. What I do remember is
that the three joint best buys were the Tokina 19-35mm f/3.5-4.5, the
Tokina 20-35mm f/2.8 and the Nikon 18-35mm f/3.5-4.5 ED. I am lucky
enough to have owned two out of these three and to have used and helped
test the third (the Tokina f/2.8) so I can happily endorse what "Amateur
Photographer" said in their review.
Based on Lisa Horton's requirement for lower distortion than she gets
from her Tokina 19-35mm f/3.5-4.5 (which is otherwise a very fine lens
and unbelievable value for money), the Tokina 20-35mm f/2.8 AT-X Pro
looks like a very, very good option. It's about the same price as the
Nikon 18-35mm and the Canon 20-35mm, has no greater distortion (and much
less than its cheaper sibling) and offers the holy grail: a constant
maximum aperture of f/2.8.
Provided it works well on Lisa's Canon bodies, which is always a major
consideration with an independent lens, I would strongly recommend it to
Lisa ... This is exactly what I did.
Now what was it you objected to again, David? <g>
David Albrecht
Tony Polson wrote:
>
> Back to Canon. My recollection of the "Amateur Photographer" review of
> wide angle zooms earlier this year is that the Canon 20-35mm did not
> perform especially well. I no longer have that issue, and would be
> grateful if anyone could supply more details. What I do remember is
> that the three joint best buys were the Tokina 19-35mm f/3.5-4.5, the
> Tokina 20-35mm f/2.8 and the Nikon 18-35mm f/3.5-4.5 ED. I am lucky
> enough to have owned two out of these three and to have used and helped
> test the third (the Tokina f/2.8) so I can happily endorse what "Amateur
> Photographer" said in their review.
>
> Based on Lisa Horton's requirement for lower distortion than she gets
> from her Tokina 19-35mm f/3.5-4.5 (which is otherwise a very fine lens
> and unbelievable value for money), the Tokina 20-35mm f/2.8 AT-X Pro
> looks like a very, very good option. It's about the same price as the
> Nikon 18-35mm and the Canon 20-35mm, has no greater distortion (and much
> less than its cheaper sibling) and offers the holy grail: a constant
> maximum aperture of f/2.8.
>
I don't get Amateur Photographer, but for what it is worth, I usually
like to reference www.photozone.de lens test section which abstracts the
results from multiple magazine tests. Note that this is different than
their user survey results.
Their rankings are:
Canon EF 2.8 17-35mm USM L 3.26 (5 reviews) = good
Canon EF 3.5-4.5 20-35mm USM 3.12 (5 reviews) = average
Tokina AF 2.8 20-35mm AT-X Pro 3.07 (5 reviews) = average
Tokina AF 3.5-4.5 19-35mm 2.67 (2 reviews) = sub-average
By comparison their reviews put the Nikkor 18-35 at:
Nikkor AF 3.5-4.5 18-35mm IF ED D 2.83 (2 reviews) = average
Note that the Nikkor 2.8 17-35 and 20-35 rate more highly. In fact, the
20-35 heads the list.
Photodo rates the same list:
Canon EF 2.8 17-35 USM L @ 3.2 w/Distortion: -4.43% - 1.13%
Canon EF 3.5-4.5 20-35mm USM @ 3.4 w/Distortion: -4.55% - -0.89%
Tokina AF 2.8 20-35mm AT-X Pro @ 2.5 w/Distortion: -3.03% - 1.97%
Tokina AF 3.5-4.5 19-35mm @ 3.3
If distortion is that important to me I generally figure that I should
be using a single focal length lens which usually has on the order of
half the distortion of a zoom equivalent.
Dave
Tony Polson
>
> I don't get Amateur Photographer, but for what it is worth, I usually
> like to reference www.photozone.de lens test section which abstracts the
> results from multiple magazine tests. Note that this is different than
> their user survey results.
>
> Their rankings are:
> Canon EF 2.8 17-35mm USM L 3.26 (5 reviews) = good
> Canon EF 3.5-4.5 20-35mm USM 3.12 (5 reviews) = average
> Tokina AF 2.8 20-35mm AT-X Pro 3.07 (5 reviews) = average
> Tokina AF 3.5-4.5 19-35mm 2.67 (2 reviews) = sub-average
>
> By comparison their reviews put the Nikkor 18-35 at:
> Nikkor AF 3.5-4.5 18-35mm IF ED D 2.83 (2 reviews) = average
> Note that the Nikkor 2.8 17-35 and 20-35 rate more highly. In fact, the
> 20-35 heads the list.
>
> Photodo rates the same list:
> Canon EF 2.8 17-35 USM L @ 3.2 w/Distortion: -4.43% - 1.13%
> Canon EF 3.5-4.5 20-35mm USM @ 3.4 w/Distortion: -4.55% - -0.89%
> Tokina AF 2.8 20-35mm AT-X Pro @ 2.5 w/Distortion: -3.03% - 1.97%
> Tokina AF 3.5-4.5 19-35mm @ 3.3
>
> If distortion is that important to me I generally figure that I should
> be using a single focal length lens which usually has on the order of
> half the distortion of a zoom equivalent.
Hi Dave,
Thanks for posting this.
I'm not in the thrall of *any* of the review sites on the Web, least of
all Photodo, and I don't believe that any "review of reviews" can be
particularly useful. I've resorted to testing every lens that I buy.
But I *do* tend to trust Dr Stewart Bell's lens test data that is
published in "Amateur Photographer". This magazine is perhaps unique in
that it derives most of its advertising income from sellers of used
equipment, both dealers and individuals. Therefore there is no sign of
bias towards, or away from, particular manufacturers. When the magazine
gets things wrong, as every magazine does sometimes, they are quick to
publish a retraction, correction or apology in order to set the record
straight.
I believe that the "review of reviews" you quote does not include the
test data that is published in "Amateur Photographer".
I've already said a lot about why I don't trust Photodo's results.
Suffice it to say that, as a travel and landscape photographer, their
results are of little interest to me, as I most often use the smaller
apertures at which Photodo doesn't even bother testing lenses. This is
probably the very worst of a long list of things that Photodo get wrong.
Badly wrong!
One fault that Photodo (Sweden) appear to share with Photozone (Germany)
is that the overall ratings do not take any account of the range of
focal lengths of a lens. A 17-35mm zoom is judged on exactly the same
criteria as a 80-210mm zoom, a 500mm telephoto or a 50mm standard lens.
This is like comparing apples with oranges.
The 'average' and 'below average' ratings at Photozone are therefore
meaningless. Confining zoom lenses to 'average' and below means there
are very few levels at which they can be compared.
I was amused to see that the 20-35mm AF-D Nikkor came top. I have been
involved in testing three of these lenses (on an optical bench, using
lens test charts, and in standardised general photography) including the
one I own. Two out of the three had colour fringing, for which this
lens is well known, and the third didn't. The distortion figures varied
so widely that at first we thought we'd mixed up the results with those
of other, completely different lenses. Then the three were re-tested
and similar results were obtained.
I was lucky; my lens was the good one.
It's worth pointing out that different magazines use different focusing
distances to check distortion, so comparisons are almost meaningless.
They can demonstrate clearly that wide angle lenses such as the 19-35mm
f/3.5-4.5 Cosina/Phoenix/Vivitart Series 1/Soligor show bad distortion
at every focal length and focusing distance, but they cannot tell you
much about the better lenses. (Any lens is better than this one!)
In conclusion, it would appear that "review variation" is almost as much
of a problem as "sample variation". I'll stick to my recommendations.
David Littlewood
I don't think I intended to disagree, more a case of suggesting that the
position was more variable than your original comments suggested. I
think the above details are very helpful, and tend to confirm my
suspicions that sample variations between examples of a particular model
are perhaps more significant than minor differences between models of
similar overall quality.
>
>Let me make this clear: I am not in any way trying to criticise Canon;
>I am a great admirer of Canon EOS gear and would have bought into that
>system last year if I'd known more about it. As it is, my familiarity
>with Nikon won the day. The point I am making is that the Canon has
>production line variability just like every other manufacturer.
Understood.
>
>> 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 couldn't agree more.
>
>Of course I assume you are talking about 'PhotographyBEWARE.com'; I am
>fiercely critical of this site because of the lack of editorial control
>and filtering. This allows almost any idiot to spout all kinds of crap
>about almost any photographic item irrespective of whether he/she has
>ever touched it, or used it, let alone owned it. It is probably the
>most misleading photo site on the Web.
I'm not sure which site you mean by photographyBEWARE. I can of course
see it is a joke. If you mean photobe.com, I have found the site so
incomprehensible on a couple of visits I left without finding any useful
(or even dubious) information. I was referring to photographyreview.com,
and photozone.de, where ratings out of 5 or 6 are derived by arithmetic
averaging of reader inputs.
>
>Of course it survives on advertising placed by "bait and switch"
>merchants. You are encouraged to buy your camera, lens or what have you
>by 'simply clicking on this link' or some suchlike.
>
>Another misleading site is the authoritative-looking Photodo.com with
>its narrow, subjective and surprisingly warped rating system. Although
>I am very critical of Photodo I still reserve my deepest disdain for
>'PhotographyBEWARE.com'. That's mainly because Photodo doesn't try to
>tempt you towards any hyperlinks to suspect photo dealers.
>
>Back to Canon. My recollection of the "Amateur Photographer" review of
>wide angle zooms earlier this year is that the Canon 20-35mm did not
>perform especially well. I no longer have that issue, and would be
>grateful if anyone could supply more details. What I do remember is
>that the three joint best buys were the Tokina 19-35mm f/3.5-4.5, the
>Tokina 20-35mm f/2.8 and the Nikon 18-35mm f/3.5-4.5 ED. I am lucky
>enough to have owned two out of these three and to have used and helped
>test the third (the Tokina f/2.8) so I can happily endorse what "Amateur
>Photographer" said in their review.
Do you happen to recall the date of the review? I have over half of this
year's APs (I was out of the country quite a bit in the first half of
the year so I missed quite a few).
The only comprehensive comparative magazine review I have is the June
1999 Practical Photography one. Now I know from your previous comments
that you do not have a very high opinion of this magazine's reviews.
FWIW, this gives similarly good ratings to the 2 Canon lenses (the 20-35
gets perhaps the highest rating of all the lenses in the survey), the 2
Minoltas, the Nikon 20-35 f/2.8, the Pentax 20-35 f/4 and the Tamron
20-40 f/2.7-3.5. The Tokina 20-35 f/2.8 AT-X Pro is downrated for poor
edge resolution wide open. Is this the same lens? It does however seem
to have the second lowest distortion figure in the review (after the
Minolta 17-35 f/3.5G).
However, given the age of this review, and the variability of samples, I
agree that this review may now be of limited value.
>
>Based on Lisa Horton's requirement for lower distortion than she gets
>from her Tokina 19-35mm f/3.5-4.5 (which is otherwise a very fine lens
>and unbelievable value for money), the Tokina 20-35mm f/2.8 AT-X Pro
>looks like a very, very good option. It's about the same price as the
>Nikon 18-35mm and the Canon 20-35mm, has no greater distortion (and much
>less than its cheaper sibling) and offers the holy grail: a constant
>maximum aperture of f/2.8.
>
>Provided it works well on Lisa's Canon bodies, which is always a major
>consideration with an independent lens, I would strongly recommend it to
>Lisa ... This is exactly what I did.
>
>Now what was it you objected to again, David? <g>
>
I wasn't really objecting to anything, Tony, I was simply trying to put
forward some alternative thoughts to ensure a better debate to enlighten
Lisa more thoroughly.
Lisa, best of luck with your choices. I think what this debate has
highlighted, as Tony says, is the need to test your example of the lens
you choose to ensure it is within the quality range you need.
If distortion *really* matters to you, I think you would be better off
looking at fixed focal length lenses. I have just had a rather cursory
check (through the viewfinder only) of my TSE 24 mm (no distortion worth
mentioning), my 35 mm f/1.4L (a very slight trace of pincushion
distortion), and my 14 mm f/3.5 Sigma (an impressively modest barrel
distortion, probably 1-2%). Now I realise that viewfinder checks are not
wholly reliable; I must do a thorough film/test chart check when I can
get a new test chart (old one fell to pieces).
--
David Littlewood
JR
I would suggest looking into a prime ultra wide. Tokina's ATX Pro 17/3.5
is great. But if you don't shoot ultra wide a lot, it may not make that
much of a difference. The 17 is my favorite lens....
JR
Karen Nakamura
If you're really worried about distortion, go prime young women, go
prime.
I bought the EF 24mm f2.8 and love it. It doesn't have USM, but it's one
fifth the price of the 17-35mm L and has better MTF ratings to boot. It
even beats the L version at F4 and higher.
- Karen
Lisa Horton
Davids. I've found that Photozone.de's ratings generally correlate
well to my own experience with lenses I've owned, so I do put some
stock in their ratings.
The impression I get from the discussion is that yes, barrel (and
pincushion) distortion is somewhat endemic to ultra-wide zooms. But
it's somewhat mitigated in more expensive lenses, sometimes
considerably. I'm not surprised that the old bugaboo of sample
variation has crept into the discussion as well. Modern production
line QA methodology dictates that this will occur, the only real
solution is individual testing and inspection which dramatically
increases production cost.
You've given me good food for thought. I've got a couple of good
prospects to look into. But I'm going to analyze my use of my current
ultra-wide zoom though, and see if something like a decent 19mm or so
prime may be my solution. I already have an acceptably good 28mm
prime and I seldom use the zoom at the long end.
I should probably mention too that I'm not trying to criticize the
Tokina 193 that I already own. I do feel that it's a fine performer
for the price and a real bargain. I don't for a moment regret buying
it since it's allowed me to explore ultrawide territory with a very
low price of admission. And it's really lightweight:)
So thanks again to all who helped!
Lisa
Martin Francis
quality and "Tonka Toy" barrel.
The reviewed Tokina 19-35 showed slight barrel distortion, and noticable
vignetting (at 19mm) and less so at the longer end. Marks were given for
constuction and value for money.
The other best buy, the Nikon 18-35, was deemed amongst the sharpest tested,
with "crisp contrast and truly faithful colour reproduction". Distortion is
supposedly minimal, as is vignetting.
Not that much of this helped the original poster..... but the review had
favourable things to say about the Canon too. The downsides were slight
pincushion at the wide end, slight vignetting wide open, and colour just on
the warm side.
--
"We're not living in the past or the present anymore, Elaine. This is the
future."
- Robert Hays, 'Airplane II- The Sequel'
"Tony Polson" <no.e...@please.com> wrote in message
news:5e54ptgin78v3uj24...@4ax.com...
MDDESKEY
>lot of effort is put into correcting it.
That's like saying money won't buy you everyhting unless you have enough of it
Martin Francis
surprise result? Cosina 19-35 getting higher marks than the Vivitar 19-35
Tony Polson
> AP June 23rd, 2001 -"Wide Boys"
> surprise result? Cosina 19-35 getting higher marks than the Vivitar 19-35
It's the best example of *wild* sample variation that I have ever seen.
Same optics, same build "quality", different cosmetics and completely
unrecognisable performance from one to the other.
The Cosina one is probably the single hand assembled version that has
done the rounds of the magazines getting reasonable reviews. The
Vivitar represents the optical quality that anyone else must buy.
David Littlewood
<Mcs...@btinternet.com> writes
>AP June 23rd, 2001 -"Wide Boys"
>surprise result? Cosina 19-35 getting higher marks than the Vivitar 19-35
>
--
David Littlewood
David Littlewood
<mdde...@aol.com> writes
>>Wide angle lenses are always prone to curvilinear distortion unless a
>>lot of effort is put into correcting it.
>
>That's like saying money won't buy you everyhting unless you have enough of it
Well, maybe that was a slightly clumsy way of putting it. What I meant
was that some lens types are prone to suffer from some aberrations more
than others; for instance, long focal length lenses are very prone to
suffer from chromatic aberration, and much of the design and
construction effort goes into solving this with fluorite of ultra-low
dispersion glass. OTOH, I don't think they suffer much from curvilinear
distortion, and the designer doesn't have the same trouble to tame it.
With wide angle lenses, the opposite is true; they are always plagued
with distortion, much effort is needed to keep it in check, possibly at
the expense of controlling other aberrations, and the result will always
be a compromise. Like all compromises, the result tends to be better if
you throw lots of money and fancy aspherical lens elements at the
problem.
Better?
--
David Littlewood