A sharp fellow asked the question of whether the 100-400/f4.5-5.6 IS lens or the 70-200/f2.8 with 2xTC is superior. A very interesting question that I have been researching on the internet.

Since then, I am slowly coming to the conclusion that photographers are subconcious liars.

At http://www.photozone.de/result2.htm the 100-400 lens is said to have no distortions at all based on survey results from 30 photographers.

At http://www.photodo.com/nav/prodindex.html actual tests show the 100-400 lens has distortions of -3.83% which is almost as bad as the notorious 17-35/f2.8 lens' -4.43% on its widest setting.

I recall reading comments from some that the 17-35 is unusable below 28mm because of all these distortion. At least at the survey web page the 45 responding were honest enough to report significant distortions at the wide end.

Perhaps people are blinded to defects because of the high price paid? Are half the photographers walking the earth in denial?

Oh please please, tell me it isn't so.

I'll just stick with my Canon FD prime lenses for now. :(

-- Howard Z (howard@howardz.com), January 29, 2001

Answers

>>Are half the photographers walking the earth in denial?<<

Absolutely not. The true percentage is probably closer to 95%.

However, to answer the question, photodo tests at a certain, specific distance (read how they perform their test). A lens that does not perform well at that distance may perform better (or worse) at other distances. Hence, you have to take "test results" with just as much salt as "user reviews." One possible interpretation of the seemingly conflicting results you mention, is that the telephoto zoom lens in question distorts lab charts when focused at a certain distance, but performs well enough in the field that most users don't notice, whereas the wide-angle zoom lens distorts enough in practical use as to be less-than-useful. Remember too, you're more-likely to be shooting something rectilinear, like buildings, with a 17-35 than a 100-400.

-- John Kuraoka (john@kuraoka.com), January 29, 2001.

I tend to agree with the denial part. It's called 'cognitive dissonance' by psychologists; where your perception of the truth is distorted by prejudice, or simply by the fact that you've just spent a small fortune on something that you then can't accept as less than perfect.

There is another factor to be taken into consideration WRT lens distortion also: Wide-angle lenses tend to be used close-up to a subject, where natural perspective distortion is already in effect. The barrel distortion of zooms at their wide end simply adds to this unnatural perspective, and the overall result is blamed entirely on the lens.
As mentioned above, telephoto lenses tend to be used in situations, and with subjects, where distortion goes unnoticed.
I've yet to find a zoom lens with a useful zooming ratio that didn't show distortion at both extremes of it's focal range.

-- Pete Andrews (p.l.andrews@bham.ac.uk), January 30, 2001.

I've found the other thought process I go through, though, is that once I notice some kind of systematic distortion it becomes all I see in the photos I take. :-) So it cuts both ways.

-- Mark Wilkins (mark_wilkins@yahoo.com), January 30, 2001.

To interject with a note of levity - I suspect the 'photographers' above are using the equipment to take photographs while the "equipment junkies" are quibbling over the specs and the price.

BTW, I'll stay with Canon FD too until something better comes along that really improves my photography. To date, in spite of collecting the best pieces Canon made, the biggest problem has been with the nut holding the equipment! :o)

Cheerio

-- Duane K (dkucheran@creo.com), January 30, 2001.

Howard, if you ask the same question to different people, you will get different opinions for sure. This is normal. That is why conscious people make conscious buys, be it cars, houses, toasters, TV sets, or cameras. If I am interested in the performance of a particular lens, I do all I can to test it myself. This usually involves going to the store and spending some time. I used to have a 17-35 EF lens for EOS; yes, it had distortions. But what is the point of buying such a lens and then use it only above 28mm? So it has distortions, big deal! Tell me what other 17-35 zoom is better than this one for EOS? You are right, there is none. User reviews? They are more often than not laughable; I bet most of them can not distinguish between intrinsic distortion of a wide-angle lens, and distortion associated to the fact that the lens is non-rectilinear. Keep a rectilinear wide-angle lens level with the world, and you will see no distortion.

-- Paulo Bizarro (pbizarro@cggp.pt), January 31, 2001.

Well, I thank you for your responses. I do want to upgrade from FD to EOS in the near future. Good quality stuff does carry a high price. It is frustrating trying to get conclusive evidence to base the purchases on. Perhaps I am being too scientific. I expect concrete undisputed answers rather than opinions.

This too shall pass.

-- Howard Z (howard@howardz.com), January 31, 2001.

Truth is......I have the 17-35, the 35-350 and the 100-400. I have heard all the 'notorious' comments, particularly about the 35-350 and what a useless lens it is. Hmmph! As a professional I use it an enormous amount, along with the 17-35. I just finished a one year contract to photograph a 22,000 acre high profile, mountain nature reserve through the seasons - landscape, people, wildlife, plants, etc etc. The kit has been bumped, bashed, and on my last trip, a few weeks ago the lenses were covered in snow and ice, wind blasted to -20 degrees, and performed faultlessly.

The important thing is that, despite the 'notorious distortion' the client is thrilled with the results. The books, posters, CD's. brochures will be published, I get paid, the lenses have earned their relatively high purchase price.

Argue if you like over theoretical considerations - real world results are what pay my bills............

-- (john.Macpherson@btinternet.com), March 10, 2001.

So, you think there is no Canon lens that is not worthy? Tell me your opinion about how much % distortion is acceptable?

Inquiring minds want to know.

-- Howard Z (greenspun@howardz.com), March 12, 2001.