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Old Sep 28, 2007, 7:49 PM   #11
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fldspringer wrote:
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Olympus is different from the rest in that they decided to do an entire re-design of their lenses when they began digital photography. Their lenses have a "near telecentric" design and throws an image circle only large enough for the 4/3 sensor.

The others chose to use legacy lenses, designed for 35mm film. If they were to design such a lens with a telecentric design, the lens mount would need to be the approximate diameter of a howitzer bore and the result would more resemble a medium format camera than a regular SLR.

Telecentric design, if I understand correctly, are easier to maintain quality as they are less sensitive to optical alignment of the lens elements. This, combined with a company that makes its main profits as a medical equipment manufacturer, leads to fewer lenses leaving the factory withoptical flaws.
'Telecentric' is something I've been referring to for some time; I just didn't know what it was called. Thank you.

Film is sensitive to light it receives from any direction, but CCD and CMOS sensors are more sensitive to light they receive straight on than they receive at an angle. As a result, when lenses designed for film SLRs are mounted on digital SLRs (with image sensors the size of a 35mm exposure) the image contains vignetting and chromatic aberration that do not appear on film images.

There are two ways to correct for this. One is to make the image sensor smaller (which is one reason many dSLRs have image sensors that are about 2/3 the size of a 35mm film exposure), or to design lenses that project the image onto the image sensor such that all the light from the lens is received almost straight on. This is 'near Telecentric'. As it happens, all lenses designed for digital SLRs are 'near Telecentric'. Sigma's DG and DC lenses are 'near Telecentric'. Tamron Di and Di II lenses are 'near Telecentric'. At the very least, Nikon's DX lenses are 'near Telecentric'. Even full frame dSLRs need telecentric lenses, so lenses that project an image suiteable for a 24x36mm exposure, whether it be for film or for CCD/CMOS sensors, can still be telecentric.

From http://en.wikipedia.org/wiki/Telecentric_lens :

"The Olympus Four Thirds System specifies a very distant exit pupil (nearly image side telecentric lenses), to avoid the vignetting and color crosstalk that occur in Bayer pattern image sensors with oblique incident rays. Many lenses that have been specially optimized for digital SLR cameras are nearly telecentric on the image side, and consequently have very small angles of chief ray angles of incidence."

And telecentric lens designs do not, in and of themselves, have a greater potential for quality. In fact, because telecentric lens designs require larger optical elements at the rear of the lens, the potential for flaws is increased, regardless of who makes them. If telecentric lens design produced products that were less sensitive to misalignment of the lens elements, then PhotoZone User Performance surveys would show consistantly high marks for all Olympus' products. Yet the 14-45, 14-54 and 40-150 show lower scores than other Olympus lenses. Another significant indication that may be seen in the PhotoZone User Performance Surveys is that, while the survey results can't be used to compare one brand with another, the surveys clearly show that Nikon and Canon users think more highly of some of their lenses than Olympus users think of theirs.

In addition, Canon and Nikon are also major manufacturers of sophisticated medical imaging equipment. Quality is quality. My own personal experience is in measuring instruments, and I know that Nikon makes some of the best optical instruments in the world, to the point where almost everyone else is an 'also ran'. It may be a small part of their business, but their QA/QC extends beyond their measuring instruments, through their medical instruments, to their spotting scopes, binoculars, microscopes, and yes, even their camera lenses.

So clearly, 'near Telecentricity' and 'being made by a medical equipment manufacturer' do not sufficiently justify your statement "fewer [Olympus] lenses leaving the factory with optical flaws."

I appreciate you supporting my suggestion that the Olympus 50-200 is a suitable substitute for the Canon 70-200, but I cannot support your assertion that Olympus has the best lineup of zoom lenses, thatOlympus lenses are consistantly good, or that a purchaser doesn't have to worry about bad copies as he or she might when purchasing a lens from, say, Canon or Nikon.

Extraordinary claims require extraordinary proof, and I don't think you've done so yet.
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Old Sep 28, 2007, 9:36 PM   #12
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TCav wrote:
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Extraordinary claims require extraordinary proof, and I don't think you've done so yet.
TCav has re-posted the contents of his emails to me. Why he decided to email privately over the last couple days and then decide to go public is a bit questionable. I did answer the content of his post, which were word for word from his two e-mails to me. I deleted those emails, and the replies I made to him.

If he chooses to also release the replies, he has my permission. I feel several points he made were not accurate and if he chooses to ignore my arguments, that is up to him.

I am away for the weekend and hope to get some good action shots of the dog trial I'll be attending. I really must get ready to hit the road at 4AM and to attempt to re-create my answers is not possible right now.

This e-mail privately - released publicly without warning is a bit awkward and sorry I'm not able to tend to it right now.

TCav, please don't e-mail me any more.

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Old Sep 28, 2007, 10:08 PM   #13
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Well,

I have to admit the technology is beyond my experience. But, the concept that you have to worry about a 'bad copy' of a 70-200 f4 is fairly silly. It really is one of the finest lenses made period. Have there been canon lenses with QC issues? Sure. but the 70-200 f4 isn't one of them.

Also the concept that made-for-film lenses are less capable is also complete hogwash.

Talk to any professional sports shooter or any professional photo journalist. 99.9% of them are using lenses made for film / full sized sensors. Their livlihood depends on the quality of the images.

Now, I'm not saying there isn't benefit to lenses designed specifically for digital - there is. But, don't discount the fact that the VAST majority of professional sports, wildlife and photojournalists use lenses designed for full sized, not aps-c sized sensors. They really wouldn't be doing that if those lenses were garbage.

Just some food for thought.
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Old Sep 28, 2007, 10:20 PM   #14
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fldspringer made some significant claims, not only about the overall quality of Olympus lenses, but their overall superiority to the lenses of other manufacturers. The OP asked for an explanation, and fldspringer replied with vague statements containing little or no substance. The OP seemed satisfied, but I was not. Rather that clutter up this topic with our debate, I communicated directly with fldspringer, in the hope that he would either reinforce or retract his claims.

He chose to do neither.

So I chose not to let his unsubstantiated claims go unchallenged.

I still have the message thread of our exchange, and if anyone asks for it, I will forward it to them. If enough people ask for it, I will post it here, pending approval by a moderator. (It is roughly 120 lines.)
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Old Sep 28, 2007, 10:26 PM   #15
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TCav, please don't e-mail me any more.
No sweat.

Does that mean you don't want me to reply to the message you just sent me?
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Old Sep 29, 2007, 3:50 AM   #16
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TCav wrote:
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fldspringer wrote:
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TCav, please don't e-mail me any more.
No sweat.

Does that mean you don't want me to reply to the message you just sent me?

Actually, I was responding to your second e-mail. I took the time to type the reply to you directly. Then I cleaned up the inbox, and then popped in here.

Surprise!!! I got to read it all again. I'll get to craft it all again on Monday night. You know, the vague statements stuff. In fact, if you like numbers, I'll see what I can do. I did it once with one of the manufacturers, and it became quiet while waiting for a response from in this forum.

TCav, you sling around alot of stuff to see what sticks. Most of the time I just let it pass even though I may disagree or know your in error. You decide to pick a bone here?

Off to the dog trial. See ya all Monday.





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Old Sep 29, 2007, 7:07 AM   #17
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You want to say that Olympus lenses are better than everybody else's lenses AND that Olympus is better able to turn out high quality lenses than everybody else?

Yes, I want to see numbers.

Enjoy the Dog Trials. I look forward to your return.

And let me state here and now, that if ANYONE EVERnotices that I've said anythingincorrect, especially in the form of advice toa novice, I invite you (I beg you!)to step in and correct me. After all, isn't that what this forum is for? To provide novices with the best advice possible?
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