Randy, the article you linked states:
"Telecentric optical path means that light hitting the sensor is traveling
closer to perpendicular to the sensor, resulting in brighter corners, and
improved off-center resolution, particularly on wide angle lenses"
on a fact basis, this is a fail they've found a good technical word and
they're abusing it, telecentric optical path means nothing like what they
describe - they are merely highlighting the benefits of a long flange to
film distance and pretending it's something that it's not. They could just
as easily have used the word (incorrectly) in the 70's and 80's when they
switched from mirror-up designed wide angles to the more modern designs.
All they did was push the lens out further from the film with the use of
appropriate lens elements.
It's closer to the perpendicular to the film as well, but it's still
convergent/divergent. Only when it's a lens system can it be parallel, and
only when it IS parallel is it parallel.
White papers (From Wikipedia again: "A white paper is an authoritative
report or guide issued either by a government, or by a company in
business-to-business marketing,.. presenting the issuing body's philosophy
on the matter... a tool for persuading customers .. considered 'grey
literature..") are not often tech documents, and I've seen my fair share of
tech documents which have as much marketing as any sales brochure.
For those confused by reading all this, PLEASE go look at the images
produced by a telecentric system- you'll be quite amazed at the sort of
things such lenses can do. ""Because light is collimated as it enters the
lens, images of identical objects are imaged with the same magnification,
even if they are at different distances from the lens" .. that's pretty
cool..
Lens designs have jumped ahead from time to time for various reasons. Sure
there were SLR's pre 60's, but on the whole they had limited lens lineups as
the majority of lens makers were still manufacturing their own old lines
with camera makers either designing their light tight boxes to fit the
lenses, or putting the lenses in appropriate barrels for the focal lengths.
Subsequently wide angles were often set very close to the film plane and
came with light fall off issues, but they did the job and produced unworldly
images unfamiliar to the general public. In the 70's camera makers got in
on the lens game big time with whole 'systems' springing up - as much for
the barbie style collectors as for any cameraman. This time saw some
seriously interesting developments in lenses such as pushing the wide angles
further out, zoom lenses became more common (especially in the 80's), and
with increased affluence came escalating sales - good times. Problem was as
with software companies, accountants get used to ever increasing sales and
they needed to get their buyers to buy not just once but again and again and
again, and good rugged old reliable cameras became a liability. It's not
all rampant capitalism though, developments brought some genuinely
beneficial products to we consumers. 1990's- Enter the boon of autofocus-
once the sneered at as the bastion of point and shoot cameras, it along with
auto metering appeared big time in SLRs, pro and high end cameras and this
is where the serious consumer churn began - initially old lens designs were
reconstituted for the new lineups, but due to their weight these were
rapidly replaced with newer designs optimized for autofocus - light weight
components were the priority and this steered lenses into the area of light
weight plastics, which saw developments in asphreric designs undreamed of
before. This produced some truly outstanding lenses (and some naff ones
too). Then we saw the rise of digital, this time whole systems were dumped,
replaced, dumped again and it brought benefits and drawbacks.. but mostly it
brought SALES. but now we had the big boys playing in the sandpit..
Electronics companies stepped into the ring and stomped flat more than a few
players, and along with their wealth, r&d skills, they brought their
marketing clout and best of all, willingness to outsource to better
qualified parties. Lens makers once again found themselves making lenses.
Zeiss and Schneider were on more cameras than they've been in forever - and
there are new players to the game too.
For me one of the best examples of new designs , a real eye opener - the
Korean Samyang 8mm fish eye. I'd coveted a fish eye lens but wasn't happy
with any I saw until I stumbled across this little beauty
http://www.kenrockwell.com/tech/8mm-f35.htm - lenses like these are a truly
great advance for photographers with an eye for what they're seeing.
Across all these years we've seen many shrill claims and barrow loads of
sales hype, but as the technical involvement of consumers has fallen, buyers
know less and less about the products. from autofocus to image processing
algorithms.. even those with technical backgrounds or loads of enthusiasm
find it harder and harder to understand all the technologies going into
these increasingly miniaturized circuits - and often even the professionals
in their respective fields became further removed from the creative process
(software writers use software they don't understand to write software,
computers design computers to parameters given to them)
I had one tech put it to me: When the secretaries had their typewriters
replaced with PCs they were sent off on week long training course, when the
techs who repaired the typewriters were given PCs to fix they were expected
to just know how to do it.. they were technicians
k
