Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > Digital Photography > The multi-element, spherical lens-based lens MUST DIE!!

Thread Tools

The multi-element, spherical lens-based lens MUST DIE!!

Posts: n/a
Rich <(E-Mail Removed)> wrote:
>On Mar 3, 8:04*pm, Bruce <(E-Mail Removed)> wrote:
>> RichA <(E-Mail Removed)> wrote:
>> >On Mar 3, 8:38 am, Bruce <(E-Mail Removed)> wrote:
>> >> RichA <(E-Mail Removed)> wrote:
>> >> >On Mar 2, 7:44 pm, Bruce <(E-Mail Removed)> wrote:
>> >> >> RichA <(E-Mail Removed)> wrote:
>> >> >> >They must eliminate the multi-element lens. It is too heavy. It is
>> >> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
>> >> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
>> >> >> >telescope with 4 elements that produces a highly-corrected (colour,
>> >> >> >astigmatism, spherical aberration) FLAT image across an entire medium
>> >> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
>> >> >> >lens that can do that with so few elements? For about $3k. Takahashi
>> >> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
>> >> >> >limited without stopping down! Multi-element lens systems based on
>> >> >> >spherical lenses are DINOSAURS.

>> >> >> You need to compare the MTF of those telescopes with the MTF of top
>> >> >> quality fixed focus DSLR lenses of comparable focal lengths. I
>> >> >> suspect that will give you the answer you need.

>> >> >A top quality 400mm DSLR lens is about $10,000 and still won't be
>> >> >diffraction-limited wide open.

>> >> Then let's all shoot through telescopes and see how good they are.

>> >Modern Photography in 1977 tested a TeleVue (Pearl River, New York,
>> >maker of high-performance apochromatic telescopes) Renaissance
>> >telescope. *This was a 4" aperture, 500mm f5.0 refractor retailing for
>> >about $2000.00. *It beat every lens they had EVER tested when it came
>> >to contrast and resolution. *TeleVue has had 6 interations
>> >(improvements) of that scope since then, each of them providing better
>> >performance. *The scope is now called the NP101 and is similar to what
>> >is called the Petzval design, 2 main elements up front, a smaller
>> >doublet midway down the tube. *And there are even better telescopes
>> >than the TeleVue available from places like AstroPhysics, TEC, etc.
>> >The average camera lens is corrected to about 1-2 waves (yellow-green
>> >light). *The average telescope is 1/4 wave, a high-end scope like
>> >those mentioned is 1/10th wave. *The mirror that went into the Hubble
>> >was 1/100th wave. *The reason telescopes have to be so accurate is
>> >that unlike a camera lens that is used at what is called, Prime focus
>> >(no extra magnificational elements) a telescope may be used in
>> >conjunction with projection optics. *Imaging trying to put a 10-20x
>> >teleconverter on a camera lens and trying to get an image out of it.
>> >They do it with telescopes all the time, to shoot planets.

>> If all this is true, why aren't we all using telecopes instead of
>> telephoto lenses?
>> Perhaps because a telescope costing $2000 in 1977 would be way out of
>> reach in today's money. *Plus, it would produce an inverted image.
>> Plus, there is a lot more to optical performance than resolution and
>> contrast.
>> You obviously have an obsession about telescopes. *Don't worry, in a
>> few days it will go away, and you will start ranting about something
>> else that is completely unrelated, but equally implausible. *
>> Do try to smile. *

>Obsession with instruments that have superior optical quality. Some
>microscopes meet that spec. Some telescopes do. Virtually no camera
>lenses do. But the use of a lens at an equivalent f.l. of
>25,000-50,000mm and getting quality results is so alien to camera
>users that there is little point in trying to educate them as to how
>such a thing is possible.


Someone wake me up when Rich finally says something sensible.

Reply With Quote

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Travelling Salesman with Spherical Coordinates. Luc The Perverse Java 12 05-05-2006 09:06 PM
Gregwired Panosaurus Spherical Tripod Head Review at XYZ Computing Silverstrand Front Page News 0 01-03-2006 04:42 AM
spherical photos Weaver Land Digital Photography 3 05-20-2004 02:50 PM
Spherical Panos using Fisheye Attachments? Bob Digital Photography 1 01-01-2004 05:23 PM
Re: Sony 717 and SPHERICAL aberation Max Burke Digital Photography 7 09-12-2003 10:40 PM