Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
08-22-2019, 04:53 AM   #16
Community Manager
Loyal Site Supporter
Ash's Avatar

Join Date: Mar 2007
Location: Toowoomba, Queensland
Photos: Gallery | Albums
Posts: 23,704
QuoteOriginally posted by WPRESTO Quote
As best I can tell. astronomical telescopes, either mirror or refractor, usually have substantial field curvature that is troublesome at typical photographic distances. a "field flattener" can correct this to some extent, but they are designed for use at infinity. Apochromatic retractors made for astronomy, having very simple optical systems by photographic standards (commonly a doublet or triplet design, either air-spaced or cemented) commonly have excellent to outstanding central IQ. I have seen excellent bird images taken with such optics, but they are expensive, very large, and not at all easy to use.
Interestingly, the ad features a series of images of varying FLs to compare with the that of the lens's 2000mm FL, and it shows a strikingly sharp image:

I'd have to be forgiven to not believe the accuracy of the images provided, as well as the hefty price tag, especially when in the ad it mentions this:
Now, our store has been authorized by ebay and PayPal to accept even more than 10,000USD lump-sum PayPal payment. Your purchase will be protected by eBay and PayPal both. Buy it now with confidence.


08-22-2019, 06:12 AM   #17
Site Supporter
Site Supporter
MossyRocks's Avatar

Join Date: Nov 2017
Location: Minnesota
Photos: Gallery | Albums
Posts: 1,778
It should be a sharp image as reflectors when focused properly will give good good results. If you look at the image it was shot to show the lens at its best. The image was shot at sunset or sunrise which means it would have been cooler with less wind. Also it was pointed up instead out across the horizon. These minimize the amount heat distortion from the ground and wind that would have blurred or distorted the image. Also by pointing it up the amount of humidity captured was minimized Finally it was shot fairly close to the structure which minimizes the amount atmosphere that can distort the image.
08-22-2019, 06:18 AM   #18
Loyal Site Supporter
Loyal Site Supporter

Join Date: Nov 2015
Photos: Albums
Posts: 2,424
There’s nothing saying that image came from that lens, is there?

That could have been shot with a Nikon superzoom or something, or even cropped.

It’s just showing field of view at low resolution, so there’s lots of ways to get there...

So I wouldn’t use that shot as an indicator of the quality of that lens...


  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
k-mount, lens, mirror, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mirror, Mirror ( in the lens ) eek ? ! ? aslyfox Pentax SLR Lens Discussion 46 04-18-2019 08:40 AM
Mirror Mirror macman24054 Monthly Photo Contests 4 11-09-2018 02:08 PM
Nature mirror , mirror, -who is the fairest of them all. dezertzebra Post Your Photos! 2 09-19-2017 09:19 AM
Mirror mirror on the wall biggles Pentax Q 4 07-01-2013 12:27 AM
Mirror, mirror... ptxbillyk Post Your Photos! 3 09-23-2008 08:52 PM

All times are GMT -7. The time now is 11:52 AM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]