Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-28-2012, 12:01 PM   #16
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Lowell Goudge Quote
Do the math. Aperture is defined as focal length divided by diameter. The inner diameter of a 49mm filter is about 47.5 mm, but realistically the front element diameter of a lens that can accept a 49 mm filter is about 45 mm, therefore, this diameter would define an inverse curve that would be close to focal lengths like 85mm at F2, 135 mm at F3.5 and 200mm at F4.5 (edit note. I initially typed 400 not 200mm)
And to be specific, the "M" series lenses come in at pretty much these exact points. The M85/2, M100/2.8, M120/2.8, M135/3.5 and M50/3.5 all take 49mm filters and are the fastest lenses easily available in these focal lengths that can make this claim (except for the other 100/2.8's as mentioned).

Actually, since 49mm is kind of a standard in the Pentax world (largely on account of the M series, I would imagine), and f/2.8 is often held as a sort of standard for what constitutes "fast" in the telephoto range, I do wonder if the M120/2.8 is actually the longest f/2.8 lens that takes 49mm filters.

04-28-2012, 12:49 PM   #17
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,615
QuoteOriginally posted by Marc Sabatella Quote
49mm is kind of a standard in the Pentax world (largely on account of the M series, I would imagine)
From the 'sixties, the Spotmatic "kit lenses" (55/1.8) had 49mm filter threads.
04-28-2012, 03:53 PM   #18
Inactive Account




Join Date: Feb 2012
Posts: 92
PENTAX - smc PENTAX DA 50-200mm F4-5.6 ED WR
04-28-2012, 05:50 PM   #19
Veteran Member
DaveHolmes's Avatar

Join Date: Jul 2010
Location: Yorkshire
Posts: 1,501
QuoteOriginally posted by SuperK5 Quote
PENTAX - smc PENTAX DA 50-200mm F4-5.6 ED WR
Yep. Mine's on a 49mm too.

Should be able to get a definitive answer if you're prepare to use the lens database... It's a really bloody good resource!

04-28-2012, 06:00 PM   #20
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
I think this is the longest one that takes 49mm filters:

https://www.pentaxforums.com/lensreviews/SMC-Pentax-A-Star-1200mm-F8-Lens.html
04-28-2012, 11:12 PM   #21
Site Supporter
Jean Poitiers's Avatar

Join Date: Apr 2011
Location: Lost in translation ...
Photos: Gallery | Albums
Posts: 16,382
Mdr ...

QuoteOriginally posted by littledrawe Quote
"Mort De Rire" ... = LOL !

A+, John Frog
05-06-2012, 03:28 AM   #22
Site Supporter




Join Date: Oct 2011
Location: Aylesbury, Bucks
Photos: Albums
Posts: 492
I was wrong about the 50-200 WR being the longest lens with a 49mm thread.

It is edged out by the F (or FA) 70-210 mm.

Don't think I'd be swapping though.
Reply

Bookmarks
  • 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!
49mm, filters, k-mount, lens, pentax lens, slr lens, step
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: K-7/K-5 battery and charger, 49mm filters, Films zhuxyg Sold Items 2 09-18-2011 04:11 PM
For Sale - Sold: Macro filters 49mm set (Worldwide) slawek Sold Items 5 12-30-2010 09:06 AM
Asahi Pentax 49mm Filters Peqpete Pentax Camera and Field Accessories 2 08-21-2010 04:19 PM
longest macro lens with AF out there? scathontiphat Pentax SLR Lens Discussion 3 05-20-2010 01:02 PM



All times are GMT -7. The time now is 02:32 PM. | See also: NikonForums.com, 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?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top