Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-17-2011, 05:17 PM   #1
Forum Member




Join Date: Oct 2011
Posts: 64
Need help finding a lense

I am looking for a 50-200mm F2.8 or better at 50mm as well as at 200mm. I have seen F4-5.6, if the F stop changes when the focal length changes, then the lens is no good to me. Is there a lens out there. I will be willing to have a lens with different focal lengths, but the F stop must stay constant. Is the 50-135 have an F 2.8 apature at 135mm as it does at 50mm?


Last edited by dndcdr; 12-17-2011 at 05:24 PM.
12-17-2011, 05:34 PM   #2
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,263
Yes, the Pentax-DA* 50-135mm F2.8 ED [IF] SDM is constant f/2.8 maximum throughout its focal range. It is also well-liked and expensive. See the reviews here: Pentax-DA* 50-135mm F2.8 ED [IF] SDM Reviews
12-17-2011, 05:37 PM   #3
Forum Member




Join Date: Oct 2011
Posts: 64
Original Poster
Thanks, money is not a problem. How about the Sigma or the Tamaron 50-200mm? Is the apature constant at 2.8 on thise lenses?
12-17-2011, 05:43 PM   #4
Loyal Site Supporter
Loyal Site Supporter
baro-nite's Avatar

Join Date: Aug 2011
Location: North Carolina, USA
Photos: Gallery | Albums
Posts: 5,294
Sigma makes a 70-200 that is constant f/2.8. Their 50-200 is not. They also make a 24-70 constant f/2.8.

12-17-2011, 05:48 PM   #5
Veteran Member
TOUGEFC's Avatar

Join Date: Nov 2009
Location: Brisbane
Photos: Gallery
Posts: 3,561
Sigma do a 50-150 constant f/2.8, which is quite good but you can only buy it used now as its dis-continued.
12-17-2011, 07:34 PM   #6
Veteran Member
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,685
If the aperture is listed as simply f/2.8 in the description, then it's f/2.8 throughout the zoom range. Variable maximum aperture zooms would be listed as f/2.8-4/4 or whatever.

General rule of thumb for telephoto zooms if you don't see the maximum aperture info in the specs for some reason:

If the zoom range is only 3X (longest focal length is three times the shortest), and it costs the better part of $1000 and/or weighs around two pounds, it's constant f/2.8. Otherwise - if the zoom range is over 3X, the costs is well under $1000, and/or it weighs well under two pounds - then it's not f/2.8 anywhere.
12-18-2011, 03:42 AM   #7
Forum Member




Join Date: Oct 2011
Posts: 64
Original Poster
Thanks, I will look at the Pentax 50-135 and the Sigma 70-200mm. I may end up getting both

12-18-2011, 03:50 AM   #8
Pentaxian




Join Date: Nov 2008
Location: Palo Alto, CA
Photos: Gallery
Posts: 2,497
Tamron 70-200/2.8, thought it does not cover 50mm, it 's great thought the range at f2.8 compared to all other lenses I tried (50-135 & Sigma 70-200mm, both a bit soft at longer end wide open).
12-18-2011, 04:43 AM   #9
Veteran Member




Join Date: Dec 2008
Location: Roodepoort, South Africa
Photos: Gallery | Albums
Posts: 3,561
Any reason why you insist on a constant aperture? Just curious.
12-18-2011, 06:26 AM   #10
Forum Member




Join Date: Oct 2011
Posts: 64
Original Poster
your shutter speed will change when you zoom in and you gro from F2.8 to 3.5. I am shooting basketball games and volleyball. I need the shutter to be as fast as possible at any focal length. I usually use fixed focal lengths but for sports, I think a zoom may be better. Why not have a lens that is a 2.8 at any focal length anyway?
12-18-2011, 10:32 AM   #11
Senior Member




Join Date: Jan 2010
Photos: Albums
Posts: 201
QuoteOriginally posted by dndcdr Quote
your shutter speed will change when you zoom in and you gro from F2.8 to 3.5. I am shooting basketball games and volleyball. I need the shutter to be as fast as possible at any focal length. I usually use fixed focal lengths but for sports, I think a zoom may be better. Why not have a lens that is a 2.8 at any focal length anyway?
cost/weight/size just to name a few
12-18-2011, 12:17 PM   #12
Veteran Member
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,685
QuoteOriginally posted by dndcdr Quote
your shutter speed will change when you zoom in and you gro from F2.8 to 3.5. I am shooting basketball games and volleyball. I need the shutter to be as fast as possible at any focal length.
You don't need a constant aperture for that, though - you just need to use an exposure mode that adjusts shutter speed automatically as aperture changes. Which is to say, any mode but M. Of couse, M is the only mode I normally shoot, so I too don't like using variable aperture zooms in any situation where I don't have time to keep hitting the green button to set shutter speed. But I'd have no problem switching to Av for sports shooting if it meant saving a ton of money and weight.
12-18-2011, 03:19 PM   #13
Veteran Member




Join Date: Dec 2008
Location: Roodepoort, South Africa
Photos: Gallery | Albums
Posts: 3,561
You can fix your shutter speed by using Tv

Or set your aperture to f/5.6; but if the K10D in your profile is still your camera, I would indeed prefer a fast lens and they are usually constant aperture. Two stops at the long end will make the world of difference (e.g. DA50-200/4-5.6 vs 70-200/2.8).

The disadvantage of constant aperture zoom: cost, size and weight But I will indeed opt for a zoom.
12-18-2011, 03:48 PM   #14
Forum Member




Join Date: Oct 2011
Posts: 64
Original Poster
Thanks for the info. I am upgrading to the k-5 and getting a zoom lens. I am leaning towards the 70-200mm f2.8 Tammie
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!
50mm, changes, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help finding S/N for tlp Pentax K-5 & K-5 II 10 03-25-2011 08:11 AM
Landscape finding my way skinja Photo Critique 3 09-07-2010 08:53 PM
Finding models StarDust Photographic Technique 13 04-08-2010 10:48 AM
Help in finding file slowpez Digital Processing, Software, and Printing 6 01-27-2010 08:50 AM
Noob Question Difference Between a Lense That Does Macro & A True Macro Lense Christopher M.W.T Troubleshooting and Beginner Help 16 07-19-2009 12:20 AM



All times are GMT -7. The time now is 02:37 AM. | See also: NikonForums.com, CanonForums.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