Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
04-28-2010, 07:40 AM   #1
Senior Member

Join Date: Apr 2010
Posts: 288
What is a good aperture rating for a zoom lens (or any lens)?

I bought a Pentax k-x and wanted to get a manual lens for it. I've seen a lot for sale but didn't know a good f-stop or aperture rating that I should be looking for.

If this should be in the beginner forum please let me know. thank you.

Last edited by justtakingpics; 04-28-2010 at 08:09 AM.
04-28-2010, 10:01 AM   #2
Veteran Member

Join Date: Dec 2009
Location: Bucharest
Posts: 482
for a general use zoom look for f2.8, fixed - that means that at any focal length the glass could stay at f2.8. Cheap zooms vary the aperture with the focal lenght.

for a prime f1.4-f2.8 are good.

the lower the f usually the higher the price so ... your choice.

an absolute must for you is a 50mm prime which is reasonable as a portrait lens or a moderate telephoto.

buy and read the Scott Kelby digital photography volume 1, 2, 3 and you're set!
04-28-2010, 10:06 AM   #3
Inactive Account

Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,216
Your first manual should be a Pentax Super or SMC Takumar 55mm 1.8--real cheap at around $25 to $35 and easy to find on eBay. You'll need an adapter to M42 screw mount, which is cheap enough too.

Great lens for the money, and you'll be a part of history. (Made in the late 60s and early 70s.)

If you want to go for a little more bucks, look for the same in a faster 50 1.4, which is going anywhere from $75 to $125 these days.
04-28-2010, 11:13 AM   #4
Senior Member

Join Date: Apr 2010
Posts: 288
Original Poster
why is 50mm important?

04-28-2010, 12:30 PM   #5
Veteran Member
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
It's not, particularly, for your dSLR, but it was for film cameras, because it was the so-called "normal" field of view (prints made this type of lens when viewed froma typical distance show objects the same sizes as they would have appeared in real life). On a DSLR, it's 35mm that serves this function. The best thing about 50mm lenses today is that they are cheap, because they *used* to be so important that so many more of them were made. And they do work out well for portraits, and some like them for other things too.

I would definitely recommend a good basic beginning book on photography - it will explain many of the these concepts quite thoroughly. The concepts are so universal that it pretty much doens't matter which book you choose - whatever the library hapens to have in that day will be fine.
04-09-2011, 12:43 PM   #6
Loyal Site Supporter
Loyal Site Supporter

Join Date: Oct 2010
Location: New York
Posts: 501
Hi Ira
quick question where do I get a good but cheap M42 screw mount adapter from? Does brand matter?
04-09-2011, 04:12 PM   #7
Loyal Site Supporter
Loyal Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: North Syracuse, NY
Photos: Gallery
Posts: 15,103
Thread Necromancy.....

If you are not modifying large numbers of M42 lenses avoid the cheap adapters. Get a genuine Pentax Adapter K and you won't be sorry.
04-09-2011, 06:32 PM   #8
reeftool's Avatar

Join Date: Dec 2007
Location: Upstate New York
Photos: Gallery | Albums
Posts: 8,750
The genuine Pentax adapters are around $30, probably a little more now, and are available from Pentax.


  • 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!
aperture, 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
For Sale - Sold: Phoenix 100-500mm f/5.6-8.0 KA auto-aperture super-zoom lens wallyb Sold Items 8 09-10-2009 07:00 PM
For Sale - Sold: CPC 80-200mm f/4 Constant-aperture Auto KA-mount Zoom Lens, Only $20 wallyb Sold Items 4 09-10-2009 07:00 PM
For Sale - Sold: Tokina AT-X 80-200mm f/2.8 Constant- and Auto-aperture Pro Zoom Lens wallyb Sold Items 10 05-21-2009 01:56 PM
Is the Pentax - 75-300mm F4.5-5.8 SMCP-FA J AL Zoom Lens a good budget zoom? Kornbread Pentax SLR Lens Discussion 7 01-16-2009 03:45 PM
A good lens for Sports, and good Zoom chuna Pentax SLR Lens Discussion 17 12-26-2008 05:15 AM

All times are GMT -7. The time now is 11:08 PM. | 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]