Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-09-2011, 07:13 PM   #1
Pentaxian
Designosophy's Avatar

Join Date: Sep 2010
Location: Northeast Philadelphia
Photos: Gallery | Albums
Posts: 1,094
Tamron 28-200mm LD is short at 200mm

I just received a used Tamron 28-200 (model 171d) and as I compared images shot with the Tamron to images shot with my Sigma 70-300, I noticed that images shot with the Tamron were much wider angle at 200mm than those shot with the Sigma. They were comparable to about 115mm on the Sigma. I got out my Takumar 135 and found that it produced tighter shots than the 200mm Tamron. It is fine at 28mm. What is going on here? Do I need to return the Tamron?

02-09-2011, 07:24 PM   #2
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,194
The stated FL is good only at infinity focusing. Most zoom lenses "cheat" at the long end at close focusing distance.

Run your test again at infinity.

Last edited by SOldBear; 02-09-2011 at 07:30 PM.
02-09-2011, 07:24 PM   #3
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,979
I doubt the discrepancy is that big, but +/- 10mm is probably an acceptable margin of error for focal length labels.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

02-09-2011, 07:30 PM   #4
Pentaxian
Designosophy's Avatar

Join Date: Sep 2010
Location: Northeast Philadelphia
Photos: Gallery | Albums
Posts: 1,094
Original Poster
I know there is some variation in focal lengths, but this is huge. I'll check the infinity focus tomorrow. I seem to remember running into something similar, though not as drastic, before. Thank you.

02-09-2011, 07:54 PM   #5
Veteran Member
KxBlaze's Avatar

Join Date: Feb 2010
Location: California
Photos: Gallery
Posts: 1,594
I agree with Adam that +/- 10mm is probably ok but if your 135mm is tighter than the 200mm I would say that is way too much and unacceptable. I would do some more test just to be 100% sure and if you conclude that it is faulty, definitely return it.
02-10-2011, 09:02 AM   #6
Pentaxian
Designosophy's Avatar

Join Date: Sep 2010
Location: Northeast Philadelphia
Photos: Gallery | Albums
Posts: 1,094
Original Poster
I discovered that the manual was included in the packing materials. It explains the phenomenon under "Precautions in Shooting."

"Tamron AF 28-200mm (model 171D) employs an internal focusing (IF) system to achieve a remarkable .52 meter (1.71 feet) M.O.D. (Minimum Object Distance) at 135mm. Because of the characteristics of this optical design, the 200mm coverage, at distances other than infinity, is wider than that coverage of lenses using an ordinary focusing system."
02-10-2011, 04:53 PM   #7
Pentaxian
Designosophy's Avatar

Join Date: Sep 2010
Location: Northeast Philadelphia
Photos: Gallery | Albums
Posts: 1,094
Original Poster
I was able to confirm today that at or near infinity, the Tamron has the coverage of a 200mm lens. And it does a decent job for a fairly early autofocus lens. Not bad at all for $50. I'll have to add it to the lens database (this model isn't in there) and post a review after I've had it a while.

Last edited by Designosophy; 02-10-2011 at 04:55 PM. Reason: Additional information
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!
200mm, images, pentax help, shot, sigma, tamron
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tamron 70-200mm f/2.8 vs. Sigma 70-200mm f/2.8 vs Pentax 50-135mm f/2.8 nah Pentax SLR Lens Discussion 27 12-08-2008 01:03 AM
birdie shots with short DA*200mm danielchtong Pentax SLR Lens Discussion 9 05-25-2008 06:09 AM



All times are GMT -7. The time now is 07:29 AM. | 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