Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-30-2009, 10:40 PM   #1
Junior Member




Join Date: Jul 2008
Posts: 32
FA 50mm 1.4 + 2x teleconverter question

hi guys, while no substitute for a macro lens or extension tubes (which are not easy to work with), can a teleconverter get close to macro magnifications? realistically speaking of course.

so assuming the FA 50mm 1.4 gets 1:6.7 magnification, the teleconverter makes it 100mm 2.8 with the same MFD (minimum focusing distance) as before, correct?

how is the magnification ratio affected? doubled i.e. 1:3.35? not sure how the math will work out.

04-30-2009, 11:04 PM   #2
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,194
I may be wrong (not the last time mind you), but I don't think the mag. ratio is proportional to the effective focal length. I think it is proportional to the square root of focal length. In this case, you end up with 1: 6.7/1.4 = 1:4.7.
04-30-2009, 11:10 PM   #3
Junior Member




Join Date: Jul 2008
Posts: 32
Original Poster
square root of focal length? then why did you divide the original magnification ratio by the maximum aperture? not sure i get that.
04-30-2009, 11:18 PM   #4
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,194
QuoteOriginally posted by chaos83 Quote
square root of focal length? then why did you divide the original magnification ratio by the maximum aperture? not sure i get that.
1.4 in this case is not the max. aperture. It is the square root of 2. 100/50: you double the focal length.

04-30-2009, 11:21 PM   #5
Junior Member




Join Date: Jul 2008
Posts: 32
Original Poster
ah ok. that makes sense now. thanks. nothing beats a dedicated macro lens i guess.
05-02-2009, 09:44 AM   #6
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,814
Here's an interesting comparison of the D FA 100mm f2.8 macro against the Vivitar 2x Macro Focusing Teleconverter. That's a specialized TC designed for macro use with 50mm lenses.

www.jr-worldwi.de: Photography
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!
2x teleconverter, 50mm, fa, fa 50mm, k-mount, macro, magnification, pentax lens, slr lens, teleconverter
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
HELP! Old 3x Teleconverter on Kx Question chefpete1 Pentax SLR Lens Discussion 4 06-29-2010 12:25 PM
For Sale - Sold: DFA 50mm f/2.8 macro, FA 50mm f/1.4, M 28mm f/3.5, Vivitar 2X teleconverter iskyfishing Sold Items 18 08-20-2009 10:39 PM
teleconverter question total.boredom Troubleshooting and Beginner Help 5 02-10-2009 11:51 AM
Teleconverter question TomInJax Pentax SLR Lens Discussion 31 03-04-2008 04:39 PM
Teleconverter question scott-devon Pentax SLR Lens Discussion 3 11-17-2006 06:19 PM



All times are GMT -7. The time now is 06:07 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