Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
07-22-2010, 02:16 PM   #1
Junior Member

Join Date: May 2010
Location: Connecticut
Posts: 32
Extension Tubes

I have three extension tubes (original pentax ones) and am unsure about the difference between the three of them. The guy that I got them from said that he used them on the 120mm lense, and sometimes used them all at the same time. I'm not sure what the difference is between each extension tube, and when you'd use all three together.

Any help is greatly appreciated.

07-22-2010, 02:39 PM - 1 Like   #2
Site Supporter
Site Supporter
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 16,964
extension tubes are used to change the maximum and minimum focus distances of the lens for close up work.

they are different lengths, and can be used individually or in any combination as desired based upon the magnification ratio desired.

as a simple point, 1:1 macro is achieved when the extenstion tube length is equal to 2 times the lens focal length and the subject is 2 times the focal length away from the lens.

the extension set tube you have is probably totalling 65mm and if used on a 120mm lens would let you achieve in total magnification of about 1:0.7, but you would have a very limited working distance range of only about 200 +/- 10 mm (as a guess)

there are tons of calculations available on the web for extension tubes.

you should seriously consider a tripod when using extension tubes
07-22-2010, 02:39 PM   #3

Join Date: Jul 2009
Location: Seattle
Posts: 9,823
Here is an overview for using extension tubes. They are for macro photography. The "poor-man's macro lens", as they say. The longer the tube, the closer you can focus. You can kind of have to just try the different lengths and/or combination of them depending on how close you are trying to focus on something.

  • 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!
camera, extension, pentax help, photography, tubes
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Extension Tubes for K7 Alex00 Pentax SLR Lens Discussion 6 05-31-2010 09:23 AM
Extension tubes Gary G Pentax DSLR Discussion 2 04-14-2010 06:28 PM
Extension Tubes audio.mann Pentax SLR Lens Discussion 7 04-08-2010 05:34 PM
extension tubes bikee4 Pentax SLR Lens Discussion 1 06-22-2008 08:52 PM
Extension Tubes kpfeifle Pentax Camera and Field Accessories 2 02-29-2008 12:24 PM

All times are GMT -7. The time now is 03:09 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]