Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-24-2011, 01:29 PM   #1
Site Supporter




Join Date: Apr 2011
Photos: Albums
Posts: 2,872
Lens - Reflection absorbing tube function

I recently had the good fortune to but a 200mm/f4 Takumar SMC lens in very nice condition. Unfortunately, when it arrived the rear, flanged, tube which has the function of absorbing stray reflections, fell out the back. (The 135mm f3.5 lens also has an equivalent piece.) I could see three dabs of glue residue, indicating this part had originally been glued in place, presumably with a glue that could be easily broken, for service work. I eventually decidied to glue the tube back in using the grade of Loctite intended to stop screw threads working loose.

This was good fortune because I obtained pictures showing what the tube does

The images attached are:
1. Before repair, bright overcast day at Pebble Beach CA.
2. Before repair, dull light in Carmel Forest CA.
3. After repair, looking direct into a bright light. The green crescent effect can be observed with the light in a variety of positions near the edge of the image (note DSLR cropping) but not with the light near the centre of the image - features in the middle of the image are not 'artistic'.
4. After repair, looking almost direct into sun on a wet day, Mawson Lakes, South Australia.
5. After repair, bright day, normal scene, Mawson Lakes.

The stray light reflections result in fogging the middle of the image.

Overall I am pleased with the lens, but it is long enough on DSLR that I have not yet had much chance to use it.

Interesting knowledge for me, as an engiener.

Attached Images
         

Last edited by tim60; 07-24-2011 at 01:35 PM. Reason: corrections and improving information
07-28-2011, 07:10 AM   #2
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
there have been several threads about internal reflections and similar symptoms in the photos.

I have a Rikenon 135F2.8 which had a shinny black rear lens group ounting ring that caused similar problems and another forum member had a 645-K mount adaptor which was shinny and reflective that did the same thing.

just goes to show how important internal reflection is
07-29-2011, 12:09 AM   #3
Site Supporter




Join Date: Apr 2011
Photos: Albums
Posts: 2,872
Original Poster
Lowell, thanks for responding. I had not found the other threads. I did think it intersting to show the effect on images of this component, and I have learned something about the lens through this experience that I would not have learned had it been in correct order when it arrived.
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!
day, glue, image, lens, light, pentax help, repair, tube
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax SR function with Tamron 70-300 lens? krishna Troubleshooting and Beginner Help 27 08-23-2010 02:04 AM
For Sale - Sold: Free - lens, lens case, m42 extension tube heliphoto Sold Items 3 11-30-2009 05:55 PM
DOF: Macro lens vs Ext. tube. pcarfan Pentax SLR Lens Discussion 10 10-24-2009 10:06 AM
For Sale - Sold: M 75-150mm lens and PK extension tube set kibipod Sold Items 9 06-23-2009 10:08 AM
DA lens & extension tube kibipod Troubleshooting and Beginner Help 2 04-17-2009 11:35 AM



All times are GMT -7. The time now is 09:55 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