Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-20-2020, 03:26 PM   #1
New Member




Join Date: Mar 2017
Posts: 7
Focal Reducer Pentax-M 28mm Element Collision

I purchased a Pentax-M 28mm f2.8 for some wide angle photos, and have just found out that the rear elelment collides with the focal reducer's elelment near infinity.

Is there anyway that I can increase the distance ever so slightly to prevent this collision?

I had tried one of the extension tubes I have, but it alters the minimum focusing distance so much so that it becomes a macro lens.

Any help is appreciated!

03-20-2020, 03:44 PM   #2
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 35,934
QuoteOriginally posted by Lazmarr Quote
I purchased a Pentax-M 28mm f2.8 for some wide angle photos, and have just found out that the rear elelment collides with the focal reducer's elelment near infinity.

Is there anyway that I can increase the distance ever so slightly to prevent this collision?

I had tried one of the extension tubes I have, but it alters the minimum focusing distance so much so that it becomes a macro lens.

Any help is appreciated!
Aside from not focusing to near infinity, probably not.

It is unlikely that there is a way to allow you to increase the distance of the rear element from the reducer that would preserve infinity focus. Have you contacted the maker of the reducer for their suggestions? Is it safe to assume that the reducer is native K-mount on the lens side and not stacked with other adapters?


Steve
03-20-2020, 03:50 PM   #3
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 4,285
Not without some surgery on the focal reducer. You would need to increase the thickness of the mount on the lens side (to add space) and decrease the thickness of the mount on the camera side by an amount proportional to the reducer factor (to reduce space and enable infinity focus). For example, if you have a 0.7X reducer, you might add 2 mm on the lens side and take-off 0.7 * 2 mm = 1.4 mm on the camera side. It should work, but the image quality might be a bit lower.

Last edited by photoptimist; 03-20-2020 at 05:08 PM.
03-20-2020, 08:07 PM   #4
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 16,480
QuoteOriginally posted by Lazmarr Quote
I purchased a Pentax-M 28mm f2.8 for some wide angle photos, and have just found out that the rear elelment collides with the focal reducer's elelment near infinity.

Is there anyway that I can increase the distance ever so slightly to prevent this collision?
Do you need infinity? If not you may be able to adjust the main lens to stop short of infinity without hitting the glass.

03-21-2020, 12:34 AM   #5
Pentaxian
Wasp's Avatar

Join Date: Mar 2017
Location: Pretoria
Photos: Gallery
Posts: 2,766
Anything you put between the lens and focal reducer will reduce the ability to focus to infinity.
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!
28mm, camera, collision, distance, pentax help, pentax-m, pentax-m 28mm element, photography, reducer pentax-m 28mm, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Focal Reducer Speed Booster Adapter Pentax K PK Lens to Micro 4/3 vytasn Sold Items 2 07-05-2018 02:39 PM
m42 to Pentax K focal reducer raff89 Pentax SLR Lens Discussion 19 01-13-2016 04:11 PM
Pentax Q and Focal Reducer ripper2860 Pentax Q 23 12-27-2015 12:26 PM
$199 focal reducer speed booster adapter Pentax PK K to Sony NEX jogiba Pentax Price Watch 91 12-07-2014 09:19 AM



All times are GMT -7. The time now is 12:31 AM. | See also: NikonForums.com, CanonForums.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