Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-21-2011, 12:43 PM   #1
Junior Member
Alfie's Avatar

Join Date: Nov 2011
Location: Vienna, Austria
Posts: 45
Prediction of required shim's thickness?

Hi to all!

I've read all posts about FF/BF and problems in manual focusing with fast lenses.

Since I'm still in love with my old glassware I ordered a KatzEye already. Now I'm wondering whether it will be possible to predict the required shim's thickness. Most members needed a change (or the ones who didn't didn't post here). If I get it right the original shim coming with the K-5 is 0.40-0.45 mm thick. If you have FF, you would go with a thinner one (let's say 0.20-0.25 mm). The party suffering from BF needed a thicker one (or applied the Post-It-trick).

See also this page (and have fun with the English; almost as bad as mine). With the original screen and my SMC Pentax-M 50mm F1.4 (f1.4, object distance 45 cm, tripod, SR off, 2" timer) I got a BF of ~6 mm. I did my best to get the MF right, but it may be an artifact as well…

I changed focusing screens regularly with my LX 30+ years ago – of course not without scratching the first one. I want to avoid try-and-error with different shims and guess it should be possible to calculate the required thickness beforehand – somehow. Any ideas – mathematicians or optometrists around?

PS: Shipping my K-5 from Austria to Greenfield, MA is not an option.



Last edited by Alfie; 11-21-2011 at 02:22 PM. Reason: +sign.
11-21-2011, 06:19 PM   #2
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,132
The .020 seems to be the most common one. When I was looking into a Katz screen for my K7, Rachel indicated that the stock shim was .4mm and her screens seemed to need the .20 most often.
Were I betting, but still wanted to be sure, I would buy the .05, .10 and .20 shims. That way, I could do .15, .2, .25 and .3. One of these combos is bound to be correct.
11-21-2011, 06:52 PM   #3
Junior Member
Alfie's Avatar

Join Date: Nov 2011
Location: Vienna, Austria
Posts: 45
Original Poster
Thicker screen may correct for BF

Hi!
QuoteQuote:
When I was looking into a Katz screen for my K7, Rachel indicated that the stock shim was .4mm and her screens seemed to need the .20 most often.
THX! Agrees whit what I guessed from the posts here = Katz Screen + thinner shim. It's a pity that testing before changing (MF with the original one) is almost impossible.

QuoteQuote:
Were I betting, but still wanted to be sure, I would buy the .05, .10 and .20 shims. That way, I could do .15, .2, .25 and .3. One of these combos is bound to be correct.
Maybe I'm lucky (BF right now) and with the thicker (?!) Katz I don't need to change the original shim…

Does anybody know what the specs for the maximum thickness of stacked shims in the mirror box are?
11-22-2011, 08:44 AM   #4
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,132
I've read of people stacking two to get closer (needing .25mm for example). I suspect that you could stack them until the screen holder won't close any more, but its going to be tricky getting them in there. I think I'd try to ensure that I don't need more than two.

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!
bf, camera, dslr, f1.4, k-5, k-5 ii, k-5 iis, k5, mm, pentax k-5, thickness
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax Prediction 2010 lurchlarson Pentax News and Rumors 47 08-20-2010 08:26 AM
Hot Filter Thickness on K10D? smigol Pentax DSLR Discussion 5 04-23-2010 03:39 PM
Focus Screen thickness ?? gregmoll Pentax DSLR Discussion 11 07-14-2009 09:56 AM
PMA Prediction... Jasvox Pentax News and Rumors 107 03-02-2009 01:46 PM
Prediction mattdm Pentax News and Rumors 8 11-29-2008 10:28 AM



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