Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-10-2013, 10:08 AM   #1
Pentaxian
jddwoods's Avatar

Join Date: Nov 2012
Location: Newark, Delaware
Posts: 532
Backwards diaphragm blades

I just purchased a used SMC DA Limited 70 mm lens from Adorama in NYC in like new condition. The lens does look brand new and hardly used, if even used at all. I did notice something strange. The diaphragm blades look like they were put on backwards. Normally the flat side faces the front of the lens and the side where they overlap is on the rear side facing into the camera when the lens is mounted. On this lens they are the exact opposite. Look into the front of the lens and you see the overlapping blades side. Is this a problem? I have not yet tried the lens to see if it impacts picture quality since if it is a problem I want to bring it back packaged exactly as I bought it. I am hoping it is not a problem issue since I got it for a good price and it is a lens I really wanted, but if this is a serious defect I would rather get it resolved as quickly as possible even if it means not having the lens. Any thoughts on this appreciated. The blades do open and close smoothly despite the apparent backwards installation.

12-10-2013, 01:09 PM   #2
Forum Member
ma-ledezma's Avatar

Join Date: Aug 2013
Location: Texas
Posts: 98
My copy is exactly the same as yours, so I believe this is normal.
12-10-2013, 01:21 PM   #3
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,001
Huh...interesting. The overlapping side faces the front on every lens I've ever noticed including dozens of old lenses sitting around me now. But picking up my DA 18-250 I see they face the back. Is that a modern change, maybe to lessen diffraction?

In any case, I consider front-facing to be "normal" if there is such a thing, and I'm quite sure you couldn't just "put them on backwards" and have the lens operate...


EDIT: I just looked around and found a couple older lenses with backward facing blades, although the vast majority are to the front. I guess it is just a design decision for each lens.
12-10-2013, 01:37 PM   #4
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,149
QuoteOriginally posted by vonBaloney Quote
I just looked around and found a couple older lenses with backward facing blades, although the vast majority are to the front. I guess it is just a design decision for each lens.
That is what I found as well when I reviewed my collection.


Steve

12-11-2013, 05:54 PM   #5
Pentaxian
jddwoods's Avatar

Join Date: Nov 2012
Location: Newark, Delaware
Posts: 532
Original Poster
Thanks for replies.I checked my lenses, I have 15 mm, 35mm, 40 mm and 100 mm DFA limiteds. Yes, I consider the 100 mm DFA a limited. All have diaphragm blades with overlapping side facing inward, opposite that of the 70 mm limited. I also have an F series 28 mm from my film days and that lens has diaphragm blades facing same as the DA 70 mm. So, it looks like it does vary from lens to lens. I tried the DA 70 mm out and it looks fine, so its a keeper.
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!
blades, diaphragm, front, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sticky Diaphragm CP140 Pentax SLR Lens Discussion 10 10-25-2012 05:40 PM
Tokina 28mm diaphragm. J. Fabiano Pentax SLR Lens Discussion 12 06-15-2012 10:23 PM
Diaphragm problem Poliyoyo Pentax SLR Lens Discussion 4 05-09-2012 09:44 PM
Pentacon 135mm F2.8 ~ 15 blades = BOKEH MONSTER ~ 6 blades = NOT ? minahasa Pentax SLR Lens Discussion 3 09-01-2011 06:26 PM
Slow Diaphragm Blades on K 28mm f3.5 VaSA Pentax SLR Lens Discussion 3 04-06-2011 04:24 PM



All times are GMT -7. The time now is 12:17 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