Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-23-2012, 11:00 AM   #1
New Member




Join Date: Oct 2009
Posts: 15
Red "8" on K,M,A,F lenses from 16 to 35

Was there the hen or the egg first ?
I don't know but I've got another metaphysical question..

Why is there a red 8 on the pentax wide angle lenses (K,M,A,F) ranging from 16 to 35 ?

Example below with the 28/3.5 :

There is also a red number in the distance scale which the hyperfocale at f8.
But why f8, why not f11 ?
Is there a reason behind ?
(best sharpness at 8 for all the range ?)

02-23-2012, 12:51 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,957
I'm not 100% sure, but I think it might have something to do with the IR markings (notice the orange line on the distance scale). Also, I believe that F8 was used for standard exposure calculations back in the old days, but I could be wrong. In any case, it was definitely a popular setting!

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

02-23-2012, 01:03 PM   #3
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
Isn't there an entire subculture devoted to "f8 and be there" perhaps Pentax was a booster for the club or something?? The Masons could be involved as well since looking at the 8 sideways it is an infinity symbol. . . . . . .
02-23-2012, 01:08 PM   #4
Pentaxian
johnyates's Avatar

Join Date: Aug 2011
Location: Saskatoon, SK
Posts: 1,175
F8 is generally the sharpest aperture on WA lenses.
When you line up the red aperture and distance you have set the hyperfocal distance. IOW everything from half the (focus scale) indicated distance to infinity will appear to be in focus.
On the pictured lens, with all the reds lined up, everything from 5ft to infinity will appear to be in focus due to depth of field. Note--this is for FF cameras, on a crop camera YMMV.

02-23-2012, 01:12 PM   #5
Pentaxian




Join Date: Oct 2007
Location: France
Photos: Albums
Posts: 804
Not at all, the red marks where to help (in the past there was no autofocus) adjusting lens on the hyperfocal distance; you have to align the red figure (f8 here) with the red mark on the barrel and the red mark on the distance scale (3 meters here); when all these marks are aligned, the depth of field of the lens goes from infinity to some distance varying with the focal lens; this works only with wide angles (so the reason that these marks do not appear beyond 35 mm). That allowed to shoot without adujsting the focus.
Regards
02-23-2012, 01:33 PM   #6
Lens Buying Addict
monochrome's Avatar

Join Date: Mar 2008
Location: Kirkwood (St. Louis) MO
Photos: Gallery | Albums
Posts: 19,449
I asked my daughter the question. She says (she recalls she was taught in college) Pentax believed at f/8 most outdoor daylight shots would meter above 1/30, therefore were hand-holdable. The objective for amateur photographers upgrading from a fixed-focus rangefinder during the Spotmatic era was to handhold without attending to focusing. Pentax marketed to enthusiast amateurs - so they made some simple guides. The markings carried over to the WA K-mounts.

Canon lenses had a more complex color-coding to indicate hyperfocal distance at various apertures.

Here's a good article on Hyperfocal distance - and a ton of other stuff linked as well.

Last edited by monochrome; 02-24-2012 at 10:57 AM.
02-23-2012, 01:40 PM   #7
Pentaxian




Join Date: Jul 2010
Location: Oregon
Photos: Albums
Posts: 1,417
QuoteOriginally posted by Adam Quote
Also, I believe that F8 was used for standard exposure calculations back in the old days, but I could be wrong. In any case, it was definitely a popular setting!
It still is.
02-23-2012, 02:13 PM   #8
Veteran Member




Join Date: Dec 2006
Location: Gabriola Island
Posts: 579
Coincidentally, I was looking at a Spotmatic II manual just a couple of days ago. Pentax used the term "Fixed Focus Setting", with the followining explanation:

"Because of the considerable depth of field of wide-angle lenses, you can use them as fixed focus lens if the diaphragm and distance scanes are set properly."

My guess is that this was aimed, as others have said, at newbies.

I do use the DOF scales on wide angles a lot for pre-focusing purposes, but tend to use f/11 while being a bit more conservative about acceptable DOF than the scales are.

John

02-23-2012, 02:18 PM   #9
Pentaxian
pete-tarmigan's Avatar

Join Date: Apr 2009
Location: Conception Bay South, New-fun-land
Photos: Gallery
Posts: 944
The manual that came with my SMC-M 28mm f2.8 said specifically that the 8 was red to indicate that f8 was the hyperfocal distance. I don't know if I still have the manual.
02-23-2012, 02:25 PM   #10
Veteran Member
joe.penn's Avatar

Join Date: Mar 2011
Location: Maryland (Right Outside Washington DC)
Photos: Gallery | Albums
Posts: 2,902
I'm an F8'errrrrrrrrrr
02-23-2012, 05:27 PM   #11
Moderator PEG Judges
Kerrowdown's Avatar

Join Date: Aug 2008
Location: Highlands of Scotland.
Photos: Gallery
Posts: 30,594
QuoteOriginally posted by goubejp Quote
Not at all, the red marks where to help (in the past there was no autofocus) adjusting lens on the hyperfocal distance; you have to align the red figure (f8 here) with the red mark on the barrel and the red mark on the distance scale (3 meters here); when all these marks are aligned, the depth of field of the lens goes from infinity to some distance varying with the focal lens; this works only with wide angles (so the reason that these marks do not appear beyond 35 mm). That allowed to shoot without adujsting the focus.
Regards
It's what he said, I remembered this from the old days.
02-24-2012, 01:24 AM   #12
New Member




Join Date: Oct 2009
Posts: 15
Original Poster
Thanks a lot for your answers..
02-24-2012, 06:02 AM - 2 Likes   #13
Loyal Site Supporter




Join Date: Jan 2008
Location: Virginia, USA
Photos: Albums
Posts: 232
Here is a copy of the page from the manual that came with the K series lenses explaining the 'Fixed Focus Marks'
Attached Images
 

Last edited by Odinz; 02-24-2012 at 07:55 AM.
02-24-2012, 09:10 PM   #14
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,187
QuoteOriginally posted by johnyates Quote
F8 is generally the sharpest aperture on WA lenses.
When you line up the red aperture and distance you have set the hyperfocal distance. IOW everything from half the (focus scale) indicated distance to infinity will appear to be in focus.
On the pictured lens, with all the reds lined up, everything from 5ft to infinity will appear to be in focus due to depth of field. Note--this is for FF cameras, on a crop camera YMMV.
This is a common feature on 35mm and wider lenses, including the lens on my Olympus XA.


Steve
02-25-2012, 06:14 AM   #15
Senior Member




Join Date: Aug 2009
Location: Houston, TX
Photos: Gallery
Posts: 141
I was taught to just line up the infinity distance mark with the line corresponding to the selected aperture. The other line would tell you the closest distance that would be in focus.

Seems very simple to me and works for any aperture.
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!
f8, k-mount, lenses, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Post your "Park Bench" "or "Picnic Table" images tessfully Mini-Challenges, Games, and Photo Stories 1346 16 Hours Ago 11:08 AM
Do custom "artistic" or even "funny" lens caps evenexist? lovemehate Pentax SLR Lens Discussion 35 02-10-2016 09:10 AM
Don't say Pentax "Q" in French ... "Q" = "cul" = "A--" Jean Poitiers Pentax Q 52 11-10-2013 06:25 AM
"Christians for a Moral America" plan boycott of "The Hobbit" MRRiley General Talk 47 01-23-2012 01:48 AM
K-x "aperture priority" records as "automatic" in meta data charlestm Pentax DSLR Discussion 3 12-05-2011 12:12 PM



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