Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-22-2014, 11:42 PM   #1
Site Supporter
Site Supporter




Join Date: Sep 2013
Photos: Gallery | Albums
Posts: 1,799
What is this strange symbol?

I noticed it on both my K30 and some of my Magic cards. This obviously has some shared history. Any guesses?

Attached Images
 
09-22-2014, 11:45 PM - 1 Like   #2
Site Supporter
Site Supporter
Digitalis's Avatar

Join Date: Mar 2009
Location: Melbourne, Victoria
Photos: Gallery
Posts: 11,694
That symbol points out the the location of the sensor plane - which is useful for macrophotography.
09-22-2014, 11:52 PM   #3
Site Supporter
Site Supporter




Join Date: Sep 2013
Photos: Gallery | Albums
Posts: 1,799
Original Poster
QuoteOriginally posted by Digitalis Quote
That symbol points out the the location of the sensor plane - which is useful for macrophotography.
Interesting. I shot this with my 35 Macro, what does this mean for macrophotography?
09-23-2014, 12:29 AM - 1 Like   #4
Site Supporter
Site Supporter
Digitalis's Avatar

Join Date: Mar 2009
Location: Melbourne, Victoria
Photos: Gallery
Posts: 11,694
QuoteOriginally posted by lithedreamer Quote
I shot this with my 35 Macro, what does this mean for macrophotography?
At infinity focus the optical center of the lens is 35mm away from the sensor - as you focus closer, there will be light loss as the optical center of the lens is shifted further away from the sensor plane. Knowing how many stops you lose from magnification can be useful when calculating correct exposure for your subject as well as flash exposure.

09-23-2014, 12:48 AM   #5
Forum Member




Join Date: Mar 2014
Posts: 79
The greek alphabet phi. Its used to show you where the sensor is.
09-23-2014, 01:02 AM   #6
PEG Moderator
Loyal Site Supporter
Kerrowdown's Avatar

Join Date: Aug 2008
Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake
Photos: Gallery
Posts: 57,760
QuoteOriginally posted by Anthen Quote
It's used to show you where the sensor is
In the old days it used to be the film plane was.

Anyway you'll be pleased to know it's also nothing to do with crop circles or aliens.

Last edited by Kerrowdown; 09-23-2014 at 01:28 AM.
09-23-2014, 02:01 AM - 1 Like   #7
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 10,510
In macro photography the extension distances are measured from the film or sensor plane of the camera. These distances are used to calculate magnification and exposure factor.

Basic formula for magnification (M)

extension ÷ focal length = M

The basic formula for Exposure Factor (EF):

(1 + M)² = EF

To calculate f-stop adjustment (fa)

fa= log(EF) ÷ log(2)

Thus a magnification of 1× = 4 EF = a 2 f-stop adjustment

09-23-2014, 02:56 AM   #8
Veteran Member
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 11,186
Look at the distance scales on your lens. Those distances are not from the end of the lens to the focused subject, but from the sensor to the focused subject. This is why that symbol comes in handy.
The distance from the end of the lens to the in-focus subject is called working distance and is not written on lenses.
09-23-2014, 06:17 AM - 1 Like   #9
Pentaxian




Join Date: Mar 2010
Location: Manila, Philippines
Posts: 1,421
Nice to see another MTG player here on PF
09-23-2014, 08:14 AM   #10
Veteran Member
Tako Kichi's Avatar

Join Date: May 2013
Location: SW Ontario, Canada (ex-pat Brit)
Posts: 1,296
The same symbol is used to designate the diameter of a circle in engineering drawings and mathematical calculations.

You can also see the symbol on almost every interchangeable lens where it is used to designate the diameter of the filter threads.

Last edited by Tako Kichi; 09-23-2014 at 08:21 AM.
09-23-2014, 08:21 AM - 2 Likes   #11
Site Supporter
Site Supporter
luftfluss's Avatar

Join Date: Jun 2011
Location: NJ
Photos: Gallery | Albums
Posts: 11,595
Its Saturn. On the other side of the camera is Jupiter. On the bottom is Uranus.
09-23-2014, 08:26 AM   #12
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 10,510
The engineering diameter symbol is different, the line is at a diagonal angle where as the upper case letter Phi and the image plane symbol the line is straight up and down. The lower case phi is often written with the line at an angle but the line does not ascend above the circle which is also open.
09-23-2014, 08:47 AM   #13
Veteran Member
Tako Kichi's Avatar

Join Date: May 2013
Location: SW Ontario, Canada (ex-pat Brit)
Posts: 1,296
I've been in and and around all sorts of engineering for over 40 years and I've seen the symbol displayed vertically and at an angle many times although strictly speaking you are correct and the symbol for diameter should have the line on a slant. In these days of CAD design you rarely see the vertical symbol but back in the days of hand drawn blueprints it was quite common especially if the draftsman was in a rush.
09-23-2014, 11:28 AM   #14
owl
Forum Member




Join Date: Jun 2008
Location: Upstate New York, USA
Posts: 92
Most SLR's have it, I noticed that Pentax's is a little more pronounced. Canon and Nikon have it in relief with no contrast from my quick look on the internet.

In engineering, I've seen it both ways as a diameter symbol, but the slant is more common.
09-23-2014, 11:59 PM   #15
Veteran Member
KevinR's Avatar

Join Date: Jan 2010
Location: Cape Town, South Africa
Photos: Gallery | Albums
Posts: 653
No, you have it all wrong. This is the ultimate proof that Pentax WR is tops. This is the camera's Load Line when floating Waterline - Wikipedia, the free encyclopedia (ships max draft when floating for the non nautical)

But seriously, good question and well answered. I never knew that symbol significance.

Last edited by KevinR; 09-24-2014 at 12:10 AM.
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!
k-30, k-50, pentax k30, pentax k50
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
What is this called & what is it for? cheekygeek Pentax SLR Lens Discussion 11 02-06-2010 02:31 PM
What's that symbol? jct us101 Photographic Technique 12 06-08-2009 06:21 PM



All times are GMT -7. The time now is 01:51 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