Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-18-2011, 07:18 PM - 1 Like   #1
New Member




Join Date: Jan 2010
Photos: Gallery | Albums
Posts: 23
Pick sweet aperture

Here is a graphical guideline for selecting sweet spot for aperture for digital cameras of all types of sensors. This graph is established based on Digital Camera Sensor Sizes: How it Influences Your Photography.

To find out the sweet aperture for your camera, first identify the type of camera/sensor you have. Then find out its sensor resolution in term of mega-pixel counts. From the horizontal axis, draw a vertical line from the sensor resolution to meet with the curve that corresponds to the camera/sensor you have, and then draw a line left to meet with the vertical axis. The intercept will be the so-called diffraction limited aperture, which is the smallest aperture before triggering the diffraction that degrades the image quality. Typically, the sweet range of the aperture is within two stops larger than the limited aperture. As also noted in the reference, this is a theorectical limit and the diffraction may not kick in at this limited aperture right away.

For example, for Pentax Kx or Canon Xsi (12 MP), the diffraction limited aperture is around f/10. The range of sweet spot is typically between f/5 - f/10 theoretically. Some readers may wonder how is this guideline applied in the field, since there is no f/10 setting in camera. Experiments (DIY lens test) actually show the camera (Xsi) is still able to resolve well at f/11. See Lens Tests - Stepwise Photography. We could therefore conclude that the sweet aperture for most of APS-C with 12 MP max. resolution is between f/5.6 and f/11.

Attached Images
 

Last edited by lanx0003; 07-19-2011 at 07:54 PM. Reason: To respond the inquiry
07-18-2011, 07:28 PM   #2
Pentaxian




Join Date: Apr 2007
Location: Oklahoma USA
Posts: 1,502
That's very interesting - thanks for posting!

Paul
07-18-2011, 08:33 PM   #3
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,859
QuoteOriginally posted by lanx0003 Quote
...Some readers may wonder how is this guideline applied in the field, since there is no f/10 setting in camera. Experiments (DIY lens test) actually show the camera (Xsi) is still able to resolve well at f/11. See Lens Tests - Stepwise Photography. We could therefore conclude that the sweet aperture for most of APS-C with 12 MP max. resolution is between f/5.6 and f/11.
You can get f10 if you set EV steps to 1/3 stops, Custom setting 1 on the K-7.

Resolution doesn't just stop dead at f11 either, it just falls off. It's a tradeoff between increased depth of field and decreased sharpness due to diffraction. I don't use f22 much, except to check for dust spots, but with a really sharp macro lens at high magnification, there's plenty of resolution to trade off.
07-18-2011, 09:08 PM   #4
Veteran Member
yeatzee's Avatar

Join Date: Feb 2009
Location: Temecula
Photos: Gallery | Albums
Posts: 3,675
F/5.6 at 2:1+ FTW!

07-18-2011, 09:15 PM   #5
Veteran Member




Join Date: Sep 2010
Location: Canberra
Photos: Gallery | Albums
Posts: 739
I thought Pentax's had a 1.5x Crop ? Does the line move much from 1.6 to 1.5 ? Judging the distance between 4/3" I'd say only fractionally - ya ? more so in the lower resolutions...
07-19-2011, 08:15 PM   #6
New Member




Join Date: Jan 2010
Photos: Gallery | Albums
Posts: 23
Original Poster
The curve for 1.5 crop factor APS-C such as Pentax or Nikon is added.

For APS-C, I usually do not observe the sharpness falls off until f/16 when the image is viewed at 100%. See the aforementioned lens test chart. At f/22, however, the IQ is seriously compromised.

I agree it is a trade-off between aperture and DOF (response to an earlier message). When we shoot landscape at wide angle, if the aperture is properly chosen, we could often get by the diffraction issue and still acquire plenty DOF. For example, at 18mm, if the focal point is 7 ft ahead, anything beyond 3 ft should be in focus at f/11 (according to DOFMaster calculator).
07-20-2011, 09:22 AM   #7
New Member




Join Date: Jul 2011
Location: Maine
Photos: Gallery
Posts: 22
Very interesting, thanks for posting it!
07-20-2011, 08:22 PM   #8
Forum Member
bobva's Avatar

Join Date: May 2011
Location: Tacoma Everett
Posts: 53
Interesting

Thank you

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!
aperture, camera, diffraction, f/11, lens, pentax help, photography, range, resolution, sensor, xsi
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sweet New Acquisitions GoremanX Photographic Technique 16 11-01-2010 03:53 AM
People Sweet Dreams alvynmcq Photo Critique 5 06-15-2010 06:13 PM
People my sweet daughter fadami Post Your Photos! 5 05-28-2010 05:36 AM
Cityscape Sweet Home AOski Photo Critique 8 11-10-2009 07:24 AM
Connor Being Sweet Taff Post Your Photos! 5 07-28-2009 08:52 PM



All times are GMT -7. The time now is 05:27 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