Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
10-16-2012, 05:02 PM   #1
Forum Member

Join Date: Jul 2012
Posts: 90
AF accuracy

Hi all,

Which is more accurate, the AF through the viewfinder or the liveview focus?
I know the difference in speed for sure>>

Are typical screw-driven lenses more accurate or are SDM systems better?


10-16-2012, 05:20 PM   #2
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,128
Contrast detect is always going to be more accurate than phase detect, especially considering that it isn't subject to front/back focus. I don't think mount type has much, if any, influence on AF accuracy, as it's all about how the AF module tells the camera to adjust the focusing ring.

Sony's new A99 has a three-stage AF system where first traditional PDAF is used for speed, then PDAF segments on the actual imaging sensor are used, and finally, CDAF is applied to fine-tuning the focus. On conventional DSLRs, PDAF alone is usually good enough, though if sharpness if of the essence and you have a lot of time on your hands, you may as well use live view.

You might want to give this article a read for more details on how PDAF and CDAF systems are implemented:
Fixing Front and Back Focus - Causes of Front- and Back-Focus -

Adam Webmaster (Site Usage Guide | Site Help | My Photography)'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:


  • 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!
af, camera, dslr, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Does sigma HSM lens improve AF accuracy on the k5? telly0050 Pentax K-5 10 09-19-2012 08:19 AM
Pentax K-5 AF accuracy Christine Tham Pentax K-5 181 02-06-2012 11:00 AM
AF speed and accuracy Hey Elwood Pentax K-5 7 01-13-2012 11:57 AM
Punchiness and Accuracy bluespearbone Pentax Camera and Field Accessories 5 08-15-2011 12:57 AM
AF vs MF logic and accuracy alvarossorio Pentax SLR Lens Discussion 11 07-27-2011 10:14 AM

All times are GMT -7. The time now is 10:19 AM. | See also:, 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?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]