Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-01-2013, 06:43 PM   #1
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,287
CDAF error?

So I decided to AF tune my 50-500mm SIgma using the "Dot Tune" method described in this post: https://www.pentaxforums.com/forums/photographic-technique/216496-anybody-tri...inetuning.html

However, when focusing in Live View the focus is consistently off. Not a teeny smidge off, really off. As in blurry image off. I can focus manually and then follow the DotTune process but I don't understand why the CDAF is off? I thought that this was the reliable standard to use. I know I have calibrated other (shorter) lenses by comparing the PDAF to the CDAF and it worked out fine.

So any ideas on what is wrong?

03-01-2013, 07:13 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,958
Happens sometimes, when you're way out of the ballpark and the camera doesn't bother hunting. I've even had it confirm focus on a blurry image.

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:

03-01-2013, 11:10 PM   #3
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,287
Original Poster
Yes but it is not random. Completely repeatable over 30 plus trials. I used two different focus targets. Moved the focus manually to the stop before focusing. I am stumped. This is all at 500mm. Will try other focal lengths tomorrow.
03-02-2013, 02:55 AM   #4
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,190
Try checking against a magnified image in live view using a 4x loupe and a high contrast target. That is pretty much the gold standard. The CDAF is...well..CDAF and not fool proof.


Steve


Last edited by stevebrot; 03-02-2013 at 03:00 AM.
03-02-2013, 01:35 PM   #5
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,287
Original Poster
QuoteOriginally posted by stevebrot Quote
Try checking against a magnified image in live view using a 4x loupe and a high contrast target.
That is essentially what I've been doing. 4x or 6x and it is clearly not in focus. A manual adjustment brings things in nicely. AFAIK there is no way to adjust CDAF, right? The only adjustment is PDAF.
03-02-2013, 02:15 PM   #6
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,325
What camera and firmware are you using? And what focal length of the lens? I dunno, I assume CD AF is not great when using tele lenses or slow lenses.
03-02-2013, 02:49 PM   #7
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,287
Original Poster
QuoteOriginally posted by Na Horuk Quote
What camera and firmware are you using? And what focal length of the lens? I dunno, I assume CD AF is not great when using tele lenses or slow lenses.
K-5 current firmware. These tests are at 500mm. Distance is about 30 feet. I am going to do some more this afternoon. I wonder if you have to fill the frame with the chart using CDAF ? Maybe it is catching something off the chart. Not usually an issue as I use center point AF but now that I think about it center point have any bearing on CDAF?
03-02-2013, 04:33 PM   #8
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,325
CD AF uses different AF rules than the PD AF, so you have to select from those. Not sure which choices the K-5 has, but some are better than others. If it has face detection, turn that off. Switch to select AF, not tracking. And then you just press the OK button and move the square around and the camera will try to maximize the contrast within that box (so, find a focus in there). Once you pressed ok to select the AF square and move it around, you can use the green button to put it back into centre.

03-04-2013, 08:47 AM   #9
Pentaxian
Fogel70's Avatar

Join Date: Sep 2009
Location: Stockholm, Sweden
Photos: Albums
Posts: 1,737
If it's a HSM lens you probably need to update lens firmware for it to work with CDAF. (if there is a updated firmware).

Sigma has had problem on HSM lenses not working with Pentax CDAF, but I'm not sure if they have updated firmware on all of these lenses.
03-04-2013, 09:50 AM   #10
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,287
Original Poster
QuoteOriginally posted by Fogel70 Quote
If it's a HSM lens you probably need to update lens firmware for it to work with CDAF. (if there is a updated firmware).
Thanks for the reply but, no this is an older screw drive lens. I think I have it dialed in for PDAF but CDAF is still off. I need to run some tests at different distances and focal lengths to see if I can determine anything else. I am sure I am missing something simple, I always thought CDAF was just 'in focus' no messing around and this has me stumped.
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!
cdaf, focus, pentax help
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Why not use CDAF to adjust PDAF? Raffwal Photographic Industry and Professionals 2 01-13-2013 10:26 AM
Is it normal for the CDAF image to be sharper than PDAF? GabrielFFontes Pentax DSLR Discussion 12 10-16-2012 06:03 PM
CDAF During Video - Video Footage Pheo Pentax K-30 & K-50 5 07-14-2012 03:38 PM
Any new CDAF tech from ME-F to K-01 ??? kales Pentax K-01 3 02-04-2012 09:58 PM
Error Error patrick9 Site Suggestions and Help 5 08-29-2011 03:20 AM



All times are GMT -7. The time now is 06:16 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