Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-09-2016, 08:08 AM   #1
Site Supporter




Join Date: Mar 2013
Posts: 14
1.7 Teleconverter focus problem

Some while ago I bought the teleconverter second hand, it remained in my bag unused, I did not get an operating manual with it and have not figured out how to find one on Ricoh Pentax support. It only seems to focus when I pre-focus manually close to the focus point, when it is a long way off it just hunts back and forth without finding focus.


I had hoped to use it with my 300mm DA* on a K5 ii, is it a lost cause? or am I doing something wrong? When mounted I put in the actual focal length 300mm, not 500mm which would be 300 x 1.7


I have the latest firmware 1.07 and it does the same with my K1


Last edited by Rayand; 06-09-2016 at 08:20 AM.
06-09-2016, 08:19 AM - 1 Like   #2
New Member




Join Date: May 2014
Photos: Gallery
Posts: 3
That's how it works. The focus on the lens needs to be in the right region cause the af movement on the Converter is quite short.

So if you want to focus on something close by the lens cannot be focused to infinity and vise versa.

And for the focal lenght use 1.7x Lens focal lenght.
06-09-2016, 08:32 AM   #3
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,001
The official instructions tell you to put the base lens at infinity, which often works well enough for far-off subjects, but on a fast telephoto lens the depth of field is so narrow you do have to adjust. So notice that there is more than one point where it can be in-focus since you've got two focusing elements. And the position of the TC before you autofocus (being based on the last thing you focused on) will be affecting where you ballpark focus the base lens. So it is prudent to sort of reset the system when making gross adjustments on the base lens by setting the base to infinity, then autofocusing on something far off. This should put the TC in a middle-ish "neutral" position, and then you can set your ballpark focus on the actual subject and the AF system will have some range fore and aft to work with -- sometimes it is all the way to the front or the back and then you move the focus on the base lens and it only has one way to go (that helps). Not sure if this is making any sense...
06-09-2016, 08:44 AM   #4
Site Supporter




Join Date: Mar 2013
Posts: 14
Original Poster
QuoteOriginally posted by vonBaloney Quote
The official instructions tell you to put the base lens at infinity, which often works well enough for far-off subjects, but on a fast telephoto lens the depth of field is so narrow you do have to adjust. So notice that there is more than one point where it can be in-focus since you've got two focusing elements. And the position of the TC before you autofocus (being based on the last thing you focused on) will be affecting where you ballpark focus the base lens. So it is prudent to sort of reset the system when making gross adjustments on the base lens by setting the base to infinity, then autofocusing on something far off. This should put the TC in a middle-ish "neutral" position, and then you can set your ballpark focus on the actual subject and the AF system will have some range fore and aft to work with -- sometimes it is all the way to the front or the back and then you move the focus on the base lens and it only has one way to go (that helps). Not sure if this is making any sense...
Thanks to both of you for that, two more questions though;

1) how do you set the TC to infinity?
2) I am going to photograph Gannets any tips for using AF-C with the TC?

06-09-2016, 10:04 AM   #5
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,001
QuoteOriginally posted by Rayand Quote
Thanks to both of you for that, two more questions though;

1) how do you set the TC to infinity?
You set the lens to infinity manually. You can't set the position of the TC (it has an element that moves -- that's how it is able to work at all) by any other method than engaging the autofocus, but when it locks focus it will then be at rest there for the next shot (so if you aren't moving it won't have to readjust). So if it happens to lock on at the extreme forward or back position (because your manual ballpark focus was only ballpark) and then you move to a different subject at a different distance and start moving the base lens focus ring to get a new ballpark focus, you're doing that with the TC in an extreme position. So what I'm saying is it will all work better if the TC is generally starting from the middle otherwise it will be limited to adjusting itself only in only direction and may not be able to lock focus. (This will start to make more sense if you play with it a bit to realize what I'm saying.)

ALSO -- another thing about the 1.7x AF is that it tends to not be perfectly calibrated to the AF system and will produce front or back focus consistently. So you should definitely test it with the base lens you what to use and see if you need to dial-in any AF adjustments. A number of people have concluded the TC isn't very good simply because they haven't really been hitting focus. But used on a top-notch fast prime results can be excellent. But it often needs an AF adjustment set in the body, and practice helps too...
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!
300mm, camera, focus, pentax help, photography, teleconverter, teleconverter focus, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problems with the focus of PENTAX SMC FA 50mm 1:1,7 magic.pill Troubleshooting and Beginner Help 4 05-01-2015 06:53 PM
Focus hunts with DA 1.4X AW AF Rear Teleconverter and other Qs DavidDwight Pentax SLR Lens Discussion 6 04-21-2015 09:03 PM
Bad focus problem with Kr + Super Takumar 1:1.4 50mm icy Pentax SLR Lens Discussion 7 12-31-2011 09:35 AM
K-7 18-55mm focus problem. dave blackburn Pentax DSLR Discussion 5 08-15-2011 06:59 AM
Infinity focus problem- M 50mm f/1.7 virgilr Pentax SLR Lens Discussion 3 01-30-2009 08:21 AM



All times are GMT -7. The time now is 11:15 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