Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-21-2010, 01:13 AM   #1
Senior Member




Join Date: Jan 2008
Location: Chennai, India
Photos: Albums
Posts: 254
Tokina 80-200mm/2.8 ATX doubt

All!

I recently picked one from marketplace here. I really like the AF speed on this lens. I feel it is soft when wide open. Yet to put to some real tests.
I have a question though. When in AF mode, the distance indicator does not move at all. The AF happens though.
This causes problem with the AF/MF clutch switch. The clutch is engaged only when the actual focus and the indicator matches.
I am overcoming this by first making the AF hunt to one end (infinity or the min focus) and then pull the clutch to MF. Going to AF is just one push.
Is this how it works (distance/focusing ring not moving in AF)? Or did I get a defective piece?
One more quesiton. Is the tripod mount removable at all? Thanks.

09-21-2010, 02:58 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,135
The former sounds like a defect. Not sure about the latter, but it doesn't look like it's removable. If it were, there should be a screw on the left side of the ring (link there is on Pentax FA* lenses).

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:

09-22-2010, 12:39 AM   #3
axl
Veteran Member




Join Date: Mar 2007
Location: Nove Zamky, Slovakia
Photos: Gallery | Albums
Posts: 7,181
The distance scale should move IMO. But I remember reading that the Tokina clytch is PITA, as the gears would engage/disengage only in certai/one position... Never had Tokina AF lens though so can't confirm
09-22-2010, 06:43 AM   #4
Veteran Member




Join Date: Aug 2009
Location: New England
Photos: Albums
Posts: 690
QuoteOriginally posted by siva.ss.kumar Quote
I am overcoming this by first making the AF hunt to one end (infinity or the min focus) and then pull the clutch to MF.
I think all you might need to do to avoid this is to make sure that whenever you switch from MF->AF or AF->MF on the lens, you first move the focus ring to the one spot you should be at to clutch in or out. On my Tokina lens, that is at infinity. While the lens will typically make it impossible to clutch to MF (pull back) at any position other than infinity, it is sometimes possible to clutch to AF (push forward) at positions other than infinity, but this will pose a problem when trying to clutch back into MF, and will require first using the AF system of the camera to focus to infinity before being able to clutch back into MF, where under normal use the lens focus could be anywhere, and just the focus ring needs to be set to infinity while in AF mode before you can pull back and clutch in to MF.

It might also help if I compare what I understand about internal focus and AF/MF switching on Pentax, Sigma, Tamron, and Tokina lenses.

On recent Pentax lenses, there is the "quick-shift" focus feature, which I have read about, and allows the user to grab the focus barrel at any time and manually focus, even when the AF system is engaged on the camera body. This feature becomes very useful if the user has changed the AF button from the default half-shutter press to the OK button, because then it is possible to use quick-shift focus to change the focus and then by not pressing the OK button, press the shutter and take the picture with the manual focus the user wants without the camera AF system re-asserting itself, and without having moved the AF/MF switch on the body (otherwise if AF is still set to the half-shutter press, if the user has quick-shift focused, when the user presses the shutter the AF system will likely change the focus before the picture is taken).

On Sigma and Tamron AF lenses, there is no quick-shift that I am aware of. I have Sigma (screw-drive, i.e. non-HSM) and Tamron lenses that have a focus clutch and an internal-focus system, i.e. with the focus ring clutch in the forward (AF) position, the internal lens moves only by the screw drive connected to the camera body and the focus ring is free spinning with no effect on the internal parts of the lens or it's focus. (Sigma sometimes calls their focus clutch system DF or dual-focus.) On these lenses you can pull the focus ring at any time and it connects the focus ring the parts inside the lens, and moving the focus ring will focus the lens. Note, however, that this will not disengage the screw drive from the lens, and it is my understanding that it is bad to manually move the screw drive motor by focusing the lens, so you should first disengage the screw drive by moving the AF/MF switch on the camera body. Also nothing will stop the AF system from working if the camera body is set to AF while the lens focus clutch is in the back (MF) position if the user does a half-press of the shutter release (or presses the OK button in that configuration), leading to a situation where either a) the user's hand is not on the focus ring and AF is slower because it is moving both the internal lens parts and the outer ring which is more mass to move or b) the user's hand is on the focus ring and damage is potentially done to the AF motor because it is struggling against a force it can't overcome.

In the case of Tokina AT-X Pro AF lenses, the only difference in my experience from it and my Sigma and Tamron lenses is that the Tokina focus clutch is only designed the engage/disengage from one place. I only have one such lens at the moment, on that Tokina lens, it is at infinity. So for instance, to switch to MF from AF on my Tokina lens, I move the focus ring to infinity (all the way to the right) and push it foward, then move the camera body switch from the MF to AF position. To switch from AF to MF, I move the camera body switch from AF to MF, then move the focus ring to infinity, and pull the focus ring back to switch to MF.

If you switch between MF and AF a lot, the Tokina method involves the most work, and you're likely to have to start over again with achieving focus. The Pentax quick-shift is the most friendly for touch-up focusing. Sigma and Tamron are in-between.

There's also one variation I forgot to mention - on my Pentax FA 100mm f/2.8 Macro lens, there's a rotary dial on the body that can switch the lens to MF, and on that particular lens, there is no need to switch the body of the camera to from AF to MF (i.e. there must be some sort of internal screw drive disconnection that happens as well as communication to the body not to AF when that lens rotary dial is moved to MF). That's the only lens I have that works that way.

10-26-2010, 03:51 AM   #5
Pentaxian




Join Date: Dec 2009
Location: Sydney, Australia
Photos: Gallery
Posts: 1,612
I resently got one from a forum member but I am having trouble too, but a different one.

What happen is that when the clutch is pulled back in MF mode on the lens, it works as a MF lens ok. But if I rotate the focusing ring to infinity and push the clutch forward into AF mode then AF can only happen in the band of infinity and 50 feet, it will not go beyond that, I can hear the AF motor screaming trying to drive the front element but it just will not move pass the 50 feet mark. And, when AF hunt between infinity and 50 feet the focusing ring rotate along which shouldn't happen according to Tokina website....

Just wondering if anyone had heard about this problem before and if there is any way of solving it....
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!
af, clutch, focus, indicator, k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Tokina 80-400mm ATX wasupdoc Sold Items 18 02-21-2009 03:42 PM
Tokina 28-70 f2.8 ATX Pro NaClH2O Pentax SLR Lens Discussion 12 03-10-2007 10:32 AM
Tokina 28-70 f2.8 ATX Pro II NaClH2O Pentax SLR Lens Discussion 5 02-24-2007 06:38 PM



All times are GMT -7. The time now is 04:56 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