Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-18-2008, 04:31 PM   #1
Veteran Member
kuuan's Avatar

Join Date: Dec 2007
Location: Austria
Photos: Gallery
Posts: 401
how does a FA 1,7 x AF Adapter work?

Can anybody lease explain me how a PENTAX SMC FA 1,7 x AF Adapter works?
Or even better, with which lenses will it work, which manual lenses ( K? M? A? M42? ) can be used with it?

thank you for any input,
kuuan

02-18-2008, 05:20 PM   #2
Pentaxian
Moderator Emeritus




Join Date: May 2007
Location: Edmonton Alberta, Canada
Photos: Gallery | Albums
Posts: 10,648
Basically it will take any lens that is f4.5 and wider then turn it into an AF lens. You can put any lens on it like an M42 with adapter, K, M or A lens as well. Also FA, FA*, DA and DA* lenses will work so that you can extend the length by x 1.7 but keep the AF. Lenses that have a max aperture smaller than f 4.5 ( IE f5.6 + because not enough light gets in to achieve focus) will work with difficulty if at all and only in brighter conditions.

The unit works differently than a true AF lens. The lens that is attached needs to be focused manually to about the right focus point and then the AF adapter fine tunes the focus.
02-19-2008, 06:03 AM   #3
Not Registered
Guest




QuoteOriginally posted by Peter Zack Quote
Basically it will take any lens that is f4.5 and wider then turn it into an AF lens. You can put any lens on it like an M42 with adapter, K, M or A lens as well. Also FA, FA*, DA and DA* lenses will work so that you can extend the length by x 1.7 but keep the AF. Lenses that have a max aperture smaller than f 4.5 ( IE f5.6 + because not enough light gets in to achieve focus) will work with difficulty if at all and only in brighter conditions.

The unit works differently than a true AF lens. The lens that is attached needs to be focused manually to about the right focus point and then the AF adapter fine tunes the focus.
With the M42 lenses you will need a piece of aluminium foil or something similar to short out the connections between lens and converter (the same for some AF lenses). Hope it helps
02-19-2008, 08:23 AM   #4
Pentaxian
Moderator Emeritus




Join Date: May 2007
Location: Edmonton Alberta, Canada
Photos: Gallery | Albums
Posts: 10,648
I've never had to do this. Are you referring to using trap focus? If so then that's an entirely different issue. This converter fine tunes the focus on any lens I've tried as long as it's fast enough.

02-19-2008, 09:16 AM   #5
Site Supporter
rvannatta's Avatar

Join Date: Aug 2007
Location: Apiary, Oregon
Photos: Gallery
Posts: 1,171
QuoteOriginally posted by kuuan Quote
Can anybody lease explain me how a PENTAX SMC FA 1,7 x AF Adapter works?
Or even better, with which lenses will it work, which manual lenses ( K? M? A? M42? ) can be used with it?

thank you for any input,
kuuan
The 'how it works' is this. -- on the camera side it has the contacts, and the
AF shaft connection that you would expect of an FA lens.---and on the lens side it has the your basic K mount.

Mechanically, the AF drive shaft moves the optic within the adapter to touch
up the focus. I think it only moves closer and its range is not as great as
the adjustment on the lens. Thus thte instructions as I understand them
suggest that you set the manual lens focus to infinity and leave it there, but if that won't work, you can back the manual focus off of infinitity.

Not the best thing since sliced bread, but if you have an expensive KA mount lens.........

Recently I've seem them priced at over $400 on ebay, and at that price they don't make much sense unless you have a $1000 lens to put it on.
02-19-2008, 10:28 AM   #6
Not Registered
Guest




QuoteOriginally posted by Peter Zack Quote
I've never had to do this. Are you referring to using trap focus? If so then that's an entirely different issue. This converter fine tunes the focus on any lens I've tried as long as it's fast enough.
If you want to lock focus this trick allows you to use any M42 lens as (almost) an autofocus lens. When I tried the m42 lenses without the aluminium foil, the adapter moved randomly or not moved at all. Since the trick worked out perfectly, I just stopped researching. It might happen that you lenses plus adapter make the contact between the lens and the adapter in a different way than mine and they dont need further intervention. In my case, a zeiss sonnar 200 and a telemax 200 3.5 with the original adapter didnt work out well without the trick.
02-19-2008, 12:58 PM   #7
Veteran Member
kuuan's Avatar

Join Date: Dec 2007
Location: Austria
Photos: Gallery
Posts: 401
Original Poster
thank you everybody for the info provided, I think I roughly got the idea.

the prizes are high indeed, according to another thread the cheaper x1,4 TC from Tamron performs very well.

Interesting that the aluminium foil also could play it's part for the adapter to work, the same trick also is recommended for the exposure metering to work properly with M42 lenses, without it a dial in of approx. + 1,5 bias is needed.
02-19-2008, 03:10 PM   #8
Veteran Member
distudio's Avatar

Join Date: Jul 2007
Location: Sydney
Photos: Albums
Posts: 440
QuoteOriginally posted by kuuan Quote
thank you everybody for the info provided, I think I roughly got the idea.

the prizes are high indeed, according to another thread the cheaper x1,4 TC from Tamron performs very well.
Of course the Tamron and the Pentax AF TC are very different devices, one provides AF pass through for AF lenses on an AF body whereas the Pentax allows non-AF lenses to become psudo-AF lenses on any AF body.

QuoteOriginally posted by kuuan Quote
Interesting that the aluminium foil also could play it's part for the adapter to work, the same trick also is recommended for the exposure metering to work properly with M42 lenses, without it a dial in of approx. + 1,5 bias is needed.
I didn't realize that the the contacts also affected the metering but it's common knowledge that foil on the contacts will allow the AF TC to function with lenses that don't make contact with the mount pins.

02-19-2008, 07:01 PM   #9
Veteran Member
kuuan's Avatar

Join Date: Dec 2007
Location: Austria
Photos: Gallery
Posts: 401
Original Poster
QuoteOriginally posted by distudio Quote
Of course the Tamron and the Pentax AF TC are very different devices, one provides AF pass through for AF lenses on an AF body whereas the Pentax allows non-AF lenses to become psudo-AF lenses on any AF body.
Oh ho, thank you for pointing out the difference! - I was not aware of 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!
adapter, af, af adapter, fa, k-mount, lenses, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax 1.7 AF adapter.. where to buy and will it work with FA 300mm? Albert Siegel Pentax SLR Lens Discussion 7 05-20-2010 05:42 PM
Nikon to Pentax Lens Adapter- Does it Work? seachunk2 Pentax SLR Lens Discussion 19 05-06-2010 10:16 AM
Will any old lens work with an adapter privateryan Troubleshooting and Beginner Help 5 12-14-2009 06:57 AM
Will this M42 to K adapter work ? thanks. pcarfan Pentax Camera and Field Accessories 5 01-28-2009 02:07 PM
Do All M42 lenses work on Pentax with an adapter.. throndor Pentax SLR Lens Discussion 16 09-16-2008 06:00 AM



All times are GMT -7. The time now is 10:15 PM. | 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