Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-14-2010, 11:36 AM   #136
Site Supporter
Rorschach's Avatar

Join Date: Nov 2007
Location: Kuusamo, Finland
Photos: Gallery
Posts: 598
Yeah, one of those is heading towards me as I type this It's a good price for a new item, especially comparing to some of the insane ebay prices I've seen for used ones.

03-14-2010, 11:55 AM   #137
Senior Member




Join Date: May 2007
Location: Baltimore, MD (USA) ; Orlando, FL (USA)
Posts: 287
Is anyone using a F 1.7x TC on a DA* 200 f/2.8?

I'm seriously considering getting one.

I'm in the market for a tele or telezoom beyond 200mm. I debated on buying the 120-400 or 135-400 or possibly the Bigma, or maybe even a prime 400. I really don't want to go to just 300mm, but more.

I love my DA* 200 f/2.8, and a 1.7x TC for 340 is an interesting proposition. Anyone using it? What type of f-stop would that be in the end, f/4 or f/4.5?
03-14-2010, 12:31 PM   #138
Pentaxian




Join Date: Oct 2006
Location: Chicago suburb, IL, USA
Posts: 1,535
QuoteOriginally posted by bjsmith Quote
I'm in the market for a tele or telezoom beyond 200mm. I debated on buying the 120-400 or 135-400 or possibly the Bigma, or maybe even a prime 400. I really don't want to go to just 300mm, but more.

I love my DA* 200 f/2.8, and a 1.7x TC for 340 is an interesting proposition. Anyone using it? What type of f-stop would that be in the end, f/4 or f/4.5?
Hi Bryan,

I occasionally use mine with my A*200/2.8 and it plays well with it, though I usually use it more with longer lenses.

The rule for TCs for max aperture is to multiply current max aperture value by the magnification of the TC, so 2.8 x 1.7 = f4.76, or f4.8 rounded.

Scott
03-16-2010, 10:03 AM   #139
Veteran Member
froeschle's Avatar

Join Date: Sep 2007
Location: Germany
Photos: Gallery
Posts: 552
Concerning the "new" version of the adapter: Has the compatibility list in the manual been updated (the original manual stems from the pre-FA era)?

Attached Images
 
03-17-2010, 07:00 AM   #140
Veteran Member




Join Date: Feb 2010
Location: Kokubunji, Tokyo
Photos: Gallery
Posts: 458
Nope!

I just checked and it's still the same old copy of the "User Manual".
03-25-2010, 01:17 PM   #141
Senior Member




Join Date: Jun 2008
Location: Paris
Posts: 175
Just received this TC recently and started playing with it coupled to an A* 300 2.8.
What really strikes me is that you have to pre-focus manually, fairly close to the right point it seems to me, before you can "finish the job" with the TC's AF. What I mean is the range of distances the TC can focus, for any given focusing distance on the lens, is a lot smaller than I thought.
Say your subject is 30ft away: it is easy to be out of the focusing range of the TC, either because you've adjusted the manual focusing ring on the lens too long, or too short.
At first, I thought that setting focus distance to infinity would enable the TC to focus correctly pretty much in every situation, except on the very closest distances.
Is that an attribute of the TC, or due to the fact that it is used in combination with a long, fast lens?
03-25-2010, 01:59 PM   #142
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by nicolas1970i Quote
Just received this TC recently and started playing with it coupled to an A* 300 2.8.
What really strikes me is that you have to pre-focus manually, fairly close to the right point it seems to me, before you can "finish the job" with the TC's AF. What I mean is the range of distances the TC can focus, for any given focusing distance on the lens, is a lot smaller than I thought.
Say your subject is 30ft away: it is easy to be out of the focusing range of the TC, either because you've adjusted the manual focusing ring on the lens too long, or too short.
At first, I thought that setting focus distance to infinity would enable the TC to focus correctly pretty much in every situation, except on the very closest distances.
Is that an attribute of the TC, or due to the fact that it is used in combination with a long, fast lens?
You need to realize this TC has the equivelent of a variable lens extension being added to the lens in the order of about 7mm.

the equiveleint extension of a 300mm lens is about 25mm therefore it can accomodate for 25% of the focusing range on a lens. Yes you need to close focus manually first, it is not full autofocus but autofocus adjust of manual focus, BUT it is easy to be close to correct focus. I use one frequently on an SMC 300F4 and it works very well. It is a question of learning how to use it
03-25-2010, 02:10 PM   #143
Senior Member




Join Date: Jun 2008
Location: Paris
Posts: 175
Ok.
Does that mean that the TC can fully autofocus, provided you've preset the manual focus ring in the right "quarter" of the full range (10ft to infinity)?

03-25-2010, 02:24 PM   #144
Loyal Site Supporter
dadipentak's Avatar

Join Date: Jul 2008
Location: Baltimore, Maryland
Photos: Gallery
Posts: 10,073
QuoteOriginally posted by nicolas1970i Quote
Is that an attribute of the TC, or due to the fact that it is used in combination with a long, fast lens?
It's an attribute of the TC: a bit strange at first but, once you get used to it, it's nbd.
03-25-2010, 03:15 PM   #145
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,134
QuoteOriginally posted by nicolas1970i Quote
Ok.
Does that mean that the TC can fully autofocus, provided you've preset the manual focus ring in the right "quarter" of the full range (10ft to infinity)?
The TC will fine tune your focus. Do it by eye, then the TC will focus it. There is a set on my Flickr site where I used the 1.7X AF with my DA* 50-135 with what were, for me, amazing results. I now have an 85-230 mm f/4.8 semi-auto focus lens. It even nailed a bird in flight for me when a Canada Goose flew by. Missed the first shot, the second is in the set.

F 1.7X AF + DA* 50-135 f/2.8 - a set on Flickr
03-26-2010, 10:31 AM   #146
Pentaxian




Join Date: Oct 2006
Location: Chicago suburb, IL, USA
Posts: 1,535
QuoteOriginally posted by nicolas1970i Quote
Just received this TC recently and started playing with it coupled to an A* 300 2.8.
What really strikes me is that you have to pre-focus manually, fairly close to the right point it seems to me, before you can "finish the job" with the TC's AF. What I mean is the range of distances the TC can focus, for any given focusing distance on the lens, is a lot smaller than I thought.
Say your subject is 30ft away: it is easy to be out of the focusing range of the TC, either because you've adjusted the manual focusing ring on the lens too long, or too short.
At first, I thought that setting focus distance to infinity would enable the TC to focus correctly pretty much in every situation, except on the very closest distances.
Is that an attribute of the TC, or due to the fact that it is used in combination with a long, fast lens?
Hi nicolas,

Realize that the original intent of the "Adapter" is to convert MF lenses to use AF, not as a TC per se. If you use it with a 50mm, the most common lens for 35mm film, I'm pretty sure that if you set the lens at infinity, the AFA will focus the full range of distances. I think that magnifying the image 1.7x is due to the fact that this is about the shortest length that could be used to allow the focusing group enough travel to function reasonably. Adding any length between the lens and the body forces some magnification and the directly proportional light loss.

Nikon also made something like this, the TC 16A, which has a similar magnification (1.6x, which is why I made the assumption about this being the shortest practical magnification), but it has a lot of compatibility issues unlike the Pentax unit. AFAIK, the Pentax 1.7x AFA is by far the best implimentation of this concept, so it's unique.

I agree with Dave that once you get used to it, it's not a big deal, and in fact, the benefits it provides (focus limiting and focusing speed, in addition to the optically good magnification) make it a valuable addition to any long tele user (I use it most often with AF lenses).

Scott
03-27-2010, 02:20 AM   #147
Senior Member




Join Date: Jun 2008
Location: Paris
Posts: 175
Thanks Scott, very interesting explanation.
Out of curiosity, anyone know what a combination of this adapter with an A 50 1.4 or 1.2 would yield in terms of IQ (for an AF 85mm f2.4 or f2)?
Say, compared to a 77mm 1.8?
03-27-2010, 06:29 AM   #148
Veteran Member
cupic's Avatar

Join Date: Apr 2008
Location: Australia-NSW
Photos: Gallery
Posts: 4,724
I think the 50mm f/1.4 will give you 85mm f/2.4,straight out multiplication


cheers
03-27-2010, 07:47 AM   #149
Inactive Account




Join Date: Oct 2007
Location: Brisbane, QLD, AUS
Posts: 3,262
Perhaps the "A" in the "AF" in this product's name should stand for "Assisted" rather than "Auto."
03-27-2010, 08:17 AM   #150
Site Supporter
Clinton's Avatar

Join Date: Feb 2010
Location: Salt Lake City, UT
Photos: Gallery | Albums
Posts: 1,800
QuoteOriginally posted by cupic Quote
I think the 50mm f/1.4 will give you 85mm f/2.4,straight out multiplication
I don't know if there's a minimum aperture on this TC, but the 50mm A/1.2 reports as a 2.8 when attached, so I assume the 1.4 wont fare any better.
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!
1.7x, af, ie, lens, pentax, pentax f 1.7x, pentax news, pentax rumors, teleconverter, vietnam, warranty
Thread Tools Search this Thread
Search this Thread:

Advanced Search



All times are GMT -7. The time now is 09:52 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