Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax Lenses

Reply
 
Thread Tools Search this Thread
Old Jul 9, 2007, 12:42 AM   #1
Senior Member
 
Rodney9's Avatar
 
Join Date: Nov 2006
Location: Yeronga, Brisbane, Queensland, Australia
Posts: 3,518
Default

Which would be best for my Pentax K100D and Sigma 70-300mm DG APO the Sigma 1.4x or 2x convertor.
Is it true the 2x gives poor quality shots, if so how is the 1.4x ?
Are either worth the money ?

Rodney
Rodney9 is offline   Reply With Quote
Sponsored Links
Old Jul 9, 2007, 1:12 AM   #2
Senior Member
 
Hayward's Avatar
 
Join Date: Jan 2007
Posts: 1,318
Default

Besides that there is another consideration, and that is exposure loss.... 1.4x will cost you a stop, but a 2x costs you two.... real fast lens, not such a big deal, but with a lens like you mention that is f/5.6 max at full zoom then you are talking the lens effectively down to f/11 max with the 2x.... pretty much limiting things to pretty full daylight or tripod, the 1.4x would be a more manageable f/8

And SR is nice but that 300mm with it 600mm, can be tought to hand hold reliably especially in low light, vs the easier 450mm. Also TC mag factoir is NOT reported so SR is still compensating for 300, not 450 or 600mm.

My personal oppinon.... try a 1.4x first.... and see if it meets your needs.... less impact in exposure, optic IQ, and handholdability.

Until I got my 100-400mm had a Tam 1.4x TC and it was fine on myto 70-300mm Sigma, but in lower light the SR 300/450mm mismatch was noticieable compared the 100-400 truly reporting the FL to the SR, and another half stop less loss (6.7 vs 8 at 400/450) .

With good TC's the IQ issue is the least difference but the exposere loss and SR/FL mismatch become rather significant.

For long lenses I's stick to the 1.4x, while 2x is OK on shorter (under 135mm) usually faster or fast lenses where the two stop loss is not so critical, as wll also be easier handheld well with undercompensating SR. (Its a shame you can't manual set the SR FL value with a AF lens even in manual.... has to be seen as an A or M lens for that)
Hayward is offline   Reply With Quote
Old Jul 9, 2007, 5:36 PM   #3
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

Hi Rodney,

Hayward has given pretty good, reasonably concise general info on TCs.

If you'd like more specifics, here's what I can offer.

For a 1.4x, I have and use the Tamron F 1.4x. It's inexpensive, and optically very very good. It's apparently made by Kenko, and their version is labeled 1.5x for some reason unknown to me. . . Both are auto focus, but remember that SR might be fooled by TCs, but I personally don't consider that too important -- just hold as best you can, and you'll soon see if you need to compensate for the extra reach. It's available for @ $100 USD, but has been sold at $69.95 for seemingly forever (maybe no longer. . .:roll. It's perceived build quality is not the best -- the plastic seems cheap -- but I've used mine for over two years, and it's highly recommended by many users, including me.

Here's a link showing it:

http://www.bhphotovideo.com/c/produc...or_Pentax.html

If the Sigma 1.4x might interest you, make sure that it's compatible with your lenses, as many are not -- and the TC, while not optically as good, is more solidly built and considerably more expensive.

There are a lot of lesser name TCs available, but I wouldn't waste my money on any of them. They don't stand up to the Tamron, Kenko, or Sigma optically, IMO.

Pentax, at this time doesn't make any AF TCs. The only one they ever made is the F 1.7x Auto Focusing Adapter which has gained infamy as of late for selling on ebay for ridiculously high prices. It's very very good (my personal favorite), and is unique in that it focuses within the TC, making it AF with any lens, whether originally AF or MF. If you can find one for under $200 USD, then this would be my recommendation if you're going to use it with lenses with max apertures of f4.5 or wider. It also automatically multiplies the f stop setting of the lens and transmits the corrected value to exif. It does not, however correct for FL for the SR system, but it does not transmit FL from the lens, even for FA or DA lenses, so you are prompted to enter the FL manually when you mount the lens/TC combo on an AR equipped body.

For 2x, I actually own 2, but use them infrequently. Neither are AF, and are basically the best that I could buy IMO, quality-wise, and they were offered cheap, so I couldn't resist getting them to try. Both are "A" capable, so they heve the electrical contacts, and can be used with full auto-exposure automation.

The first one is the Vivitar 2x Macro Focusing TC ("A" version). This TC, in addition to being a competent 2x TC for tele work, also has an extension tube-like helicoid which allows the lens attached to focus closer to the point where you get anything from @ 1:5 to 1:1 macro capability. I use it with an FA 50/1.4 to give me a pretty good 100mm f2.8 1:1 macro, and with the D FA 100.2.8 Macro to give me a decent 200mm f5.6 @1.5:1 macro. Optically, it's very good, IMO, and it's built like a tank. I gave @ $75 USD for mine.

The second one is a Pentax A Rear Converter S, which originally sold for (I'm guessing) over $150 USD, and I obtained in EX+ condition for $73. Most of the Pentax Rear Converters seem to go for well over $100 on ebay these days. Optically, it's very good, and it's also built like a tank, but I usually opt for a little less reach with AF capability, and grab the 1.7 AFA. I really haven't tested this TC thoroughly tho.

The Pentax Rear Converters (1.4x and 2x) come in two flavors each, the S and the L. The S models can be used with any lens, but the L types are like the Sigmas, and have an extended front element and can only be used with lenses with a recessed rear element (most lenses don't have this).

Probably too much info, but I obviously like to talk about my gear. . .:-)

Scott
snostorm is offline   Reply With Quote
Old Jul 9, 2007, 6:31 PM   #4
Senior Member
 
robar's Avatar
 
Join Date: Mar 2005
Location: D/FW area Texas
Posts: 7,590
Default

my 2¢ rodney. using a zoom with a 2X TC, no matter which, i've never been happy with the IQ. go with a 1.4. i think you'll be happy.

roy
robar is offline   Reply With Quote
Old Jul 9, 2007, 10:57 PM   #5
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

robar wrote:
Quote:
my 2¢ rodney. using a zoom with a 2X TC, no matter which, i've never been happy with the IQ. go with a 1.4. i think you'll be happy.
I'll go along with Roy here. Especially if it's f5.6 at the long end -- f11 would severely challenge the AF system, and would be too dark to manually focus except on the brightest of days. The image degradation of the 2xs also is too much except for the very best lenses. Stick with a 1.4x.

Scott
snostorm is offline   Reply With Quote
Old Jul 10, 2007, 12:30 AM   #6
Senior Member
 
Gumnut's Avatar
 
Join Date: Jul 2005
Location: Perth, Western Australia
Posts: 1,259
Default

have a look in cash convertors (etc)

most convertors in there sell for under $10


at least you wont be wasting much money to find out if you like the results
Gumnut is offline   Reply With Quote
Old Nov 1, 2007, 1:21 PM   #7
Senior Member
 
PinonMesaJon's Avatar
 
Join Date: Jan 2007
Posts: 116
Default

snostorm wrote:
Quote:
......There are a lot of lesser name TCs available, but I wouldn't waste my money on any of them. They don't stand up to the Tamron, Kenko, or Sigma optically, IMO.

Pentax, at this time doesn't make any AF TCs. The only one they ever made is the F 1.7x Auto Focusing Adapter
........
The Pentax Rear Converters (1.4x and 2x) come in two flavors each, the S and the L. .....
I'm looking at investing in a teleconverter (I think), but have very little knowledge about them. Your post brought a bit of confusion and a couple of questions.

First, you mentioned that Pentax only made the 1.7x AF, but then mentioned the 1.4 and 2x. What's the difference between the teleconverter and the rear converter (or am I misunderstanding your points here)? Or are you just referring to the AF capability of the 1.7x?

Second, I understand that you suggest a 1.4x for various, goodreasons. But, on an even playing field, what's your suggestion, as far as IQ goes, for the best mfgr for a 1.4x TC - Tamron, Sigma, Pentax???

Thanks in advance,

Jon
PinonMesaJon is offline   Reply With Quote
Old Nov 1, 2007, 4:02 PM   #8
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

PinonMesaJon wrote:
Quote:
Quote:
I'm looking at investing in a teleconverter (I think), but have very little knowledge about them. Your post brought a bit of confusion and a couple of questions.

First, you mentioned that Pentax only made the 1.7x AF, but then mentioned the 1.4 and 2x. What's the difference between the teleconverter and the rear converter (or am I misunderstanding your points here)? Or are you just referring to the AF capability of the 1.7x?

Second, I understand that you suggest a 1.4x for various, goodreasons. But, on an even playing field, what's your suggestion, as far as IQ goes, for the best mfgr for a 1.4x TC - Tamron, Sigma, Pentax???

Thanks in advance,

Jon
Hi Jon,

I was referring to the AF capability of the P F 1.7x AFA. All the rest of the Pentax mfg'd TCs are Manual Focus only (so far, fingers crossed).

IMO, I'd rate them for IQ, from best to worst, Pentax, then Tamron, then Sigma. From a build quality standpoint only, reverse the Sigma and Tamron. Remember that the Pentax TCs (they called them Rear Convertors) are manual focus.

I'd look for the Tamron/Kenko 1.4x AF TC. It will give you the most versatility since it will work with any lens tho it will be manual focus with lenses that are originally MF.

As a side note : The Tam/Kenkos also have the contacts to work with SDM lenses, but my experience has been that they don't work well with at least my copy of the DA*50-135. Even in very good light, the focus typically hunts three times, then gives up without locking. On the second try, it'll lock almost immediately -- pretty frustrating.

Scott
snostorm is offline   Reply With Quote
Old Nov 1, 2007, 5:14 PM   #9
Senior Member
 
PinonMesaJon's Avatar
 
Join Date: Jan 2007
Posts: 116
Default

snostorm wrote:
Quote:
IMO, I'd rate them for IQ, from best to worst, Pentax, then Tamron, then Sigma. From a build quality standpoint only, reverse the Sigma and Tamron. Remember that the Pentax TCs (they called them Rear Convertors) are manual focus.

I'd look for the Tamron/Kenko 1.4x AF TC. It will give you the most versatility since it will work with any lens tho it will be manual focus with lenses that are originally MF.
Thanks, Scott! Just the info I was looking for.

Are the Tamron 1.4X AF TC's still mfg'd? IOW, can I get one new?
PinonMesaJon is offline   Reply With Quote
Old Nov 1, 2007, 5:41 PM   #10
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

Hi Jon,

If you follow the link in my first post, it'll lead you to B&H's page for the Tamron and it shows it to be in stock presently, so I'd guess that it's also in stock at other dealers if you'd prefer to purchase it somewhere else.

Scott
snostorm is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 1:09 AM.