teleconverter advice please

obxeye · 01-07-2010, 02:50 PM

what brands are reliable and what brands should i stay away from?
tia

SOldBear · 01-07-2010, 03:03 PM

What lens(es) do you plan to use the TC with?

**Ash** · 01-07-2010, 03:06 PM

Forget about using a TC for SDM lenses or any lens slower than f/4.
Other than that, any of the AF TCs for Pentax are good, particularly the Pentax genuine TCs.
I have the Tamron 1.4x TC and it is very good quality, and relatively inexpensive.

Oggy · 01-08-2010, 04:00 AM

Try to avoid them altogether. You'll probably get a better picture.

**dadipentak** · 01-08-2010, 05:08 AM

Originally posted by Ash

Forget about using a TC for SDM lenses

Why do you say that, Ash? I use TCs with my DA*300mm and have gotten decent results.

dgaies · 01-08-2010, 08:11 AM

Originally posted by dadipentak

Why do you say that, Ash? I use TCs with my DA*300mm and have gotten decent results.

Same here. My 1.4x works pretty well with both the DA*50-135 and DA*300.

**Lowell Goudge** · 01-08-2010, 08:15 AM

there are some issues you need to consider.

first of all, if the combination of TC and lens result in a maximum aperture more than F6.7 then AF will either not function or hunt very badly.

Second, there are not many TCs made for the pentax KAF2 mount which include power contacts for SDM motors, and some of these may not work because they do not recognize the SDM communications. these need to be tested case by case

third, Sigma teleconverters do not support SDM yet, and sigma teleconverter design has the TC front element extending into the rear of the lens, and therefore only fit on a select few lenses, not even all sigma lenses. To use this TC requires the lens have a clearance of 35mm diameter, 10-12mm deep between the flange of the lens and the rear element. Note some pentax rear converters are similar and require even more clearance. Sigma TCs also do not modify the aperture or focal length reported.

finally, there is the pentax SMC-F 1.7X Auto Focusing TC. This TC has screw drive moveable elements that provide a range of auto focus once a lens is manually focused close to the focus point. This TC also has electronics to modify the reading of aperture to correct for the addition of the TC

**dadipentak** · 01-08-2010, 08:44 AM

Thanks for the explanation, Lowell. I have the Tamron 1.4x which works with SDM and the AF 1.7x. In both cases, I shoot MF a lot anyway since the situation often requires it. I'm pretty pleased with the IQ though.

**Lowell Goudge** · 01-08-2010, 08:52 AM

Originally posted by dadipentak

Thanks for the explanation, Lowell. I have the Tamron 1.4x which works with SDM and the AF 1.7x. In both cases, I shoot MF a lot anyway since the situation often requires it. I'm pretty pleased with the IQ though.

I chose not to comment on IQ because there are lots of different opinions on this point when using TCs.

I have found the SMC-F 1.7x AF TC to be excellent, as well, I have the same view of the sigma TCs, I only use my Sigma TCs on one lens, an origonal APO 70-200 F2,8 ED (Non DG Non Macro)

In my opinion, this is the best sigma 70-200 produced, but not all people share that opinion.

eclipsed450 · 01-08-2010, 08:53 AM

I just picked up a $10 2x teleconverter at a local antique store, threw it on my 50mm f2 lens, and got these ice crystals on my windshield the other morning:

**dadipentak** · 01-08-2010, 11:17 AM

Originally posted by eclipsed450

I just picked up a $10 2x teleconverter at a local antique store, threw it on my 50mm f2 lens, and got these ice crystals on my windshield the other morning: ]

That strikes me as an odd application but I can't argue with the results--very nice!

eclipsed450 · 01-08-2010, 11:31 AM

Originally posted by dadipentak

That strikes me as an odd application but I can't argue with the results--very nice!

why an odd application?? thanks

**dadipentak** · 01-08-2010, 12:14 PM

Originally posted by eclipsed450

why an odd application?? thanks

Why use a TC r/t shoot with the 50mm alone?

**Ash** · 01-08-2010, 12:21 PM

Originally posted by dadipentak

Why do you say that, Ash? I use TCs with my DA*300mm and have gotten decent results.

Originally posted by dgaies

Same here. My 1.4x works pretty well with both the DA*50-135 and DA*300.

Yes, I've seen a few as yourselves confirming TCs with 300s work fine. Point taken.
The OP is asking this question not to put on a 300, he has an 18-250, which the TC would struggle with also.

But as a general rule for a newbie I wouldn't recommend it on any other SDM/HSM zooms given their disappointing AF hunt and lack of focus locking at the long ends of zooms (50-135 and 70-200 comes to mind - both f/2.8). The long ends of the zooms is where it really matters.

I'm yet to hear someone testing out a TC with the 60-250... interested to hear how it fares at the long end...

eclipsed450 · 01-08-2010, 12:24 PM

Originally posted by dadipentak

Why use a TC r/t shoot with the 50mm alone?

because i couldn't have focused that close with just the 50mm, the TC brought the lens closer without me having to move, giving a macro look...that picture i posted is uncropped...

01-07-2010, 02:50 PM	#1
obxeye Inactive Account Join Date: Oct 2009 Location: nc Posts: 73	teleconverter advice please what brands are reliable and what brands should i stay away from? tia

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01-07-2010, 03:03 PM	#2
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	What lens(es) do you plan to use the TC with?

01-07-2010, 03:06 PM	#3
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Forget about using a TC for SDM lenses or any lens slower than f/4. Other than that, any of the AF TCs for Pentax are good, particularly the Pentax genuine TCs. I have the Tamron 1.4x TC and it is very good quality, and relatively inexpensive.

01-08-2010, 04:00 AM	#4
Oggy Inactive Account Join Date: Sep 2009 Location: West Sussex UK Posts: 235	Try to avoid them altogether. You'll probably get a better picture.

01-08-2010, 05:08 AM	#5
dadipentak Site Supporter Join Date: Jul 2008 Location: Baltimore, Maryland Photos: Gallery Posts: 11,590	Originally posted by Ash Forget about using a TC for SDM lenses Why do you say that, Ash? I use TCs with my DA*300mm and have gotten decent results.

01-08-2010, 08:11 AM	#6
dgaies Veteran Member Join Date: Oct 2009 Location: Maryland / Washington DC Posts: 3,917	Originally posted by dadipentak Why do you say that, Ash? I use TCs with my DA300mm and have gotten decent results. Same here. My 1.4x works pretty well with both the DA50-135 and DA*300.

01-08-2010, 08:15 AM	#7
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,892	there are some issues you need to consider. first of all, if the combination of TC and lens result in a maximum aperture more than F6.7 then AF will either not function or hunt very badly. Second, there are not many TCs made for the pentax KAF2 mount which include power contacts for SDM motors, and some of these may not work because they do not recognize the SDM communications. these need to be tested case by case third, Sigma teleconverters do not support SDM yet, and sigma teleconverter design has the TC front element extending into the rear of the lens, and therefore only fit on a select few lenses, not even all sigma lenses. To use this TC requires the lens have a clearance of 35mm diameter, 10-12mm deep between the flange of the lens and the rear element. Note some pentax rear converters are similar and require even more clearance. Sigma TCs also do not modify the aperture or focal length reported. finally, there is the pentax SMC-F 1.7X Auto Focusing TC. This TC has screw drive moveable elements that provide a range of auto focus once a lens is manually focused close to the focus point. This TC also has electronics to modify the reading of aperture to correct for the addition of the TC

01-08-2010, 08:44 AM	#8
dadipentak Site Supporter Join Date: Jul 2008 Location: Baltimore, Maryland Photos: Gallery Posts: 11,590	Thanks for the explanation, Lowell. I have the Tamron 1.4x which works with SDM and the AF 1.7x. In both cases, I shoot MF a lot anyway since the situation often requires it. I'm pretty pleased with the IQ though.

01-08-2010, 08:52 AM	#9
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,892	Originally posted by dadipentak Thanks for the explanation, Lowell. I have the Tamron 1.4x which works with SDM and the AF 1.7x. In both cases, I shoot MF a lot anyway since the situation often requires it. I'm pretty pleased with the IQ though. I chose not to comment on IQ because there are lots of different opinions on this point when using TCs. I have found the SMC-F 1.7x AF TC to be excellent, as well, I have the same view of the sigma TCs, I only use my Sigma TCs on one lens, an origonal APO 70-200 F2,8 ED (Non DG Non Macro) In my opinion, this is the best sigma 70-200 produced, but not all people share that opinion.

01-08-2010, 08:53 AM	#10
eclipsed450 Guest	I just picked up a $10 2x teleconverter at a local antique store, threw it on my 50mm f2 lens, and got these ice crystals on my windshield the other morning:

01-08-2010, 11:17 AM	#11
dadipentak Site Supporter Join Date: Jul 2008 Location: Baltimore, Maryland Photos: Gallery Posts: 11,590	Originally posted by eclipsed450 I just picked up a $10 2x teleconverter at a local antique store, threw it on my 50mm f2 lens, and got these ice crystals on my windshield the other morning: ] That strikes me as an odd application but I can't argue with the results--very nice!

01-08-2010, 11:31 AM	#12
eclipsed450 Guest	Originally posted by dadipentak That strikes me as an odd application but I can't argue with the results--very nice! why an odd application?? thanks

01-08-2010, 12:14 PM	#13
dadipentak Site Supporter Join Date: Jul 2008 Location: Baltimore, Maryland Photos: Gallery Posts: 11,590	Originally posted by eclipsed450 why an odd application?? thanks Why use a TC r/t shoot with the 50mm alone?

01-08-2010, 12:21 PM	#14
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Originally posted by dadipentak Why do you say that, Ash? I use TCs with my DA300mm and have gotten decent results. Originally posted by dgaies Same here. My 1.4x works pretty well with both the DA50-135 and DA*300. Yes, I've seen a few as yourselves confirming TCs with 300s work fine. Point taken. The OP is asking this question not to put on a 300, he has an 18-250, which the TC would struggle with also. But as a general rule for a newbie I wouldn't recommend it on any other SDM/HSM zooms given their disappointing AF hunt and lack of focus locking at the long ends of zooms (50-135 and 70-200 comes to mind - both f/2.8). The long ends of the zooms is where it really matters. I'm yet to hear someone testing out a TC with the 60-250... interested to hear how it fares at the long end...

01-08-2010, 12:24 PM	#15
eclipsed450 Guest	Originally posted by dadipentak Why use a TC r/t shoot with the 50mm alone? because i couldn't have focused that close with just the 50mm, the TC brought the lens closer without me having to move, giving a macro look...that picture i posted is uncropped...