2x converter, worth it or just get longer lens?

Glen_S · 08-11-2009, 10:16 AM

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I recently purchased the Pentax 18-250 lens for my K10D, and I must say its a great every day lens. However we were out on a canoe trip the other evening and I was trying to get some closeups of some Pelicans and found I could not get as close as I wanted without spooking them.

I am thinking about getting a 2X converter, but a quick search brought up a Sigma for about $300. I''m wondering if this is worthwhile or should I just put the $$ towards a longer lens. I've never used a converter before, can I expect decent pictures from it, do I lose much speed etc.? Do I need to spend $300 or can I pick up a decent one for less?

I'm looking at one on ebay for about $90 - anyone here have experience with these?

thanks!

tr13 · 08-11-2009, 10:22 AM

Don't buy cheap AF converters.
Search for 7 element versions, use strings like "7 MC teleconverter pentax", "7 elements teleconverter pentax".
I have recently tested not very widely known non-AF old Telemore95 II by Komura.
To be short - no go with my modern lenses, and pretty good with my old fast zoom.
Each teleconverter must be matched to perticular lens, so it can work ok with one and very bad with another.

mille19 · 08-11-2009, 10:23 AM

I use a 1.7X converter with my DA* 300mm F4 and get good results.

I don't think I'd advise using a 2X with the 18-250mm that would make it a 500mm F11 so you would need really bright light and up the ISO to use it.

Converters are best used on fast prime lenses.

bymy141 · 08-11-2009, 10:26 AM

Originally posted by Glen_S

I recently purchased the Pentax 18-250 lens for my K10D, and I must say its a great every day lens. However we were out on a canoe trip the other evening and I was trying to get some closeups of some Pelicans and found I could not get as close as I wanted without spooking them.

I am thinking about getting a 2X converter, but a quick search brought up a Sigma for about $300. I''m wondering if this is worthwhile or should I just put the $$ towards a longer lens. I've never used a converter before, can I expect decent pictures from it, do I lose much speed etc.? Do I need to spend $300 or can I pick up a decent one for less?

I'm looking at one on ebay for about $90 - anyone here have experience with these?
thanks!

I have a Kenko 1.5X TC and the 18-250mm Tamron, the combination has lost of problems with focusing on my K10D. Manual focus is fine.

- Bert

GerryL · 08-11-2009, 11:05 AM

I'd stay away from 2X converters not unless you have very good fast lens to compensate for the light loss of using these.
A 1.5X or 1.7X usually is better.
The Kenko 1.5X costs $99 I think at Amazon.

**blackcloudbrew** · 08-11-2009, 11:52 AM

I have a kenko 1.5x and use it with my longer teles. It clearly does have focusing problems as in low light it hunts more. However, the manual clearly says that below f4 this will happen and it does. I use it with my DA 55-300 and have used it with my DA 17-70 SDM just fine. As was said above, in manual focus it's just fine.

Frankly, I haven't tried in on my Tamron 18-250 but that seems like too much range for a t/c.

imtheguy · 08-11-2009, 11:52 AM

Originally posted by mille19

I use a 1.7X converter with my DA* 300mm F4 and get good results.

I don't think I'd advise using a 2X with the 18-250mm that would make it a 500mm F11 so you would need really bright light and up the ISO to use it.

Converters are best used on fast prime lenses.

If I may interject a semi-related question to this thread, which 1.7x TC do you use with the DA*300? The SDM works ok? How would you rate the IQ impact? thanks.

KyPainter · 08-11-2009, 11:59 AM

I have both the Tamron-F AF Tele-converter (2X Pz-AF BBAR MC7) and the Vivitar 2X Macro Focusing Teleconverter with electrical contacts but no AF. I've tried each with a variety of lenses, from modern zooms to old fast primes, and as far as I'm concerned the loss of IQ is too great to justify using them.

The *only* times I've gotten as good or better images by using a 2X teleconverter instead of just cropping or blowing up an image taken without one is when focusing on really distant small objects. I'm fairly certain the only reason for that is the added magnification allowed for more accurate focus, certainly with my eyes, maybe with the autofocus.

Of the two, the Tamron performs more consistently and provides better images. That surprised me based on what many say about the vivitar. Of course the Tamron doesn't help for close focusing and the Vivitar will let you get very close with a 50mm on it.

Marc Sabatella · 08-11-2009, 01:02 PM

Not only do you lose two stops of light with a 2X TC - thus making the lens f/11 at best, and effectively disabling AF - you also lose quite a bit of IQ with most TC's. You're usually better off just cropping. You could also try a 500/8 mirror lens as an alternative, although with these, it's usually only *somewhat* better than cropping.

SOldBear · 08-11-2009, 01:28 PM

I have a Tamron 18-250mm (essentially the same as the Pentax counterpart).

I also have 3 AF teleconverters: Tamron 1.4X, Pentax 1.7X, and Tamron 2X, all considered high quality.

The only TC that sort-of works with the 18-250mm is the Tamron 1.4X. Even then, at 250mm lens setting (350mm effective), the AF hunts a lot. It needs something contrasty to lock on.

There's not enough light for the 1.7X and the 2X to work.

In terms on IQ, it's better to take the photo without the TC and crop a bit more during post processing.

Teleconverters do have their place, it's just not with the 18-250mm.

Eruditass · 08-11-2009, 01:52 PM

what camera are you using and what size will you be printing at? All those megapixels are there for some significant cropping.

Marc Sabatella · 08-11-2009, 02:20 PM

Originally posted by KyPainter

The *only* times I've gotten as good or better images by using a 2X teleconverter instead of just cropping or blowing up an image taken without one is when focusing on really distant small objects. I'm fairly certain the only reason for that is the added magnification allowed for more accurate focus, certainly with my eyes, maybe with the autofocus.

That's a great observation, and actually has a lot to do with why I think I can get somewhat better results from my cheap Samyang-made Vivitar 500/8 mirror than I can by simply cropping an image from my DA50-200.

Of course, sometimes - as when birds - it's just *fun* to be able to see things bigger / "closer" in the viewfinder. I don't necessarily *need* better results than cropping to find it worthwhile. But most 2X TC's are likely to give results *worse* than cropping.

Quicksand · 08-11-2009, 04:28 PM

Originally posted by Marc Sabatella

But most 2X TC's are likely to give results *worse* than cropping.

I agree 200%. I had a 2X Vivitar Macro Focusing Teleconverter for a while, but sold it. It was OK for macro use, but as a teleconverter, my results were always inferior to just cropping -- less sharp, less contrasty.

mille19 · 08-11-2009, 11:51 PM

It's the Pentax 1.7x AF converter I use.
The SDM does not work because the AF is done in the converter.
The IQ is very good, I only use it in good light and stop down to F8.
The image attached was taken with this combo.

tr13 · 08-12-2009, 12:23 AM

I don't aggree that cropping is better.
With Telemore 2x converter (as far as I remember about $20 :-) ) I have it is not so.
I use it with 80-200m F3.5 lens. Manual focusing is pretty good.

Look here: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/69025-telemore...converter.html

Usable at F3.5 and F4, but be warned about abberations.
At F5.6 it is very-very good. At F8 it is razor sharp, and no, you can't get same results but cropping. I checked this.

08-11-2009, 10:16 AM	#1
Glen_S Senior Member Join Date: Feb 2008 Location: Alberta, Canada Photos: Gallery Posts: 105	2x converter, worth it or just get longer lens? Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. I recently purchased the Pentax 18-250 lens for my K10D, and I must say its a great every day lens. However we were out on a canoe trip the other evening and I was trying to get some closeups of some Pelicans and found I could not get as close as I wanted without spooking them. I am thinking about getting a 2X converter, but a quick search brought up a Sigma for about $300. I''m wondering if this is worthwhile or should I just put the $$ towards a longer lens. I've never used a converter before, can I expect decent pictures from it, do I lose much speed etc.? Do I need to spend $300 or can I pick up a decent one for less? I'm looking at one on ebay for about $90 - anyone here have experience with these? thanks!

08-11-2009, 11:51 PM	#14
mille19 Senior Member Join Date: Jan 2008 Photos: Gallery \| Albums Posts: 101	It's the Pentax 1.7x AF converter I use. The SDM does not work because the AF is done in the converter. The IQ is very good, I only use it in good light and stop down to F8. The image attached was taken with this combo. Attached Images

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08-11-2009, 10:22 AM	#2
tr13 Veteran Member Join Date: Jul 2009 Location: Russia Posts: 343	Don't buy cheap AF converters. Search for 7 element versions, use strings like "7 MC teleconverter pentax", "7 elements teleconverter pentax". I have recently tested not very widely known non-AF old Telemore95 II by Komura. To be short - no go with my modern lenses, and pretty good with my old fast zoom. Each teleconverter must be matched to perticular lens, so it can work ok with one and very bad with another.

08-11-2009, 10:23 AM	#3
mille19 Senior Member Join Date: Jan 2008 Photos: Gallery \| Albums Posts: 101	I use a 1.7X converter with my DA* 300mm F4 and get good results. I don't think I'd advise using a 2X with the 18-250mm that would make it a 500mm F11 so you would need really bright light and up the ISO to use it. Converters are best used on fast prime lenses.

08-11-2009, 10:26 AM	#4
bymy141 Veteran Member Join Date: Aug 2007 Photos: Gallery Posts: 1,563	Originally posted by Glen_S I recently purchased the Pentax 18-250 lens for my K10D, and I must say its a great every day lens. However we were out on a canoe trip the other evening and I was trying to get some closeups of some Pelicans and found I could not get as close as I wanted without spooking them. I am thinking about getting a 2X converter, but a quick search brought up a Sigma for about $300. I''m wondering if this is worthwhile or should I just put the $$ towards a longer lens. I've never used a converter before, can I expect decent pictures from it, do I lose much speed etc.? Do I need to spend $300 or can I pick up a decent one for less? I'm looking at one on ebay for about $90 - anyone here have experience with these? thanks! I have a Kenko 1.5X TC and the 18-250mm Tamron, the combination has lost of problems with focusing on my K10D. Manual focus is fine. - Bert

08-11-2009, 11:05 AM	#5
GerryL Veteran Member Join Date: Jan 2009 Location: CA Posts: 2,731	I'd stay away from 2X converters not unless you have very good fast lens to compensate for the light loss of using these. A 1.5X or 1.7X usually is better. The Kenko 1.5X costs $99 I think at Amazon.

08-11-2009, 11:52 AM	#6
blackcloudbrew Loyal Site Supporter Join Date: Mar 2009 Location: Cotati, California USA Photos: Gallery \| Albums Posts: 4,460	I have a kenko 1.5x and use it with my longer teles. It clearly does have focusing problems as in low light it hunts more. However, the manual clearly says that below f4 this will happen and it does. I use it with my DA 55-300 and have used it with my DA 17-70 SDM just fine. As was said above, in manual focus it's just fine. Frankly, I haven't tried in on my Tamron 18-250 but that seems like too much range for a t/c.

08-11-2009, 11:52 AM	#7
imtheguy Site Supporter Join Date: Mar 2009 Location: Virginia Beach Photos: Gallery \| Albums Posts: 2,950	Originally posted by mille19 I use a 1.7X converter with my DA* 300mm F4 and get good results. I don't think I'd advise using a 2X with the 18-250mm that would make it a 500mm F11 so you would need really bright light and up the ISO to use it. Converters are best used on fast prime lenses. If I may interject a semi-related question to this thread, which 1.7x TC do you use with the DA*300? The SDM works ok? How would you rate the IQ impact? thanks.

08-11-2009, 11:59 AM	#8
KyPainter Forum Member Join Date: Oct 2007 Location: Owensboro, Kentucky Posts: 69	I have both the Tamron-F AF Tele-converter (2X Pz-AF BBAR MC7) and the Vivitar 2X Macro Focusing Teleconverter with electrical contacts but no AF. I've tried each with a variety of lenses, from modern zooms to old fast primes, and as far as I'm concerned the loss of IQ is too great to justify using them. The only times I've gotten as good or better images by using a 2X teleconverter instead of just cropping or blowing up an image taken without one is when focusing on really distant small objects. I'm fairly certain the only reason for that is the added magnification allowed for more accurate focus, certainly with my eyes, maybe with the autofocus. Of the two, the Tamron performs more consistently and provides better images. That surprised me based on what many say about the vivitar. Of course the Tamron doesn't help for close focusing and the Vivitar will let you get very close with a 50mm on it.

08-11-2009, 01:02 PM	#9
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Not only do you lose two stops of light with a 2X TC - thus making the lens f/11 at best, and effectively disabling AF - you also lose quite a bit of IQ with most TC's. You're usually better off just cropping. You could also try a 500/8 mirror lens as an alternative, although with these, it's usually only somewhat better than cropping.

08-11-2009, 01:28 PM	#10
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	I have a Tamron 18-250mm (essentially the same as the Pentax counterpart). I also have 3 AF teleconverters: Tamron 1.4X, Pentax 1.7X, and Tamron 2X, all considered high quality. The only TC that sort-of works with the 18-250mm is the Tamron 1.4X. Even then, at 250mm lens setting (350mm effective), the AF hunts a lot. It needs something contrasty to lock on. There's not enough light for the 1.7X and the 2X to work. In terms on IQ, it's better to take the photo without the TC and crop a bit more during post processing. Teleconverters do have their place, it's just not with the 18-250mm.

08-11-2009, 01:52 PM	#11
Eruditass Veteran Member Join Date: Jul 2009 Photos: Gallery Posts: 2,207	what camera are you using and what size will you be printing at? All those megapixels are there for some significant cropping.

08-11-2009, 02:20 PM	#12
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by KyPainter The only times I've gotten as good or better images by using a 2X teleconverter instead of just cropping or blowing up an image taken without one is when focusing on really distant small objects. I'm fairly certain the only reason for that is the added magnification allowed for more accurate focus, certainly with my eyes, maybe with the autofocus. That's a great observation, and actually has a lot to do with why I think I can get somewhat better results from my cheap Samyang-made Vivitar 500/8 mirror than I can by simply cropping an image from my DA50-200. Of course, sometimes - as when birds - it's just fun to be able to see things bigger / "closer" in the viewfinder. I don't necessarily need better results than cropping to find it worthwhile. But most 2X TC's are likely to give results worse than cropping.

08-11-2009, 04:28 PM	#13
Quicksand Pentaxian Join Date: Apr 2008 Location: Central Ohio (formerly SF Bay Area) Posts: 1,519	Originally posted by Marc Sabatella But most 2X TC's are likely to give results worse than cropping. I agree 200%. I had a 2X Vivitar Macro Focusing Teleconverter for a while, but sold it. It was OK for macro use, but as a teleconverter, my results were always inferior to just cropping -- less sharp, less contrasty.

08-12-2009, 12:23 AM	#15
tr13 Veteran Member Join Date: Jul 2009 Location: Russia Posts: 343	I don't aggree that cropping is better. With Telemore 2x converter (as far as I remember about $20 :-) ) I have it is not so. I use it with 80-200m F3.5 lens. Manual focusing is pretty good. Look here: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/69025-telemore...converter.html Usable at F3.5 and F4, but be warned about abberations. At F5.6 it is very-very good. At F8 it is razor sharp, and no, you can't get same results but cropping. I checked this.