Correct Sequence of Teleconverters (Metering With Teleconverters)

**Lowell Goudge** · 09-18-2012, 10:07 AM

Originally posted by MMurphy37

Would just the 2x Macro Focusing Tele-Converter with the 50mm f/1.8 create and accentuate enough lens aberrations to effectively ruin a photo? What else can reduce these problems other than using a more narrow aperture? It seems with the 2xMFTC that the macro-mode looks sharp as far as I can I tell, but when used in "normal" mode I can see a slight but noticeable reduction in sharpness. Could there possibly be an "optimal" range, where focal length, focus distance, and aperture all meet to produce an image with the least amount of any kind of distortion?

The only way to really tell would be to shoot a flat target using the macro focusing TC and then compare that to a true 100mm macro at the same target and magnification.

I have not done that yet with my macro focusing TC, and I do have an SMC-M 100/4 macro as well as an M 50/2 to compare apples and apples

desertscape · 09-18-2012, 12:51 PM

You would probably be better off using a 100mm lens with tubes instead of trying to use your 50 with 2x.

MMurphy37 · 09-18-2012, 02:33 PM

Originally posted by desertscape

You would probably be better off using a 100mm lens with tubes instead of trying to use your 50 with 2x.

Probably, but this is a good learning experience. If I can learn how to avoid the effects of lens aberration on a TC, I'll do much better without one.

For my Pentax, I have 3 extension tubes. Would these produce and accentuate lens aberrations as well? What about the use of longer focal length lenses?

**baro-nite** · 09-18-2012, 03:36 PM

Originally posted by MMurphy37

If I can learn how to avoid the effects of lens aberration on a TC

You can reduce CA by stopping down. Lens distortion is inherent in the lens (or lens/TC combination).

Originally posted by MMurphy37

I have 3 extension tubes. Would these produce and accentuate lens aberrations as well?

I'm pretty sure the answer is no, other than the magnification that comes from adding extension. That is, you won't be introducing new aberrations, as you may with a TC.

desertscape · 09-18-2012, 05:20 PM

Yes, stopping down will reduce longitudinal chromatic but it will not reduce lateral chromatic. A really good converter will be corrected well for each and will not add them but an average converter could easily. I use the 1.4X converter from Pentax for their 6x7 and it is a great one; no image degradation.

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09-18-2012, 10:07 AM	#16
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,892	Originally posted by MMurphy37 Would just the 2x Macro Focusing Tele-Converter with the 50mm f/1.8 create and accentuate enough lens aberrations to effectively ruin a photo? What else can reduce these problems other than using a more narrow aperture? It seems with the 2xMFTC that the macro-mode looks sharp as far as I can I tell, but when used in "normal" mode I can see a slight but noticeable reduction in sharpness. Could there possibly be an "optimal" range, where focal length, focus distance, and aperture all meet to produce an image with the least amount of any kind of distortion? The only way to really tell would be to shoot a flat target using the macro focusing TC and then compare that to a true 100mm macro at the same target and magnification. I have not done that yet with my macro focusing TC, and I do have an SMC-M 100/4 macro as well as an M 50/2 to compare apples and apples

09-18-2012, 12:51 PM	#17
desertscape Pentaxian Join Date: Feb 2009 Location: Arizona Posts: 1,272	You would probably be better off using a 100mm lens with tubes instead of trying to use your 50 with 2x.

09-18-2012, 02:33 PM	#18
MMurphy37 New Member Join Date: Sep 2012 Posts: 21 Original Poster	Originally posted by desertscape You would probably be better off using a 100mm lens with tubes instead of trying to use your 50 with 2x. Probably, but this is a good learning experience. If I can learn how to avoid the effects of lens aberration on a TC, I'll do much better without one. For my Pentax, I have 3 extension tubes. Would these produce and accentuate lens aberrations as well? What about the use of longer focal length lenses?

09-18-2012, 03:36 PM	#19
baro-nite Loyal Site Supporter Join Date: Aug 2011 Location: North Carolina, USA Photos: Gallery \| Albums Posts: 5,295	Originally posted by MMurphy37 If I can learn how to avoid the effects of lens aberration on a TC You can reduce CA by stopping down. Lens distortion is inherent in the lens (or lens/TC combination). Originally posted by MMurphy37 I have 3 extension tubes. Would these produce and accentuate lens aberrations as well? I'm pretty sure the answer is no, other than the magnification that comes from adding extension. That is, you won't be introducing new aberrations, as you may with a TC.

09-18-2012, 05:20 PM	#20
desertscape Pentaxian Join Date: Feb 2009 Location: Arizona Posts: 1,272	Yes, stopping down will reduce longitudinal chromatic but it will not reduce lateral chromatic. A really good converter will be corrected well for each and will not add them but an average converter could easily. I use the 1.4X converter from Pentax for their 6x7 and it is a great one; no image degradation.