FA 50mm 1.4 + 2x teleconverter question

chaos83 · 04-30-2009, 10:40 PM

hi guys, while no substitute for a macro lens or extension tubes (which are not easy to work with), can a teleconverter get close to macro magnifications? realistically speaking of course.

so assuming the FA 50mm 1.4 gets 1:6.7 magnification, the teleconverter makes it 100mm 2.8 with the same MFD (minimum focusing distance) as before, correct?

how is the magnification ratio affected? doubled i.e. 1:3.35? not sure how the math will work out.

SOldBear · 04-30-2009, 11:04 PM

I may be wrong (not the last time mind you), but I don't think the mag. ratio is proportional to the effective focal length. I think it is proportional to the square root of focal length. In this case, you end up with 1: 6.7/1.4 = 1:4.7.

chaos83 · 04-30-2009, 11:10 PM

square root of focal length? then why did you divide the original magnification ratio by the maximum aperture? not sure i get that.

SOldBear · 04-30-2009, 11:18 PM

Originally posted by chaos83

square root of focal length? then why did you divide the original magnification ratio by the maximum aperture? not sure i get that.

1.4 in this case is not the max. aperture. It is the square root of 2. 100/50: you double the focal length.

chaos83 · 04-30-2009, 11:21 PM

ah ok. that makes sense now. thanks. nothing beats a dedicated macro lens i guess.

**Just1MoreDave** · 05-02-2009, 09:44 AM

Here's an interesting comparison of the D FA 100mm f2.8 macro against the Vivitar 2x Macro Focusing Teleconverter. That's a specialized TC designed for macro use with 50mm lenses.

www.jr-worldwi.de: Photography

04-30-2009, 10:40 PM	#1
chaos83 Junior Member Join Date: Jul 2008 Posts: 32	FA 50mm 1.4 + 2x teleconverter question hi guys, while no substitute for a macro lens or extension tubes (which are not easy to work with), can a teleconverter get close to macro magnifications? realistically speaking of course. so assuming the FA 50mm 1.4 gets 1:6.7 magnification, the teleconverter makes it 100mm 2.8 with the same MFD (minimum focusing distance) as before, correct? how is the magnification ratio affected? doubled i.e. 1:3.35? not sure how the math will work out.

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04-30-2009, 11:04 PM	#2
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	I may be wrong (not the last time mind you), but I don't think the mag. ratio is proportional to the effective focal length. I think it is proportional to the square root of focal length. In this case, you end up with 1: 6.7/1.4 = 1:4.7.

04-30-2009, 11:10 PM	#3
chaos83 Junior Member Join Date: Jul 2008 Posts: 32 Original Poster	square root of focal length? then why did you divide the original magnification ratio by the maximum aperture? not sure i get that.

04-30-2009, 11:18 PM	#4
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by chaos83 square root of focal length? then why did you divide the original magnification ratio by the maximum aperture? not sure i get that. 1.4 in this case is not the max. aperture. It is the square root of 2. 100/50: you double the focal length.

04-30-2009, 11:21 PM	#5
chaos83 Junior Member Join Date: Jul 2008 Posts: 32 Original Poster	ah ok. that makes sense now. thanks. nothing beats a dedicated macro lens i guess.

05-02-2009, 09:44 AM	#6
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Here's an interesting comparison of the D FA 100mm f2.8 macro against the Vivitar 2x Macro Focusing Teleconverter. That's a specialized TC designed for macro use with 50mm lenses. www.jr-worldwi.de: Photography