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#11
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wrote in message
... Compare the MTF charts. If the nikon is about half as far as the sigma is from the top of the chart, then the combo should be about equally sharp. If the MTFs are about the same, then you will go much softer with the combo. Sorry... MTF charts? |
#13
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"greg" wrote in message
news:ipwYc.262420$J06.144757@pd7tw2no... Sorry... MTF charts? MTF charts show sharpness at infinite focus. The X-direction scale is radial distance (distance from the center), while the Y-direction is pair lines per mm. The 3 lines show different contrast levels (highest contrast is the one with the highest lines per mm), but I forgot what the dashed line represents. Here's the chart for the Sigma AF 135-400 f/4.5-5.6 APO Aspherical RF, which is the lens I assume you have: http://www.photodo.com/pix/lens/mtf/SIAF13540045APO.gif And here's the chart for the Nikkor AF 80-200 f/2.8ED (2 ring version): http://www.photodo.com/pix/lens/mtf/NIAF8020028D.gif I wouldn't say that the Nikkor has 2 times the sharpness of the Sigma, but from a weight reduction point of view, the tradeoff might be acceptable if you use the TC-20E II (I remember that you have to file off a tab on the teleconvertor if you using non-AFS lenses) Aaron |
#14
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"greg" wrote in message
news:ipwYc.262420$J06.144757@pd7tw2no... Sorry... MTF charts? MTF charts show sharpness at infinite focus. The X-direction scale is radial distance (distance from the center), while the Y-direction is pair lines per mm. The 3 lines show different contrast levels (highest contrast is the one with the highest lines per mm), but I forgot what the dashed line represents. Here's the chart for the Sigma AF 135-400 f/4.5-5.6 APO Aspherical RF, which is the lens I assume you have: http://www.photodo.com/pix/lens/mtf/SIAF13540045APO.gif And here's the chart for the Nikkor AF 80-200 f/2.8ED (2 ring version): http://www.photodo.com/pix/lens/mtf/NIAF8020028D.gif I wouldn't say that the Nikkor has 2 times the sharpness of the Sigma, but from a weight reduction point of view, the tradeoff might be acceptable if you use the TC-20E II (I remember that you have to file off a tab on the teleconvertor if you using non-AFS lenses) Aaron |
#15
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"Aaron Ng" .NOSPAMau wrote in message ...
"greg" wrote in message news:ipwYc.262420$J06.144757@pd7tw2no... Sorry... MTF charts? MTF charts show sharpness at infinite focus. The X-direction scale is radial distance (distance from the center), while the Y-direction is pair lines per mm. The 3 lines show different contrast levels (highest contrast is the one with the highest lines per mm), but I forgot what the dashed line represents. These are MTF vs image height plots. Vertical coordinate is contrast, not spatial frequency. In these plots there are only small number of discrete spatial frequencies shown, each showing how the contrast at that spatial frequency varies as a function of image height. In the photodo charts the solid and dashed lines represent the sagittal and tangential directions, respectively. Brian www.caldwellphotographic.com |
#16
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"Aaron Ng" .NOSPAMau wrote in message ...
"greg" wrote in message news:ipwYc.262420$J06.144757@pd7tw2no... Sorry... MTF charts? MTF charts show sharpness at infinite focus. The X-direction scale is radial distance (distance from the center), while the Y-direction is pair lines per mm. The 3 lines show different contrast levels (highest contrast is the one with the highest lines per mm), but I forgot what the dashed line represents. These are MTF vs image height plots. Vertical coordinate is contrast, not spatial frequency. In these plots there are only small number of discrete spatial frequencies shown, each showing how the contrast at that spatial frequency varies as a function of image height. In the photodo charts the solid and dashed lines represent the sagittal and tangential directions, respectively. Brian www.caldwellphotographic.com |
#17
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"brian" wrote in message m... These are MTF vs image height plots. Vertical coordinate is contrast, not spatial frequency. In these plots there are only small number of discrete spatial frequencies shown, each showing how the contrast at that spatial frequency varies as a function of image height. In the photodo charts the solid and dashed lines represent the sagittal and tangential directions, respectively. Brian www.caldwellphotographic.com Thanks Brian! |
#18
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"brian" wrote in message m... These are MTF vs image height plots. Vertical coordinate is contrast, not spatial frequency. In these plots there are only small number of discrete spatial frequencies shown, each showing how the contrast at that spatial frequency varies as a function of image height. In the photodo charts the solid and dashed lines represent the sagittal and tangential directions, respectively. Brian www.caldwellphotographic.com Thanks Brian! |
#19
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"greg" wrote in message news:3LpYc.251265$M95.155288@pd7tw1no...
Hi folks, I have a question about quality. I have a Sigma 135-400mm f4.5-5.6 lens (it's 5.6 at over 200mm). I almost always only use this to shoot motorsports outdoors. I also have a Nikon 80-200mm f2.8 lens. Get the Simga 70-200 EX, all the 70-200 class lenses rate the same optically, and the Sigma is much better built and much less expensive than the plastic Nikon... http://www.photozone.de/2Equipment/easytxt.htm#Ztelef Also the Sigma 1.4X TC has almost no image degradation at all, using it is not noticable. The others' TC's degrade image quality dramatically, much like the Simga 2X. Also, the Sigma 80-400 OS is much sharper than the 70-200 EX at 200mm. But I'm wondering about quality or other detrimental effects of using the teleconverter. I've never used one before. Will the image sharpness, contrast, colour, etc. be comparible to the Sigma lens, or do I pay a cost besides the stops? Forget about any TC besides the Sigma 1.4X EX APO, and don't consider the Simga 2X either. Better idea is to get the Sigma 80-400 OS, it is significantly sharper than any of the above and a lot stronger. If you have to shoot at f/2.8, the Sigma 70-200 EX is the best buy, about $800 less than your lower optically rated Nikkor. |
#20
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"greg" wrote in message news:3LpYc.251265$M95.155288@pd7tw1no...
Hi folks, I have a question about quality. I have a Sigma 135-400mm f4.5-5.6 lens (it's 5.6 at over 200mm). I almost always only use this to shoot motorsports outdoors. I also have a Nikon 80-200mm f2.8 lens. Get the Simga 70-200 EX, all the 70-200 class lenses rate the same optically, and the Sigma is much better built and much less expensive than the plastic Nikon... http://www.photozone.de/2Equipment/easytxt.htm#Ztelef Also the Sigma 1.4X TC has almost no image degradation at all, using it is not noticable. The others' TC's degrade image quality dramatically, much like the Simga 2X. Also, the Sigma 80-400 OS is much sharper than the 70-200 EX at 200mm. But I'm wondering about quality or other detrimental effects of using the teleconverter. I've never used one before. Will the image sharpness, contrast, colour, etc. be comparible to the Sigma lens, or do I pay a cost besides the stops? Forget about any TC besides the Sigma 1.4X EX APO, and don't consider the Simga 2X either. Better idea is to get the Sigma 80-400 OS, it is significantly sharper than any of the above and a lot stronger. If you have to shoot at f/2.8, the Sigma 70-200 EX is the best buy, about $800 less than your lower optically rated Nikkor. |
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