400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter

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?

On Mon, 30 Aug 2004 02:24:59 GMT, wrote:

In message ,
AstroPax wrote:

On Sun, 29 Aug 2004 15:01:50 -0700, Randall Ainsworth
wrote:

You're best to avoid converters with anybody's lens.

I disagree.

Although, I will admit that less conversion is usually better.

Anyway, a Nikon TC-14EII (1.4 conversion factor) with a Nikkor VR
70-200mm f/2.8G produces satisfactory results.

For example:

http://www.xmission.com/~hound/astro...e/bald_003.htm

http://www.xmission.com/~hound/astro...golden_001.htm

Are those crops of original pixels?

If not, we can't tell anything about your TC from a shrunk-down image.
You've then shrunk away most of its effect!

Sure, I know what you mean. Sorry about that.

Anyway, with a Nikkor VR 70-200mm f/2.8 & TC-14EII @ 240mm, spot
metered and focused on the eagle's eye.

Original image is 3008x2000 (2,464KB).

Here is a 100% crop to 1280x1024, with no additional post-processing
(260KB):

http://www.xmission.com/~hound/astro...63_cropped.jpg

Original EXIF data:

http://www.xmission.com/~hound/astro...p/Dsc_0263.txt

-Astro

"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

"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

"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

"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

"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!

"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!

"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.

"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.