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greg 08-29-2004 07:02 PM

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

I'm considering selling the Sigma lens, and buying a Nikon TC-20E II
teleconverter (the money should be comparible). This would, effectively,
turn the Nikon lens to a 160-400mm f5.6 lens for those times I need a longer
lens. One less heavy lens to schlump around the track, and from a strict
numbers point of view, it should give me the same lens length and speed as
the Sigma.

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?

Thanks in advance!
Greg



Randall Ainsworth 08-29-2004 10:01 PM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
In article <3LpYc.251265$M95.155288@pd7tw1no>, greg <john@smith.com>
wrote:

> 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.


You have my deepest sympathy.

> I'm considering selling the Sigma lens, and buying a Nikon TC-20E II
> teleconverter (the money should be comparible). This would, effectively,
> turn the Nikon lens to a 160-400mm f5.6 lens for those times I need a longer
> lens. One less heavy lens to schlump around the track, and from a strict
> numbers point of view, it should give me the same lens length and speed as
> the Sigma.


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

Fred McKenzie 08-29-2004 10:17 PM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
<< Will the image sharpness,
contrast, colour, etc. be comparible to the Sigma lens, or do I pay a cost
besides the stops? >>

Greg-

Of course you pay a cost. The question is whether that cost results in
acceptable images compared to images from the Sigma lens. It could go either
way.

Do you use the Sigma at maximum zoom most of the time? If not, then use of the
Nikon alone may meet most of your needs and probably produce better images.
Use of the teleconverter would then be an option.

Fred


AstroPax 08-29-2004 10:40 PM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
On Sun, 29 Aug 2004 15:01:50 -0700, Randall Ainsworth
<rag@nospam.techline.com> 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

-Astro


JPS@no.komm 08-30-2004 12:15 AM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
In message <3LpYc.251265$M95.155288@pd7tw1no>,
"greg" <john@smith.com> wrote:

>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?


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.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><


JPS@no.komm 08-30-2004 02:24 AM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
In message <nam4j0h0qdp7de9f3gbklcg842lr3uerl8@4ax.com>,
AstroPax <astro@skiutahlocals.com> wrote:

>On Sun, 29 Aug 2004 15:01:50 -0700, Randall Ainsworth
><rag@nospam.techline.com> 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!
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><


greg 08-30-2004 02:37 AM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
<JPS@no.komm> wrote in message
news:7bs4j0h3vhes1oke061gonlutdfa85mjno@4ax.com...
>
> 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?



AstroPax 08-30-2004 03:24 AM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
On Mon, 30 Aug 2004 02:24:59 GMT, JPS@no.komm wrote:

>In message <nam4j0h0qdp7de9f3gbklcg842lr3uerl8@4ax.com>,
>AstroPax <astro@skiutahlocals.com> wrote:
>
>>On Sun, 29 Aug 2004 15:01:50 -0700, Randall Ainsworth
>><rag@nospam.techline.com> 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


Aaron Ng 08-30-2004 06:05 AM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
"greg" <john@smith.com> 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



brian 08-30-2004 01:18 PM

Re: 400mm f5.6 lens vs 200mm f2.8 lens with 2x teleconverter
 
"Aaron Ng" <aaronNOSPAM.ngNO@SPAMstudent.NOunswSPAM.eduNOSPAM .NOSPAMau> wrote in message news:<cgufc6$gc6$1@tomahawk.unsw.edu.au>...
> "greg" <john@smith.com> wrote in message
> news:ipwYc.262420$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


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