Canon 1.4 extendor

Archived from groups: rec.photo.digital.slr-systems (More info?)

Folks
anyone here have experience with the Canon 1.4 extender on a 70 200 F4 L
series lens. Interested in any reduction in autofocus speed or image
degradation on a Canon 20D.

regards

--
Don From Down Under

Archived from groups: rec.photo.digital.slr-systems (More info?)

Wilt, thanks but what about image degradation?

regards

Don
"wilt" <wiltw@aol.com> wrote in message
news:1125621682.089350.243660@f14g2000cwb.googlegroups.com...
>I have the 70-200 f/4L and the 1.4x II, and there is no perceivable
> change in speed of autofocus
>

Archived from groups: rec.photo.digital.slr-systems (More info?)

Just copied from a web site for Canon DSLR...

"It is important to understand that the use of a teleconverter is
subject to a number of conditions, including the following.


1: T-cons can not be used with all lenses. Only the lenses listed in
the charts will physically "fit" the T-cons. If it's not listed. It
won't "FIT".
2: T-cons will decrease the effective aperture of any lens to which it
is attached.
3: In many cases, the increased f/stop will result in a loss of
Autofocus.
In some cases, the use of a T-con will result in use of only the center
AF point for autofocus.
4. Additionally, EF Extenders reduce lens drive speed. The EF 1.4x or
1.4x II reduces lens drive speed by approximately 50~67% depending on
the lens in use.
The EF 2x or 2x II reduces lens drive speed by up to approximately 75%.

This speed reduction gives the AF system more time to detect focus.
This can be helpful since the depth of focus is reduced with the longer
effective focal length and the chance of defocus increases. However,
the reduced tracking speed and smaller maximum apertures caused by the
use of Extenders can be a disadvantage with fast moving subjects,
particularly in low light.
5. T-cons WILL degrade the final image quality f the lens in use.

(the degree to which this is perceptible varies depnding on the lens
with which it is used)"

Archived from groups: rec.photo.digital.slr-systems (More info?)

In message <1125672364.501256.150900@g44g2000cwa.googlegroups.com>,
"wilt" <wiltw@aol.com> wrote:

>Don,
> I can try to run a test this weekend to characterize. But keep in
>mind that any extender takes the fundamental primary lens resolution
>and simply magnifies it (I'm sure some expert in lens optics will tell
>us that statement is not exactly true necessarily) so that the same
>image is merely spread out at the focal plane into a higher amount of
>sensor (or film) for the same subject.

Whether or not it is worth using depends on the difference between lens
resolution and medium resolution, as well as anti-aliasing properties
for digital.

If you're shooting ISO 3200 film, the grain is so coarse that you could
probably stack two TCs, even on a medium-quality lens, and still see
more detail. Same would apply with something like a Sigma DSLR; the
pixel pitch is so coarse that a TC is very likely to grab more detail.
The original Canon 1D, even moreso. Fine-grain B&W film or low-ISO slide
film or a Canon 1DsII or Nikon D2X with their fine pixel pitch will have
less room for useful magnification. Of course, it all depends on what
you plan to do with the images as well; If you're just rattling off
low-MP JPEGs for someone who isn't going to do any cropping from
full-res pictures, then you can use TCs to greater effect as well.

You also lose lots of light with TCs, and that, indirectly, can force
poor images (motion blur, under-exposure, poor wide-open optics or too
little DOF). In fact, the minimum hand-holdable shutter speed will also
be magnified with the TC. If you can hand-hold a 200mm lens at 1/320,
you're going to need 1/500 with a 1.4x TC, so you lose even more light
than the 1.4 squared would imply, in low-light, hand-held situations.

I use a 2x TC frequently with my 100-400L IS. The makes the widest
f-stop f/11, and I don't like shooting at anything slower than 1/640,
even with the IS. On a cloudy day, even at ISO 1600 this can lead to
gross under-exposure. Images come out sharpest when all flash, or
strong flash-fill are used. The trick is to know when to use it, and
when it is best left off.
--

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

Archived from groups: rec.photo.digital.slr-systems (More info?)

In message <1125672688.339704.57930@g47g2000cwa.googlegroups.com>,
"wilt" <wiltw@aol.com> wrote:

>5. T-cons WILL degrade the final image quality f the lens in use.
>
>(the degree to which this is perceptible varies depnding on the lens
>with which it is used)"

It also depends on the resolution of the medium. The coarseness of
grain and pixel pitch varies about as much as lens resolution varies.
--

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

Archived from groups: rec.photo.digital.slr-systems (More info?)

<So a 2X convertor on a
100mm f/2.8 lens makes it into 200mm f/4 lens. >

I meant to write: "100mm f/2.8 lens makes it into 200mm f/5.6 lens"
(doh)

Archived from groups: rec.photo.digital.slr-systems (More info?)

Dave

thanks, and to all others also for comments etc. Became a bit superfluous
as I was unable to purchase one for this weekend to shoot as I was hoping.

regards

Don
"Dave R knows who" <kilbyfan@spamnotAOL.com> wrote in message
news:yn3Se.11735$p%3.46901@typhoon.sonic.net...
>
> "Don" <mackie.don@bigpond.com> wrote in message
> newsjARe.18796$FA3.9498@news-server.bigpond.net.au...
>> Folks
>> anyone here have experience with the Canon 1.4 extender on a 70 200 F4 L
>> series lens. Interested in any reduction in autofocus speed or image
>> degradation on a Canon 20D.
>>
>
> Great cobmination. Very little image degradation (nothing a little USM
> can't help most of the time). I never noticed any speed diff with the
> 1.4x on that lens. On my 100-400mm I noticed the 1.4x slowed it down a
> bit on a 1D.
>

Archived from groups: rec.photo.digital.slr-systems (More info?)

<JPS@no.komm> wrote:

> In message <1125672688.339704.57930@g47g2000cwa.googlegroups.com>,
> "wilt" <wiltw@aol.com> wrote:
>
> >2: T-cons will decrease the effective aperture of any lens to which it is
> >attached.
>
> Did they literally say that? That is not correct; a TC does not alter
> maximum aperture; it alters minimum f-stop.

It doesn't change the aperture, but it does decrease the effective
aperture. Just like they said. :-)

Archived from groups: rec.photo.digital.slr-systems (More info?)

In message <1h2bj1w.1xd3k6b1h7q5shN%usenet@mile23.c0m>,
usenet@mile23.c0m (Paul Mitchum) wrote:

><JPS@no.komm> wrote:
>
>> In message <1125672688.339704.57930@g47g2000cwa.googlegroups.com>,
>> "wilt" <wiltw@aol.com> wrote:
>>
>> >2: T-cons will decrease the effective aperture of any lens to which it is
>> >attached.
>>
>> Did they literally say that? That is not correct; a TC does not alter
>> maximum aperture; it alters minimum f-stop.
>
>It doesn't change the aperture, but it does decrease the effective
>aperture. Just like they said. :-)

Aperture is an absolute size, not a ratio. F-stop is a ratio.
--

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

Archived from groups: rec.photo.digital.slr-systems (More info?)

<<you insist your correctness instead of apologizing. >>

One assumes that one has offended, which I apparently have done in your
case. I did not deliberately try to offend by assaulting you
individually. And I do not think one needs to apologize, when I have
merely passed on information (which in your opinion is not correct --
but we are each entitled to have opinions...1st amendment right!). Not
everyone posts 100% facts, but posts to the best of their knowlege.
You obviously now consider my posts offensive and do not allow apparent
transgressions to pass on as 'water under the bridge', and you are
holding an apparent grudge against me for that, and continue to
criticize my posts for that. For that I am sorry. I hold no such
grudge, and hope you can let this all pass, in the interests of
peaceful information exchange rather than personal vendetta.

Archived from groups: rec.photo.digital.slr-systems (More info?)

<JPS@no.komm> wrote:

> In message <1h2bj1w.1xd3k6b1h7q5shN%usenet@mile23.c0m>, usenet@mile23.c0m
> (Paul Mitchum) wrote:
> ><JPS@no.komm> wrote:
> >> In message <1125672688.339704.57930@g47g2000cwa.googlegroups.com>,
> >> "wilt" <wiltw@aol.com> wrote:
> >>
> >> >2: T-cons will decrease the effective aperture of any lens to which it
> >> >is attached.
> >>
> >> Did they literally say that? That is not correct; a TC does not alter
> >> maximum aperture; it alters minimum f-stop.
> >
> >It doesn't change the aperture, but it does decrease the effective
> >aperture. Just like they said. :-)
>
> Aperture is an absolute size, not a ratio. F-stop is a ratio.

And since the aperture size is expressed as a ratio to the focal length,
the *effective* aperture is the size, minus the loss of light through
the teleconverter.

You're right that the language is not precise, but it's also not
incorrect.