DIFFERENCE BETWEEN ORDINARY ZOOM AND TELECONVERTER LENS

Wolfgang Weisselberg wrote:


You can combine teleconverters for even more degraded images.

-Wolfgang

Not always.

I have the Nikon 14-E II and the 20-E II (I think that is their part
numbers) which are the 1.4x and 2x for the AF-S series of lenses. These
are the Nikon lenses that focus rapidly using motors in the lens, rather
than the camera body.

You can not physically mount the two teleconverters together. Either
teleconverter will mount on the reasonably expensive 70-200 f/2.8 AF-S
IF-ED VR lens I have, but neither teleconverter will mount on the other.
Nor can these teleconverters be used on all AF-S lenses - they only work
on the long(ish) telephotos.

Focusing is slightly slower on the 1.4x than on the zoom, but the 2x is
quite noticably slower. This is using the latest pro-spec F6 body.

Nikon also do a 1.7x for this series of lenses.

wrote:

AF with TCs is generally unusable, and will make you lose shots due to
futile hunting. I always use MF with TCs. I only use AF when it
outperforms me. On my 10D, I would use MF even without a TC for 300mm+.

I wonder how you find 'focussed' in these situations.

I cannot see 'in focus' on the viewwer without split screen,
I can only see 'badly out of focus'. And guessing ranges does
not work for me ...

-Wolfgang

wrote:
Wolfgang Weisselberg wrote:

You can combine teleconverters for even more degraded images.

With some lenses, a 2x and 1.4x stacked are still limited mainly by the
sensor (probably completely with a D30 or 1D). The Canon 300mm f2.8L IS
and 500mm f4L are two examples.

Do you refer to AF (of which I know --- and which at least in
the case of Canon can reportedly sometimes be tricked to work
somewhat with a 3rd party teleconverter) or to something else I
am missing completely?

-Wolfgang

wrote:
Wolfgang Weisselberg wrote:

You can combine teleconverters for even more degraded images.

With some lenses, a 2x and 1.4x stacked are still limited mainly by the
sensor (probably completely with a D30 or 1D). The Canon 300mm f2.8L IS
and 500mm f4L are two examples.

Do you refer to AF (of which I know --- and which at least in
the case of Canon can reportedly sometimes be tricked to work
somewhat with a 3rd party teleconverter) or to something else I
am missing completely?

-Wolfgang

In message ,
Wolfgang Weisselberg wrote:

wrote:

AF with TCs is generally unusable, and will make you lose shots due to
futile hunting. I always use MF with TCs. I only use AF when it
outperforms me. On my 10D, I would use MF even without a TC for 300mm+.

I wonder how you find 'focussed' in these situations.

Think least less-focused. The same principal as with anything that
doesn't snap into perfection; feel how wide the useful band is, travel
from one edge to the other, and then backtrack half-way.

I cannot see 'in focus' on the viewwer without split screen,
I can only see 'badly out of focus'. And guessing ranges does
not work for me ...

I don't know how much telephoto work you've done, but "guessing" is only
for wide lenses. The DOF at 20 feet with a 300mm lens is shallow enough
that a couple of inches off can mean total lack of focus.
--


John P Sheehy

In message ,
Wolfgang Weisselberg wrote:

wrote:
Wolfgang Weisselberg wrote:

You can combine teleconverters for even more degraded images.

With some lenses, a 2x and 1.4x stacked are still limited mainly by the
sensor (probably completely with a D30 or 1D). The Canon 300mm f2.8L IS
and 500mm f4L are two examples.

Do you refer to AF (of which I know --- and which at least in
the case of Canon can reportedly sometimes be tricked to work
somewhat with a 3rd party teleconverter) or to something else I
am missing completely?

I don't expect any lens to autofocus well with a TC. I consider manual
focus a given with a TC. If one autofocuses well with a TC, that's a
plus, but borderline cases can be extremely frustrating; you could point
the camera at something contrasty in the sun and get good focus, then
point it in the shade and it hunts the wrong extreme and then stops, and
your subject has moved or changed. Most of the worst experiences I have
ever had behind a camera were lost shots because the lens was in AF
mode, but went the wrong way, or the image *WAS* in focus, but the
braindead camera couldn't recognize this fact, and the shutter wouldn't
trip.
--


John P Sheehy

Wolfgang Weisselberg wrote:

wrote:

Wolfgang Weisselberg wrote:


You can combine teleconverters for even more degraded images.


With some lenses, a 2x and 1.4x stacked are still limited mainly by the
sensor (probably completely with a D30 or 1D). The Canon 300mm f2.8L IS
and 500mm f4L are two examples.


Do you refer to AF (of which I know --- and which at least in
the case of Canon can reportedly sometimes be tricked to work
somewhat with a 3rd party teleconverter) or to something else I
am missing completely?

-Wolfgang

It appears that JPS is refering to image quality and not AF performance
as such.
That stacking a 2x and a 1.4x TC doesn't degrade the image (sharpness
and colour fringing, I suppose) enough to show on a D30 or 1D and
nothing about how it affects the AF at all.
My film SLR (a Minolta XG2) is MF only anyway, so I only notice that the
viewfinder becomes slightly darker when using a TC.
The AE still works fine, it even works fine with uncoupled lenses that
are/can be focused stopped-down.

Wolfgang Weisselberg wrote:

wrote:

Wolfgang Weisselberg wrote:


You can combine teleconverters for even more degraded images.


With some lenses, a 2x and 1.4x stacked are still limited mainly by the
sensor (probably completely with a D30 or 1D). The Canon 300mm f2.8L IS
and 500mm f4L are two examples.


Do you refer to AF (of which I know --- and which at least in
the case of Canon can reportedly sometimes be tricked to work
somewhat with a 3rd party teleconverter) or to something else I
am missing completely?

-Wolfgang

It appears that JPS is refering to image quality and not AF performance
as such.
That stacking a 2x and a 1.4x TC doesn't degrade the image (sharpness
and colour fringing, I suppose) enough to show on a D30 or 1D and
nothing about how it affects the AF at all.
My film SLR (a Minolta XG2) is MF only anyway, so I only notice that the
viewfinder becomes slightly darker when using a TC.
The AE still works fine, it even works fine with uncoupled lenses that
are/can be focused stopped-down.

wrote:
Wolfgang Weisselberg wrote:
wrote:

AF with TCs is generally unusable, and will make you lose shots due to
futile hunting. I always use MF with TCs. I only use AF when it
outperforms me. On my 10D, I would use MF even without a TC for 300mm+.

I wonder how you find 'focussed' in these situations.

Think least less-focused. The same principal as with anything that
doesn't snap into perfection; feel how wide the useful band is, travel
from one edge to the other, and then backtrack half-way.

Hmmm .... then it's for (semi)static targets only ...

I cannot see 'in focus' on the viewwer without split screen,
I can only see 'badly out of focus'. And guessing ranges does
not work for me ...

I don't know how much telephoto work you've done, but "guessing" is only
for wide lenses. The DOF at 20 feet with a 300mm lens is shallow enough
that a couple of inches off can mean total lack of focus.

That's why guessing doesn't work for me. :-)

Actually, it does not even work for me for P&S cameras and their
huge DoF.

-Wolfgang