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Teleconverters (extenders) for Canon

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Dave Werner said:
Andrew Grant said:
Dave Werner said:
In keeping with that theme I must say that I've never used a 1.4 so
I'm not the one to ask. However with the 70-200 f4L working so
wonderfully with the 2xII (look at these new samples or the
previous batch) I can't see why a 70-200 f4L owner should settle
for only 1.4x
Click to expand...
He might want to use AF.
Click to expand...
You call a 5.6 lens on a D-30 AF? ;)

I'll take MF...
Click to expand...
Plenty of Canon lenses AF on the D30 at 5.6 without serious problems, the 100-400 IS and 28-135 IS are two common examples.
 
Yes, what I mean is that if you are not aligned well, the distance to the corners will be different than the distance to the center.

At 200mmF2.8 and a chart 12x18, the total DoF is about 1.5 inches and you will be about 14 Feet from the chart. The DoF will be about .5 inches in front to 1.0 inch behind the chart assuming you are aiming at the center of the chart.

Having looked at the math a little and playing with some string, I think you are ok if you can get the center of the lens within a couple of inches of dead center of the target (up, down, left and right). I guess if one is very careful and has a plumb bob dropped from the center of the camera the right length to just touch a line on the floor (that way you know the height is right) that is perpendicular to the target, then you could keep the tollerance as you move the camera back and forth.

I had not thought of the plumb bob trick (there are probably some equivalent simple tricks) when I made my test shots and I did not have nearly as nice a tripod as I have now.

Karl
DavidP said:
I'm assuming that you're taking a plane that's perfectly
perpendicular to the axis of the lens, at the exact focus distance,
then comparing how far each point along that plane is to the plane
of the test chart that's mounted on the wall. If the lens is
perfectly aligned, then "runout" is zero.

Is that correct?
Karlg said:
2. Unless you print the image out VERY large (say at least 2 feet
high), the average person cannot use the chart to test the outer
part of the image at wide apertures. The problem is that the DoF
is so short at say F2.8 that even a very minor alignment problem
with will "runnout" to greater than the DoF. We found this out the
hard way with people thinking they had a lens problem until others
ran a DoF calculation. DoF improves with the Square of the height
of the chart, but most people don't have printers larger than
13-inchs (many not more than 8 inches). I guess one could tape
together multiple printouts - or simply print out center portion of
the image that just covers the focus rectangles as large as
possible and tape the other targets where you want them on a wall.
Click to expand...
--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Click to expand...
--Karl
 
What you seem to be implying here is that the "plane" of critical sharpness isn't really a plane perpencidular to the lens axis, but that it's a portion of a sphere as measured from the lens "center".

In other words, are you saying this? :

Assume the test target is mounted on the wall 14 feet away, and the test target is 2' x 3' in size. This means that the upper-left-hand portion of the target is 1.8 ' from the center of the target.

And, a string from the lens "center" would be 14 feet to the center of the target, but 14.1 feet from the lens "center" to the upper-left-hand-corner of the test target, and might not be in focus depending on DOF.

Is the above what you're saying?

If so, then you are, indeed, implying that a lens doesn't bring a PLANE into proper focus, but it brings a portion of a sphere into proper focus.

That may be correct, I'm not sure. I just want to make sure that's what you're saying . . and if you can provide a link or reference that states this fact.

I had always assumed that a lens brings a PLANE into proper focus. (That plane being perpencidular to the lens axis). Perhaps that's just the simplifying assumption that's generally made.
Karlg said:
Yes, what I mean is that if you are not aligned well, the distance
to the corners will be different than the distance to the center.

At 200mmF2.8 and a chart 12x18, the total DoF is about 1.5 inches
and you will be about 14 Feet from the chart. The DoF will be
about .5 inches in front to 1.0 inch behind the chart assuming you
are aiming at the center of the chart.

Having looked at the math a little and playing with some string, I
think you are ok if you can get the center of the lens within a
couple of inches of dead center of the target (up, down, left and
right). I guess if one is very careful and has a plumb bob
dropped from the center of the camera the right length to just
touch a line on the floor (that way you know the height is right)
that is perpendicular to the target, then you could keep the
tollerance as you move the camera back and forth.

I had not thought of the plumb bob trick (there are probably some
equivalent simple tricks) when I made my test shots and I did not
have nearly as nice a tripod as I have now.
Click to expand...
--The Unofficial Photographer of The Wilkinsons http://thewilkinsons.crosswinds.net
 
For the ideal lens, the very simple fomular applies.
Let;
a be the distance to the subject from lens center
b be the distance to the focal plane
f be the focal length of the lens.
then,
1/a + 1/b = 1/f.

And this fomular doesn't contain any term for the size of the subject or size of the image. In other words, whole subject plane and the image plane is paraerell to each other.
DavidP said:
In other words, are you saying this? :

Assume the test target is mounted on the wall 14 feet away, and the
test target is 2' x 3' in size. This means that the
upper-left-hand portion of the target is 1.8 ' from the center of
the target.

And, a string from the lens "center" would be 14 feet to the center
of the target, but 14.1 feet from the lens "center" to the
upper-left-hand-corner of the test target, and might not be in
focus depending on DOF.

Is the above what you're saying?

If so, then you are, indeed, implying that a lens doesn't bring a
PLANE into proper focus, but it brings a portion of a sphere into
proper focus.

That may be correct, I'm not sure. I just want to make sure that's
what you're saying . . and if you can provide a link or reference
that states this fact.

I had always assumed that a lens brings a PLANE into proper focus.
(That plane being perpencidular to the lens axis). Perhaps that's
just the simplifying assumption that's generally made.
Karlg said:
Yes, what I mean is that if you are not aligned well, the distance
to the corners will be different than the distance to the center.

At 200mmF2.8 and a chart 12x18, the total DoF is about 1.5 inches
and you will be about 14 Feet from the chart. The DoF will be
about .5 inches in front to 1.0 inch behind the chart assuming you
are aiming at the center of the chart.

Having looked at the math a little and playing with some string, I
think you are ok if you can get the center of the lens within a
couple of inches of dead center of the target (up, down, left and
right). I guess if one is very careful and has a plumb bob
dropped from the center of the camera the right length to just
touch a line on the floor (that way you know the height is right)
that is perpendicular to the target, then you could keep the
tollerance as you move the camera back and forth.

I had not thought of the plumb bob trick (there are probably some
equivalent simple tricks) when I made my test shots and I did not
have nearly as nice a tripod as I have now.
Click to expand...
--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Click to expand...
----------------------------------------------------------------------------------- http://www.sesee.com/Photo/Galleries/Galleries.asp
 
Hello,
Has anyone compared a Canon 70-200/2.8 with the Sigma 70-200/2.8
and added the 2xII Canon to the Canon and the 2x Sigma to the Sigma ?
Has anyone images comparing both..
I'm looking for a 70-200/2.8 and extender 2x...
(looks like the best option for me as I'm not a professional)

In this forum there are a lot of messages favouring either the Canon/Sigma, so has anyone both and can provide some comparison material.. images..
Thanks for the info !
 
John,

first off, love the shots...

second, it looks like you'll be able to answer just the very question i have...

i'm shopping for the 300 f4 right now, and was wondering for your opinion on this lens... especially in low light... how does IS work with this lens and the extenders...
John MacLean Photography said:
SC said:
I would like to see some samples of this with telextenders and
maybe also compared with the 100-400IS
Click to expand...
Most of these super tele shots were taken on Fuji NHG II 800 film
w/300 f4 IS and original Canon 2X. Some may also be cropped

http://www.johnmaclean.com/costarica/costaricahome.html

http://www.johnmaclean.com/costaricaextras
--
See my used gear
http://www.johnmaclean.com/forsale
Click to expand...
 
Works very well including AF. Here are some images

http://www.photo.net/photodb/folder?folder_id=186193
Dave Werner said:
I’m hoping that with this post I can start up a thread of
lens plus teleconverter tests.

I’ve posted positive results about the specific pairing of
the 70-200 f4L and the Canon 2x II teleconverter. Since then
I’ve seen several mistaken generalizations posted relating to
my test and equally mistaken generalizations relating to a test on
the Luminous Landscape site for the 2x with a 70-200 2.8L.

Any test of a specific teleconverter with a specific lens is just
that, specific, to that pair. Just because the 70-200 f4L works
well with the 2x II does not mean that the 2x II will necessarily
work well with a 70-200 f2.8L or any other lens. Likewise if a
Canon 2x doesn’t work well with a Canon 2x 70-200 f2.8L does
not mean that it necessarily will not do a good job with some other
lens.

Lenses and converters should be evaluated as pairs. So please add
your test images to this thread and lets try to build up a good
list of combinations with test images!

I’ll start the ball rolling with a combination test of the
Canon 2x II converter on the 70-200 f4L zoom and the 200 2.8L
prime...

--
Dave Werner
Click to expand...
 
Pasha said:
John,

first off, love the shots...
Click to expand...
Thanks!
Pasha said:
second, it looks like you'll be able to answer just the very
question i have...

i'm shopping for the 300 f4 right now, and was wondering for your
opinion on this lens... especially in low light... how does IS work
with this lens and the extenders...
Click to expand...
I assume you mean the AF in low light? I was using an EOS-1n mostly on MF. It's EZ to focus either way. The IS is a dream. My buddy had the non IS 300/2X and a lot of his handheld shots suffered from shake. I exposed Fuji 800 ISO neg @ 600, and he was shooting Astia 100, sometimes exposed @ 200 and pushed +1 in E-6. So I had +1.5 - 2.5 stops of film speed, in addition to IS (2 stops) for 3.5 - 4.5 stops more safety net. I figured I'd rather have tack sharp and possibly grainy frames, than fine grain shakers!

With the 2X, I think IS is a must. It's a compromise to have a 600 f8, but it can work. Next time I visit CR I want at least a 500 f4 IS! And money grows on trees!--See my used gear http://www.johnmaclean.com/forsale
 
These are D30 test images shot with a Canon 300mm/f4.0L with and without a Canon 2X II tele-converter. Camera was tripod mounted and self timer actuated. Aperture was wide open.



The Canon 300mm f4.0L is one of the sharpest lenses I've ever tested (even wide open). The Canon 2X II doesn't degrade it much at all. (There is loss of depth of feild in the image, but look at the grass and weeds in the plane of focus.)

Please E-mail any questions directly. I haven’t been active on the forum recently, and don’t anticipate a change until things there settle down.

Good Luck!
--Dave Werner
 
I have no problem focusing with my f5.6 lens on my D30 and I had no problems even at 6.3 when I owned a sigma 28-300. In fact I have had no problems focusing with the D30 at any time and I am seriously wondering what everyone is talking about with their problems in this department.

Robus
Dave Werner said:
Andrew Grant said:
Dave Werner said:
In keeping with that theme I must say that I've never used a 1.4 so
I'm not the one to ask. However with the 70-200 f4L working so
wonderfully with the 2xII (look at these new samples or the
previous batch) I can't see why a 70-200 f4L owner should settle
for only 1.4x
Click to expand...
He might want to use AF.
Click to expand...
You call a 5.6 lens on a D-30 AF? ;)

I'll take MF...

--
Dave Werner
Click to expand...
--Robus
 
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