Using extension tubes?

I have never used extension tubes and would appreciate feedback on
some questions I have about it.


1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?


2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?


3. What effect does using different tube lengths have?


Thanks,

Brian

"Brian Stirling" wrote in message
news
I have never used extension tubes and would appreciate feedback on
some questions I have about it.


1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?


2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?


3. What effect does using different tube lengths have?

Basically, the function of extension tubes is to allow your lens to focus
closer than it is otherwise capable. The amount of extension will effect
macro ratios differently depending on the focal length and focussing
capabilities of the lens you have mounted. The longer the lens, the more
extension you will have to add to make macro gains. Remember, too, that it
doesn't enlarge anything without you moving your rig closer to the subject.
Also, you will almost universally lose the ability to focus on infinity with
tubes in place. You'll lose light, but with TTL metering, your camera will
compensate for this.

Brian Stirling wrote in
news
1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?

A simplified description, but yes. It's not limited to normal and tele
lenses however. You can add thin tubes to wide angles for some striking
perspectives.

2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?

I am certain that someone can do the maths on this, and i am also certain
that someone ain't me ;-) However, the most prominent function of an
extension tube is the light loss, both in finder and on sensor of course.
The camera will AE and AF as Canon's tubes transmit the electrical
contacts. You don't want AF in macro photography however, better to set MF
and focus by moving your upper body slightly.

In my experience it's no point using tubes with tele lenses above, say,
200mm, if not to get better close focus. You get a great working distance
for sure, but that deattaches you from your subject, and the larger lens is
also harder to hold.

3. What effect does using different tube lengths have?

You get closer and you lose light the longer the tube.

For minimal light loss, a good close-up lens may be preferred.

"Brian Stirling" wrote in message
news
I have never used extension tubes and would appreciate feedback on
some questions I have about it.


1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?


2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?


3. What effect does using different tube lengths have?


Thanks,

Brian

OT (but still macro specific) and might not suit your purposes but would a
reversing ring (instead of an extension tube) work for you? I understand
(but have no experience doing this) that mounting a short lens (50mm
possibly) in front of a moderate tele lens can achieve very high levels of
magnification.
Good Luck
me

"Brian Stirling" wrote in message
news
I have never used extension tubes and would appreciate feedback on
some questions I have about it.


1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?


2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?


3. What effect does using different tube lengths have?


Thanks,

Brian

OT (but still macro specific) and might not suit your purposes but would a
reversing ring (instead of an extension tube) work for you? I understand
(but have no experience doing this) that mounting a short lens (50mm
possibly) in front of a moderate tele lens can achieve very high levels of
magnification.
Good Luck
me

I have never used extension tubes and would appreciate feedback on
some questions I have about it.


1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?

Kind of. Extension tube allow your lens to focus closer than designed and
therefore allow for an increased magnification


2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?

A Canon or Kenko (much cheaper just as good) tube has the following effect

Metering - The tube allows for TTL metering so you can meter as normal

Light Loss - Tubes cause light loss. How much depends on the tubes but, if
you are using TTL the meter only reads incomming light and it's already
factored in. If using a hand held meter I hope you like math. (Actually the
compensation according to the Kodak Close-Up Photo book I just opened is
less than a 1/3 of a stop.)

Magnification increases with tubes, Depth of field decreases.

Minimum focusing distance - To figure out how much closer to a subject you
can get you need to know the minimum focusing distance of the lense. I'm
going to assume the the effect on magnification and focusing distance are
equal is so than you can get 1/12 closer with a 25mm tube

Brightness of Image- You are losing light so your image will be darker by
about 1/12





3. What effect does using different tube lengths have?

More tube increase each of the above effects. To achieve 1:1 Magnification
with a 300mm lens you need 300mm of extension.

Good luck
Ray


Thanks,

Brian


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I have never used extension tubes and would appreciate feedback on
some questions I have about it.


1. As I understand it the use of extension tubes is mainly used to
convert normal and telephoto lenses to macro lenses -- is that
correct?

Kind of. Extension tube allow your lens to focus closer than designed and
therefore allow for an increased magnification


2. If I were to add a 25mm tube (Canon EF 25 II) between my camera
(Canon 1Dm2) and a 300mm lens (Canon EF 300mm /4.0) what would the
effect be on: minimum focus distance, image size, image brightness
(EV), camera function (AE/AF)?

A Canon or Kenko (much cheaper just as good) tube has the following effect

Metering - The tube allows for TTL metering so you can meter as normal

Light Loss - Tubes cause light loss. How much depends on the tubes but, if
you are using TTL the meter only reads incomming light and it's already
factored in. If using a hand held meter I hope you like math. (Actually the
compensation according to the Kodak Close-Up Photo book I just opened is
less than a 1/3 of a stop.)

Magnification increases with tubes, Depth of field decreases.

Minimum focusing distance - To figure out how much closer to a subject you
can get you need to know the minimum focusing distance of the lense. I'm
going to assume the the effect on magnification and focusing distance are
equal is so than you can get 1/12 closer with a 25mm tube

Brightness of Image- You are losing light so your image will be darker by
about 1/12





3. What effect does using different tube lengths have?

More tube increase each of the above effects. To achieve 1:1 Magnification
with a 300mm lens you need 300mm of extension.

Good luck
Ray


Thanks,

Brian


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Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.786 / Virus Database: 532 - Release Date: 10/29/2004