Extension tubes

Hi all,

I recently received an extension tube set (Kenko). I am looking forward
to getting started on a bit of macro photography.

I received a manual sheet in german that seems to contain all sorts of
exposure and magnification advice / data. Does anybody have an English
version of this, or know where I could find this information elsewhere?

Also I had found a very interesting web site with details of a basic
macro (with extension tubes) technique. How to place the flash, how to
expose correctly using the flash : f11 for 1/200 and the flash if I
remember correctly (but that is the problem I don't really remember).

I will be giving it a try this week-end. Hope somebody can help me out
so I know where to start...

Nelkahn

Nelkahn wrote:
Hi all,

I recently received an extension tube set (Kenko). I am looking
forward to getting started on a bit of macro photography.

I received a manual sheet in german that seems to contain all sorts of
exposure and magnification advice / data. Does anybody have an English
version of this, or know where I could find this information
elsewhere?

Also I had found a very interesting web site with details of a basic
macro (with extension tubes) technique. How to place the flash, how to
expose correctly using the flash : f11 for 1/200 and the flash if I
remember correctly (but that is the problem I don't really remember).

I will be giving it a try this week-end. Hope somebody can help me out
so I know where to start...

Nelkahn


I suggest starting using them without flash and using the built in
exposure meter and focus controls. Doing that should let you get started
without any other special instructions as the build in functions of your
camera should take control.

You can find books (check your local library) for charts showing the
exposure compensation required for different distances.

Have fun.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math

Hi,

I just received the Kenko set myself, I have a 90mm Tamron macro. And now
with the tubes I can also insert my Canon 2x tele converter... I have not
measured yet, but this set should give me something like more than 2,5x
magnification. However, there is so little working distance, that even in
cloudy soft light I might shadow the target. Perhaps I should just use the
tubes...

What kind of lens you have? If you have for example a 50mm lens the
situation is simple. You get perhaps something about 1,3x (correction: seems
to be 1.5x according to the table below) magnification with all the tubes. I
think there should be working distance left, but I am not sure. Never
accidently hit the target with lens when trying to achieve focus. The focus
plane can be closer than the front lens element.

Other than working distance the second problem is exposure time. When using
tubes, needed exposure increases for two reasons. The tubes make the lens
system darker and when you get closer to the target the so called effective
aperture becomes smaller. Small effective aperture is caused by target size
being small compared to the front lens element. Or something like that.
Eventually some flash system may be necessary to get results. For example
when photographing plant details even a tiny bit of wind can be a problem.

I have the paper of course, but unfortunately no scanner. The information is
very basic. There are some interesting bits. "With cameras of
through-the-lens metering and automatic exposure type it (tubes) gives
perfect coupling except when combined with electronic flash AE unit." I do
not quite know what that means, I would have thought that a TTL flash works
normally also. Later there is a bit of info about using independent flash
unit. It is very terse and I do not quite understand details of this issue.
"With Canon type of tube, be sure to attach master lens only after tube has
been properly attached to camera body." Apparently failing to do show can
cause erronous coupling resulting in exposure metering malfunction.
The listed precautions are very basic like small DOF and increased camera
shake effects. Tripod use is rightly promoted as is cable release. Mirror
lock-up is not mentioned, but I think macro photography is one of best
situations to use MLU.
One interesting note is that light entering the camera though viewfinder
will have increased effect for metering, because the tubes decrease light
amount entering through lens. I use manual mode and my head covers the
viewfinder when I am choosing the exposure, so the values will be correct.
It could be a good idea to shade the viewfinder with hand when using the
cable release...
Nikon tubes only work for AI system lenses.

The number table is just a table. I do not have the stamina to enter it all,
I give couple of examples. It talks about a normal 50mm lens with 50cm near
focus. Let take couple of 50cm focus rows.
With only 12mm tube magnification is 0.35, field coverage 6.9 X 10.3 cm,
working distance about 16cm, and exposure factor 1.8
With all tubes mag is 1.47, field coverage 1.6 X 2.4 cm, working distance
less than 5cm, and exposure factor 6.1

Some formulas and info at the end also.

There are small fragments of data in the paper which I do not understand,
but only in couple places. I have NOT included all, but have tried to
include the most useful data. Also do remember, that I have not taken a
single photo using tubes. I have only used a macro objective and tried the
tubes on it to see the effect.

So perhaps some seasoned macro expert can fine-tune the details.

Could you perhaps mail or write news about the web site you found?

--markus

"Markus Malmqvist" wrote in message
...
Hi,

I just received the Kenko set myself, I have a 90mm Tamron macro. And now
with the tubes I can also insert my Canon 2x tele converter... I have not
measured yet, but this set should give me something like more than 2,5x
magnification. However, there is so little working distance, that even in
cloudy soft light I might shadow the target. Perhaps I should just use the
tubes...


The tubes make the lens
system darker and when you get closer to the target the so called
effective
aperture becomes smaller.

Markus,

Your one statement baffles me. Yes, the extension tube affects the
effective aperture and call for more light, but the statement that the tubes
make the lens system darker makes no sense to me. From my training in
optics, I understand that the extension tubes merely allow you to move the
lenses further from the film plane than the lens' focus adjustment would
allow. Can you explain what you mean?

PSsquare

"PSsquare" wrote in message
.. .

"Markus Malmqvist" wrote in message
...
Hi,

I just received the Kenko set myself, I have a 90mm Tamron macro. And
now
with the tubes I can also insert my Canon 2x tele converter... I have
not
measured yet, but this set should give me something like more than 2,5x
magnification. However, there is so little working distance, that even
in
cloudy soft light I might shadow the target. Perhaps I should just use
the
tubes...


The tubes make the lens
system darker and when you get closer to the target the so called
effective
aperture becomes smaller.

Markus,

Your one statement baffles me. Yes, the extension tube affects the
effective aperture and call for more light, but the statement that the
tubes
make the lens system darker makes no sense to me. From my training in
optics, I understand that the extension tubes merely allow you to move the
lenses further from the film plane than the lens' focus adjustment would
allow. Can you explain what you mean?

You are correct.
I think by "darker" he simply means that the aperture is effectively
smaller...which will, of course, exhibit a "darker" image in the view-finder
(as would be true ANY time the aperture is smaller). This is no different
than a smaller aperture without tubes though...so you just increase exposure
accordingly...and...it's not "dark" as far as the final image is concerned.
Your viewfinder will still be visibly darker.

"Mark M" wrote in message
news:lgOEc.2756$876.782@fed1read07...

"PSsquare" wrote in message
.. .

"Markus Malmqvist" wrote in message
...
Hi,

I just received the Kenko set myself, I have a 90mm Tamron macro. And
now
with the tubes I can also insert my Canon 2x tele converter... I have
not
measured yet, but this set should give me something like more than
2,5x
magnification. However, there is so little working distance, that even
in
cloudy soft light I might shadow the target. Perhaps I should just use
the
tubes...


The tubes make the lens
system darker and when you get closer to the target the so called
effective
aperture becomes smaller.

Markus,

Your one statement baffles me. Yes, the extension tube affects the
effective aperture and call for more light, but the statement that the
tubes
make the lens system darker makes no sense to me. From my training in
optics, I understand that the extension tubes merely allow you to move
the
lenses further from the film plane than the lens' focus adjustment would
allow. Can you explain what you mean?

You are correct.
I think by "darker" he simply means that the aperture is effectively
smaller...which will, of course, exhibit a "darker" image in the
view-finder
(as would be true ANY time the aperture is smaller). This is no different
than a smaller aperture without tubes though...so you just increase
exposure
accordingly...and...it's not "dark" as far as the final image is
concerned.
Your viewfinder will still be visibly darker.


Yes. I thought that just calling the lens system darker would be actually
more exact than calling the aperture smaller, because with tubes the same
diaphragm opening will give darker image (= more exposure needed) than
without tubes.
I think the effective aperture phenomenon caused by subject proximity can be
seen as a separate issue even though the tubes do take away the possibility
to focus far. I admit that this is not one of the clearest issues in
photography.

--markus

Markus Malmqvist wrote:

snip

Could you perhaps mail or write news about the web site you found?


I will as soon as I find it again. That is the problem at the moment.
Somehow useful web site addresses have a very high probability of
getting lost.

Thanks for all the replies.

Daniel

In article ,
"Markus Malmqvist" writes:

Yes. I thought that just calling the lens system darker would be actually
more exact than calling the aperture smaller, because with tubes the same
diaphragm opening will give darker image (= more exposure needed) than
without tubes.
I think the effective aperture phenomenon caused by subject proximity can be
seen as a separate issue even though the tubes do take away the possibility
to focus far. I admit that this is not one of the clearest issues in
photography.

Do you mean the fact the the effective f stop reduces as you move
the lens further from the image plane?

If you had a hypothetical 50mm lens with a diameter of 25mm focused at
infinity then the f stop of the lens would be 50 / 25 = f2. Now if you
had to move the lens to be at 100mm from the film plane as you were
focusing to a subject that was very close if you re-calculated the f number
using the lens to film distance rather than focal length you get
100 / 25 = f4. You have lost 2 stops. This ties in with light fall
of due to the inverse square law.

I think this is right, it all seems logical.


--

http://www.petezilla.co.uk