Extension tube on d70/rebel xt kit lens?

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

Thanks for the info! Just to clarify...are you saying that normally
the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
13mm extension tube it is reduced to 3 or 4cm...is that correct?

By the way, I have never used extension tubes before...   Do you know
if there is a ratio or some formula that can indicate what
magnification and focus distance would be attained with different
length tubes?

Thanks, Brian

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

http://www.photo.net/learn/optics/lensFAQ (et al.)

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

Hey, thanks for the additional info and the link (which after a quick
overview seems like it might take a while to get through) - very
helpful!



Brian

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

what is the focusing distance with the body cap? j/k!

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

Brian wrote:

> Hey, thanks for the additional info and the link (which after a quick
> overview seems like it might take a while to get through) - very
> helpful!

You can google up almost every optical equation under the Sun. Your
specific question is answered by adding "e/f" -- e == extension, f ==
focal length -- to the non-extended maximum magnification the lens.

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

In article <1118698036.493282.256590@f14g2000cwb.googlegroups.com>,
Brian <ripcurl187@yahoo.com> wrote:
>Thanks for the info! Just to clarify...are you saying that normally
>the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
>13mm extension tube it is reduced to 3 or 4cm...is that correct?

I believe that he means that the kit lens, mounted on the 13mm
tube and set to 70mm zoom, will focus between 35 cm (13.7") and
somewhere between 3 to 4 cm (1.18" to 1.57").

>By the way, I have never used extension tubes before...   Do you know
>if there is a ratio or some formula that can indicate what
>magnification and focus distance would be attained with different
>length tubes?

With relatively simple prime lenses (fixed focal length) you
should be able to calculate what the effective range would be. But you
would need to know just how far the focus adjustment moves the lens.
With internal focus lenses, telephotos and wide angle lenses, and
especially with zooms, there are too many things going on optically to
make it easy to predict the results. The best bet is to grab the lens
and the set of extension tubes and experiment. (Or, if you want fewer
pieces to juggle, try a bellows instead.) Hmm ... does Nikon offer a
bellows with the electrical contacts for the CPU lenses?

Enjoy,
DoN.

--
Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

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

Brian wrote:
> Anyone tried this? If so, with what level of success? (I don't have
> either [yet], but I'm thinking about the potential of maybe being able
> to use the kit lens for some macro work)?
>
> Any comments?
>
> Thanks! Brian
>
I have tried it with the D70 and 18-70 kit lens with surprisingly good
results. (I didn't think that tubes on a short zoom lens was a good
idea) One 13mm tube was all that I needed to get to about 1:2 ratio.
Using combination of zoom and focus, a 13mm tube seems to get from about
35cm to about 3 or 4 cm at 70mm.
The D70 kit lens is IF (internal focus), and does not focus anywhere
near as close as the Canon 18-55 kit lens.
If you get tubes, make sure that you get ones with the electronic
contacts so that you get metering.

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

DoN. Nichols wrote:

> In article <1118698036.493282.256590@f14g2000cwb.googlegroups.com>,
> Brian <ripcurl187@yahoo.com> wrote:
>
>>Thanks for the info! Just to clarify...are you saying that normally
>>the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
>>13mm extension tube it is reduced to 3 or 4cm...is that correct?
>
>
> I believe that he means that the kit lens, mounted on the 13mm
> tube and set to 70mm zoom, will focus between 35 cm (13.7") and
> somewhere between 3 to 4 cm (1.18" to 1.57").
>
Yes - that is correct. Zooming back below 50mm the minimum focus
distance becomes so close that it is practically unusable - and
pointless as the magnification ratio is no better than achievable at 70mm.

>>By the way, I have never used extension tubes before...   Do you know
>>if there is a ratio or some formula that can indicate what
>>magnification and focus distance would be attained with different
>>length tubes?
>
>
> With relatively simple prime lenses (fixed focal length) you
> should be able to calculate what the effective range would be. But you
> would need to know just how far the focus adjustment moves the lens.
> With internal focus lenses, telephotos and wide angle lenses, and
> especially with zooms, there are too many things going on optically to
> make it easy to predict the results. The best bet is to grab the lens
> and the set of extension tubes and experiment. (Or, if you want fewer
> pieces to juggle, try a bellows instead.) Hmm ... does Nikon offer a
> bellows with the electrical contacts for the CPU lenses?
>
AFAIK, no they don't. But, I the tubes that I have are "marumi" brand,
and it looks like they could be disassembled and the mounts with
contacts used to construct "CPU" bellows. Some creative engineering
would be needed to connect the aperture stop-down lever between the lens
mount and body mount.

For the OP, the canon 18-55 kit lens is not IF, and your paragraph above
explains why a 13mm tube would probbaly give a completely different
result on that lens. The Canon 18-55, including the so-called "mark II"
on the 350D is a very special piece of equipment. I was using one the
other day, and took some very soft shots with a 350d. For photography,
a body cap is possibly a less expensive and more useful accessory for a
Canon DSLR owner. ;-)

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

In article <1118700538.944346@ftpsrv1>,
Frederick <nomailplease@nomail.com> wrote:
>DoN. Nichols wrote:
>
>> In article <1118698036.493282.256590@f14g2000cwb.googlegroups.com>,
>> Brian <ripcurl187@yahoo.com> wrote:
>>
>>>Thanks for the info! Just to clarify...are you saying that normally
>>>the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
>>>13mm extension tube it is reduced to 3 or 4cm...is that correct?
>>
>>
>> I believe that he means that the kit lens, mounted on the 13mm
>> tube and set to 70mm zoom, will focus between 35 cm (13.7") and
>> somewhere between 3 to 4 cm (1.18" to 1.57").
>>
>Yes - that is correct. Zooming back below 50mm the minimum focus
>distance becomes so close that it is practically unusable - and
>pointless as the magnification ratio is no better than achievable at 70mm.

Which probably explains why my "28-105mm f3.5-4.5 D" Nikon lens
limits the zoom range from 50mm to 105mm when the macro mode is engaged.

>>>By the way, I have never used extension tubes before...   Do you know
>>>if there is a ratio or some formula that can indicate what
>>>magnification and focus distance would be attained with different
>>>length tubes?
>>
>>
>> With relatively simple prime lenses (fixed focal length) you
>> should be able to calculate what the effective range would be. But you
>> would need to know just how far the focus adjustment moves the lens.
>> With internal focus lenses, telephotos and wide angle lenses, and
>> especially with zooms, there are too many things going on optically to
>> make it easy to predict the results. The best bet is to grab the lens
>> and the set of extension tubes and experiment. (Or, if you want fewer
>> pieces to juggle, try a bellows instead.) Hmm ... does Nikon offer a
>> bellows with the electrical contacts for the CPU lenses?
>>
>AFAIK, no they don't. But, I the tubes that I have are "marumi" brand,
>and it looks like they could be disassembled and the mounts with
>contacts used to construct "CPU" bellows. Some creative engineering
>would be needed to connect the aperture stop-down lever between the lens
>mount and body mount.

You would also need to add something to the bellows to allow it
to compute the variable aperture loss when the lens is moved out on the
bellows. I think that really, with a bellows, you do need to stick with
a manual mode of operation.

>For the OP, the canon 18-55 kit lens is not IF, and your paragraph above
>explains why a 13mm tube would probbaly give a completely different
>result on that lens. The Canon 18-55, including the so-called "mark II"
>on the 350D is a very special piece of equipment. I was using one the
>other day, and took some very soft shots with a 350d. For photography,
>a body cap is possibly a less expensive and more useful accessory for a
>Canon DSLR owner. ;-)

A spectacular endorsement. :-)

Enjoy,
DoN.

--
Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

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

350d kit lense works well with tubes *that it fits*. The construction
allows you to add up about 70mm tubes at 35mm focal lenght without
the focus point being located inside the lense. That makes the front
almost touch the subject and gets you at 2X magnification!

The construction of the lens means a lot. For example, my Sigma
18-50/2.8 allows only 25mm at 50mm focal lenght or the front element
hits the subject.

Beware, most extention tubes do not fit EF-S lenses. EF-S lenses have
the extending plactic part at the back of the lense and it won't fit in
all extention tubes (including older canon tubes). My tubes are modified
because of that.
--
Harri

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

Brian wrote:
> Thanks for the info! Just to clarify...are you saying that normally
> the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
> 13mm extension tube it is reduced to 3 or 4cm...is that correct?
>
> By the way, I have never used extension tubes before...   Do you know
> if there is a ratio or some formula that can indicate what
> magnification and focus distance would be attained with different
> length tubes?
>
> Thanks, Brian
>
Brian,

With your lens at infinity focus and an extension of 35mm you can get to
1/2 life size. With 70mm of extension you would get life size.

Fl/extension = reproduction ratio. Use actual FL of lens!!

How close it will focus (working space) depends on focal length.

If it were me, I'd opt for one of the Nikon or Canon high-end diopter
"filters". With extension tubes you lose 1 stop of light at 1/2 life
size and 2 stops at life size. (Remember, you'll need to stop down for
depth of field), with diopters you won't lose any light.

I've seen some very nice work done with the Canon version (250D for
lenses under 200mm and 500D for over 200mm) and I'm sure the Nikons (5T
& 6T I think) would do as well, but only come in 52 and 62mm sizes.

Hope this helps,
Dave

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

>
> With your lens at infinity focus and an extension of 35mm you can get to
> 1/2 life size. With 70mm of extension you would get life size.
>
> Fl/extension = reproduction ratio. Use actual FL of lens!!

SHOULD BE Ext/Fl

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

Dave wrote:

> Brian wrote:
>
>> Thanks for the info! Just to clarify...are you saying that normally
>> the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
>> 13mm extension tube it is reduced to 3 or 4cm...is that correct?
>>
>> By the way, I have never used extension tubes before...   Do you know
>> if there is a ratio or some formula that can indicate what
>> magnification and focus distance would be attained with different
>> length tubes?
>>
>> Thanks, Brian
>>
> Brian,
>
> With your lens at infinity focus and an extension of 35mm you can get to
> 1/2 life size. With 70mm of extension you would get life size.
>
> Fl/extension = reproduction ratio. Use actual FL of lens!!
>
> How close it will focus (working space) depends on focal length.
>
> If it were me, I'd opt for one of the Nikon or Canon high-end diopter
> "filters". With extension tubes you lose 1 stop of light at 1/2 life
> size and 2 stops at life size. (Remember, you'll need to stop down for
> depth of field), with diopters you won't lose any light.
>
> I've seen some very nice work done with the Canon version (250D for
> lenses under 200mm and 500D for over 200mm) and I'm sure the Nikons (5T
> & 6T I think) would do as well, but only come in 52 and 62mm sizes.

You can also use a canon on a nikon, it doesn't matter. That's correct
that they are rated/designed for a given focal length range but that
doesn't seem very critical. I got the canon 500D +2 diopter for my 200mm
lens but here's a test on my 45mm lens:
<http://www.edgehill.net/1/?SC=go.php&DIR=California/Bay...;
Full pixels crop and looks darn sharp to me. Better than I got from the
big lens, maybe because that one is a zoom & the 45mm is a prime.

Also you may not need a large one on a long zoom because you will only
use it at full telephoto, you'd have to check that at a camera shop
before buying.


--
Paul Furman
http://www.edgehill.net/1
san francisco native plants