Extension tubes

[cnhoff]

Hi,

 

i have 70-200 f4 which focuses down to 1.2m. What amount of extension

would i need to get it to focus to around half that amount or even to

50cm (about 20in)?

 

What brand would you buy, the Canon ones are damn expensive...

[dave_nelson___atlanta__ga]

I have no idea what length you would need, but the Kenko set is mighty cheap and work great for me on a 70-200 2.8L.

 

<p><a href="http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=375102&is=REG&addedTroughType=search"><u> $ 159.00 at B&H</u></a>

[darrick_coleman1]

I have the same lens (got it Thursday) and was wondering the same thing. Also, will the picture quality with using an extension be similar to using a dedicated macro lens? Does the picture quality deteriorate at all (shouldn't as it isn't passing through any extra glass)?

[paul -]

An even better bargain than the Kenko set is the <a href="http://www.adorama.com/MCAETEOS.html?searchinfo=pro%20optic%20eos&item_no=2">"Pro Optic Auto Extension Tube Set for Canon EOS" ($84.95)</a> from Adorama.

[cnhoff]

I think you don't lose picture quality but you do lose some light. Have to look that up though when i get home...

[panos_voudouris]

"Does the picture quality deteriorate at all (shouldn't as it isn't passing through any extra

glass)?"

 

It doesn't pass any glass but you are changing the characteristics of the lens, by forcing it

to focus somewhere where it normally wouldn't. So strictly speaking it does. Not sure how

much though...

[cnhoff]

I got the results here http://ca.geocities.com/lokejul/jlcalc.htm

 

Lens focuses from 0.97m-3.53m with an EF12 (12mm extension) and

from 0.79m-1.97m with an EF25 attached.

 

Thanks anyway!

[darrick_coleman1]

Does anyone have examples of pics taken through extension and through a dedicated macro lens so we can see some comparisons?

[jorge_garcia1]

Some macro lenses have extension builded inside them.

 

It is said that adding extension produces more difraction but no other quality loss.

 

Regards

[mark_chappell]

<I>i have 70-200 f4 which focuses down to 1.2m. What amount of extension would i

need to get it to focus to around half that amount or even to 50cm (about 20in)</i><P>

 

Depends entirely on the focal length -- the longer the focal length, the more the

extension that will be needed. I've used that lens for close-ups with extension tubes (as

for most of <A HREF="http://biology.ucr.edu/personal/MACphotos/mammals/

deermouse.html"> these deer mice images</a> but you should also consider something

like the 500D close-up lens, which reduces focus distance to about 0.5 meters. With that,

the lens stays in focus as you zoom -- completely unlike when using extension tubes.<P>

 

This lens does surprisingly well for close ups, either with extension, teleconveters, 500D,

or in combination. But not quite as tack-sharp as a real macro lens.

[cnhoff]

Perhaps i have not made myself clear here.

 

I use a Nikon 6T +3 diopter for macros up to (nearly) life size with great results. What i want to do is to lower the minimum focusing distance for general shooting like e.g. John Shaw mentions it in his books.

[eosdoc]

Christian put in half the data, and so got the answer half-right. See:<BR><a href=

http://ca.geocities.com/lokejul/jlcalc.htm

>http://ca.geocities.com/lokejul/jlcalc.htm</a><BR>

<a href=

http://tinyurl.com/bcmsh

>http://www.canon.com/camera-museum/camera/lens/ef/data/ef_70~200_4l_usm.html</a><BR>

<a href=

http://www.a1.nl/phomepag/markerink/mounts.htm

>http://www.a1.nl/phomepag/markerink/mounts.htm</a>

<P>

The lens calculator uses the working distance, and not the

focus distance from the film plane. In addition, the internal

focus lens changes focal length as you focus away from infinity.

<P>

At its closest focus, the EF 70-200 longest focal length is closer

to 170mm, producing a magnification of 0.21x at a working distance

of 0.984m.

<P>

With the lens set to its longest focal length, the lens focuses

from 0.78-2.58 m with an EF12 (12mm extension) and from 0.63-1.23 m with an EF25 (27.25mm extension) attached.

Note that these are working distances, measured from the front

of the lens (front nodal point).

<P>

If you keep your zoom at the long end, you would need a ridiculous

100 mm of extension to be able to focus down to half the original. And a ludicrous 200 mm of extension to get down to

50 cm (about 20in)!

<P>

However, using the zoom at the short end makes it easier to focus

closer, amd with more magnification. Just under 50 cm with

just the EF12, and just under 25 cm with the EF25.