Extension tube - One more question

Canon EF 17-40mm f/4.0L USM

09/25/2006 04:48:32 PM · #1

I can't seem to find a straight answer to this question:

I have a 105mm macro lens that gets 1:1 macro. If I use a 27.5 extension tube on this lens, will I get "better" than 1:1? I don't need exact numbers, just need to know how the tube will work on my 105.

Thanks,

KenSkid

Ecce_Signum

Canon EOS-5D Mark II

09/25/2006 05:00:29 PM · #2

Yes, you will get a higher magnification (able to focus closer)but, you will lose dof (think low single figure mm's).

09/25/2006 05:06:54 PM · #3

yes
maybe
it depends -- from my PB-6 manual (bellows) extention starts at 48mm-208mm for 1:2-2:1 (1/2-2x) for a 105/f4 macro
and 1/6-1/1.1 for 105/f2.5 (133mm-208mm)

what you have to do is try it ;)

09/25/2006 05:13:18 PM · #4

reproduction ratio= extention/focal length
(for lenses focused at infinity)
again from the bellows manual ..

Canon EF 17-40mm f/4.0L USM

09/25/2006 05:20:12 PM · #5

So....my 105mm macro will gain .26?

27.5/105= .261

So does this mean 1:1.261 in place of 1:1 ?

1/4 gain in mag is fine with me for this cheap tube...

Skid

Originally posted by ralph:

reproduction ratio= extention/focal length
(for lenses focused at infinity)
again from the bellows manual ..

Ecce_Signum

Canon EOS-5D Mark II

09/25/2006 05:31:16 PM · #6

or, you could reverse a 50mm lens on your 105 and go EXTREME!

09/25/2006 05:46:01 PM · #7

Funny you should say that. Over the weekend I was experimenting with my old Canon 1.4 50mm lens "handheld" over the 105mm. Was too complicated "holding" the lens but managed to get a few shots. Here is one....what do you thing the mag is on something like that?

Skid

Edit: Do you have any other shots?

Originally posted by Ecce Signum:

or, you could reverse a 50mm lens on your 105 and go EXTREME!

Message edited by author 2006-09-25 17:46:46.

09/25/2006 07:03:59 PM · #8

you peaked my curiousity
all at are min. focus (1:1 with no extention)
105mm ,00mm extention , side to side is 59/64th of an inch (1:1)
105mm ,20mm extention , side to side is 47/64th of an inch 1.26:1
105mm ,36mm extention , side to side is 40/64th of an inch 1.48:1
105mm ,68mm extention , side to side is 31/64th of an inch 1.9:1

i have not checked working distance but ir probably reduces at the same rate as the magnification

105mm + 68mm extention

Message edited by author 2006-09-25 19:05:15.

09/25/2006 07:37:54 PM · #9

Hmmm so with the ebay extension I just purchased for $25 I'll get about 1.33 : 1 when used with my 105mm....

This will be about what I'm looking for...

Thanks,

Originally posted by ralph: