Extension Tubes

Rogerdodge · Post by **Rogerdodge** » Thu Jun 21, 2007 5:38 pm

I have looked a little bit on the web for this, but am still a bit confused.
So, here's hoping that we have a knowledgable person on this group who can help.
I am thinking about getting a set of extension tubes to use with my 180mm macro lens (1:1 magnification on 35mm), the lengths are - 35, 20 & 12 mm.
So, what effect will these have, singly and combined, on the magnification factor?
Is there a calculation for this?
I am hoping for 5:1 or bigger (yes - I will be using flash and a tripod!)
Thanks
Roger Harding

Chris · Post by **Chris** » Fri Jun 22, 2007 3:31 pm

Roger,

The magnification factor of a lense can be determined using the equation:

Magnification = Extension/Focal Length

So your 180mm lens already has a built in extension of 180mm (using crafty optics) to achieve 1:1 reproduction. So using your rings, you can increase the extension to 192mm, 200mm, 212mm, 215mm, etc... to a maximum of 247mm.

This would give a maximum magnification of 247/180 = 1.37:1

Theoretically, you would need 720mm additional tubes to achieve 5:1. Practically, I think this would be impossible as the minimum focussing distance would get nearer and nearer to 0.

To achieve 5x magnification, you're better off starting with a shorter lens and bellows... sorry, I hope I'm wrong!
Regards,

Chris

Rogerdodge · Post by **Rogerdodge** » Fri Jun 22, 2007 4:28 pm

No - you are right!
My calculations also told me that there was a 'built in extension' of 180mm
(bie = focal lengthXmagnification = 1x180)
However, I thoght this could not be right considering the physical length of the lens.
I thus got the same answer as you -
Long extension, loss of a couple of stops of light, and no real increase in magnification. I just hoped my calculations were wrong...........
Now...where did I put that old 50mm lens?
Thanks for your reply.
Roger

Gruditch · Post by **Gruditch** » Sun Aug 26, 2007 2:02 pm

I got a Sigma 1.4x tele converter today,( birthday boy

). And I thought I would give it a go on my Sigma 150mm f/2.8 Macro, Its a pretty good set up a 210mm Macro at f/4.

Gruditch

Denise · Post by **Denise** » Sun Aug 26, 2007 8:08 pm

Happy Birthday Gruditch.

Nice photo's.

Denise

Gruditch · Post by **Gruditch** » Mon Aug 27, 2007 6:37 am

Thanks Denise

Gruditch

Trev Sawyer · Post by **Trev Sawyer** » Mon Aug 27, 2007 11:41 am

Hey Gruditch,
It was MY birthday too!!
I may also invest some of my birthday money in a set of extension tubes, but my main present arrived 2 days early.... the Camberwell Beauty

Hope you had a good 'un!

Trev

Martin · Post by **Martin** » Mon Aug 27, 2007 1:00 pm

Keep taking shots like those and it's only a matter of time before you win the monthly competition Mr Gruditch !

Martin.

Gruditch · Post by **Gruditch** » Mon Aug 27, 2007 4:35 pm

Cheers Trev hope you had a good one too, and thanks for your coments Martin, I was debating weather to exchange the last pic for my S S Skipper in the August comp.

Gruditch

Trev Sawyer · Post by **Trev Sawyer** » Mon Sep 17, 2007 7:31 pm

Hey Gruditch,
I've picked up a Sigma 1.4 x APO tele converter, but the Sigma 150mm APO lens is not on the list of lenses it is designed for (in the instruction sheet). Is it OK to use... the instructions say if used with the wrong lens it can damage both the lens and converter. I'm pretty sure it SHOULD be OK, but just wanted to check. Presumably it will only work on manual focus setting too.

Cheers.

Trev

Gruditch · Post by **Gruditch** » Mon Sep 17, 2007 7:49 pm

Hi Trev, it works great with the 150mm, For piece of mind check this link to the Sigma site, it says you can use the 150mm Macro with the x 1.4.

http://www.sigma-imaging-uk.com/lenses/macro/150mm.htm

Gruditch

Trev Sawyer · Post by **Trev Sawyer** » Mon Sep 17, 2007 9:07 pm

Many thanks Gruditch,
Pity the season is nearly over... I could definitely get into this photography lark

Trev

eccles · Post by **eccles** » Fri Sep 21, 2007 7:33 pm

@Roger, I don't know which camera system you have but if you have a Canon dSLR then the Canon MPE-65 seems to be the lens you want. It works from 1:1 to 5:1 but will not focus at infinity, i.e. you cannot use it for anything but close up work.

Rogerdodge · Post by **Rogerdodge** » Sun Sep 23, 2007 5:34 pm

The MPE-65 is on my wish list - it is a wonderous bit of kit - I already have the MT24-EX Twin Flash which just about essential with it.
Sadly it is also quite expensive - and there are other demands on my cash at the moment.
Cheers
Roger

Superfly · Post by **Superfly** » Fri Jan 25, 2008 9:32 pm

Hi all,
would the Sigma 2x tele converter also work with a sigma 150mm macro or would it become an unwieldy beast? I'm unsure whether to get the sigma 150 and try with teleconverters or whether to try extension tubes on my canon 28-135mm EF IS. Don't know if this will allow me to go tripod free or whther the IS is knocked out by the extension tubes. My wife has just read this and accused me of being a nerd. Any ideas? (on the lens gear, not the wife!!)

Martin · Post by **Martin** » Fri Jan 25, 2008 9:49 pm

Is should work with extension tubes, it certainly does with my Canon100-400 IS and Jessops tubes...and it is definitely the cheaper of the two options.

Martin.

Superfly · Post by **Superfly** » Fri Jan 25, 2008 10:04 pm

Thanks Martin,
I have just bought some on ebay for £55 which is much kinder on the ol' wallet!

Steve

Gruditch · Post by **Gruditch** » Sat Jan 26, 2008 7:31 am

The x2 converter will not work with the Sigma 150mm, not sure why but it don't

Gruditch

Extension Tubes

Extension Tubes

Re: Extension Tubes