Extension tubes & close focus distance?

[thisisengland]

What is the ideal focal length to use an extension tube with for macro photography?

I have been offered an old 135mm SLR lens all manual controls and wondering if the focal length of that is too much for close up work as the close focus distance is 1.3m ? So far I have only tried macro with my kit lens.

Also, what are the benefits of using macro mode on my DLSR (Nikon D3000) as opposed to just setting it on manual mode?

 

[Brachytron]

There is no "ideal" focal length for use with tubes - it depends on what magnification you want. If you use the 135mm lens, you will need 135mm tube to get lifesize (1:1) magnification. It is easier to achieve 1:1 if you use a 50mm lens as you then only need 50mm extension tubes. However, you will be very close to your subject and lighting may be an issue. Let us know what you want to achieve.

 

[thisisengland]

Hi Brachytron thanks for the reply.
I am looking to do some indoor macro work and a bit of outdoor nature macro from time to time, but I think most of the macro stuff I try will be done indoors.
I have a ring flash so hopefully that will be able to provide the extra light needed? I think going by what you said, a 50mm lens would be better for me then as 135mm extension tubes is probably going to be expensive and erm....very long

I will get looking on ebay for an old manual 50mm lens....will old Nikon lenses fit a modern Nikon DLSR?

 

[vaizki]

The extension tube math (grossly simplified) goes like this:

Extra magnification = tube length / lens focal length.

So for example I have a Canon FD 50mm/3.5 Macro which offers 1:2 maximum magnification, with a 25mm tube I get 50:25=1/2 more for a total of 1:1 (lifesize). Similarly 100mm of tubes would give 2:1 more for a 2.5:1 super magnification.

The maximum magnification of your lens can be checked on it's specs. There's also a lot of light falloff and exposure compensation math but your DSLR will take care of all of that. When you use old manual focus lenses on tubes, you can use adaptors to fit almost any system lens to any body (as there's no electronics, just light passing through).

Not a Nikon man myself but I'd imagine a 55mm f/3.5 Micro would be something to look at on ebay etc.