Extension Tubes

[shenk1]

I'm thinking about getting a set of Kenko extension tubes (12-20-36mm) to couple up with my Tamron 90mm macro lens on a Sony330 body.

Good idea or not?

Will I get auto focus etc (it says I should)?

As I'm looking at insect piccies then what macro effect will I get considering the lens is 1:1?

Last year was may first go with macro and I'm hooked but with limited funds and skill I'm trying to learn the cheap way but not so cheap they are a waste of money

Any advice is very welcome!

Cheers, shenk1

[glsammy]

I've got a set of these and they work fine.
Yes you do get the full function as they have the necessary through contacts.
One of the unexpected rules with the amount of magnification you get is that the longer the lens, the less the effects of the tubes.
The actual formula is : Total extension used / Focal length used = Magnification.
So on a 50mm lens, 25mm extension will give you 1/2X, whilst on a 100mm will only give you 1/4X.
I've used them successfully with my 400mm lens though, using it as a macro lens. Normally that lens will not focus on anything closer than 3.5mtrs. Here's a shot of a Damselfly using extension tubes:

One other point. You always lose your infinity focus once you've got them fitted, but you don't lose any image quality as there's no glass in them to degrade the image.

[Kayleigh]

I am just getting into working with a canon I have no idea how extension tubes work can someone explain the basics in a pm if you dont want it to hijack this thread but I thought it might help others who are new to this I too want to take macro shots of insect ect this summer when they wake up.

[glsammy]

Originally Posted by Kayleigh

I am just getting into working with a canon I have no idea how extension tubes work can someone explain the basics in a pm if you dont want it to hijack this thread but I thought it might help others who are new to this I too want to take macro shots of insect ect this summer when they wake up.

I thought that's what I'd done in my post.
Obviously not clearly enough!
The principle is simple. You add the tube between the camera and your lens. Not all tubes come with electrical contacts so for them, you have to work out your exposure settings yourself. The type mentioned above, do have contacts so you get the correct shutter speed and aperture settings showing as usual and the camera will meter correctly.
Tubes always reduce the minimum focus distance of the lens used, meaning you can get closer to your subject thereby getting a larger image in your picture. Often it's just best to experiment. Add a 12mm and look and see how large the in focus subject looks like. If it's not large enough, then add another one. It's quite possible to stack a complete set of tubes if you like! I tried this with my 150mm macro lens. The only problem then is that the image looks darker in your viewfinder and may be difficult to judge focus.
As I said in my first reply, you lose infinity focus, so don't expect to swing round for a shot of a flying bittern as your trying to get that close up insect.

[Kayleigh]

Originally Posted by glsammy

I thought that's what I'd done in my post.
Obviously not clearly enough!
The principle is simple. You add the tube between the camera and your lens. Not all tubes come with electrical contacts so for them, you have to work out your exposure settings yourself. The type mentioned above, do have contacts so you get the correct shutter speed and aperture settings showing as usual and the camera will meter correctly.
Tubes always reduce the minimum focus distance of the lens used, meaning you can get closer to your subject thereby getting a larger image in your picture. Often it's just best to experiment. Add a 12mm and look and see how large the in focus subject looks like. If it's not large enough, then add another one. It's quite possible to stack a complete set of tubes if you like! I tried this with my 150mm macro lens. The only problem then is that the image looks darker in your viewfinder and may be difficult to judge focus.
As I said in my first reply, you lose infinity focus, so don't expect to swing round for a shot of a flying bittern as your trying to get that close up insect.

We crossed posts Graham I only just saw this..
Thank you, I need to look at them to get a feel of what they are like its hard to imagine them.

[glsammy]

Originally Posted by Kayleigh

We crossed posts Graham I only just saw this..
Thank you, I need to look at them to get a feel of what they are like its hard to imagine them.

They are very simple tubes.
Here's a set all joined together:



You can split them into the three separate tubes.

[Kayleigh]

Originally Posted by glsammy

They are very simple tubes.
Here's a set all joined together:



You can split them into the three separate tubes.

Stupid question does the lens ie tamaron AF70-300mm fit on one end and those fit on the camera body.
Or do you need a macro lens.

[Jim Ford]

Originally Posted by Kayleigh

I am just getting into working with a canon I have no idea how extension tubes work can someone explain the basics in a pm if you dont want it to hijack this thread but I thought it might help others who are new to this I too want to take macro shots of insect ect this summer when they wake up.

Basically, the further the lens elements are away from the sensor, the nearer you can get to an object and have it in focus.

Put the camera in manual focus mode and set the lens to infinity. Now rotate the focus ring to the nearest focus distance. As you move towards the minimum focusing distance, the elements move further away from the body. There's a maximum practical mechanical limit to how far the elements move out. By fitting extension tubes between the lens and body you greatly increase this maximum distance. A purpose designed macro lens has a much greater range of movement 'built in', so it doesn't need tubes.

Jim

[Kayleigh]

Originally Posted by Jim Ford

Basically, the further the lens elements are away from the sensor, the nearer you can get to an object and have it in focus.

Put the camera in manual focus mode and set the lens to infinity. Now rotate the focus ring to the nearest focus distance. As you move towards the minimum focusing distance, the elements move further away from the body. There's a maximum practical mechanical limit to how far the elements move out. By fitting extension tubes between the lens and body you greatly increase this maximum distance. A purpose designed macro lens has a much greater range of movement 'built in', so it doesn't need tubes.

Jim

Thanks Jim it makes a bit more sense now..

[Geoff F]

Very basically, Kayleigh, imagine a 1 ins thick washer (spacer) which fits between the lens and camera. It locks into the camera in exactly the same way as a normal lens and your lens then twists and locks into the tube, which has become an extension to the camera.

The advantage of tubes is that because they don't have any glass elements you won't suffer any loss of image quality.

As Graham said, you do lose a little bit of light so you may need to increase ISO or use flash. But it isn't normally a huge difference. I have found that the camera readings for recommend shutter speed/aperture can sometimes be a bit faulty so you need to check your review screen/histogram fairly frequently. But any error seems to be consistent.

But the other downside is cost. A 25 mm Canon tube will cost around £100 although it is very well made. Some of the very cheap alternatives are poorly constructed and you may lose autofocus with them.

And with regard to size. From my experience of using them with the Canon 70-300 lens, I would say you only really need the 25 mm size. 12 mm just isn't sufficient for most uses.

While I found that this set up worked reasonably well it isn't a true alternative for a good 'proper' macro lens. However, using a tube on a macro lens will get you really close.