Eaxtension Tubes - Could somebody please explain

dinners

dinners

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Phil
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Hi

I've been considering a set of extension tubes as I'd like to do a bit of macro but I've a few questions......

First up - I've a Canon 40D with a few lenses but no macro lens.

My 2 X teleconverter tends to be used for extra length on a long lens but from memory does nothing for me macro wise ???

They seem to come either 'with' or 'without' electrical contacts. Can somebody tell me whether it matters or not ?

If I was to use my 50mm 1.8 could I auto focus with electrical contacts ?

What about aperture selection ?

Also what sort of size (magnification) can be achieved as I'd really like to get 1:1

Any help / advice / suggestions on the matter appreciated.

Phil
 
dinners said:
Hi

I've been considering a set of extension tubes as I'd like to do a bit of macro but I've a few questions......

First up - I've a Canon 40D with a few lenses but no macro lens.

My 2 X teleconverter tends to be used for extra length on a long lens but from memory does nothing for me macro wise ???
Click to expand...

Not a recommended route, but using a 2x TC retains your minimum focusing distance while doubling focal length.

They seem to come either 'with' or 'without' electrical contacts. Can somebody tell me whether it matters or not ?
Click to expand...

It matters a great deal. Without lens-to-camera communication you have to do everything manually. Focusing is okay (manual focus is the way to go anyway) and exposure control isn't too tricky, but setting the aperture is a right pain. You have to fit the lens without the tubes, set the aperture and hold it with the stop down button while physically removing the lens again. The aperture will stay stopped down when you refit the tubes, but the image will of course be dark so you can see sweet FA. Then you have to do it all again to change the f/number. Only possible at all using a tripod.

If I was to use my 50mm 1.8 could I auto focus with electrical contacts ?

What about aperture selection ?
Click to expand...

No problem with the 50 1.8. See above re aperture selection.

Also what sort of size (magnification) can be achieved as I'd really like to get 1:1
Click to expand...

With a set of Kenko tubes you'll get a bit over 1:1, and full lens-to-camera coupling. These are what most people seem to be using. I bought a set for £80 off here.

Any help / advice / suggestions on the matter appreciated.

Phil
Click to expand...

Think about getting a ring flash. Macro is very hard without as you get light loss (two stops at 1:1) and need a high f/number for depth of field. When you add the need for a high shutter speed to control camera shake caused by the high magnification, you're in trouble without really bright light.
 
Thanks for the reply - that helps quite a bit.

Manual focus wouldn't really bother me but the aperture sounds a right faff so I'll have a look at something with the contacts.

Regarding the ring flash - I see what you mean about combining smaller apertures & faster shutter speeds. Hmm - might have to find some very still, flat things on a sunny day LOL

PS

As I've only ever used my 2X teleconverter for distance I wasn't actually aware that the minimum focus distance remained the same.

Thanks

Phil
 
dinners said:
Thanks for the reply - that helps quite a bit.

Manual focus wouldn't really bother me but the aperture sounds a right faff so I'll have a look at something with the contacts.

Regarding the ring flash - I see what you mean about combining smaller apertures & faster shutter speeds. Hmm - might have to find some very still, flat things on a sunny day LOL

PS

As I've only ever used my 2X teleconverter for distance I wasn't actually aware that the minimum focus distance remained the same.

Thanks

Phil
Click to expand...

Marumi Ring Flash seems like a bit of a bargain at £109. Does E-TTL too :)

http://www.warehouseexpress.com/buy-marumi-drf14c-ring-flash-for-canon/p1026071
 
May I ask whether the effective aperture is changed using extension tubes?
With regards to incoming light, and diffraction problems?
 
Most things have been said but that bit about the aperture is more hassle than I can be bothered with - if you've got the cheapy non-electrical ones (you can buy a full set for less than £10) then it leaves the aperture wide open so I just work with it like that. I quite like the extreme shallow dof anyway.

Saying that, I was pleased when I bought a set of the kenko electrical ones!
 
Right. The general thing is the more space between the camera and lens the more magnification you get. But as the light has that much more to travel, the pics may need more time. Plus the focus thins. A lot.

Second thing is it will only increase the magnification of the lens.

Eg I bought a 200mm f4 manual to use with them (thanks to cowasaki for the tubes) and it didn't magnify like I thought. I got the working distance. But not the magnification. This was because it's a 1:4 ratio so it only came down to 1:1.5 ish. Manual lens allowed movement on aperture of the lens. Useful!
But on my 105mm 1:1 lens it magnified. Lots. :) I posted one or two pics in the macro section, should want to look for them. The 105mm is a d lens but still has the aperture control If required.

Overall they are brilliant, but if you can borrow some and a 1:1 lens, do this first :)
 
I use manual lenses for macro as AF is supposed to be useless up close and I like being able to turn a second ring behind the focus ring for aperture control. It's easy and more controllable, the hard part is getting focussed as the depth of field is so thin- and if you stop down to get the DOF then it is so dark you need a seperate light to be able to see to focus!
 
coldpenguin said:
May I ask whether the effective aperture is changed using extension tubes?
With regards to incoming light, and diffraction problems?
Click to expand...

With tubes the effective f/number is changed - at 1:2 it is reduced by one stop, and by two stops at 1:1. It's only the effective aperture that changes with tubes, the actual aperture remains the same physical size and the f/number is only valid at infinity focus.

ecniv said:
Right. The general thing is the more space between the camera and lens the more magnification you get. But as the light has that much more to travel, the pics may need more time. Plus the focus thins. A lot.

Second thing is it will only increase the magnification of the lens.

Eg I bought a 200mm f4 manual to use with them (thanks to cowasaki for the tubes) and it didn't magnify like I thought. I got the working distance. But not the magnification. This was because it's a 1:4 ratio so it only came down to 1:1.5 ish. Manual lens allowed movement on aperture of the lens. Useful!
But on my 105mm 1:1 lens it magnified. Lots. :) I posted one or two pics in the macro section, should want to look for them. The 105mm is a d lens but still has the aperture control If required.

Overall they are brilliant, but if you can borrow some and a 1:1 lens, do this first :)
Click to expand...

ecniv, that is an unusually innovative take on the laws of physics... ;)
 
topcatproduction said:
I use manual lenses for macro as AF is supposed to be useless up close and I like being able to turn a second ring behind the focus ring for aperture control. It's easy and more controllable, the hard part is getting focussed as the depth of field is so thin- and if you stop down to get the DOF then it is so dark you need a seperate light to be able to see to focus!
Click to expand...

This is one nice thing about using manual tubes - you can fit any manual lenses as long as you have the right adaptor. I've used old Olympus manual lenses on mine.
 
Some useful links....

http://www.mplonsky.com/photo/article.htm
http://www.beautifulbugs.com/beautifulbugs/howto.htm


The tamron 90mm f2.8 a good alternative to the sigma 105mm and canon 100mm macro lenses.

The Kenko are a cheaper alternative to the canon branded tubes, plus canon only do a 12mm and 25mm tube, while you get 12mm, 20mm & 36mm tubes with the kenko set and offers more flexibility for similar money. You might need to check whether you getting the right set, some of the Kenko tubes aren't EF-S lens compatible.

http://www.the-digital-picture.com/Reviews/Kenko-Extension-Tube-Set-Review.aspx
 
ecniv said:
Right. The general thing is the more space between the camera and lens the more magnification you get. But as the light has that much more to travel, the pics may need more time. Plus the focus thins. A lot.

Second thing is it will only increase the magnification of the lens.

Eg I bought a 200mm f4 manual to use with them (thanks to cowasaki for the tubes) and it didn't magnify like I thought. I got the working distance. But not the magnification. This was because it's a 1:4 ratio so it only came down to 1:1.5 ish. Manual lens allowed movement on aperture of the lens. Useful!
But on my 105mm 1:1 lens it magnified. Lots. :) I posted one or two pics in the macro section, should want to look for them. The 105mm is a d lens but still has the aperture control If required.

Overall they are brilliant, but if you can borrow some and a 1:1 lens, do this first :)
Click to expand...

To work out the magnification with a tube, divide the tube extension by the focal length. Thus a 50mm lens with the Canon 25mm tube will give 0.5 lifesize (or 1:2). Your 200mm with the 25mm = 0.125 lifesize and the 105mm = about 0.25mm. This is at infinity focus, so focusing closer will give more mag, hence why your macro magnified lots.

You will lose light in a similar way. At lifesize (e.g. 50mm extension on a 50mm lens), you will lose 2 stops; 25mm extension on 50mm lens = 1 stop etc.
 
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