Extension tubes

[sheltiesmama]

I have a question for all of you experts (or not so expert). I was desperate for a good macro lens but the prices are just too much at this time. After reading some different posts on the subject, I ordered a set of the Kenko extension tubes. Has anyone had experience with these and if so what is your opinion of them? I have tried them a couple of times and wasn't real happy with the results. As I am also a newbie at all of this I can't decide if I should continue to try them and hope for better results or send them back and save up for a good macro. It's very possible I'm doing something wrong in my use of them. Now for a stupid question, so nobody laugh out loud. If all the tubes do is extend the lens and has no magnification shouldn't they also work to extend my telephoto lens.Or were these tubes to be used as an extension just for an existing macro lens? The directions I got with the tubes were next to useless and I can't really find more info on the net. Even though the tubes were a lot less expensive than a new lens, it's still a lot of money to me. I use a Nikon D40 and love the camera so far but I really love macro work and wanted to get better shots. Thanks in advance for any help you can give me and I hope this isn't posted in the wrong place.

[emtab]

He sheltiesmama,
I shoot with Kenko extension tubes and have generally had very good results shooting some very small orchids. I'll try to answer a couple of your questions and give you a couple of tips that I have found to work well.

Extension tubes will work on almost any lens, they are not intended for macro lenses. I use mine on my 50mm prime and 70-200 telephoto. Be careful about how many of the extension tubes you are putting onto a lens. For my 50 mm lens I rarely put more than 20mm of extension on, usually only 12mm. (More extension equals shallower DOF and closer focus.) If you put too much on your DOF will be so small and you'll be so close that it will be very difficult to get what you want. On my telephoto I often shoot with 32 mm (stacked 12 and 20mm rings) or sometimes 38mm.
Also, be careful of the focal length - if you're shooting at 18mm with extension you will have a difficult time getting focus as DOF will be extremely small. I don't ever put the extension tubes on my 12-24mm lens as I find it becomes almost impossible to get focus, and when you do, DOF is teeny. Try with your telephoto and about 30mm of extension and see how you do.

Only you can make the decision as to whether or not extension tubes are right for you as opposed to a macro lens. I found that they are an acceptable improvisation given that I don't shoot a ton of macro and allow me to use a quality of lens that I would be unwilling to purchase only for macro use.

Hope that helps,
emtab

[VegasMike]

ok, from the not so expert- my understanding is that the extension tubes allow separation between the lens and the sensor. This allows you to move the lens closer to your subject since you can now move closer to "fill" up the sensor. The neat thing is that if you have the set of three, you can stack them in different combination's. I don't know about using them on a telephoto, unless it's like my Sigma 70-200 2.8 macro. I might need to try it and see what it does.

[Quo Fan]

I have a set of tubes such as you describe. I usually use one of my zoom lenses, because I can use the zoom as a coarse focus, and the focus ring as a fine focus. The tubes allow me to get REALLY close to the subject, so I have to use off-camera lighting.

[JFSanders]

Shirley, post a picture of what you are getting when you use the tubes. Secondly, when using extensions understand that the area of correct focus will be VERY small as in .05 inches in some cases. Such as when you have all of them stacked and sitting under a zoom lens. What I suspect you are experiencing is the lens focus ending up actually inside the lens and not on the sensor. Minimum focal length at 36mm of extension is somewhere around 90 mm depending on the lens being used.

There was a Flickr discussion on extension tubes and their usefulness and limitations.

See here: Flickr: Extension Tube Users (Macro) discussion topics

[sheltiesmama]

Originally Posted by JFSanders

Shirley, post a picture of what you are getting when you use the tubes. Secondly, when using extensions understand that the area of correct focus will be VERY small as in .05 inches in some cases. Such as when you have all of them stacked and sitting under a zoom lens. What I suspect you are experiencing is the lens focus ending up actually inside the lens and not on the sensor. Minimum focal length at 36mm of extension is somewhere around 90 mm depending on the lens being used.

There was a Flickr discussion on extension tubes and their usefulness and limitations.

See here: Flickr: Extension Tube Users (Macro) discussion topics

Thanks to all that have answered this and I must say I'm still confused, but that's just me trying to take in all the info.

JFSanders....you asked me to post a pic and this is the only one I've saved. I got upset and deleted all the rest. Crazy huh? I don't know if this is a good shot or a bad one. I do know it's a little blown out. BTW, it's a hand held shot. I'd go out and try to take some more but it's raining. I also took a quick look at the group on FlickR, looks very interesting. Thanks for the help




EXIF:
Camera: Nikon D40
Exposure: 0.008 sec (1/125)
Aperture: f/5.6
Focal Length: 30 mm
ISO Speed: 200
Exposure Bias: 0 EV
Flash: Auto, Fired, Return not detected

[JFSanders]

Ok, looking at the picture. Go to the spot where yellow parts are next to the white stem. If you look at that junction you will see some of the yellow ones are in focus and the ones in front and in back are not. This is due to the depth of field problem. At 30mm focal length and a aperture of f/5.6 your depth of field is about 1/8th of an inch deep. So everything in that plane is in focus. Everything in front of and behind is out of focus. If you stop down to f/11 or even farther and slow your shutter speed down to get proper exposure your depth of field will deepen and more of the flower will be in focus.

[sheltiesmama]

Originally Posted by JFSanders

Ok, looking at the picture. Go to the spot where yellow parts are next to the white stem. If you look at that junction you will see some of the yellow ones are in focus and the ones in front and in back are not. This is due to the depth of field problem. At 30mm focal length and a aperture of f/5.6 your depth of field is about 1/8th of an inch deep. So everything in that plane is in focus. Everything in front of and behind is out of focus. If you stop down to f/11 or even farther and slow your shutter speed down to get proper exposure your depth of field will deepen and more of the flower will be in focus.

Thanks for the info. This makes a lot of sense. I will give this a try and will also study more on the FlickR group. I think if I take a deep breath and start over with it, I'll like the tubes . Thanks again for all your help.

[daft_biker]

I use Kenko tubes too and believe extension tubes can be used on all lenses....they work on macro lenses, wide angles, 50mm, standard zoom....everything I've tried mine on. Wide lenses and some zooms may only allow a small amount of extension before the working distance(the space between the end of the lens and the subject) becomes impractically short and they don't do much on long lenses but otherwise they should work fine.

The increase in magnification you get from extension tubes is related to the focal length of the lens in use. For example if you wanted to shoot at lifesize (also known as 1:1 or 1x) you could do it by using an extension tube the same size as the focal length of the lens, with the lens set to infinity focus. Try 50mm of tubes on a 50mm with the focus at infinity....you might need a tripod and ideally a focus rail so you have a geared rail the camera can slide forward and back on to fine tune focus. If you put more tubes on you should get even closer....or less tubes if you don't want to be so close.

DoF is dependant on the magnification and aperture - it doesn't matter whether you use extension tubes, bellows, teleconvertors or a macro lens as DoF in macro is just as limited whatever kit you use. Feel free to use as much extension as you can, if you want to

[AgBeard]

I use Kenko extension tubes - be aware they will not work with EF-S lens.

Here is shot of my macro setup, using Canon's remote software to 'drive' the camera, including fine focusing & DOF preview.



Here is a stamen within a lily taken with extension tubes.