Kenko Ext Tubes

[Neil]

Hi Folks.
Just treated myself to a set of tubes.12-20 & 36mm's.
I didnt want to spend the big bucks for a good macro lens so opted for the tubes,$249.00
May I ask the learned members can you please explain how I should use these tubes.
I plan on using my 50mmF1.8 & 18-70mm F3.5-F4.5 len's,could I also use my 70-200mm F2.8?
I did take a few pics just to try them out.Lets see how this goes!
All 3 pics were taken with the 50F1.8+12mm Ext Tube.
I noticed the DOF was really shallow,macro right.
What happens when you use muliple tubes together.
Whats the difference using the 12-20 and36mm tubes.
Please comment on pics and suggest some examples I might try to shoot with this set-up.
Thanks Neil.

[clockdoc]

Nice sharp images. You are correct that depth of field will be VERY small when using extension tubes. Even stopping down won't help that much so choose your subject and angle of shooting very carefully. The longer the extension, that is using longer tubes or adding tubes together gives you a much larger image, approaching a 1:1 ratio and possible larger. The drawback of using tubes is that exposure times are increased. However your camera's metering system will take care of that. Experiment with your different lenses and see how close you can focus at varying focal lengths. In general, the wider the angle of view, the closer you will have to get to the subject for it to be in focus. With telephoto lenses you will have to move farther away. I look forward to seeing more of your work.

[wulf]

It is an inevitable consequence of getting extremely close. Using my Raynox adaptor on my 70-300mm lens, I can get much closer than a 1:1 ratio but, even stopped down to a tiny hole (and with the camera and subject static so I can leave the shutter open to get enough light), DoF is so minimal that it becomes a real problem.

Wulf

[PLouie]

For $240 you could have gotten Sigma's EX 50mm f2.8 Macro Lens from Amazon. It's very sharp and is from Sigma's pro line of lenses. I think you should have gone with that. It would have been the better deal. You get a 50mm portrait lens and a dedicated Macro lens capable of 1:1 magnification. Also, no fuss and worry about DOF and putting tubes on.

I have the 105mm version which is basically the same but at a longer focal length.

[inkista]

The OP's in Ontario, so the price was probably in Canadian dollars, amazon.ca doesn't do camera stuff, and the Sigma you recommend would be $370 for the OP. Just saying.

To add to what clockdoc posted, the longer the tube, the higher the magnification, and the smaller your effective aperture (not unlike using extenders). I think I read somewhere that magnification for a non-macro lens is calculated as tube_length/lens_focal_length. So, if you stacked all three tubes (12+20+36 = 68mm) and used it with your 50mm, the magnification would be 68mm/50mm, or 1.36:1 which is larger than lifesize.

So, you'd actually get more magnification with a wider lens, which in my head is completely counterintuitive. Sorry, I'm not sure what the formula is for how many stops you lose.

[clockdoc]

Many years ago we used to use a 4x5 view camera for copying photographs and other flat documents. I recall having to use some formula to calculate "bellows draw" (the same as using extension tubes except with bellows the 'draw' distance is only fixed by the length of the bellows)which occurred when the extension of the bellows exceeded the focal length of the lens. Thankfully, with today's digital cameras, we don't have to do those calculation because of thru-the-lens metering systems. However if anyone is interested, I found an excellent reference on the web at http://shutterbug.com/refreshercours...72/index1.html
I liked their closing remark in that you could use a 20 foot piece of pipe as a extension tube if you could figure out a way to attach it to your camera. Unfortunately the light loss would be so great, exposure would be an insane "Saturday at f/8!" 8-)

[inkista]

Well, if you're on a seriously low budget, there's always the Pringles can approach.

[Neil]

Just realizedconfused:
I should have posted this thread under the Macro forum.
Maybe one of the moderators would be kind enough to re-locate it.

Thanks to all for comments and opinions.
Next week when I get some free time I will take a series of shots with my 3 lens and the 3 different tubes to see what results I get.
Will post them when completed.
Neil.

[wulf]

Originally Posted by Neil

Maybe one of the moderators would be kind enough to re-locate it.

My pleasure.

Wulf