With older lenses the aperture was controlled by a lever mechanism, which is missing in a lot of the current lenses, probably including your Sony. You can try setting the aperture manually with the camera, turn off the camera, and take off the lens to see if it stays set where you left it when you turned the camera off. I have heard that this works for Canon.
If it will do that, you can set the aperture by that procedure, but it will be terribly slow if you want to change aperture during shooting. For the cost, it's better to have ext tubes that will work with all the functions of the lens you are using.
All but two of the lenses in my collection have aperture rings, and work with the ext tubes that were made for the older lenses from the 70's and 80's, so I can use them, but do not have light metering. I have to shoot and correct from seeing what's on the LCD.
What Yo said is also true. an 11 mm ext tube on a 24mm lens will put the front element of the lens almost in contact with the subject to focus, but the same ext tube on a 180mm is just about right for things about the size of your hand at a distance of about 4 or 5 ft.
Message edited by author 2010-09-24 21:27:43.
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