CGrindahl
Offline
• • • • • •
Upload & Sell: Off
|
INTRODUCTION: It has been suggested by a member who came across this thread that it might be useful for those unfamiliar with the use of extension tubes if I added a short explanation of what they are and how they work, so here goes.
Unlike extenders that have lenses built in that magnify the image, extension tubes are empty tubes that simply change the distance between the camera lens and the camera sensor. If you wear glasses you've doubtless had the experience of looking through them as you move the glasses farther from your face. It changes the magnification of whatever you're looking at. This is what happens with extension tubes.
Every lens has what is called the MFD, or minimum focusing distance. When you mount a tube between the lens and the camera body, you are reducing that distance. You also effectively eliminate focus at infinity. The longer the tube, the closer to the subject you MUST be in order to gain focus. The trick in working with tubes is to find the best length of tube for each different focal length of lens you use. The goal is to have the subject you’re shooting occupy as much of the field of view as possible.
I've mounted tubes on lenses from 20mm to 300mm. My narrowest tube, the 12mm, mounted on a 20mm lens puts me so close to the subject that I'm practically touching it with the front lens element. Needless to say, from that perspective I’m generally capturing only a very small portion of whatever is in front of the lens. On the other hand, with all three tubes from a set I own mounted on the 300, a total of 68mm, I still have about a foot of working distance and am able to capture the entire subject.
I'm shooting with manual focus lenses, so I'm not concerned with whether the tubes I use allow for communication between the lens and camera body. But if you're shooting with AF lenses and want to have the camera register information about the lens and the shot, you would wish to have tubes that have electrical contacts. There are a number of companies marketing tubes with electrical contacts, the most prominent of which is Kenko.
Generally work with tubes is done by manual focusing for the simple reason that when tubes are mounted the focal plane becomes VERY narrow and can be challenging for even the best cameras to find. Yet it is important to note that the focus ring of the lens may not have adequate range to achieve focus, so you need to be able to physically move closer and farther away from your subject as you attempt to find focus. I do that by gently rocking back and forth as I examine the image in the viewfinder. This actually becomes easier than turning the focus ring of the lens, since the slight movement required to turn the ring can move the lens in relation to the subject, disturbing focus. Some folks use tripods with a focusing rail that allows the camera to slide closer and farther from the subject, often using live view on the rear of the camera to evaluate focus.
When shooting with tubes it is useful to stop down aperture, which widens the focal plane and to a certain extent counters the effect of the tubes that narrows the plane. Needless to say, this all becomes clearer as one experiments with tubes. Relax and enjoy yourself!
After being introduced to extension tubes last autumn I've been taking great pleasure in mounting them with one of Nikon's great manual focus lenses and getting up close and personal to things in my world. I'm not much of a bug person, so classical macro work doesn't attract me. I also don't own a tripod and prefer natural light, so I can't do the really precise closeup work that many on this forum do exceptionally well. I respect folks doing that work but simply don't have the patience to do that. I can, however, slap on an extension tube wherever and whenever and grab a few photos of what is around me. At the moment, at least in northern California, that includes some very nice flowers. So I'll post a few of my recent photos taken with an assortment of lenses coupled with one or another extension tube from an old set marketed by Vivitar. I'll begin with a shot I took today with the 300 f/4.5 AI-s ED-IF with a 36mm tube attached to my D700... hand held of course with the lens wide open.
What would delight me is having other members show us what they're doing with extension tubes, so COME ON DOWN. Tell us about the lens and tube, then show us what you've produced with them. It should be fun! 
Shot with the 135 f/2.8 AI with a 12mm extension tube at f/5.6.
Shot with the 105 f/2.5 AI-s with a 12mm extension tube at f/2.5.
Shot with the 180 f/2.8 AI-s ED with a 12mm extension tube at f/2.8
Edited on Mar 18, 2013 at 06:00 PM · View previous versions
|
