Extenders vs Extension Tubes With Telephoto Lenses.

[Dave Johnson]

I've heard of photographers using ext tubes with telephoto lenses on several occasions and never really understood the reasons why they used them instead of extenders. I understand that ext tubes will increase the size of the subject in the viewfinder, but will also affect the focus range ie. The minimum focus distance will decrease on the 'short end' and the lens will be unable to focus to infinity on the 'long end'. This would be useful perhaps for set ups where the photographer will pre focus on a perch and wait for the bird to come in, but wouldn't an extender do the same job only better as you still have the freedom of focusing to infinity in an instant should the need arise? I've also considered an ext tube helping to blow or smooth out a busy background better than a extender can but I'm really just picking at straws :e3As you can probably tell, I'm totally confused and would appreciate if anyone could shed some light on this subject for me (and anyone else who might be puzzled by this). Thanks very much.

Dave J.

[Charles Glatzer]

Dave,

It is not an either or situation, as both serve two completely different purposes.

The only thing an extension tube does is allow you to focus the lens physically closer to the subject. The more extension the closer you can focus. Note -you do loose more focus on the far end as you increase extension.

A converter does not alter the lens minimum focus, but it does magnify the image by increasing focal length.

You can use the two together, or independently depending on the magnification needs, and working distance required.

Chas

[Dave Johnson]

Thanks for the reply Charles, I understand the capabilities of each a little better now. I own a 12mm ext tube which I use for macro work sometimes, but don't as yet own an extender for my 500mm F4 so can't do any comparisons and thought I'd ask here. I understand the benefits of tubes in macro but just can't grasp when and in what situations one would use tubes with a telephoto lens?

Dave J.

[Charles Glatzer]

Dave, extension tubes are used with the big 500/600/800 to allow closer focus to the subject, thus making the subject larger (increasing magnification) in the frame. I often used an extension tube on my 600 when shooting small birds like warblers.

[Diane Miller]

To expand a little on Charles' answer: Long telephoto lenses have fairly long minimum focus distances; often 15-18 ft. In some situations, such as small birds attracted to a feeder setup, the eternal photographer's frustration with not being able to get close enough to the subject is often reversed; the subject is too close -- inside your minimum focus distance. Extension tubes enable you to focus closer, just as they do with a macro lens. And they don't reduce the maximum aperture, as a teleconverter does.

I haven't seen much discussion about any optical quality loss. There is no glass, so I assume it would be minimal. But I wonder if there is a slight (maybe almost theoretical) amount of loss. The minimum focus distance on a lens is set by the manufacturer based on the point at which quality loss begins to be noticeable. Many factors are juggled with any lens design. But I assume since infinity focus is sacrificed, that obtaining closer focus is without loss of quality.

[Charles Glatzer]

To expand a little on Charles' answer: Long telephoto lenses have fairly long minimum focus distances; often 15-18 ft. In some situations, such as small birds attracted to a feeder setup, the eternal photographer's frustration with not being able to get close enough to the subject is often reversed; the subject is too close -- inside your minimum focus distance. Extension tubes enable you to focus closer, just as they do with a macro lens. And they don't reduce the maximum aperture, as a teleconverter does.

I haven't seen much discussion about any optical quality loss. There is no glass, so I assume it would be minimal. But I wonder if there is a slight (maybe almost theoretical) amount of loss. The minimum focus distance on a lens is set by the manufacturer based on the point at which quality loss begins to be noticeable. Many factors are juggled with any lens design. But I assume since infinity focus is sacrificed, that obtaining closer focus is without loss of quality.

Diane,

Extension tubes do effect max aperture, although not as great as a converter.
The light loss with an extension tube is greater for a given extension with shorter focal length lenses.
And, the more the extension the greater the light loss.

[Diane Miller]

Charles, that's what I had thought (makes sense -- you are moving the iris diaphragm farther away from the sensor) but haven't used them much. I did try the 12mm tube with my 600 recently and thought it still showed f/4. Maybe the loss wasn't enough to bump it to 4.5. Or maybe I saw it wrong. Will check again -- thanks!

[David Stephens]

TCs and ETs both allow you to get more pixels on a small subject. A TC does so by increasing focal length while an ET does so by allowing you to shoot closer to the subject. Using both allows even more magnification. If you've got a long lens, I recommend that you try them both for things like butterflies, hummingbirds, bumble bees, etc. You have luxurious working distances for small subjects and you get very good, almost macro, magnification.

[Dave Johnson]

Thanks Charles, Diane and David for your comments. I picked a 1.4x extender up last weekend and will try the combinations next time out.
David, I'm very interested in the macro options available for butterflies etc as I've struggled to get close them with a 100mm macro lens up to now. I can see where a ext tube would come in handy here. I was thinking birds & mammals, where extra working distance is always needed and just couldn't figure out why one would want to restrict that. Thank you for opening up some new avenues, it's much appreciated.

Regards, Dave J.

[David Stephens]

Thanks Charles, Diane and David for your comments. I picked a 1.4x extender up last weekend and will try the combinations next time out.
David, I'm very interested in the macro options available for butterflies etc as I've struggled to get close them with a 100mm macro lens up to now. I can see where a ext tube would come in handy here. I was thinking birds & mammals, where extra working distance is always needed and just couldn't figure out why one would want to restrict that. Thank you for opening up some new avenues, it's much appreciated.

Regards, Dave J. The 1.4x TC will get you started, then add a 25mm ET and move in even closer. The total magnification that you can achieve will be related to focal length of you base lens, combined with it's minimum focus distance, then you enhance that with your 1.4X TC and then enhance it further by getting closer with a ET, or two (you can stack them). It'll give you a whole new view of your garden.

[Diane Miller]

If I remember correctly, the combination gives more magnification if the TC is on the camera end and the extender on the lens end.

[David Stephens]

If I remember correctly, the combination gives more magnification if the TC is on the camera end and the extender on the lens end.
I typically put my ET between the TC and the body, with the TC attached to the lens. (Attach the TC to the lens first). I understand that some reverse the order, but I've never bothered to try. The ET allows you also to get closer without the TC. You just won't get as much magnification.