Do tele-converters keep the same minimum focus? Like if I have a 200mm that focuses to 1.3M, if I add a 1.4X teleconverter, will this result in a 280mm lens that still focuses to 1.3M? [I realize one loses one stop of speed, and likely some (quite a lot?) of sharpness.] How bad really is the sharpness degradation? OK if stop down fa few stops?

I asked Google to search for: teleconverter "minimum focus" There were about 1300 search results. Many of those web pages indicated that the minimum focus of the lens was maintained. OTOH, in a few cases the product listing said using that teleconverter would give a 1:1 image -- that sounds substantially closer than a normal telephoto lens. I would say that you'll have to ask ... and/or use a local camera shop and try that setup before you buy. MGD

Here's the situation...Here's the situation... When a teleconverter is used on a lens AT INFINITY FOCUS - the converter multiplies the focal length by a factor the the converter (a 2X converter will turn a 100mm lens into a 200mm lens with a 2 stop loss. When the converter is put behind a lens focused at minimum focusing distance (say, behind a 100mm Macro), it doubles the MAGNIFICATION - NOT the focal length. Look at it this way (please test it, if in doubt). Take a 100mm lens focused at infinity - then put a 2x behind it - you get 200mm focused at infinity. Take the same 100mm lens and put 50mm extension behind it, you get 1/2 life size on the neg.... Now, in this order, put the 100mm, then the 2x, then the 50mm extension - and you get 1/4X on the neg - but without altering the focus of the lens at all, you can swap position of the extension and the 2x and jump directly to 1X on the neg! the first case - putting the 2x directly behind the lens, doubles the focal length (to 200mm), and then the 50mm extension yields 1/4X magnification. The second option - putting the 2x BEHIND the 50mm extension doubles the MAGNIFICTION - so 100mm with 50mm extension = 1/2X...doubled = 1X (try it!) Another thing - converters have developed a bad rep - mainly because paople tend to use them with wide open apertures (have to due to the 2 stop loss of light). They actually perform pretty well when shot at a smaller aperture (required in Macro work) The loss in quality of a 2x doesn't come close to the loss of precision most photographers take given the additional magnification and loss of light. Excellent images can be obtained with some additional care with a 2X converter. (BUT I WOULD invest in a GOOD 2X - or preferably a 1.4X). Wolf

...Let me finish this 12-pack and I'll explain it a bit better tomorrow.....

Thanks a bunch, folks!

The Tamron 90mm SP, regarded as a hot macro lens about 20 years ago in its Adaptall-2 form, could be used with a Tamron x2 teleconverter specifically for the extra magnification. All the Tamron tele-zooms of the time had magnification scales too, one of the features of the range. When you think about it, the difference between magnifying the image and increasing the focal length is practically non-existent. Put a wide-angle shot into your computer (easier than doing it in an enlarger), crop and scale to match the same view through a long lens, and the only obvious difference is the image resolution -- pixels or grain, do the magnification with the camera if you can. But I hadn't much thought about the extension-tube effect. I have a set, but if I wanted big macro images, I still have a Tamron 80-200mm and teleconverter. But that particular Tamron converter has to go between the lens and the Adaptall mount. The teleconverter quality will certainly make a difference, and they give you that longer lens too, without adding a lot of weight to your kit.

Given the same composition, the difference between magnifying the image and increasing the focal length is VERY different, because you're completely changing the perpective when you go to a different focal length (cutting down the background coverage as you increase focal length).