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question that has been bugging me.....what is the
Old 12-19-2002, 04:16 PM   #1 (permalink)
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defference between extension tubes...and 1.5/2.0 doublers besides the fact that the later has glass??? [img]/ubbthreads/images/graemlins/confused.gif[/img]
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Re: question that has been bugging me.....what is the
Old 12-19-2002, 05:07 PM   #2 (permalink)
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Extension tubes are commonly used for Macro shots...they decrease the lens' minimum focusing distance and are usually sold in 5mm, 10mm, 25mm, and 50mm. The longer the extension tube, the closer the lens can focus. It goes both ways, however, the longer the tube, the shorter the maximum (infinity) focus becomes. Not a whole lot of light loss unless you start stacking them.
Doublers of course, double a lens' focal length. You normally have a light loss in f stops comparable to the multiplier on the doubler. i.e. for a 1.5X doubler, you would increase a 300 f/2.8 to a 450 f/4.2 or f/4.5 depending on your camera. So, you decrease your maximum aperature...
Hope this helps,
Charles Roberts
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Re: question that has been bugging me.....what is the
Old 12-19-2002, 07:33 PM   #3 (permalink)
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It does indeed....

Jayson
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The best Teleconverter...
Old 12-19-2002, 11:24 PM   #4 (permalink)
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Is a 6mb digital camera like the Canon D30, D60, Nikon D100, Nikon D1, Nikon D1H, Nikon D1x, Fuji S1, Fuji S2, etc. Put any lens on these cameras and you get instant teleconverter ;-) Why pay $250 for a teleconvertor when you can pay $2000+ for one ;-)
 
 
FWIW - probably not much
Old 12-20-2002, 08:19 AM   #5 (permalink)
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I made an "extension tube" for my K-mount Pentax by buying a cheap no-name 2X teleconverter and removing the glass, just using the mount. Worked acceptably as a tube, although I didn't have auto-anything to test the electronic coupling.
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Re: The best Teleconverter...
Old 12-20-2002, 08:54 AM   #6 (permalink)
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He who dies with the most Expensive toys...Wins...right?
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Re: question that has been bugging me.....what is the
Old 12-21-2002, 09:26 AM   #7 (permalink)
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Doublers or teleconverters increase the focal length of your lens (simultaneously decreasing your aperture and image quality at a factor of how good or bad the glass is), in other words, it "zooms" you in. Extension tubes allow you to focus on an object that is closer to your lens, allowing you to get closer. The primary difference is one of visual perspective (compressed space vs exaggerated space). Another is optical quality, where a teleconverter will definitely diminish your sharpness, perhaps to a minimal degree depending on how good the glass is, whereas an extension tube will probably decrease the quality only slightly if at all, depending on just how optically well your lens resolves objects at a very short focusing distance (if it's a macro lens you probably won't be hurting your image at all). In either case, critical focusing becomes essential, and a fast shutter doesn't hurt a bit, either.
 
 
Re: The best Teleconverter...
Old 12-21-2002, 12:04 PM   #8 (permalink)
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Welll... acutally you just get all your images automatically cropped down from a 35mm frame to the 23mm or so in the center of the frame. A 1.4x comverter changes certain optical charactics. It is two very different things.
 
 
Re: The best Teleconverter...
Old 12-21-2002, 03:41 PM   #9 (permalink)
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Sorry, but wrong "He who dies with the most expensive toys" is dead and the heir wins by inheriting all those toys.

My place
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Actually ...
Old 12-21-2002, 04:02 PM   #10 (permalink)
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Actually a doubler, or teleconverter increases the apparent telephoto effect by a factor equaling the power of the teleconverter. A 2x effectively doubles focal length of a lens, but will use up (absorb) 2 f-stops. A 1.5 power will increase the focal length by a factor of 1.5 and absorb 1 1/2 stops of light. Quality can suffer from a little to a whole hell of a lot, depending on the brand.

Extension tubes change the relationship between the optical center of focus of a lens and the film plane (position of the film) within the camera. This allows the lens to focus much closer to an abject, which in turn causes the object's image to appear larger on the film. It also steeply shortens the area of acceptable focus in front of the lens and also absorbs light. by a ratio of 1 f-stop per 25mm of extension. Ther is no loss of quality, but focus is highly critical, as the depoth of field can be in millimeters.

You may be confusing doublers with a dioptric lens, which is a simple magnifying glass, made of optical quality glass, magnifies the image before it reaches the lens. These are often called "close up filters", but that isn't correct as they ar enot filters, but lok and mount sort of like a filter. There is no loss of light, but image quality may be somewhat degraded.
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