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Old Mar 31, 2005, 7:47 PM   #1
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Has anyone tried this combination?

I purchased my Canon 20D about a month ago, and bought the Canon 75-300 mm ultrasound stabilized telescopic zoom lens. It seems to work quite well, but like most camera nerds I started lusting after bigger and bigger lens.

I tried out a Canon EOS 100-400 LS lens at the local photo store, but didn't think that it was that much a better lens then the 75-300 -- and certainly not a $1000 better lens.

While thinking of various lens options, I had a brainstorm today. My previous camera was a Sony F707 digital camera. When I got it (about three years ago or so) I visited this forum looking for ways to perhaps add a zoom option to the camera. I was directed to the Olympus B-300 1.7 teleconverter, which attaches to the front of the normal lens. It appeared to me to work quite well.

The front mount teleconverter is interesting, in that while you multiply the focal length by 1.7, you don't take a hit in the speed of the lens, since the teleconverter lens is actually larger than the lens you mount it to. It appears to me to be that you probably keep about the same f-stop setting.

My brainstorm today was that the diameter of the F707 lens and the Canon 75-300 mm lens is the same -- 58 mm. So I was able to attach the B-300 to the Canon 75-300 lens.

So what I get with the teleconverter is basically convert a 75-300 mm f4-5.6 lens to a 125-510 mm f4-5.6 lens -- and it stays as a ultrasonic stabilized lens. In addition, the autofocus seems to work just fine.

I've posted a picture I took at full zoom on an overcast day here in Oregon. According to mapquest, the street sign is about 400 meters (one-fourth mile) from my back deck, where I took the picture. It's far enough away that unless you have very good vision (at least 20/20) you won't see the sign, and certainly won't be able to read it.

The cost? The B-300 was about $200, when I bought it. I understand that Olympus no longer makes the B-300, but has almost an exact replacement that costs less than $200.

So what do you think?




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Old Apr 2, 2005, 5:41 AM   #2
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its really blurry, however your concept is good.
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Old Apr 2, 2005, 2:57 PM   #3
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Here's some more on the combination.

The first picture is from the same vantage point, using the Canon EOS 17-85mm lens set at 50 mm. The F setting is 5.7, and the shutter speed is 1/500 of a second. The street sign in question is in front of the house that's in the middle of the picture.


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Old Apr 2, 2005, 3:03 PM   #4
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Here's the same vantage point, using the Canon EOS 75-300 mm Image Stabilized Lens, with the focal length at 200 mm, the f-stopat 16and the speed at 1/500th of a second. The ASA is set at 1600.
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Old Apr 2, 2005, 3:18 PM   #5
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Here's the same vantage point, but with the B-300 teleconverter attached to the front of the Canon 75-300 lens. The Canon zoom at set to 300 mm, and the B-300 teleconverter has a multiplication factor of 1.7, making this combination at 510 mm lens. An ASA setting of 1600 is again used, with a f-stop of 16 and a shutter setting of 1/350th of a second. The image has been cropped; the original resolution of the picture was about 3600 x 2400; the cropping is about 1280 x 1040.
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Old Apr 2, 2005, 3:24 PM   #6
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Finally, here's what the combination looks like together.
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