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Old Feb 12, 2005, 1:33 AM   #51
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Old Feb 12, 2005, 1:39 AM   #52
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Old Feb 12, 2005, 2:31 AM   #53
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marigil wrote:
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Hi Fred,

May I suggest that you repeat your test with an object 40 or 50ft away. I've noticed that up to 30ft the images are slightly softer only. But at greater distances your dept of field is dramatically affected. I have pictures that show this but I have no way to post them, can I somehow send them to you and you could post them for me?
The pictures were shot with the tcon17 6mm and 7mm from the centre of the front element of the camera lens,F8, 12x zoom.

Gilles
I hope this will help confuse everyone. These are the results of test conducted by a Japanese fellow. I have never seen such a complete and methodical test in my 57 years of photography. They make for interesting viewing. I am in the process of making an adapter that does not need step rings to accept different mm mounts. I hope you guys are wrong because I cannot afford to test every lens on the market. I have much more to read off this fellow's web sight, but in broken English, he chose the three best tele-extenders regardless of magnification. The three were 1) LX10, 2) Tcon14B and 3) Sony HDG1758. I love all you guys, but unless you really know what you are doing and can control the test without prejudice, the results can be skewed

These shot wre taken from his huge sample and show various results with different lenses set to 9x. I selected this grouping because that is within the usable zoom range of all the TCs.

http://lovelife.smugmug.com/gallery/392355



http://translate.google.com/translate?sourceid=navclient-menuext&hl=en&u=http%3A%2F%2Fnighthead%2Ea dzoo%2Ejp%2Ffz%2Ftelecon%2Ftelecon1%2Ehtm



http://translate.google.com/translate?sourceid=navclient-menuext&hl=en&u=http%3A%2F%2Fnighthead%2Ea dzoo%2Ejp%2Ffz%2Ftelecon%2Ftelecon%2Ehtm






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Old Feb 12, 2005, 11:17 AM   #54
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Gilles - Once again, thanks for all the work you've put into this and for posting the comparisons and your conclusions. The tl55shots do seem to confirm the earlier tcon17 results indicating thattheoptimumdistance (in terms of focus, ca, noise, etc)between the rear tele lens element and the camera lens (distance A) is directly dependent on the distance between the subject and thefront telelens element(distance B).
In other words; the greater distance B, the greater distance A.

Camera >A< Tele > B< Subject

Playlong - The Japanes siteyou refer to doesn'tshow anyvariation on distance B, so that information doesn't really impact Gilles results. Likewise, none of this really impacts your projected adapter design. The option to get the camera lens and converter lens as close as possible is still quite viable. No reason to loose your love life. Just remember to play short.
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Old Feb 12, 2005, 5:29 PM   #55
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Thanks Fred for your comments and support, I agree with you that having the converter lens and camera lens as close as possible is still viable and important because it improves performance considerably within distances that most photographers shoot. These converters will rarely be used at distances greater than 50ft, if you want a good closeup of the subject, which is why a tele is being used in the first place. My findings are interesting because they show simply that placing the lens closer doesn't necessarily improve performance over the entire telephoto range and depending on the lens design the distances from the camera lens vary considerably for the same performance.
Because the tl-55 was much further from the camera lens, I wondered how the tcon17 would perform at a similar distance so I decided to test it at 13mm. The results were about the same as the tests I did with the tcon17 at 7mm.
I think at this time I would like to close this thread and I hope that this information has been usefull, especially for anyone that may have had difficulty getting good performance from their tele converter, or anyone who is considering purchasing one.
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