Macro Tubes
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Posted 08/02/2010 - 22:15
If you are using a 50mm manual lens with macro tubes how do you calculate the focal length to dial into the camera?
Regards Barrie K20D K200D DA*300 A50/2.0 A50/1.7 FA50/1.4 FA135/2.8 FA35 DA70/2.4 DA18-55 DA17-70 DA55-300 DA*50-135 Samsung 12-24 Tamron 28-300XRDi 70-200/2.8 Sigma Macro 50,105,180 170-500 400/5.6MF 24/2.8
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Posted 08/02/2010 - 22:30
Mike-P wrote: I set mine to the focal length of the lens. So does it not change if you use different lengths of tube? typo Regards Barrie K20D K200D DA*300 A50/2.0 A50/1.7 FA50/1.4 FA135/2.8 FA35 DA70/2.4 DA18-55 DA17-70 DA55-300 DA*50-135 Samsung 12-24 Tamron 28-300XRDi 70-200/2.8 Sigma Macro 50,105,180 170-500 400/5.6MF 24/2.8 Last Edited by bforbes on 08/02/2010 - 22:31
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Posted 08/02/2010 - 22:31
Quote: I set mine to the focal length of the lens. Agreed. Mine are auto tubes so I just leave them at the focal length set by the camera, which is that of the lens, not had any problems doing this. Dont Worry, Be Happy.
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Posted 08/02/2010 - 22:33
You beat me to the post Barrie
 , no my auto tubes set the focal length of the lens regardless of the number of tubes fitted. Dont Worry, Be Happy.
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Posted 08/02/2010 - 22:34
No just give them the focal length since tubes won't change them.
I believe when you use a TC then you should change it though. Stefan K10D DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55 AF-540FGZ Last Edited by Anvh on 08/02/2010 - 22:34
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Posted 08/02/2010 - 23:12
I can't get my head round this, because are are totally altering the optical relationship between the lens and the sensor.
impotentspider wrote: You beat me to the post Barrie , no my auto tubes set the focal length of the lens regardless of the number of tubes fitted. auto as in auto focus or auto as in "PKA". If it's auto focus then would the camera not just detect the lens without knowing whats going on in between, as happens with auto focus teleconverters? If it's PKA are you not asked to dial in the focal length? Regards Barrie K20D K200D DA*300 A50/2.0 A50/1.7 FA50/1.4 FA135/2.8 FA35 DA70/2.4 DA18-55 DA17-70 DA55-300 DA*50-135 Samsung 12-24 Tamron 28-300XRDi 70-200/2.8 Sigma Macro 50,105,180 170-500 400/5.6MF 24/2.8
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Posted 08/02/2010 - 23:15
bforbes wrote: I can't get my head round this, because are are totally altering the optical relationship between the lens and the sensor. A 50mm lens is a 50mm lens no matter how far away you hold it from the sensor. The focal length doesn't change just because you're using it for macro work...  Bodies: K10D | Spotmatic SP K Lenses: DA12-24 | DA35 Macro Limited | FA43 Limited | FA77 Limited | D-FA100 Macro M42 Lenses: Takumar 58/2 | Super-Takumar 50/1.4 (early)
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Posted 08/02/2010 - 23:25
It's academic anyway if using a tripod. You length you dial into the camera is for the Shake Reduction, but you'll have SR turned off.
~Pete
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Posted 08/02/2010 - 23:27
iceblinker wrote: It's academic anyway if using a tripod. You length you dial into the camera is for the Shake Reduction, but you'll have SR turned off. Correct It's the engineer in me needing to know how things work. Regards Barrie K20D K200D DA*300 A50/2.0 A50/1.7 FA50/1.4 FA135/2.8 FA35 DA70/2.4 DA18-55 DA17-70 DA55-300 DA*50-135 Samsung 12-24 Tamron 28-300XRDi 70-200/2.8 Sigma Macro 50,105,180 170-500 400/5.6MF 24/2.8
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Posted 08/02/2010 - 23:32
Yep focal length stays the same but you alter the focus distance.
bforbes wrote: If it's auto focus then would the camera not just detect the lens without knowing whats going on in between, as happens with auto focus teleconverters? Don't know about the TC but there is a "chip" in the lens with his data and that gets transferred through the "info-contact"  Focussing just goes through the AF sensor so no need for feedback from the lens about that, however it does give the camera some info about focusing but nothing exciting. I believe that hardly any TC do give the right focal length automaticly only the Pentax ones does give it through correct so focal length + TC magnification. Stefan K10D DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55 AF-540FGZ
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Posted 08/02/2010 - 23:39
My tubes are auto and if I am using an A lens or newer then the camera chooses the focal length (which I presume is the lens). If using a M42 or M/K mount then I dial in the lens myself. Never use a tripod and have never had a problem doing it that way. But if it's wrong and I will get sharper shots any other way then all advice gratefully received. (apart from use a tripod).
 My FLICKr My PENTAX GALLERy Last Edited by Mike-P on 08/02/2010 - 23:40
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Posted 09/02/2010 - 21:56
Mike, if your shots get any sharper we'll all be cutting our fingers on them...
Kris Lockyear Ask a question and be a fool for five minutes. Keep quiet, and be a fool forever. Chinese proverb. Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4. |
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