TP: Data transfer between lens and body. |
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Dorset Mike ![]() Senior Member ![]() Joined: 20 February 2007 Country: United Kingdom Location: Poole, Dorset Status: Offline Posts: 535 |
![]() ![]() ![]() ![]() Posted: 25 May 2007 at 15:09 |
Can anyone tell me (or direct me to a web site) how data is transferred between a lens and the camera body? Is it say some of the pins define the lens focal length others define aperture, or is it more complex like serial or parallel data transmission where the body reads successive locations within the lens chip.
I would suspect the latter as 5 pins on the older lenses could only have given a maximum of 32 conditions if it relied on static binary levels, whereas accessing locations within the chip gives far more. Cheers MIKE |
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Cheers MIKE,
5D, A350: 50/1.7; 28-75/2.8;80-200/2.8 APO Kit; 500/8; Tam 17-50/2.8; 18-280; 70-300/4-5.6: 90/2.8; MC7 2X; Tokina 11-16/2.8: 80-400/4-5.6; Kenko 1.4X: Min A200 bridge |
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nigelbrooks ![]() Emeritus group ![]() Joined: 15 March 2006 Country: England Location: Ealing, London Status: Offline Posts: 8526 |
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Afternoon Mike.
For the hell of me I can't find the site (I think it was Russian) but I do recall mention of "31 data elements", which would almost tie-in with static binary over five pins, being read from the lens when the ROM was 'interrogated'. If I find the page I will post a link to it here. EDIT: OK the site was Malaysian not Russian -oops! and here's the link. Edited by nigelbrooks - 25 May 2007 at 16:53 |
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I've been away!
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analytical ![]() Senior Member ![]() Joined: 30 January 2007 Country: United States Location: Texas Status: Offline Posts: 3069 |
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If one pin is power and another ground, then that's only three data pins, and 8 static states. |
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Pete Ganzel ![]() Senior Member ![]() Joined: 05 August 2006 Country: United States Location: Little Canada Status: Offline Posts: 941 |
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Hi Mike:
A lot of work has been done by folks who post here. See postings by vasimv like this; Focus Confirmation Several useful things have come of this such as focus confirmation with non AF lenses. What I have found is that the protocol is serial, (specifically, SPI). Here is a pinout of the Minolta AF lens connector. ![]() The data stream is over a single wire, two if you count Gnd. All of the lens focus and focal length encoders I've looked at are four or five bit binary, the lens chip translates that into serial data. Pete Edited by Pete Ganzel - 26 May 2007 at 02:03 |
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