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#1
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What exactly is the "flange distance" on an SLR camera lens?
I am retrofitting instruments which used film camera backs to digital
SLRs, and one important property is what is called the "flange distance". There are tables on the Web that users have collected for various SLR mounts: http://www.a1.nl/phomepag/markerink/mounts.htm http://en.wikipedia.org/wiki/List_of_lens_mounts etc. But none of what I can find actually defines this "flange distance". One would assume it is the axial distance of the focal plane of the lens (for an infinity target) from "something" on the lens mount. The question is whether that "something" is the shoulder that mates to the opposing surface on the camera, or the tip of the bayonet ears which project out from the shoulder, or what? Notably some Wikipedia authors are trying: http://en.wikipedia.org/wiki/Flange_focal_distance Calling it, "the distance from the mounting flange--the metal ring on the camera and the rear of the len--to the film plane". However, there is no diagram and no defintion of what "metal ring" is meant. And to add to the confusion, mechanical features on various mounts vary enough (some are "male" bayonets, others female receptacles, etc) that no universal definition is possible. I would guess it's the shoulder, at least on mount types having a shoulder, but then my measurements of focal planes on some lenses, and measuring the film position on some old SLR bodies, do not seem to consistently match the distances the tables give. So, anyone have any authoritative definitions to offer? |
#2
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What exactly is the "flange distance" on an SLR camera lens?
In article , Richard J
Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. |
#3
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What exactly is the "flange distance" on an SLR camera lens?
"Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. |
#4
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What exactly is the "flange distance" on an SLR camera lens?
Deep Reset wrote:
"Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. "Universally" is undoubtedly an overstatement; but I'm quite surprised at the range of cameras I've found that marking on -- cheap film P&S, for example. And it's certainly on my D200. |
#5
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What exactly is the "flange distance" on an SLR camera lens?
"David Dyer-Bennet" wrote in message
. net... Deep Reset wrote: "Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. "Universally" is undoubtedly an overstatement; but I'm quite surprised at the range of cameras I've found that marking on -- cheap film P&S, for example. And it's certainly on my D200. It's on all of our Canon DSLRs, too. -- Skip Middleton www.shadowcatcherimagery.com www.pbase.com/skipm |
#6
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What exactly is the "flange distance" on an SLR camera lens?
On Wed, 14 Feb 2007 16:43:05 -0800, "Skip"
wrote: "David Dyer-Bennet" wrote in message .net... Deep Reset wrote: "Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. "Universally" is undoubtedly an overstatement; but I'm quite surprised at the range of cameras I've found that marking on -- cheap film P&S, for example. And it's certainly on my D200. It's on all of our Canon DSLRs, too. Not on my 50 year old Leica (at least not on a cursory examination) but is on my 40 year old Yashica. |
#7
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What exactly is the "flange distance" on an SLR camera lens?
"J. Clarke" wrote in message
... On Wed, 14 Feb 2007 16:43:05 -0800, "Skip" wrote: "David Dyer-Bennet" wrote in message e.net... Deep Reset wrote: "Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. "Universally" is undoubtedly an overstatement; but I'm quite surprised at the range of cameras I've found that marking on -- cheap film P&S, for example. And it's certainly on my D200. It's on all of our Canon DSLRs, too. Not on my 50 year old Leica (at least not on a cursory examination) but is on my 40 year old Yashica. Hmm, are you sure? 'Cause it's on my 50+ year old Exactas, IIRC. -- Skip Middleton www.shadowcatcherimagery.com www.pbase.com/skipm |
#8
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What exactly is the "flange distance" on an SLR camera lens?
On Wed, 14 Feb 2007 19:28:44 -0800, "Skip"
wrote: "J. Clarke" wrote in message .. . On Wed, 14 Feb 2007 16:43:05 -0800, "Skip" wrote: "David Dyer-Bennet" wrote in message se.net... Deep Reset wrote: "Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. "Universally" is undoubtedly an overstatement; but I'm quite surprised at the range of cameras I've found that marking on -- cheap film P&S, for example. And it's certainly on my D200. It's on all of our Canon DSLRs, too. Not on my 50 year old Leica (at least not on a cursory examination) but is on my 40 year old Yashica. Hmm, are you sure? 'Cause it's on my 50+ year old Exactas, IIRC. If it is there it's well hidden. Bear in mind though that Leicas are not SLRs. |
#9
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What exactly is the "flange distance" on an SLR camera lens?
"J. Clarke" wrote in message
... On Wed, 14 Feb 2007 19:28:44 -0800, "Skip" wrote: "J. Clarke" wrote in message . .. On Wed, 14 Feb 2007 16:43:05 -0800, "Skip" wrote: "David Dyer-Bennet" wrote in message use.net... Deep Reset wrote: "Scott Schuckert" wrote in message ... In article , Richard J Kinch wrote: So, anyone have any authoritative definitions to offer? I'm not sure if it's "authoritative", but this is what I've been using for the last 40 years: Ignore the lens itself. It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. The former should be obvious; the latter is universally "universally" ? shown with a symbol - a horizontal line through a circle - inscribed on the top of the camera. Even my DSLR has a "film plane" mark. "Universally" is undoubtedly an overstatement; but I'm quite surprised at the range of cameras I've found that marking on -- cheap film P&S, for example. And it's certainly on my D200. It's on all of our Canon DSLRs, too. Not on my 50 year old Leica (at least not on a cursory examination) but is on my 40 year old Yashica. Hmm, are you sure? 'Cause it's on my 50+ year old Exactas, IIRC. If it is there it's well hidden. Bear in mind though that Leicas are not SLRs. No, but the film plane indicator was there so there could be critical measurements from film plane to subject, for instance for macro. Parallax could be a problem for RF cameras, at close range, at least I guess it would be, and would make such a measurement necessary, I'd think. -- Skip Middleton www.shadowcatcherimagery.com www.pbase.com/skipm |
#10
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What exactly is the "flange distance" on an SLR camera lens?
Scott Schuckert writes:
It's the distance from the front surface of the bare lens mount on the front of the camera, to the film plane. OK, now define "front surface". Seems obvious on the Canon EF mount, but on the old Canon FD mount that used an opposite "gender", the bayonet stuck out still further from what I would call the "front surface", so does that bayonet then count as the real "front surface"? |
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