Your latest acquisition

tim60 · 10-05-2018, 04:54 AM

Originally posted by Racer X 69

So lenses are not three dimensional?

For measurement purposes lenses are 2-D - length and diameter.

The camera body is 3-D - which according to von Helmholtz, 1882, required three distinct measurements of length properties in each of three orthogonal directions to measure the size. I got von Helmholtz' book dredged out of the store at the Barr Smith Library once, about 25 years ago.

Helmholtz is the Helmholtz of the coils, which were one of the rudimentary steps towards WiFi.

tim60 · 10-05-2018, 05:00 AM

Originally posted by pepperberry farm

this discussion doesn't seem like a rabbit-hole at all....

(gets popcorn)

Why should it. Charles Dodgson used to work at University of Up-The-Road-a-Bit-That-Likes-To-Tell-Us-It-is-Rathe-Old. And the bit he does not tell us about Alice is that she had three sons, two of whom died on the Western Front. And given the bizarre things he did put in the book, why could he not have said that?

**pepperberry farm** · 10-05-2018, 05:06 AM

no - no rabbit hole here at all...

(eyeroll)

(:

**UncleVanya** · 10-05-2018, 06:19 AM - **1 Like**

Both are 3D. One simply has two dimensions that are the same due to the shape. One could by the logic given say ludicrous things like a sphere is a 1D object which is clearly wrong.

Racer X 69 · 10-05-2018, 07:23 AM

Originally posted by tim60

For measurement purposes lenses are 2-D - length and diameter.

Lenses are generally cylindrical.

A cylinder is a three dimensional object.

photoptimist · 10-05-2018, 07:49 AM - **1 Like**

Originally posted by UncleVanya

Both are 3D. One simply has two dimensions that are the same due to the shape. One could by the logic given say ludicrous things like a sphere is a 1D object which is clearly wrong.

Indeed!

Perhaps the issue is in the distinction between the number of physical dimensions in the physical object versus the minimum number of numerical dimensions required for a description of the object.

In that sense, a sphere is a 3-dimensional object that requires only a 1-dimensional description.

A a cylinder (or lens) is a 3-dimensional object that requires only a 2-dimensional description*.

A simple brick is a 3-dimensional object that requires a 3-dimensional description.

A DSLR body is a 3-dimensional object that might require at least five dimensions of description if we want to more fully describe the upper height of the viewfinder hump versus lower height of the main body or the thickness of the main portion of the body versus the depth of grip.

As for the "tasteful" deployment of SMUs as a universal unit of acquired photographic equipment size, a lens can be measured with a single stack with the number in the stack indicating the length of the lens and the relative width-ratio of SMU-to-lens showing the lens diameter. Using SMUs to show body size of a recently acquired camera might require a stack next to the grip (to show height and depth) and a line of cookies across the back of the camera.

*Obviously, fully describing the size of some lenses might be more complicated with added numbers to describe the size with and without the hood or the added size of a removable tripod foot.

Racer X 69 · 10-05-2018, 07:51 AM - **1 Like**

Some lenses are truncated cones.

**Canada_Rockies** · 10-05-2018, 08:10 AM - **1 Like**

And some lenses are a small cylinder into a big cylinder attached to a middle sized cylinder with a conical shape on the end of that. And some are even more complex objects.

**Cerebum** · 10-05-2018, 08:40 AM - **1 Like**

My brain hurts

photoptimist · 10-05-2018, 09:52 AM - **2 Likes**

Originally posted by Canada_Rockies

And some lenses are a small cylinder into a big cylinder attached to a middle sized cylinder with a conical shape on the end of that. And some are even more complex objects.

Exactly

SMC Pentax-AF 35-70mm F2.8 Reviews - M Zoom Lenses - Pentax Lens Reviews & Lens Database

**ChrisPlatt** · 10-05-2018, 01:15 PM - **2 Likes**

Originally posted by Cerebum

My brain hurts

You Tube

Chris

**Cerebum** · 10-05-2018, 02:10 PM

Originally posted by ChrisPlatt

Monty Python's Flying Circus - MY BRAIN HURTS! - YouTube

Chris

In a nutshell
(Cheese shop sketch)

**Canada_Rockies** · 10-05-2018, 02:13 PM - **1 Like**

Originally posted by Canada_Rockies

And some lenses are a small cylinder into a big cylinder attached to a middle sized cylinder with a conical shape on the end of that. And some are even more complex objects.

Originally posted by photoptimist

Exactly

SMC Pentax-AF 35-70mm F2.8 Reviews - M Zoom Lenses - Pentax Lens Reviews & Lens Database

I was actually thinking of one of these at the time:

**UncleVanya** · 10-05-2018, 02:41 PM

Where's the throws hands up in the air and runs around giggling insanely emoji?

Racer X 69 · 10-05-2018, 04:21 PM - **2 Likes**

Originally posted by UncleVanya

Where's the throws hands up in the air and runs around giggling insanely emoji?

This is the closest I can manage.

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10-05-2018, 04:54 AM	#14086
tim60 Pentaxian Join Date: Apr 2011 Photos: Albums Posts: 8,755	Originally posted by Racer X 69 So lenses are not three dimensional? For measurement purposes lenses are 2-D - length and diameter. The camera body is 3-D - which according to von Helmholtz, 1882, required three distinct measurements of length properties in each of three orthogonal directions to measure the size. I got von Helmholtz' book dredged out of the store at the Barr Smith Library once, about 25 years ago. Helmholtz is the Helmholtz of the coils, which were one of the rudimentary steps towards WiFi.

10-05-2018, 05:00 AM	#14087
tim60 Pentaxian Join Date: Apr 2011 Photos: Albums Posts: 8,755	Originally posted by pepperberry farm this discussion doesn't seem like a rabbit-hole at all.... (gets popcorn) Why should it. Charles Dodgson used to work at University of Up-The-Road-a-Bit-That-Likes-To-Tell-Us-It-is-Rathe-Old. And the bit he does not tell us about Alice is that she had three sons, two of whom died on the Western Front. And given the bizarre things he did put in the book, why could he not have said that?

10-05-2018, 05:06 AM	#14088
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,764	no - no rabbit hole here at all... (eyeroll) (:

10-05-2018, 06:19 AM - 1 Like	#14089
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,445	Both are 3D. One simply has two dimensions that are the same due to the shape. One could by the logic given say ludicrous things like a sphere is a 1D object which is clearly wrong.

10-05-2018, 07:23 AM	#14090
Racer X 69 Moderator Man With A Camera Join Date: Jun 2010 Location: The Great Pacific Northwet, in the Land Between Canada and Mexico Photos: Gallery \| Albums Posts: 28,073	Originally posted by tim60 For measurement purposes lenses are 2-D - length and diameter. Lenses are generally cylindrical. A cylinder is a three dimensional object.

10-05-2018, 07:49 AM - 1 Like	#14091
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,127	Originally posted by UncleVanya Both are 3D. One simply has two dimensions that are the same due to the shape. One could by the logic given say ludicrous things like a sphere is a 1D object which is clearly wrong. Indeed! Perhaps the issue is in the distinction between the number of physical dimensions in the physical object versus the minimum number of numerical dimensions required for a description of the object. In that sense, a sphere is a 3-dimensional object that requires only a 1-dimensional description. A a cylinder (or lens) is a 3-dimensional object that requires only a 2-dimensional description. A simple brick is a 3-dimensional object that requires a 3-dimensional description. A DSLR body is a 3-dimensional object that might require at least five dimensions of description if we want to more fully describe the upper height of the viewfinder hump versus lower height of the main body or the thickness of the main portion of the body versus the depth of grip. As for the "tasteful" deployment of SMUs as a universal unit of acquired photographic equipment size, a lens can be measured with a single stack with the number in the stack indicating the length of the lens and the relative width-ratio of SMU-to-lens showing the lens diameter. Using SMUs to show body size of a recently acquired camera might require a stack next to the grip (to show height and depth) and a line of cookies across the back of the camera. Obviously, fully describing the size of some lenses might be more complicated with added numbers to describe the size with and without the hood or the added size of a removable tripod foot.

10-05-2018, 07:51 AM - 1 Like	#14092
Racer X 69 Moderator Man With A Camera Join Date: Jun 2010 Location: The Great Pacific Northwet, in the Land Between Canada and Mexico Photos: Gallery \| Albums Posts: 28,073	Some lenses are truncated cones.

10-05-2018, 08:10 AM - 1 Like	#14093
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	And some lenses are a small cylinder into a big cylinder attached to a middle sized cylinder with a conical shape on the end of that. And some are even more complex objects.

10-05-2018, 08:40 AM - 1 Like	#14094
Cerebum Site Supporter Join Date: Oct 2017 Location: Lancaster Photos: Gallery Posts: 3,829	My brain hurts

10-05-2018, 09:52 AM - 2 Likes	#14095
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,127	Originally posted by Canada_Rockies And some lenses are a small cylinder into a big cylinder attached to a middle sized cylinder with a conical shape on the end of that. And some are even more complex objects. Exactly SMC Pentax-AF 35-70mm F2.8 Reviews - M Zoom Lenses - Pentax Lens Reviews & Lens Database

10-05-2018, 02:10 PM	#14097
Cerebum Site Supporter Join Date: Oct 2017 Location: Lancaster Photos: Gallery Posts: 3,829	Originally posted by ChrisPlatt Monty Python's Flying Circus - MY BRAIN HURTS! - YouTube Chris In a nutshell (Cheese shop sketch)

10-05-2018, 02:13 PM - 1 Like	#14098
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by Canada_Rockies And some lenses are a small cylinder into a big cylinder attached to a middle sized cylinder with a conical shape on the end of that. And some are even more complex objects. Originally posted by photoptimist Exactly SMC Pentax-AF 35-70mm F2.8 Reviews - M Zoom Lenses - Pentax Lens Reviews & Lens Database I was actually thinking of one of these at the time:

10-05-2018, 02:41 PM	#14099
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,445	Where's the throws hands up in the air and runs around giggling insanely emoji?

10-05-2018, 04:21 PM - 2 Likes	#14100
Racer X 69 Moderator Man With A Camera Join Date: Jun 2010 Location: The Great Pacific Northwet, in the Land Between Canada and Mexico Photos: Gallery \| Albums Posts: 28,073	Originally posted by UncleVanya Where's the throws hands up in the air and runs around giggling insanely emoji? This is the closest I can manage.