Amazing Human Eye (not sure where else to put this)

[Pabs]

It just amazes me how accurate the human eye is at seeing square / detecting slightly out of square
Here is a sliver sawn to make this peice of ply square.

In a dynamic situation (in an human head bobbin around)
Against any background in most lighting
Amazing!

The trouble comes translating this into action and sawdust!!

 

[Spectric]

It just amazes me how accurate the human eye is at seeing square / detecting slightly out of square

But at the same time the brain has the ability to use this info from the eye to deceive, think of the occasions where rather than being perpendicular or level you fix something relative to something else and even though not technically correct it is perceived as correct because there are two datums the same.

 

[Pabs]

But at the same time the brain has the ability to use this info from the eye to deceive, think of the occasions where rather than being perpendicular or level you fix something relative to something else and even though not technically correct it is perceived as correct because there are two datums the same.

almost delightfully flawed!

 

[TRITON]

My father used to tell me he could tell if a casting was out, by eye, when placed into the cnc machine. Said he couldn't understand why he could tell but once they actually took the measurements they always found it needed readjusted.
This might be a casting 50t in weigh. Big engineering on ships etc.

 

[Jacob]

My father used to tell me he could tell if a casting was out, by eye, when placed into the cnc machine. Said he couldn't understand why he could tell but once they actually took the measurements they always found it needed readjusted.
This might be a casting 50t in weigh. Big engineering on ships etc.

Sorry to mention the dreaded word sharpening but one of the main themes of the modern trend is the sheer impossibility of judging 30º by eye!
I think the basic angles; 90, 45, 30, are quite easy to hit reasonably closely.

 

[thetyreman]

yes training the eye is a big part of being a craftsman, I found I've managed to improve my eye a lot, to the point now where I notice every gap and every mistake builders, joiners make everywhere I go, you can't 'unsee' it.

 

[Daniel2]

yes training the eye is a big part of being a craftsman, I found I've managed to improve my eye a lot, to the point now where I notice every gap and every mistake builders, joiners make everywhere I go, you can't 'unsee' it.

Ha ha, I've got the same problem.

 

[TRITON]

.

 

[Sgian Dubh]

.

Okay? I don't understand the full stop comment. I've seen this a few times and I always wonder what the comment is meant to say.

Or, maybe the full stop indicates the writer deleted a message for some reason, but decided leaving the . was important.

Anybody got any better ideas?

And yes, our eyes are very good at detecting things that are even only slightly out of whack. For instance, our eyes can detect a sag of as little as about 1 - 2 mm in a loaded bookshelf with a ~600 mm span.

To broaden the discussion a bit, fingertips are excellent for spotting the slightest discrepancies in a flat surface, such as planer ripple, small depressions or visually very hard to see bumps, tearout, almost imperceptible steps at the shoulder line of joints, and so on. Slainte.

 

[Phil Pascoe]

You can't delete altogether you have to leave something.

 

[Sgian Dubh]

You can't delete altogether you have to leave something.

I didn't know that. Thanks. I guess I didn't know because I can't ever recall needing or wanting to delete a whole post. Maybe I'm just too bull headed and suffer from over-confidence that whatever I've said is okay, ha, ha. Edit a post somewhat, yes, but complete deletion, never. Slainte.

 

[eribaMotters]

We have mentioned the eye, but what about the sense of touch. When I started wearing varifocals I lost the ability to move in closer to magnify and see in more detail. Using fingertips you can feel if a joint has a lip or a hinge is not set flush. You can feel a human hair in thickness, or at least I could before I started dropping lumps of heavy wood on the ends of fingers or hitting them with things I should not have.

Colin

 

[Deadeye]

It just amazes me how accurate the human eye is at seeing square / detecting slightly out of square
Here is a sliver sawn to make this peice of ply square.
View attachment 151931View attachment 151952View attachment 151953
In a dynamic situation (in an human head bobbin around)
Against any background in most lighting
Amazing!

The trouble comes translating this into action and sawdust!!

Am I being daft, or was the original out by the thickness of the sliver plus the kerf of the saw (3mm or so)?

 

[danst96]

I have an uncanny ability to judge the volume of things, usually liquids. I can pour from one container to the next without measuring and will hit the amount almost to the ml, I don't know why and sometimes it scares me.

It's weird things like I enjoy making cocktails, I'll make the drink in a shaker, then I'll take any old glass and will put ice in and will sometimes consciously add in or take out a couple bits of ice, even though I don't know the actual volume or drink or the cup and then I'll pour in the drink and the changes I consciously made to the ice without measuring anything mean the drink just fits in.

Yeh, it's weird.

 

[Pabs]

Am I being daft, or was the original out by the thickness of the sliver plus the kerf of the saw (3mm or so)?

I thought that until I asked SWMBO who confidently told me dont be daft the saw cuts plumb to the long side so won't influence the angle of the shaving.

 

[Pabs]

I have an uncanny ability to judge the volume of things, usually liquids. I can pour from one container to the next without measuring and will hit the amount almost to the ml, I don't know why and sometimes it scares me.

It's weird things like I enjoy making cocktails, I'll make the drink in a shaker, then I'll take any old glass and will put ice in and will sometimes consciously add in or take out a couple bits of ice, even though I don't know the actual volume or drink or the cup and then I'll pour in the drink and the changes I consciously made to the ice without measuring anything mean the drink just fits in.

Yeh, it's weird.

I tend to become more generous with my estimation of liquids as the evening drags on.. especially if its the inlaws.

 

[Deadeye]

I thought that until I asked SWMBO who confidently told me dont be daft the saw cuts plumb to the long side so won't influence the angle of the shaving.

Ah. I'd misunderstood the situation. I thought it was turning a rectangle into *a* square, rather than "square" as in right-angled. In the former, the kerf matters; in the latter it doesn't.

 

[Pabs]

.....but what about the sense of touch.

Colin it's in some ways even more freaky that the eye.

I imagine if I was tasked with setting up sensitive pressure-triggered actuators (that sent a full-bandwidth signal of coordinates from all dimensions to a large supercomputer which, in real time, can interpret where the actuators are in space and how the minute variation in amplitude of said actuators affect said signals and - delivery efferent signals toward multiple large pully-type beams which return a pleasing nod or a frank grimace depending).....

plus having spent years studying it (personally) and as a species we're still no closer than leonardo at figuring it all out (in general terms)

 

[saleemtaibjee]

The human eye is very good at judging fractions of lengths. So if you know the total length (or diameter if a circle), and can judge a fraction of this total, you can come to a very reasonable estimate of the part length. I use this all the time at work down the microscope.

 

[Fergie 307]

But at the same time the brain has the ability to use this info from the eye to deceive, think of the occasions where rather than being perpendicular or level you fix something relative to something else and even though not technically correct it is perceived as correct because there are two datums the same.

If you look at the Parthenon it appears that the upright columns are all vertical and parallel, in fact they were deliberately made splaying out slightly so that the eye perceived them to be vertical. Likewise the plinth it stands on is not actually straight, but appears so. Very clever.