Things you always wanted to know the answer to [Vol. 3]

[Halmyre]

Roofless Toothless said:

CR6ZZ said:

227bhp said:

Why do some animals (cats &dogs) eyes reflect light and others (humans, birds etc) don't?

Because they have a layer at the back of the rods and cones (Tapetum lucidum) that reflects light back, thus giving the receptors another "go" at capturing light. Enables animals to see better in low light conditions.

What causes all the red eye in my photographs then?

The bright flash reflecting from the eye's retina.

[Roofless Toothless]

Halmyre said:

Roofless Toothless said:

CR6ZZ said:

227bhp said:

Why do some animals (cats &dogs) eyes reflect light and others (humans, birds etc) don't?

Because they have a layer at the back of the rods and cones (Tapetum lucidum) that reflects light back, thus giving the receptors another "go" at capturing light. Enables animals to see better in low light conditions.

What causes all the red eye in my photographs then?

The bright flash reflecting from the eye's retina.

How is that different from what CR6ZZ said? The rods and cones are in the retina, I thought.

[Moonhawk]

Halmyre said:

Roofless Toothless said:

CR6ZZ said:

227bhp said:

Why do some animals (cats &dogs) eyes reflect light and others (humans, birds etc) don't?

Because they have a layer at the back of the rods and cones (Tapetum lucidum) that reflects light back, thus giving the receptors another "go" at capturing light. Enables animals to see better in low light conditions.

What causes all the red eye in my photographs then?

The bright flash reflecting from the eye's retina.

Yep - even though humans don't posses a Tapetum lucidum - the retina is still slightly reflective.

The eye is also shaped like a retro reflector - and as such any bright light that is coincident with the viewing angle (like in a camera with a flash mounted very close to the lens) will show a strong reflection back along the angle of incidence. The reflected light appears red because the retina is that colour in humans.



To avoid red eye - the flash should ideally be mounted as far away from the lens axis as possible. Anti red eye flash in camera phones tries to combat red eye by emitting a bright flash just before the main flash used to take the image. This has the effect of causing the pupil to contract and thus give less opportunity for light to enter the eye and reflect off the retina.

[Halmyre]

Roofless Toothless said:

Halmyre said:

Roofless Toothless said:

CR6ZZ said:

227bhp said:

Why do some animals (cats &dogs) eyes reflect light and others (humans, birds etc) don't?

Because they have a layer at the back of the rods and cones (Tapetum lucidum) that reflects light back, thus giving the receptors another "go" at capturing light. Enables animals to see better in low light conditions.

What causes all the red eye in my photographs then?

The bright flash reflecting from the eye's retina.

How is that different from what CR6ZZ said? The rods and cones are in the retina, I thought.

The extra lining in the animal's eyes just reflect back lower levels of light (torches, headlights etc.) If you look through image-intensifier night-sights, you can see the reflection from a human's eyes.

[FiF]

john2443 said:

Jonboy_t said:

On the speed limit subject, what’s the point of ‘national speed limit’? Why not just 50/60/70 on the appropriate roads?

So that if it changes, the law is just re-written to say 40/50/60 instead of having to go and change eleventy billion signposts.

That's before you even get to the issue that different vehicles have different limits on the same road. If you've ever driven in from a ferry port you will see an attempt to explain it on road signs, however the situation is so complicated that even trying to explain basics the signs are too crammed to be an effective means of providing the information.

And all tgat is without even touching on the issues of car derived vans, ie when us it a van or not, dual purpose vehicle or not, it might look like a motor home but... and so on, not to mention confusion in some minds whether it's the DVLA designation or the specific bits of the vehicle regulations etc which are most important.. Frankly the law is a dog's breakfast, and the NSL and inaction by the various authorities allows it to remain so, and of course exist as a bit of a cash cow.

[BristolRich]

Which is quicker at removing burnt on Sheppard's Pie from a LeCruset Pot?

Leaving it to soak in cold water for hours and hours on end?
Leaving it to soak in hot water, frequently replacing the cooling water with hot?

Dishwashers and pressure washers are not applicable.

[FiF]

Roofless Toothless said:

Shakermaker said:

Roofless Toothless said:

Guide dogs.

Why do I not uncommonly see people out training guide dogs, but relatively rarely notice a blind person actually using one?

Perhaps you live close to a Guide Dogs training school, for dogs which are then spread out across a wider region?

I did some work a few years ago with a couple of chaps from one of the leading Guide Dogs charities, and as we went about our business with their dogs, we were talking about the training the dogs have to go through. It is very impressive, but not that many dogs actually make it through compared to how many are taken in for training - so you'll see a higher number of trainees than you will actual dogs in service.

Thank you. I consider my question to be comprehensively answered.

The other thing I would add, if I may, is that there aren't enough guide dogs. So for example a family member has a colleague who had a guide dog for years. That dog reached its retirement age and now she has been waiting quite a long time for a new dog.

Also there are dogs who are assistance dogs in other ways than for the blind. For example medical alert dogs, and another very worthy cause.

http://www.telegraph.co.uk/christmas/0/love-bits-m...

[glenrobbo]

BristolRich said:

Which is quicker at removing burnt on Sheppard's Pie from a LeCruset Pot?

Leaving it to soak in cold water for hours and hours on end?
Leaving it to soak in hot water, frequently replacing the cooling water with hot?

Dishwashers and pressure washers are not applicable.

I assume it became burnt on due to the extremely high temperatures encountered during the re-entry phase.
As it has been firmly stuck on for over 56 years, I think you are wasting your time attempting to remove it now.

Just bin it.

[Shakermaker]

Voldemort said:

My (and probably your) driving licence includes the first five characters of my surname. What if you don't have a five character surname..?

I have a 4 letter surname, all are included in the driving licence number, the rest of which is then a combination of placeholder letters/numbers and various bits of your date of birth split up so that it can be checked quickly by those "in the know" that it is valid.

[fomb]

Jonboy_t said:

On the speed limit subject, what’s the point of ‘national speed limit’? Why not just 50/60/70 on the appropriate roads?

It's because not everyone has the same limit. In a 30 everyone does 30, but on a motorway trucks etc have a different limit to cars.

[Dr Jekyll]

fomb said:

Jonboy_t said:

On the speed limit subject, what’s the point of ‘national speed limit’? Why not just 50/60/70 on the appropriate roads?

It's because not everyone has the same limit. In a 30 everyone does 30, but on a motorway trucks etc have a different limit to cars.

Until recently LGVs had a 40 limit in single carriageways but there were plenty of posted 50 limits.

[Nimby]

Shakermaker said:

Voldemort said:

My (and probably your) driving licence includes the first five characters of my surname. What if you don't have a five character surname..?

I have a 4 letter surname, all are included in the driving licence number, the rest of which is then a combination of placeholder letters/numbers and various bits of your date of birth split up so that it can be checked quickly by those "in the know" that it is valid.

I have a 4 letter surname. The 5th character in my driver number is a "9".

[SpeckledJim]

Nimby said:

I have a 4 letter surname.

Oooh! Oooh! Sir! Sir!

Is it Nimb?

[Shakermaker]

Nimby said:

Shakermaker said:

Voldemort said:

My (and probably your) driving licence includes the first five characters of my surname. What if you don't have a five character surname..?

I have a 4 letter surname, all are included in the driving licence number, the rest of which is then a combination of placeholder letters/numbers and various bits of your date of birth split up so that it can be checked quickly by those "in the know" that it is valid.

I have a 4 letter surname. The 5th character in my driver number is a "9".

Maybe 9 is the placeholder, as that is also the 5th character in my licence number

[RizzoTheRat]

Nimby said:

I have a 4 letter surname. The 5th character in my driver number is a "9".

Same here, 10% chance or is it always 9?

[Voldemort]

Anyone hereabouts got a three letter surname and a driving licence ?

[Speed 3]

RizzoTheRat said:

Nimby said:

I have a 4 letter surname. The 5th character in my driver number is a "9".

Same here, 10% chance or is it always 9?

and me....

The DOB section is a quirk too as although its not supposed to be DDMMYY, in my case it is because of the actual digits.

[Bullett]

I used to work in Blockbusters, the driving license was often used as a form of ID.
I once met a Mr Peniston, he was unhappy with his d/l number.

[RATATTAK]

Where do you look on a license to see how many points are on it ?

[talksthetorque]

Does this work for everyone then?

NNNNNYMMDDYIIRrr


N Surname
Y Year
M Month
D Day
I Initial
R Random Number
r Random Letter

?

Edited by talksthetorque on Thursday 23 November 21:54