FIRE - what has more influence: Crown angle vs table size

[yssie]

it really does if you are out of focus range?

I'm short-sighted and I've definitely experienced this. Only upside of needing contacts, really. Assume something like my (...simplistic) paintjob is happening. I'm sure there's a better description out there somewhere.
Seeing dispersion with astigmatism must be really gnarly.

 

[Serg]

But here is a fun game - if you are unlucky enough to need glasses - try looking at diamonds close up without - the fire you see seems to be greater

@Garry H (Cut Nut)

Can anyone tell me why this works - try it - it really does if you are out of focus range?

If you need glasses and you do not use its then you squint ("screw up one's eye") to receive sharper image.
in other words such person reduces pupil size that is the reason of bigger fire.
if you take photos with different apperture then the photo with smaller apperture has higher fire.

 

[Karl_K]

Glasses and contacts combine small fans back together.

 

[yssie]

@Garry H (Cut Nut)
If you need glasses and you do not use its then you squint ("screw up one's eye") to receive sharper image.
in other words such person reduces pupil size that is the reason of bigger fire.
if you take photos with different apperture then the photo with smaller apperture has higher fire.

For the nearsighted the most colour from dispersion is visible when deliberate effort is made to not squint - ie. Allow the diamond to remain blurry and out of focus. Inherent inclination is to squint so this does take some effort.

That said, should you choose to squint to focus, everything you note re. reducing aperture size is true; but you'll see less coloured dispersion than if you left your vision unfocused given identical ambient light.

 

[Diamond Girl 21]

It is not exactly the same, one is pleasing to many people and one is not.
I find "arrows" to be pleasing as long as they behave properly and go bright when they should.
I do not like the looks of a bow tie on a oval or Marquise cut.
To me it makes them look off.
Patterns are important.
There are pleasing patterns and there are blah patterns.
Not everyone likes the same patterns but there are some that have wider appeal than others.

Forgive my uneducated response, but isn't that the same basic theory GIA teaches? That there is a wider reference range because essentially, beauty is in the eye of the beholder?

 

[Karl_K]

Forgive my uneducated response, but isn't that the same basic theory GIA teaches? That there is a wider reference range because essentially, beauty is in the eye of the beholder?

No
They dont teach paterns if anything the opposite is what they teach.

 

[AV_]

negative dynamical contrast but some positive spatial contrast

To my mind & eye, the pattern matters for dynamical contrast as well; it may well be that the squareish shapes of old brilliants [& their reinterpretations too, ref. @diagem] let the pattern of dynamical contrast 'rhime' with the face up static patern much more than perfect rounds.

[still have not read through]

 

[AV_]

These two image examples were used by me in the argument, can you notice an optical occurrence?

I am surprised that some facets predicted to be brighter by the ASET, are no longer so.

Would the corners of the table light up over 30 degrees of tilt? [not insisting that they should, just curious - I find this diffcult to read in ASET shots]

 

[Diamond Girl 21]

No
They dont teach paterns if anything the opposite is what they teach.

I respectfully disagree. I took the GD lab class in 2017. Pattern was taught as part of evaluation of face-up appearance in scintillating. We were actually taught quite a bit about it, as we had to assign pattern grades of EX, VG, G, F, and P. This was to be considered as part of the overall cut grade.

I'm not saying this to be contrary @Karl_K, as I have the greatest respect for you and all the experts on this forum. However, I sometimes feel like Alice going down the proverbial rabbit hole when it comes to cut.

 

[Karl_K]

@Diamond Girl 21 its kewl

 

[Karl_K]

However, I sometimes feel like Alice going down the proverbial rabbit hole when it comes to cut.

Rofl
It gets deep at times, some times in manure and at times in new ideas and theories.

 

[OoohShiny]

Can anyone tell me why this works - try it - it really does if you are out of focus range?

I am guessing it's because as light passes through the lens/cornea, it should normally meet at a single point at the back of the eye if one has perfect vision, but when one is long or short sighted, the focus point is in front of or behind the back of the eye - which means that a complete rainbow fan (i.e. seen as white light with perfect vision) will fan out by the time it hits the back of the eye, meaning one will see a rainbow rather than a single white light source?

EDIT: Should have clicked onto the next page before answering, as Yssie has already said what I wanted to but with pictures