Urgent: Light return on H&A- what does it tell me?

[mm]

I am looking to buy a princess stone from a pricescope vendor, and they say they can''t supply an idealscope image, but can supply an image taken on a H&A scope. They provided this example image for me, with the image from my stone to follow shortly.

As you can see from the image, it doesn''t look like an idealscope image would be. It is dark around the edges and corners, and whiter in the middle. I am guessing this is because H&A scopes allow white light in from the top (thorugh the window in the tube below the eye-piece), as well as "coloured light" that is reflected off the H&A scope walls.

So, is there any way I can tell whether the white areas are just full of leakage, or are actually showing the reflection of white light that entered from above?

Can i tell anything from thei image on the likely light performance of this stone?

cheers
mm

 

[aljdewey]

----------------
On 6/9/2004 8:24:30 PM mm wrote:











I am looking to buy a princess stone from a pricescope vendor, and they say they can't supply an idealscope image, but can supply an image taken on a H&A scope.

Can i tell anything from thei image on the likely light performance of this stone?

cheers
mm
----------------

Nope.....an H&A viewer doesn't measure light performance. Completely useless. Why can't they supply an idealscope?

 

[mm]

don't know- guess they don't have one? I know it's not expensive, but I don't know how to ask them to get one.

cheers
mm

 

[valeria101]

That's some unique sight

It may be that the shop doesn't carry an Iscope and providing professional photos via one doesn't sound as easy as spending $20 on the toy.

I wish I had a collection of princess cuts' immages via the H&A viewer to use for reference... but don't. The GemAdviser models do thta though, and obviously there is a relation between the two immages, but not very straightforward. I do not know of any "official" discussion of the relation between the two types of readings.

 

[oldminer]

No one should think a H&A viewer does exactly what the I-S does. The images may have some points of similarity, but just because someone might compare one image to the other does not mean that similar information is displyed in these two images.
So, don't be misled.

A H&A viewer displays if a diamond has been cut with careful symmetry in the faceting style to produce the H&A effect. Diamonds cut with such care are normally very nicely cut and perform well, but it may not be the case on the occasional stone. An H&A viewer does not really predict brilliancy.

An I-S shows the symmetry of cut and also the light return / leakage of a given stone. The I-S does not predict the parameters of cut. The diamond could have a shallow crown or be soemwhat deep, but if it has a good I-S image, then it is effective in light return.

Hope this helps you.

 

[verticalhorizon]

What, in the construction, differentiates the average consumer type H&A viewer from the IdealScope?

 

[mm]

I think its the direction the light enters.

The basic idealscope is just a plastic "stamp loupe" of 7 x magnification with a pink plastic insert. There is a smallish (10mm) hole in the top of the plastic insert that you can view through.

The light comes in from below the diamond, hits the pink surface and then enters the diamond. If the light reflection is good, you see a lot a pink bouncing up to your eye, and some black. I think the black is actually the reflection of your eye (or the cameras lense), looking in through the top hole. If there are white areas, its where the pink light was not reflected up to your eye- and can be assumed to show some form of light leakage.

The H&A scope I have seen allows light in from the top- usually through a gap in the tube. The tube is coloured/reflective and the coloured light is picked up by the arrows or heart facits and reflected up to your eye. The idealscope shows similar patterns as well.

But because the H&A scope allows light in from above, apparently you can't tell if the white areas are leaking, or reflecting the white light coming in from above.

If the H&A scope used light from below, prevented the entry of light from above, and had a reflecting coloured surface inside, it would do pretty much the same thing.

cheers
mm