Backlight too strong on Ideal-scope images

[Garry H (Cut Nut)]

Some Ideal-scope photos are taken with too much back-light. They look leaky and all you wonderful helpful prosumers may be inclined to ding and not recommend such diamonds.

The very center indicates the back-light strength (as often mentioned by Karl).

If that area is pale then a good stone will have the same degree of paleness just inside the table.
I just made this little DiamCalc video to help someone understand the issue for this image:

 

[Karl_K]

Interesting Garry.
Some images to back it up.

 

[LittleKite]

This is very interesting! I was playing with the idealscope tool, I noticed that when the background light is relatively strong, the stone looks leaking. I was wondering how to tell what is an appropriate brightness of the background light. Now I know that we can use the center of the stone as the reference.

Once I read an article discussing whether the center of a MRB stone should be red or green on ASET images. It turns out that both are ok and the exact point for the center to turn between red/green can be determined based on depth and table size. I wonder whether there is any equation to calculate it.

 

[Garry H (Cut Nut)]

ASET - Once I read an article discussing whether the center of a MRB stone should be red or green. It turns out that both are ok and the exact point for the center to turn between red/green can be determined based on depth and table size. I wonder whether there is any equation to calculate it.

The answer is that at about 40.8 degrees the light from the center region is coming from the boundary between green and red on the ASET scope.
This can vary a little based on your eye sight and how far the diamond is from the scope.

 

[LittleKite]

Interesting. I did a simple test. When I move the stone closer to the loupe, the center is red. When I move it away from the loupe, the center is green.
What is considered the best/reference position of the stone? Should the table surface be "inside" or "outside" the edge of the ASET scope? I hope I described my question clearly...

 

[Garry H (Cut Nut)]

Interesting. I did a simple test. When I move the stone closer to the loupe, the center is red. When I move it away from the loupe, the center is green.
What is considered the best/reference position of the stone? Should the table surface be "inside" or "outside" the edge of the ASET scope? I hope I described my question clearly...

Flush with the end of the scope is best.
Different pavilion angles will give different results

 

[LittleKite]

Flush with the end of the scope is best.
Different pavilion angles will give different results

When I aligned the table facet with the edge of the scope, the center was green; when the stone moved inside by around 1mm, the center turned red. This means the pavilion angle is exactly 40.8, as reported in the GIA report.

 

[Garry H (Cut Nut)]

When I aligned the table facet with the edge of the scope, the center was green; when the stone moved inside by around 1mm, the center turned red. This means the pavilion angle is exactly 40.8, as reported in the GIA report.

You will receive your ASET Diploma in the mail as we have cancelled the real life presentations this year!

 

[Chiswickian]

LittleKite. Did you get the response you wanted regards how to tell the correct backlight level? I'd be keen to know this also, and if you can use the table centre as a reference point, how to do that to ensure the backlight is correct for the rest of the ASET image?

 

[LittleKite]

LittleKite. Did you get the response you wanted regards how to tell the correct backlight level? I'd be keen to know this also, and if you can use the table centre as a reference point, how to do that to ensure the backlight is correct for the rest of the ASET image?

I have an ASET scope and did some experiments with it. The key is that the center always has light return and should not be "too white". I used this approach to adjust background light when checking my ring. It worked very well.