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95-98% accurate color grading machines.
- Thread starter diagem
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I see this thread has evolved.....but hopefully it isn't considered threadjacking if I address the original thread title..
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We have a GRAN DC 3000 table top Colorimeter, here in-house. We use it to get a 'pre-grade' handle on the color of loose diamonds before we submit them to GIA for grading. We find that it is 'reasonably' accurate and will often dovetail with the subsequent grade given by GIA. It is not perfect however, and I cannot say it would qualify with 98% accuracy........in fact, I doubt it.
We have a GRAN DC 3000 table top Colorimeter, here in-house. We use it to get a 'pre-grade' handle on the color of loose diamonds before we submit them to GIA for grading. We find that it is 'reasonably' accurate and will often dovetail with the subsequent grade given by GIA. It is not perfect however, and I cannot say it would qualify with 98% accuracy........in fact, I doubt it.
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I have owned 2 Gran colorimeters, an Austron, and an SAS2000. All gave some correspondence with GIA color grades with the SAS2000 head and shoulders better than the other two. However, none of the four graded like the GIA in enough cases that one could rely on them with reasonable assurance. Only the SAS2000 was competent enough to give enough details about the spectrum and UV fluorescence that one might understand why the GIA and the machine grade would differ.
All the above place the diamond in a fixed position and take 1 to 31 readings. In theory, more readings, such as what happens with the SAS are going to get tighter results. however, diamonds have differing colors as you revolve them or measure them off their center positions. Some fancy shapes intensify colors away from the center and the GIA does take this into account in a subjective way. None of them grade body color from the side as GIA does with the near colorless series of stones most likely to be measured on machines or in a lab. Marty Haske has done the best of the group with his SAS2000, no doubt in my mind on that.
ImaGem's has a GL3100 which combines all the Sarin measurement stuff with color and fluorescence grading. It currently grades color and fluorescence from the top, not the side view, although it is capable of grading the side view which the others do not have provisions for. The SAS2000 certainly could be modified, but it does not take multiple scans of a stone being rotated as is done in the GL3100. The rotation and multiple scans combined have the potential to create more accuracy and ImaGem believes they do this. ImaGem can take hundreds of scans as the stone is rotated, but I believe the number used is far less. A great deal of testing was done to get to the right number of scans to provide what they would term excellent results.
ImaGem can be programmed to color grade any color of transparent material. It just requires enough GIA graded diamonds to create the database for grading. You can well imagine that there are many colors with very limited numbers of GIA documents available for testing. This has been a real hurdle and handicap. What I hope for in the future is the adoption of such technology for testing by major labs where the device can be readily "taught" the grading process for darker and unusual color diamonds.
The highly accurate and repeatable numbers approaching 98% right now is for a limited color range, D-J, where most of the other devices also function with differing extents of success. None of the developers of these machines has adequate access to diamonds outside the most commercially accepted range. It is in the fancy colors, the fancy shapes, with and without UV fluorescence, and the full range of D-Z where we really need a single device which does the majority of the work in an efficient way and with truly credible results. A large job is ahead.
All the above place the diamond in a fixed position and take 1 to 31 readings. In theory, more readings, such as what happens with the SAS are going to get tighter results. however, diamonds have differing colors as you revolve them or measure them off their center positions. Some fancy shapes intensify colors away from the center and the GIA does take this into account in a subjective way. None of them grade body color from the side as GIA does with the near colorless series of stones most likely to be measured on machines or in a lab. Marty Haske has done the best of the group with his SAS2000, no doubt in my mind on that.
ImaGem's has a GL3100 which combines all the Sarin measurement stuff with color and fluorescence grading. It currently grades color and fluorescence from the top, not the side view, although it is capable of grading the side view which the others do not have provisions for. The SAS2000 certainly could be modified, but it does not take multiple scans of a stone being rotated as is done in the GL3100. The rotation and multiple scans combined have the potential to create more accuracy and ImaGem believes they do this. ImaGem can take hundreds of scans as the stone is rotated, but I believe the number used is far less. A great deal of testing was done to get to the right number of scans to provide what they would term excellent results.
ImaGem can be programmed to color grade any color of transparent material. It just requires enough GIA graded diamonds to create the database for grading. You can well imagine that there are many colors with very limited numbers of GIA documents available for testing. This has been a real hurdle and handicap. What I hope for in the future is the adoption of such technology for testing by major labs where the device can be readily "taught" the grading process for darker and unusual color diamonds.
The highly accurate and repeatable numbers approaching 98% right now is for a limited color range, D-J, where most of the other devices also function with differing extents of success. None of the developers of these machines has adequate access to diamonds outside the most commercially accepted range. It is in the fancy colors, the fancy shapes, with and without UV fluorescence, and the full range of D-Z where we really need a single device which does the majority of the work in an efficient way and with truly credible results. A large job is ahead.
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