Scanner Test Targets - Calibration of Scanners

[kimba325]

To those labs that are ISO accredited and do on screen anaylsis/comparison:

Were you required to calibrate your scanners to ensure proper resolution capture was being done?

We recently came across the SWGIT standard for Testing Scanner Resolution for Latent Print Imaging (1/13/12) after seeing that SWGFAST had posted draft for comment on the STANDARD FOR FRICTION RIDGE DIGITAL IMAGING.

Has anyone already implemented the use of test targets? If so, which one are you using? The SWGIT procedure references ISO-16067-1 Reflective Scanner Test Chart and T-90-N-CG Ultra Resolution Target. There is a rather large cost difference between the two. If you have any recommendations or suggestions, I would be interested in hearing them.

Thanks for any help!
Kim

[George Reis]

I was thinking that I could buy one of the targets, create a set of step-by-step instructions for profiling, then "rent" the target with the instructions to agencies. But, if it would take an agency a week or two to get the target back to me, then it would only be available to about 25 to 50 agencies in any given year - assuming agencies that wanted to calibrate their scanners would be willing to wait until the target was available. On the other hand, it seems kind of crazy for every agency to spend $700 for a test target. And, how many agencies will actually want to do this?

It's great that the SWG groups have come up with something a bit more objective for this process, but I'm not sure that this is the best solution. Will agencies that don't have $700 to profile their $50 scanner suddenly have no identifiable prints (the SWGFAST document is a standard, not a guideline, after all)? Will the next step be to also profile digital cameras? I'm not saying that this is a bad idea, I just think that there are probably simpler, and less expensive solutions.

[ER]

There is a plastic target for $99. We have one of their other plastic targets, and it works fine. Not sure that we would need the fancy chrome and glass target for our purposes.

Also, the SWG documents do state that some prints photographed on inferior equipment at less than 1000ppi may still be identifiable.

Yes, there is another document that details how to check digital cameras.

This isn't quite a calibration but more of a QA check. It doesn't answer the question: Can this device capture at 1000ppi? The question it is meant to answer is: When I capture at 1000ppi, can this device distinguish features that are 40 microns wide?

That seems a worthwhile question to answer. At least for $99.