Why do such wide variances ocer?

After doing much reading here I think I’m slowly starting to understand things but after doing some scans I’m confused as to why the same disc can return different results.

These are my scans of the same disc taken over the last three days:

Then there’s this one that I also did yesterday and the quality score shot down to 4?

All drives will show some variance when scanning discs, and discs of more questionable burn quality will show more variance than discs of excellent quality.

Especially when it comes to single spikes as the two spikes seen in your first and third scans, you might experience that some spikes are there every time you scan the discs, while other spikes are there some times and they’re gone at other times.

This is becasue scanning is an interaction between the disc and the drive, and some problems will be more or less intrinsic to the disc and will always show up in a scan (provided that the scanning application doesn’t drop samples or remove spikes automatically), while other problems are transient as a result of the drive not always being able to read the disc perfectly at a certain location at high speed.

The Nero CD-DVD Speed quality score is a number based solely on the highest PIF value, and that’s why you can get wildly varying quality scores on the same problematic disc.

Many thanks for the reply and info DrageMester.

So the main variable is with the drive, I take it that regardless of which scan I look at that these are poor scans, and is this why I see many adverse comments on Ritek G05 media (these are actually Ridisc extreme ff white printables 8x -R)?

Is it better to take a number of scans and take an average?

Any other comments?

The main problem with G05 isn’t how they scan when new, but how long they last. They can deteriorate very quickly, sometimes being unreadable after as little as a couple of weeks.

No (unless, maybe, you scan with different drives). The changes in your scans above are almost insignificant despite what the way it looks at first sight.

As DrageMester mentions, it’s those single spikes that change the overall perspective and the quality score. Take the spikes off and your scans are twins.

The first one looks like a “real” spike, as it’s the peak of a cluster of PIFs, so in my book this is a mediocre burn.

Not susprising, coming from a printable G05, and Ridisc-branded at that… poor media most of the time. And as Qyngali mentions, with a very short lifetime expectancy. The ones I had for testing were unreadable after three weeks. :Z