DVD's and sun exposure....

[Dr Mordrid]

Andy G. posted this to the DMN MSPro forum;

Just saw this posted in different forum, very interesting!

"Expose DVDs to sunlight

A German magazine has exposed DVD media to UV irradiation. The amount of irradiation equaled about 20 days of exposure to direct sunlight in Germany (meaning, for Spain, California, or even Australia, it would equal less than 20 days...).


The following discs were not even recognized any longer (no manufacturer IDs mentioned. For some discs, it's clear who made them, for some it's not):

- princo dvd-r

- intenso dvd-r (digital disc dessau?)


The following discs were recognized, but crap afterwards

- verbatim dvd+r

- intenso dvd+r

- sony dvd+r

- tdk dvd+r

- maxell dvd+r


The following discs did not suffer damage at all / did not suffer significant damage:

- verbatim dvd-r

- maxell dvd-r

- tdk dvd-r

- traxdata dvd-r (probably ritek g03, certainly not Vivastar!)

Apparently, Mitsubishi uses different dyes for dvd- and dvd+, because only this could explain why their dvd+r died, whereas their dvd-r didn't. "

Hmmmmm.....

Dr. Mordrid

[gt40]

hmmm, indeed.
I've been using the verbatim dvd-r's for data and the dvd+r's for video( Unfortunatly my standalone dvd player won't recognize dvd-r's).

[William]

I don't agree with the conclusion, without more information on the tests (and drives used). There are a wealth of factors that could bodge these results, including (but certainly not limited to) speed written, which verbatim line of media was used, age of media, shelf time of media (very important in this), physical handling, etc. This is just off the top of my head, there will be more

Maybe all this was carefully controlled, but if they weren't, you can't draw conclusions from that data.

[Dr Mordrid]

Their test method of simulating 20 days of sunlight with UV exposure is a reasonable one and used in many labs for testing paints, coatings, dyes etc.

This would also indicate to me the length of exposure was only a few hours or perhaps a single day, depending on the intensity and wavelenth(s) of the lamp used.

As for the rest; a reasonable person would burn all of them with the same content at the same speed and get disks manufactured during the same quarter if possible...but as you pointed out you never can tell

Dr. Mordrid

[William]

We open another can of worms if we assume that they were recorded at the same speed too; what if Verbatim optimised + for a different write strategy that they did for - For instance if both were tested at 1x, and - was optimised for this when + was optimised for 4x you'd expect far more read problems with +.

Of course, there is also the question of how they defined "damage". And how many of each disc they tested. Then there's that whole accelerated aging debate too.... (It implies that they weren't exposed for 20 days; which by definition makes it an accelerated aging test, which quite a few people regard as highly questionable (I'm realtively neutral on them however))

The results aren't worthless, but they aren't as useful/interesting as they might first appear either.

[Brian Ellis]

I agree, as presented here, the results are hardly scientific.

However, were these discs blank or recorded? I would expect a slightly better light resistance to burnt discs than virgins.

However, are we sure it is a UV phenomenon? I think it much more likely that it is light in the 600 nm range that is more likely to bugger up blank discs, and there is plenty of that in sunlight.

In any case, scientific or not, the moral is clear. Do not expose CD-Rx or DVD+/-Rx to sunlight!

[jeff b]

Very interesting, indeed... Years ago, while working on a product that used EPROMS (one's that can be erased using UV light), I put a couple of these on the dashboard of my car for a whole summer. None of them suffered any erasure from the sunlight, however. I was surprised by this.

It was suggested to me at that time that the diffuse nature of sunlight, despite the component wavelength that would erase the EPROMS, was insufficient to do the job in that length of time.

Perhaps 20 days for DVD's just isn't enough to affect all of them across the board.

Jeff B

[William]

They won't be affected on a dashboard, car windshields filter out the UV component (that's why those self polarising dark glasses don't work whilst you're driving)

[jeff b]

Doh! Yes, a dozen years later, it's that simple. Too bad I hadn't gotten into videography back then, else I would've known that from working with camera lenses.

Jeff B

ps - of course, that doesn't explain why it didn't occur to me when I posted... DOH!

[wkulecz]

Yes that's why EPROMs had an expensive quartz window to let the short wavelength UV light in. Sunlight has very low intensity (fortunately for life on Earth) at the wavelength needed to erase EPROMs -- which needed a rather dangereous "germicidal" UV light. I did have one erased by the soft X-rays from a CRT after a several months -- reprogrammed it, and put a bit of lead foil overtop since the layout couldn't be changed.

"Real" sunlight is poor for a test because it varies with latitude, season, time of day and weather.

I've had audio CD-R rendered unreadable presumably from a few minutes of direct, intense sunlight on the dye surface -- I had burned the CD, and played it inside and while loading the caddy for my wife's car player/changer got distracted and left the disk face up in the sun for a while, it was completely unplayable afterwards.

--wally.

[Flying dutchman]

What magazine was that, BTW?