Can this be right?

[AdamW]

In Understanding Digital Photography Bryan Peterson says, "Every time you open and and close a JPEG on your computer, the file degrades due to data being lost; and eventually, with repeated openings and closings, the file would be rendered useless." (p.18) He goes on to say that because of this, you should save a copy of every JPEG you want to keep as a TIFF.

I think he's got to be mistaken. I know that saving a JPEG changes it, but simply opening it and closing it shouldn't change the structure of the data. What about opening a JPEG from a read-only media, like CD-Rs?

[Norm in Fujino]

You're right; he's wrong. Merely opening and closing the file (without saving) does nothing. In fact, even resaving does very little, until about the 50th resave (or somthing like that; I've seen some tests before and particularly when you start out with a good compression ratio, saving makes virtually no change until many, many iterations.)

[Elisha]

i've opened and re-saved a 2mb file and once it re-saves its around 900k

[Nickcanada]

That's different because you are saving it after viewing. The file size will change depending on your saving settings and so on. I believe what Adam is referring to is the author is claiming that after simply opening a JPEG to view, not even saving, the file degrades. Doesn't make much sense to me either. It's not the first time I have heard this question concerning this book either. How is the rest of the book?

[AdamW]

Nick--

That is what I meant.

As to the rest of the book, I've only skimmed it, but it appears to have a lot of overlap with Exposure. That's not necessarily a bad thing, because I can certainly stand to review that stuff anyway. I'll just trust him on photography stuff and be wary of the computer science stuff.;)

Adam

[Nickcanada]

Thanks Adam, I have heard very good things about the book from many people who I respect, so I'm sure there is lots of good stuff in there....

Should we give you a homework assignment?? A full ten page review by Monday??? :D

Sorry just a little payback from all the tortuous assignments given to me in school. :D

[AdamW]

Well that's what I get for telling you all that I'm a high school teacher. Actually, I had already decided I was gonna post a mini review, so you'll get it in a couple of days. I'll probably do it in a new thread in this forum.

By the way, I found another error, but this seems like a typo: he talks about "1 megabyte" memory cards when he must mean "1 gigabyte."

For the thrilling conclusion, stay tuned, same bat-time, same bat-channel.;)

[Phill D]

With the Batman references any relation to the Adam West who played the Batman character on TV? Back on topic though I've got Understanding Exposure & thought it was a good book so could you include some coments on the duplication between the two to see if the digital one is worth getting as well.

[AdamW]

No relation to Batman (although I heard that a lot as a little kid in the 60s.) Just too much television and popular culture references taking up valuable space in my brain.

I'll post a dual review this weekend.

[zmikers]

No relation to Batman (although I heard that a lot as a little kid in the 60s.) Just too much television and popular culture references taking up valuable space in my brain.

I'll post a dual review this weekend.

Thanks for that, that would be great. We'll just look for your symbol shining in the sky, then we'll know your ready ;)

[AdamW]

Actually, I prefer the Bat Phone (http://www.guyswithtowels.com/images/articles/batphone.jpg).

To our friends who weren't in the States in the 60s: the above comments reference the cheesey, low-budget Batman television show (http://en.wikipedia.org/wiki/Image:Batman1966_1.gif), starring Adam West. It was notable for it's use of fairly major stars (http://en.wikipedia.org/wiki/Batman_%28TV%29:_Guest_appearances_and_episodes) as villians and in cameos (Julie Newmar (http://en.wikipedia.org/wiki/Julie_Newmar) and Eartha Kitt (http://www.1966batfan.com/cat2.htm) as Catwoman had almost as much of an, um, impact on my, ah, development as did Diana Rigg as Mrs Emma Peel. (http://en.wikipedia.org/wiki/Emma_Peel))

;)