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Monday, 23 March 2009

Comments

Well. 600 times is a lot of times. As it is I will still stick to *.jpg for convenience and use other formats when needed

I don't quite understand the relevance of this one, since I don't think many people constantly re-save their JPEGs at successively higher compression levels. If anything, it seems an argument that JPEG with normal compression is really quite good.

Just be sure to understand what he is doing: The quality with which the image is compressed is 1 in the first iteration and 0 in the last. So this is not about accumulation of errors while always compressing with the same settings.

Relevance? I thought it was just a cool abstract animation.

That is what Fickr will look like in 100 years. Good thing it's free.

I agree with the others: it actually might have proved the opposite of what it intended ("Jpgs are evil"). I didn't really see much degradation until what would have been the 100-150 mark, so the typical 1-3 times resaving is unlikely to cause problems.

I guess the bigger proof is the many millions of times a day photographers who know what they're doing nonetheless use jpg; if jpg was such a horribly destructive thing, they'd stop after one experience with it.

The importance of RAW, to me, is more in the additional bits. That gives some extra headroom for adjusting exposure when I get it wrong. I haven't measured how much of that is eaten by noise, so maybe I'm fooling myself.

Weird, just totally weird...

But then I figure RAW is weird too!

I knew I shouldn't have been saving my jpegs over 50 times, but I could never quite put my finger on why...

Thanks Mike!

"I don't quite understand the relevance of this one..."

I wonder if you might not actually mean IMPLICATION, rather than relevance, as in, what the hell is Mike trying to imply here?

In fact I don't mean this link to imply anything. I just thought it was kinda neat to watch the image degrade. There's no big didactic point lurking below the surface, no admonition, no point pro or con anything. At least not from me. (Not this time, anyway. Although I guess I don't blame anyone for being suspicious! [s])

Mike

JPEG is evil. But not due to compression. I have one of my all time favourite images. A photo of a grey nurse shark I took years ago on a Nikon coolpix. It's nearly perfect. Fabulous composition, great light. I had a 19mm (equiv) lens about 5 inches away from her nose when I pressed the shutter. I've made well over 50 prints for friends.

I was switching between jpeg and RAW. RAW was so slow. 12 seconds to write a single image. So I was trying to speed things up.

I only got one great shot. In jpeg. And the whole underside of her is blown out, due to the lower dynamic range. All the RAW shots have detail (and are boring)but not that single nearly perfect jpeg. That was the last time I ever took a shot in jpeg that I thought might be interesting.

Gordon

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