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03-17-2010, 01:12 PM   #76
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QuoteOriginally posted by justinr Quote
It therefore follows that if the record of what one particualar pixel recieved (nothing, for instance) is amalgamated with the records of other pixels and cannot be seperated out afterwards, ie it is assumed to be the same, then definitive information has been lost.
True. But this doesn't happen with RAW - you *can* completely separate out each individual pixel,so it *is* lossless. not sure where you got the idea it was otherwise.

03-17-2010, 02:03 PM   #77
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QuoteOriginally posted by Marc Sabatella Quote
True. But this doesn't happen with RAW - you *can* completely separate out each individual pixel,so it *is* lossless. not sure where you got the idea it was otherwise.
Simple.

If we go back ten years to when digital was making itself felt and a 3mp camera was a wonder to behold many of us film folk got digital savvy via the scanner. What we worried about then was only jpeg's or TIFFs, and we had good reason to because PC memory and processing power was so much lower and slower. I was shooting MF and even the occasional 4X6 which could quite happily tie up 300mb if I set the resolution high enough.

Then digital capture really took off and I guess film finally lost out when the first 5mp cameras came along as this was reckoned to have about the same resolution as a 35mm frame. It was then that we started hearing about RAW which we were assured was a total and uncompressed record of the what the pixels received. It therefore followed that for a given camera there can only be one size of RAW file, and to begin with that was how it worked. That is why RAW means a totally unadulterated file to me. Now if techniques have been developed to allow compression of these RAW files and yet they still differ from jpeg's (in colour depth for instance) then that is a different type of file altogether to my mind. Perhaps we are arguing over semantics here and the meaning of the word RAW has drifted and changed or perhaps we should think of another name for these half way houses, but that is where I am coming from.

Now as far as jpegs are concerned I'm still not happy about the answers I've received in that if they are more 'efficient' then why not set them at 5mb and then boast of how jpegs from your camera can be blown up even larger? Accuse me of short sighted cynicism if you like but I imagine that there is some sort of marketing ploy at work here. If you are a camera manufacturer and have 10 million pixels to play with why not make the most of them, unless it discourages people from upgrading of course.
03-17-2010, 02:10 PM   #78
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QuoteOriginally posted by simico Quote
Justinr, just drop the jpge file size thing 'cause you clearly got it all wrong and don't seem to understand how it really works. Jpg file size doesn't mean and matter much, to begin with. Your K10D uses higher and/or better compression than you ist, that's all.

Damn Brit, you adobergb snob Adobergb is just a tiny bit wider than srgb, and it's mostly in the less usefull range. Use Prophoto or Wide gamut if you want a significantly wider color space... not that the end results will be significantly better than using srgb all the way, but do whatever floats your boat
Perhaps you could point me to where I change my K20 settings to shoot ProphotoRGB.

Yes when I process them in Raw the settings are set to Prophoto but the camera is set to AdobeRGB.
03-17-2010, 05:11 PM   #79
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QuoteOriginally posted by Damn Brit Quote
Perhaps you could point me to where I change my K20 settings to shoot ProphotoRGB.

Yes when I process them in Raw the settings are set to Prophoto but the camera is set to AdobeRGB.
But you said you shoot RAW. What difference does it make what your camera is set to? Except to generate JPG files which have a colour space embedding method that is incompatible with most software (including your web browser, btw).

03-17-2010, 05:21 PM   #80
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QuoteOriginally posted by justinr Quote
Whatever the debate about jpeg size I'm a lot happier with todays results from the K10 having adjusted my techniques a little-



Still some soft focussed ones amongst the the files but I think this was because I didn't allow enough time for AF to work or too close etc.
Very nice, were the soft ones from after or before the pub.
Happy St. Paddies day!
03-17-2010, 06:27 PM   #81
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QuoteOriginally posted by justinr Quote
Now as far as jpegs are concerned I'm still not happy about the answers I've received in that if they are more 'efficient' then why not set them at 5mb and then boast of how jpegs from your camera can be blown up even larger? Accuse me of short sighted cynicism if you like but I imagine that there is some sort of marketing ploy at work here. If you are a camera manufacturer and have 10 million pixels to play with why not make the most of them, unless it discourages people from upgrading of course.
Oy, that's not cynicism, that's paranoia. By the way, TIFF files can be compressed too. They can be compressed losslessly and with loss. I can use JPG compression, LZW compression, ZIP compression and a bunch of other compression methods in TIFF files, or I can leave them uncompressed.

Here's the REAL difference between lossless and lossy compression:

Lossless
======
You take a file, you compress it. It takes up less space on your hard drive because all duplicate data has been combined together, along with information on which address space this duplicate data needs to show up at. When you uncompress it, you end up with the exact same original file, bit for bit, without any difference whatsoever (this is what's used for RAW compression)

Lossy
====
You take a file, you compress it. It takes up less space on your hard drive because of the same reasons above AND some of the data was deleted. When you uncompress it, you end up with a file that is different from the original. Bits are missing, others have been moved around. For music and pictures, this isn't necessarily such a big deal depending on the algorithm used (this is what's used for JPG, MP3, most WMA and WMV, MPG, DIVX, etc)

Now as far as pictures are concerned, I think a bit of pixel-peeping is in order. So here's a picture I took with my K-7 using a Super Takumar 50mm F1.4. Shutter speed was 1/25 @ ISO400 and I think the aperture was F4.5 or so.

I developed these from RAW, then used Gimp to create a bunch of files with different compression levels. Here's a nearly-pristine version saved with all the maximum JPG settings and compression at 100/100 (Gimp has tons more JPG compression options than Photoshop):


So here are some 100% crops of different compression versions. Keep in mind, I kept re-saving the entire, unedited original uncompressed file into a JPG at varying compression levels.

Here's one from the uncompressed version (straight from RAW, there was no re-saving it)

This file is a 34.3mb TIF file. It is uncompressed.

And here's another one after I saved the image at maximum JPG settings:

I'd say the difference is imperceptible. Detail lines like this are where JPG compression tend to show the most. This file was 10.9mb.

This one was saved at 95/100 compression level, the rest left at best quality:

Again, no perceptible difference. This file was 3.8mb. That's a huge difference! And yet there's absolutely no perceptible difference in quality. Also remember that this is a 14 megapixel image, and it's already about the same size as your 10 megapixel images.

This one was saved at 80/100 compression level, the rest still at best quality:

Wow, I can maybe start to make out some compression artifacts around the contrast lines. Keep in mind of course that this is a 100% crop, which wouldn't actually be noticeable in a normal-sized print. File size for this one was 1.3mb!!!

This second-last one was saved at 40/100 compression level, and still everything else at maximum:

Now the compression artifacts are more obvious. The JPG squares are becoming more visible. Still when viewed in full size, you'd be hard pressed to tell they're there. File size was 465kb (wow, for a 14 megapixel image?!?)

This last one was also saved at 40/100 compression level, but the subsampling was set to its worst quality:

That is one fugly picture. The JPG squares are clearly visible. Everything looks bad. And not surprisingly, the file size for this one was 342kb.

What does this mean in the grand scheme of things? By all means, please tell me which one of these was saved at 100/100 (455kb) and which one at 95/100 (155kb)?





(no fair looking at filenames)

Just to complete the trifecta, here it is at 40/100 and low quality settings (25kb):


ewwwwwwwwww, that's fugly!

Oh, and this one's for Damn Brit. Here's what your camera's AdobeRGB JPG files look like when they come straight from the camera and into a web browser:

The colours are all wrong. They're all slightly darker and grayer than the original. This isn't the best example since red is fairly well matched in both colour spaces, but the difference is still pretty evident. It's much worse with greens and blues.
03-17-2010, 06:40 PM   #82
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QuoteOriginally posted by justinr Quote
It was then that we started hearing about RAW which we were assured was a total and uncompressed record of the what the pixels received.
Anyone who ever wrote that the advantage of RAW is that it is "uncompressed" doesn't know the first thing about software. I'm guessing you never actually saw such a claim, but rather misinterpreted a comment about lossy versus lossless compression.

There are two kinds of compression - lossy and lossless. The former is what JPEG uses, has always used. The latter is what RAW uses (if it uses compression at all). It's also what TIFF uses, and probably other formats too. Lossless compression is in no way whatsoever a problem. The effect of lossless compression is completely invisible. Not a single bit of information is lost from a single byte of data. Lossless compression preserves *every single bit* of information. Again, *every single bit*. That's why it's called lossless. The word "lossless" doesn't mean "only a little loss" - it means *no* loss.

QuoteQuote:
Now if techniques have been developed to allow compression of these RAW files
Lossless compression has been around for *decades* - far longer than RAW formats, or indeed digital cameras, have been. There's nothing new about lossless compression.

QuoteQuote:
Perhaps we are arguing over semantics here and the meaning of the word RAW has drifted
It hasn't shifted - not in the slightest. The definition of RAW has *never* hinged on whether the file has included lossless compression. That's just something you misunderstood when it was initially explained (or whoever explained it didn't understand). The data remains RAW whether losslessly compressed or not. We don't need different names for the image type depending on whether it's compressed, any more than we need different names for the image type depending on whether the last digit of the filename is odd or even. it' a *completely* irrelevant distinction.

QuoteQuote:
Now as far as jpegs are concerned I'm still not happy about the answers I've received
Nor am I, actually. I'm quite surprised the higher quality setting on your K10D results in smaller file sizes than the highest quality setting on your *ist for the same pictures. Something seems amiss. JPEG compression doesn't magically get more efficient - the algorithms have not changed in the last few years. Smaller file means more loss.
03-17-2010, 06:49 PM   #83
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QuoteOriginally posted by Marc Sabatella Quote
Nor am I, actually. I'm quite surprised the higher quality setting on your K10D results in smaller file sizes than the highest quality setting on your *ist for the same pictures. Something seems amiss. JPEG compression doesn't magically get more efficient - the algorithms have not changed in the last few years. Smaller file means more loss.
Untrue. Even in Photoshop, if you don't select "Baseline Optimized" when choosing JPG parameters, the file size gets bigger but the resulting picture is not affected. This setting changes how much calculation is needed to compress/decompress the image. De-selecting it makes the image load faster on super-slow computers, which is more or less irrelevant nowadays. Same with "Progressive", which affects the order that the rows are saved in but not the resulting final image. This allows a picture to be visible as it's loaded gradually over slow connections, which is mostly irrelevant in this age of high speed Internet. There are other similar JPG options which Photoshop does not expose but which can still be set by some manufacturers.

03-17-2010, 07:29 PM   #84
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QuoteOriginally posted by GoremanX Quote
But you said you shoot RAW. What difference does it make what your camera is set to? Except to generate JPG files which have a colour space embedding method that is incompatible with most software (including your web browser, btw).
Oh shut up Frank, I wasn't talking to you.
03-18-2010, 02:11 AM   #85
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QuoteOriginally posted by Marc Sabatella Quote
JPEG compression doesn't magically get more efficient - the algorithms have not changed in the last few years. Smaller file means more loss.
Untrue! You have to do your homework The algorithms do changed and there are also dozens of parameters that alter how it works and what the end result will be. Even if K10D uses exactly the same algorithm as ist (which I hardly believe*), K10D may (and probably does) use different parameters.

*: don't forget that K10D has more processing power than ist, which allows it to use more processing-intensive calculations that were not feasible with the less processing power of earlier models. Just how raw developer softwares can use better, more sophisticated, more complex and processing power hungry algorithms (for demosaicing, noise reduction, etc) as the processing power of personal computers increased by large amounts over the past years.

Last edited by simico; 03-18-2010 at 02:22 AM.
03-18-2010, 02:17 AM   #86
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QuoteOriginally posted by Damn Brit Quote
Perhaps you could point me to where I change my K20 settings to shoot ProphotoRGB.

Yes when I process them in Raw the settings are set to Prophoto but the camera is set to AdobeRGB.
It's in Custom setting 5-snob-23
As it's been already pointed out to you multiple times, that setting only applies to jpg created by the camera. If you shoot raw then that setting matters as much as (jpg) quality level or digital filters
03-18-2010, 05:03 AM   #87
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Well gentlemen I must admit to being somewhat impressed by the intensity and volume of the response. All this for a paranoid idiot, it really is quite flattering.

Alas I haven't the time to go through all the points one by one so a simple question from a simple fellow.

The ist struggled at times to produce reasonable A4 prints, especially if I had to crop them. In my brainless way I thought the answer lay in upping the pixel count as this would produce larger files for me to then cut down with more safety margin. But I find that the jpegs from a 10mp sensor are the same size as those from the 6mp sensor (approx) so am I any further forward?

The nitty gritty is this. If the ist would usually enlarge to around A4 from a max quality jpeg then what will a file from the K10 safely go to?


Justin.
03-18-2010, 05:17 AM   #88
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QuoteOriginally posted by justinr Quote
The nitty gritty is this. If the ist would usually enlarge to around A4 from a max quality jpeg then what will a file from the K10 safely go to?
If you put your JPG misconceptions aside, the reality is this:

6 megapixels = 3008x2008 = 10x8 @300dpi (very close to A4, but not quite)

10 megapixels = 3872 x 2592 = 13x9 @300dpi (larger than A4)

This is without any interpolation from scaling, and without any cropping.
03-18-2010, 06:59 AM   #89
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I don't know why you struggled to do A4 prints with the DS. I have made many 11X14 and 16X20 with mine. And they must be good enough, they sold.
03-18-2010, 03:52 PM   #90
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QuoteOriginally posted by Marc Sabatella Quote
Anyone who ever wrote that the advantage of RAW is that it is "uncompressed" doesn't know the first thing about software. I'm guessing you never actually saw such a claim, but rather misinterpreted a comment about lossy versus lossless compression.



Mmmm.....

Found this in Wikipedia-

# Most raw formats do not use compression or implement light lossless data compression to reduce the size of the files without affecting image quality. But some others use lossy data compression where quantization and filtering is performed on the image data.[14][15] Many recent cameras let photographers choose between no compression, lossless compression or lossy compression for their raw images.

Wikipedia is, as you are no doubt aware, open to editing by interested parties so should you wish to clear up this misunderstanding then I'm sure it will be appreciated.
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