JPEG to TIFF

<p>Since my point and shoot exports in JPEG format only, is there any point in then converting it to TIFF?</p>

<p>Well, sure. If you intend to open one of those files, work on it, save it, and open it again for more work... then, yes. That way you avoid the continuing erosion crated by the JPG format's lossy compression, nibbling away at the image quality.</p>

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<p>That way you avoid the continuing erosion crated by the JPG format's lossy compression</p>

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<p>There is not a progressive loss of quality coming from jpg.<br>

This idea comes from Adobe users.<br>

Adobe jpg algorithm produces that degradation, it is not a jpg degradation.<br>

Different products don't degrade the image at each save.</p>

 

<p>I was wondering though, if the JPEG straight off the camera is intact and contains all the colour information etc, that would have been present in a RAW file. We always read that JPEG is a lossy format, does that include the first generation of the file off the camera? This may also be a stupid question but if one converts a JPEG image to TIFF, the resulting file is much larger, so what is the extra data and where does it come from?</p>

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<p>I was wondering though, if the JPEG straight off the camera is intact and contains all the colour information etc, that would have been present in a RAW file. We always read that JPEG is a lossy format, does that include the first generation of the file off the camera? Also if one converts a JPEG image to TIFF, the resulting file is much larger, so what is the extra data and where does it come from?</p>

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<p>First of all you are comparing objects that are not comparable.<br>

Raw information are to be processed to produce an image.<br>

In any case, after raw processing, you get an image (a bitmap) in some RGB color space.<br>

If you save it as tiff the bitmap is included into the file.<br>

If you save it as jpg the bitmap is compressed and then included into the file.<br>

The jpg compression is lossy, something is lost, but the appearence is preserved if high quality is used (90% is generally very very good).<br>

When you load a jpg, the image is decompressed and, in memory, you get a bitmap (same size of the original bitmap, but tone values are a slightly different).<br>

If you save the bitmap coming from a jpg as a tiff, you get the same size of the original bitmap saved as tiff (the number of pixel is the same).</p>

<p> </p>

<p>Converting camera JPEGs to TIFF is a good "stop loss" strategy. When you open a JPEG file in Photoshop (or other editing program), it is expanded into a non-compressed format. If you resave it, it is re-compressed with losses. TIFF files are not compressed, hence are not degraded on resaving if no editing has occurred. It's also a good idea to save the originals as 16-bit TIFF files if you are making changes. You avoid roundoff errors in editing, which would otherwise accumulate causing degradation on successive open/edit/save cycles.</p>

<p>If you haven't changed anything in the file, the loss is relatively small. However, there are many compression strategies, and files resaved from Photoshop are compressed according to a different scheme, and nearly always change size (indicating something has happened).</p>

<p>The only way to save a JPEG file without recompression is to copy it from one location to another with a file utility (e.g., Windows Explorer).</p>

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<p>If you haven't changed anything in the file, the loss is relatively small</p>

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<p>If you changed the image, you have changed your bitmap.<br>

The loss is relative to the current bitmap, not to the original one.<br>

And the quality of jpg is the same of the original, if you use the same quality setting.</p>

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<p>This is good stuff to know. So it seems to me from your comments that once the JPEG has been exported from the camera so long as it hasn't been modified and saved as another generation of JPEG, it's full quality will be intact. Saving to TIFF is the logical thing to do if further manipulations are required in a photo editing application. Makes sense. Interesting about the bitmap information too, about how different formats expand and contract the data. Thanks folks. </p>

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<p>"it's full quality will be intact"</p>

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<p>Yes, except: it's full quality has already been "nibbled" a little, simply by being jpeg to begin with. There will be some "artifacts" present, but not too bad. At least you are preventing <em>further</em> degradation.</p>

<p>Now, will that be 16 bit tiff, or 8 bit ;)</p>

<p>When a file undergoes JPEG compression, the bitmap is <strong>not</strong> preserved. It is divided into a set of sub-bitmaps wherein all the pixels are condensed into a single pixel together with some information regarding the detail that is otherwise discarded. A new, full bitmap is regenerated from this information when the JPEG is decompressed. However, if the JPEG file is 1/4 the size of the corresponding TIFF, it means nearly 3/4ths of the original image data has been discarded, lost forever. With a non-lossy compression algorithm,, the amount of size reduction is typically less than 15%.</p>

<p><strong>If</strong> a JPEG file is opened then resaved, <strong>and</strong> no changes have been entered, <strong>and</strong> if the same algorithm is used as in the original compression, then very little further information is lost the second time around. That's a very special and, in mathematical terms, trivial solution. If you wish to copy a file, copy it and suffer no loss whatsoever.</p>

<p>Reading this thread brought up some questions from me too:<br>

I take all my shots in RAW. Then, when I "spot" a photo which I know will be a true "keeper", I convert it from RAW directly to TIFF, work on it if needed (P.P.) then save that TIFF file. If I need to have this photo printed, I go to the my favorite shop and they will convert it to JPEG 300dpi for printing.<br>

Is this a good way to do things or is it better to print directly from the TIFF file, and, if that is possible, would that be better than using a top quality JPEG?<br>

I did some experimenting: RAW from the camera, processed in ACR, saved in JPEG format and later converted to TIFF for CS4 PP ... I did not notice much degradation.<br>

JP</p>

<p>Any information loss due to in-camera jpeg compression is permanent and the lost information is unavailable forever. So the extent of improvement during post-processing manipulation is the same for the jpeg and the tiff versions.<br>

Converting a jpeg to a tiff can not improve an image's information content. Actually nothing can improve the image's information content. But, as mentioned above, it will eliminate any possible (but avoidable) degradation that may occur from saving the same jpeg over and over again.</p>

<p>We had the same issue with our first couple of digital compact cameras that we used to take a lot of family photos. We archived the jpegs but treated them as originals that were never saved over. Any edits we saved as 8-bit TIF or PSD files.</p>

<p>Well, I guess I'll keep my method:<br>

Raw>TIFF>JPEG when needed.<br>

JP</p>

<p>i shoot jpeg all the time in my 2 dslrs. i have already setup the dslrs to take the high quality jpeg that i want. the setup took about 2 1/2hrs per dslr.<br>

my workflow is as follows-download pic to the pc, open the group in windows image and fax viewer to delete the real duds(nothing is changed or saved in the windows viewer, this is a delete the dud operation only). then open in pse7(cs2 is available if needed) do all pping(this is for me 1 minute or less), use save as a tiff. all further work is done off the tiff. the original untouched jpeg is put in a holdall folder untile it reaches 4.1gb then it is burned to dvd. once the pic is in the pc there is zero image degradation of IQ since all work is coming off the tiff. if i ever need to make another tiff, the original file is still available. </p>

<p>Gary,<br />Did it really take 2 1/2 hours for your settings? What exactly did you do ... curious.<br />JP</p>

You can edit JPEG in GIMP with minimal further degradation, because it has more sophisticated JPEG encoding libraries than Photoshop. Use the "Save with original settings" option. Another strategy is to downsample your JPEGs 50%, save as TIFF, then edit with Photoshop. Very few P&S models have adequate color and resolution at 100% anyway.

<p>I've been following this thread from its start. Once the original question was answered, I've seen lots of different opinions about how to prevent further degradation, but what I don't see is a clear factual answer. Does anyone have that?</p>

<p>The clear factual answer is saving your file as TIFF, or PSD, or in any other format that doesn't feature lossy compression. That, and staying out of domination parlors.</p>

<p>Without going into detail, I strongly recommend that Milo study up on TIFF, RAW, and JPEG formats elsewhere (e.g. authoritative books, all of which will give the same answers), rather than trying to learn the answers here.<br /><br />With all due respect, many of the answers given above are dangerously incorrect. This is unusual for photo.net, but it merits mentioning. The theory is important, but apparently you're not going to find it here.<br /><br />As a practical suggestion, for JPG-only cameras, saving in TIFF, then reopening in Adobe CS4 ACR can add some facilities that don't exist in Photoshop proper. Once that avenue is exhausted, all edits should be in TIFF or PSD, until and only if you need to compress for e-mailiing or Web viewing.<br /><br />And, as Charles notes, of course keep yourself and your images out of the domination parlors... and go STUDY the theory instead of looking for a quicky explanation.</p>

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I stand by my assertion. The JPEG FAQ #10 says: "If you decompress and recompress an image at [exactly] the same quality setting first used, relatively little further degradation occurs. This means that you can make local modifications to a JPEG image without material degradation of other areas of the image. (The areas you change will still degrade, however.)"

 

The photo industry really needs a universal AND compact lossless format. Converting out-of-camera JPEG to TIFF is a good way to consume disk space, but I'm not sure it produces results superior to GIMP editing, especially if the TIFF is re-encoded by Photoshop at a different quality setting for web display. If you print directly from TIFF, then yes, certainly it is a better workflow.

 

This is why photo.net gurus recommend RAW.

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<p>I stand by my assertion. The JPEG FAQ #10 says: "If you decompress and recompress an image at [exactly] the same quality setting first used, relatively little further degradation occurs.</p>

 

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<p>What’s the measurable matrix for “relatively little further degradation”? Its degradation. Its degradation that’s avoided completely by moving away from the JPEG format no? </p>

<p>Bill, I think that people do not want to recomend a process that has any degradation because there is no way to tell how many times the file may be edited. And once a image is damaged, there is no real way to undo the damage. I agree that if handled right a file may not be impacted in its life by the degradation caused by jpg compression. But, someone who does not know about jpg degradation will not follow good file handling practices. So, their chance of having degraded images is more likely.</p>

<p>Also, I think you are over looking the fact that TIFF does support compression, LZW and ZIP. Both of which are good loss less algorithms. There really isn't much else that can be done if the process is to stay loss less. The only reason that jpg compression is better is that it throws away data and homgenizes data. It was never intended for originals, but for copies good enough for the web. </p>

<p>GIMP has nothing to do with it. These formats and algorithms are defined seperately from the image editors.</p>

<p>RAW is recomended for different reasons. It too can take up a lot of disk space, and some of the newer ones do incorporate loss less compression and are very similar to TIFF.</p>

<p>To the OP, Milo G, conversion to a loss less format is only recomended on files that you are going to be editing (i.e. where you save the image again). Even then, if you don't edit/save your jpgs more than a couple of times then more than likely your going to be fine. If you plan on doing a lot of editing to a file there are other reasons that combine to make conversion to a better format desirable. If you need the extra facilities, then convert. If you are not aware of any need then maybe not convert until you have the need.</p>

<p>My original concern was for the quality of the JPEG coming out of the camera and I assumed that being first generation there would be no loss of data. From the comments so far it appears there is some compromise as the camera does the first round of processing to match whatever the controls are set at. Presumably that's why they invented RAW. Interestingly, I would think that all cameras produce some form of RAW image, since that is what comes directly off the sensor before the firmware takes over. However, since the average PS market wants instant results, there's no point in providing that option. It would be nice to see a TIFF option in a camera's firmware. Is anyone doing that?<a href="../digital-darkroom-forum/00UWGa"></a></p>

<p>Milo, I think this might be a good read:</p>

<p>http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf</p>