jpeg/tiff quality

[paris_tremayne]

<p>Hi, I recently purchased a Pentax K 200 and I ahve been taking photos using RAW. However when I save images as a TIFF file the file size is around 30megabytes, and so in order to not very quickly take up the entire space of the computer I decided to save the files as highly compressed jpegs which are under one megabyte each. I thought to myself that I can save it back to TIFF when I wish tp print it. I have been told that this damages the picture, but I was surprised that when I converted the file back from a low quality JPEG to a TIFF the file actually went back to being around 30 megabytes. And so I am wondering whether this means that the file is back to its original quality or not. Do I have to save my files as TIFF s right from the word go or is it ok to save them as JPEG s then just convert that JPEG into a TIfF if and when I choose to print them?<br>

Thanks for your help</p>

[rainer_t]

<p>How do you think the jpg-compression manages it to compress a 30Meg tiff to a 1Meg jpg-file?</p>

<p>Jpg is a <strong>lossy</strong> compression ... it <strong>throws away</strong> information. Once jpg-compression is applied on the image the information is gone. Even if you convert the jpg to tiff ... the resulting tiff will still have 30Megs ... but it will<strong> NOT</strong> contain any more information than the 1Meg jpg.</p>

<p>By doing what you're doing, you're converting your images into cr*p ... well that's said too much ... nevertheless ... compressing a 30Meg tiff into a sub-1Mpg jpg you're throwing away too much. Change jpg-quality (this can usually be selected before storing a jpg) to a higher value ... the resulting jpg shall be around 3-5Megs in average. With that setting the losses are quite low.<br>

By the way ... it will not make any difference if you print from a jpg or if you print from a jpg converted to tiff.</p>

[edelson1]

<p>Highly compressed jpegs can "lose" quite a bit of information during the lossy compression process. Converting them back to tiff will not recover any information, as it really was lost when you first compressed the image. The fact that the file ends up the same "size" is not an indication of improved "quality", and the conversion will not improve your printed output. While each time you convert a jpeg to tiff will not alter the original jpeg's quality, repeated saving of a jpeg will degrade image quality, as lossy compression occurs every time you "re-save" the image, even if you did not edit it in any way (remember, this is on saving only, not opening and converting to tiff, although as I already mentioned, conversion to tiff is not recovery process for lost information).<br>

Given the steady decreasing cost of storage, there really is no good excuse to save an image using a lossy, highly compressed format over a lossless format. However, if you create a final image that is sized, sharpened, and fit for opening and directly printing without any further editing, a high quality (low compression) jpeg can be a reasonable choice for storage, although that may mean having several copies of an image filed (monitor display optimized, 4X6, 8X12, 12X18, etc.) which can simply be opened and closed (not re-saved) for use/view. That's an issue of how extensive a filing system you want to maintain.<br>

Henry</p>

[paris_tremayne]

<p>Thanks for your help people, I appreciate it.<br>

It appears as though the obvious thing to do would be to save the files as TIFFs and just buy an external hardrive.... Lucky I didn't delete the RAW files from the camera itself.<br>

cheers</p>

[david_henderson]

<p>Personally I don't convert raw files to anything ( well apart from a DNG) without having a specific purpose in mind. I keep one copy on an external drive that I don't touch much. Another on a second internal hard drive which is the one that I edit non destructively so I can always take it right back to the beginning if I want. If I make a jpeg for the web or a CD, I'll probably delete it right after unless I can forsee the need for others. I can't see that much use for Tiffs from digital files apart from high end printing and submissions to stock agencies. </p>

[leicaglow]

<p>Hi Paris, My feeling is the RAW file is like the negative. A JPEG is like a copy of it (maybe not so great of copy, depending on how much compression you use). Once you've thrown away the negative, you're stuck with just the copy. A TIFF file has some limitations, but is defintely a better copy of the negative than the JPEG, plus it is a text file description of the image, and should compress very tightly (without detail loss--except for what was in the RAW file), using a ZIP program.</p>

[JAPster]

<p>In my opinion, you are better off avoiding, if possible, graphics file conversions, because you always introduce some degree of image degradation, however small, when you convert the file from one format to another. They simply have not made a graphics file converter that is 100% efficient and 100% correct and 100% color-true.<br>

A better approach is to sit back, think through what you are intending to do with the images, and decide what level of image quality you have to have in order to meet your requirements. Then select the file format that's going to deliver that level of quality.<br>

If your particular work requirement demands the absolute highest level of image detail, right down to the individual pixels, then shooting in RAW or TIFF makes the best sense. For example, NASA often takes astronomical pictures and records them in TIFF to capture as much image detail as possible w/o losing any of it.<br>

If the problem is lack of disk space on your C drive, this is easily addressed by purchasing and installing one of the many models of external USB 2 multi-Gigabyte hard-drives. These are available in sizes from 80GB all the way up to 1024 GB (1 Terabytes). Choose one made by Maxtor, Seagate, Western Digital, and it will likely be a quality unit.<br>

Wish I could say more, but I'm in a Public LIbrary, and they are running us out! :)</p>

<p>Good luck<br>

AP<br>

Atlanta</p>

[don_e]

<p>"Hi, I recently purchased a Pentax K 200 and I ahve been taking photos using RAW. However when I save images as a TIFF file..."</p>

<p>Did you delete the RAW files? If so, I suggest you do not do so again. But if disk space is an issue, and you do not want to buy a larger hard disk, I suggest shooting highest quality jpeg and forget about RAW and eliminate the tiff/jpeg conversions. Odds say there's better image quality doing that than what you are doing now...or even if not, you will resolve your disk space issue a bit as well as simplifying your workflow.</p>

<p>If you have the RAW files, then nothing besides time has been lost. Go from most data to least data; most flexible to least flexible when you change file type or size, and do not reverse directions. Lots of disk space is simply a requirement for digital or scanned film photography. Either that, or shoot a lot less.</p>

<p> </p>

[don_e]

<p>Reading on...you did not delete the raws. Ok. Good. Another option is to use .png instead of .tif as it uses far less disk space and has a lossless compression. More disk space is the best thing to do.</p>