Printing Digital Images (1 Viewer)

[jpoyner]

I have original images stored as jpegs, will I get a better print from them if I change them to .tiff format or does this only make a difference when re-saving the files after altering them?

JP

 

[scampo]

To my knowledge, it is impossible to improve on an image file once it has been saved. Jpegs are the most common format for normal use. When you save, always "ask" PS to save at maximum quality.

 

[Pops_uk]

It’s my belief when images are stored as Jpegs (on your hard drive), they will deteriorate every time you open or edit them, if you have the option and the space save as Tiff
Glyn

 

[Andy Bright]

Converting them to Tiff format for printing will not make the image any better or worse, just makes them very big! As you say, it's only when it comes to resaving a jpeg do you lose any quality.

Glyn: Just opening a jpeg dosn't cause any deteriation....thank god!
Regards,
Andy

 

[Mike D]

It’s my belief when images are stored as Jpegs (on your hard drive), they will deteriorate every time you open or edit them, if you have the option and the space save as Tiff
Glyn

Never heard of this one. I see no reason why the image should, or even could deteriorate simply through opening. After all, it is digital data, a series of ones and naughts stored on the computer. As long as when you save the image you make sure the quality is highest there should be no problem.
I have some jpgs on my computer and use them a lot for CD covers etc. As good today as they were 2 years ago.
Use the originals as just that - originals. After opening if you intend to do some changes save the open file to another name so if all goes pear-shaped you still have your original.

 

[christineredgate]

JP,why not immediately transfer your images to a cd once you have put them onto the pc,then if there are any problems you will have the pristine originals to fall back on.
I am far from an expert on this subject,but I have been led to believe that there is a slight deterioration in quality the more one keeps altering them,so it is recommended that when working on a pic,save one ,and then re open to work on the picture,but if things go wrong you can always return to the saved ,untouched one.
Christine.

 

[Bluetail]

I don't do digital cameras (yet), but I do work with graphics a bit. I always convert jpgs, gifs etc to bmps. As I understand it bitmaps are an uncompressed format, so you should be able to edit them without a deterioration of quality.

But, like Christine says, I always save a master copy somewhere.

Jason

 

[Glen Tepke]

Opening and working on a jpg does not cause any deterioration, but saving a file in jpg format always causes some degradation, even if you save at high quality. If you repeatedly open a file to work on it and save as jpg, then reopen, edit some more and resave as jpg, etc, the cumulative degradation can be significant. In that case, save your intermediate files as TIFF, PSD or some other uncompressed format, which as Andy said, will be much larger files. When you are finished and ready to print or publish to the web, then save your final version as a jpg of appropriate size - high quality for printing, lower quality (smaller file size) for the web. You can then delete your TIFF file, or save it if you think you might want to work on it some more without starting over from your original (which you have saved in its original format, of course). Glen

 

[jpoyner]

Thanks for all the replies, seems to have answered my question, it's a steep learning curve this digital photography, but good fun.
One other thing while on the subject of storing photos (this has probably been discussed before, sorry if it has), I read a disturbing article the other day concerning the life of CD's.....anyone had any experience with "old" CD's becoming unreadable. I guess it pays to buy the best quality, but I was told that actually most of the CD recordables you buy are all made by the same few manufacturers????
Are we all going to end up losing our valuable photo archives after a few years?

JP

 

[JonB]

I'd have to say that CD's are much less susceptible to degradation over time than floppies were (pure speculation). Floppies have an average lifetime of around 10 years, which I can corroborate from some at work that have been around that long - about 10% of them were degraded to the point where they weren't readable. CD's, on the other hand, don't use magnetic storage, which slowly demagnetizes over time - it's all optical. I haven't seen any hard numbers, but I'd think you can confidently expect at least 20 years from a CD so long as you're reasonably careful not to scratch it. Personally, I wouldn't be surprised if the actual numbers are closer to 40 years or more. It's reasonable to expect that eventually the film sandwiched between the plastic layers in the CD may deteriorate over time, but I wouldn't anticipate this to happen until a lot of years have passed. If you're worried, though, if you make a copy of the CD every decade, I'd think you'd be pretty safe.

 

[Pops_uk]

A long but interesting article against the storing of images in the JPG format can be found here

http://www.xtremepccentral.com/modules.php?s=&name=Sections&sop=viewarticle&artid=26]A%20Case%20Against%20Jpeg%20Images:[/url]%20http://www.xtremepccentral.com/modu...ore hitting that "save" button.” Regards Glyn

 

[Mike D]

This is a quote from the Usenet FAQ regarding the life of CDs:

The manufacturers claim 75 years (cyanine dye, used in "green" discs), 100 years (phthalocyanine dye, used in "gold" discs), or even 200 years ("advanced" phthalocyanine dye, used in "platinum" discs) once the disc has been written. The shelf life of an unrecorded disc has been estimated at between 5 and 10 years. There is no standard agreed-upon way to test discs for lifetime viability. Accelerated aging tests have been done, but they may not provide a meaningful analogue to real-world aging.
_________________________________________________

In my experience I have had a disc fail (unable to read media type of problem) within a short time of burning.

If the data is valuable always make two copies and store one safely as the master.

 

[scampo]

Hmm... Regarding the "anti-jpeg argument" on the website given: the "original" image is of course itself a million miles away from the original thing itself, however "prized" that is, so whichever format is chosen for saving the image we are faced with real issues of compromise. An example is that obvious compromises occur with contrasting shadow areas and specular reflections - both "fail" to reproduce well in pixels.

Jpegs certainly do print beautifully up to large sizes - so I don't think I necessarily agree with the results of the tests on that web page at a practical level, even if the theory is sound within the context of the test itself rather than within the context of photography itself. It is true, however, that most of us perhaps do no longer need such high levels of compression of files given by the jpeg process and the availability of CD-ROMs and large hard drives.

 

[Woody]

Hi All,

I don't know what the article says but the problem lies in the way in which jpeg compression works. It literally 'throws out' information which it sees as uneccessary. JPEG (Joint Photographic Experts Group) is known as a 'lossy' compression because of this.

TIFF (Tagged Information File Format) uses LZW (Lempel Ziv Welch, after its' creators) compression which works differently. If it sees two identical pixels next to one another it simply records the pixel with the info 'x2' Thus it compresses files without irreversibly deleting data and losing quality. It does not compess files as much as JPEG does but the total lack of image quality loss makes it worth the extra file size IMHO.

I work in digital graphics and I have never had a compressed TIFF file go bad on me but I have had many corrupted JPEGS (mostly unexpected end of file errors). They also tend to cause printing problems when imported into Quark files.

My advice would be to use jpegs for screen use only and tifs for print.

CDs should be fine for a considerable number of years if not exposed to extremes of temperature, excessive moisture levels, or abraisive materials etc. and they will probably be outmoded before they degrade enough to worry about anyhow!

Woody

 

[scampo]

It's true that jpeg discards some file information but then so does the digital recording process itself - and in a big way, of course (as did silver halide recording for that matter). It is what is thrown out that counts and for most purposes it must be true that what a jpeg file rejects is fine for most people most of the time.

The problem with corrupt jpegs is interesting. I wonder if that is a feature of the software used or of hardware? Also, Quark is not used by many "amateurs" so is a reason for only a few to consider jpegs more closely.

 

[Jay Turberville]

A long but interesting article against the storing of images in the JPG format can be found here

That article's demonstration is a great example of what happens to images of that type. Meaning images with hard graphic lines and saturated and solid colors. That image is about as unlike any typical photograph as I can imagine and I don't see it as particularly relevant. Additionally, magnified views must be shown in order to make the damage easily perceived. I'm betting the differences - even with this poor example - would be difficult to pick up if the image were printed at 200 DPI.

It is absolutely true that JPEG compression introduces artifacts and destroys data that cannot be recovered. The real question though, is how much data is lost and is it significant?

The following is a quote from a "challenge" I posted during a discussion of this topic on a camera forum.
............................................................
Based on my experience in the world of professional video and the
used of Motion JPEG for video production, I entered the world of
digital photography with the firm conviction that multiple
applications of JPEG compression is a "bad" thing. But discussions
in another groups and actually doing some comparison convinced me
that the difference between saving in a lossless format and in JPEG
at the Maximum quality setting in Photoshop was so small as to have
no practical significance. I have just done a new comparison and the
sample images I created can be found in this directory:

http://www.jayandwanda.com/JPEG/

(But I really urge people to do critical tests like these for
themselves.)

What I did was open up an image that was taken with my CP995 at Full
size but with Normal JPEG compression (not FINE, even though I
usually shoot at FINE). I made a simple adjustment to the levels to
get the backlit flowers to "pop" a bit. I then immediately saved the
file as an LZW compressed TIFF and as a JPEG at the Maximum quality
setting. (The LZW TIFF is about 5MB and the Maximum quality JPEG is
about 2MB.) The images were re-opened and cropped sections were set
side-by-side at 300% magnification. I saved that view and it is
located at:

http://www.jayandwanda.com/JPEG/compare.jpg

If people think they can tell me which side is the TIFF and which is
the JPEG, I'd be happy to compile the results and report back how
well they jibe with the truth. It is my opinion that there is no
significant difference even though [most pixels are] slightly different.

The fact is that the various RGB values for each pixel seem to vary
by a value of 0 to 3. If you copy one image over the other in
Photoshop and set the top layer to "Difference", you can then move
your cursor over the apparently black image and read the difference
between pixels in the Info window. It is typically something like
0,1,1 or 0,0,2. So the additional JPEG save cycle does degrade the
image - but it is a very, very small amount that I maintain is not
visually perceivable.

I suggest people check for themselves. For myself, I no longer save
TIFFs. I save Maximum quality JPEGs instead. I might save the
occasional complex layering job as a PSD, but this is rare.
.........................................................

I have also found that many images can be save ten or more times at Photoshop's highest JPEG quality setting and the error stacking isn't much more significant. But test for yourself.

Any digital file can be corrupted. JPEGs are no different. I have seen no objective data that they are any worse and my experience suggests no such fragility. But why take chances with any digital file? I make duplicate archives of my origninal files (which are Fine JPEGs for the most part) on good quality CD-R. I can always go back to them if I need all of my original data. If you are really concerned, store the second archive set off-site somewhere.

If I modify the image, I save it as a JPEG with Photoshop's best quality setting. I can't see a practical difference at 300% magnification which leads me to believe that nobody can see the difference when printed.

 

[scampo]

As I was suggesting, Jay, it's the practical contextual application that counts and many of us have seen or produced very fine quality enlargements from jpegs.

 

[Pops_uk]

Hi Jay, We both agree that a Joint Photographic Experts Group format image is automatically decompressed when opened. A higher level of compression results in lower image quality, and a lower level of compression results in better image quality, (we agree albeit, the difference is minimal at Photoshop’s highest setting) but with to days processing power of your average personal computer and the cheapness of storage (media) why, settle for second best?
Regards Glyn

 

[scampo]

Second best?

Stick with silver halide in that case...

 

[christineredgate]

On reading all this info I am now very confused,as usual!!.So Glyn and Steve C,which is the preferred option.To save as JPEGS,but how does one find the highest setting,is it the largest file,or is there a set of numbers in Photoshop,or should one change the whole batch to TIFF before transferring to a cd.The only thing is one would need to be able to change the whole lot in one go otherwise with 50-60 pics at a time it would take forever.I did have a try at batch processing once but could not quite get the hang of it,was a little complicated.
There was a thread on this forum some time ago re the quality of cd storage and then I read in a digi photo book that it was all a myth that the quality deteriorated ,albeit as was mentioned,yes perhaps every 10 yrs do a quick copy onto a fresh disc.
Christine.