JPEG - Tiff discussion

[Alastair]

Ok, so I'm a part of a Yahoo group called 'colortheory' (it's from the US otherwise it would be colourtheory) and there was a bit of a pissing match between a few of the guys about 8-bit and 16-bit colour and whether or not you could tell the difference between the two.

Then a production guy chimed in and this is what he said about the whole thing - and I received his permission to repost his comments here:

Hi,

I've found this whole discussion very interesting actually; sorry to see that top-notch, intelligent professionals such as yourselves can't engage in a heated discussion without it getting personal. I'm going to throw my two cents in here just for fun, hoping I can contribute slightly to the dialog and confirm Paul's findings.

We publish more than 20 major magazines including Elle, Woman's Day, Car and Driver, Popular Photography and many others. We did an extensive test on JPEG compression levels and bit depth modes with actual image content from our magazines, printing Kodak Approvals of a sample suite of images saved separately in Photoshop JPEG compression levels from 2 through 12. We showed these samples to a room full of industry professionals and color experts and not one of these experienced pair of eyes could tell the difference between a compression level of 6 and a level of 10 or 12. Only images saved in compression level 4 or lower showed artifacts on the proof. We settled on a standard file format of 8-bit JPEG level 8 for all of our image workflows since no one could tell the difference in either proof or print between the uncompressed TIFFS and the JPEGs.

The bit-for-bit techno-geeks can't carry the day here; I used to be one myself and have learned that prepress, printing and color management is still an art, not purely a science, and always has been.

Steve

Steven Hirsch, Systems Manager
Hachette Filipacchi Media, U. S.


So there you have it. *The next time you try to cram all those uncompressed Tiffs onto a CD, forget it. *JPEGs will probably do the trick just fine. *Go figure.

Oh, and he wanted me to post the DISC website - The committee which developed the industry-wide specification for digital image submission criteria to publishers.: DISC (http://www.disc-info.org)

-Alastair.

[Alastair]

But let me also say (because I forgot to) that it's probably foolhardy to now down-sample all those images you have to JPEGs. *These guys are running their images on offset presses, rather than inkjets or other much higher-res output devices. *And they are talking about the final files, at the final size.

-Alastair.

[Digiteyesed]

I prefer to shoot in RAW and keep my images in a 16-bit colour space for manipulation. I find this does much less damage to the tonality of the file. Downsampling to 8-bit is usually the very last step I perform before sending an image off for printing.

Here's an example:
http://digiteyesed.com/special/08_vs_16_bit.php

Best,

Sean McCormick

[ba5r]

I would also like to put my .02cents into this as I've done some extensive work when it comes to file formats with jpg, bmp, tiff, raw, you name it, i've probably worked with it.

Anyways, what I failed to see recognized in the comment quoted was the lossy/lossless attributes of jpg and tiff. *With regards to quality, I agree that compression level quality get pretty dramatic from 4 and under but, that being the case, its still not a good idea to start taking our images and downsampling them to that number. *Tiff files are not as degradable as a jpg saved at level 4 - meaning that each time you save over a jpg file you lose a little bit of genuine pixels. *This is bad news for the photographer who likes to work on their photographs, save it, and work on it again, later, save it, send it off to preflight, proofers, who may or may not resave the file a number of times after that. *You get the point.

The benefits of smaller files are good when saving as a jpg but would you really want to? *Sure we'll save a few megs or so but nowadays DVDs are becoming common and you can cram just as many tiffs into one DVD as you would jpgs into a CD (depending on what camera it came from of course). *Also the gig/dollar ratio is getting so much cheaper that getting a 200MB hard drive is going for as much as a 40GB hard drive a couple years ago. *So as technology changes for the better so do our options of keeping our images in tip top shape.

Last point that I want to make is that the original poster of the comment didn't specify what the initial size of the image was as well as the size of the final output. *Since he works for a magazine, I would imagine that its no bigger than letter size. *Anyways this also plays a big role in his tests because as you all know, a 1mp file saved at jpg level 4 is much different from a phase one h25 file saved at level 4. *you can still blow up that phase file to poster file and still recognize what the image is while the 1mp 1/2.7" sensor blown up to poster would probably look more like the macbeth colour chart with all its giant squares. in this respect 'size matters' lol.

Just to sum it up, to me, working with a jpg as opposed to tiff is just like scanning an image from a print as opposed to a negative. go big or go home.