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TIFFS and JPEGS (1 Viewer)

Clive Watson

Clive Watson

Looks like I picked the wrong week to quit ampheta
OK, no doubt this will be obvious to some people...

JPEGs lose data when saved whereas TIFFs are lossless, right?

But with a JPEG, if you go Save As, then Options, you can adjust the compression factor, the least compression (and therefore highest quality) being 1.

So if you do this with a JPEG, is it as good as a TIFF? No doubt it isn't that simple, but if so, could someone explain why?
 
Tiffs are lossless, they can also carry lots of other data, they can be multipage, multi layered but they are also large.

Jpegs are made smaller by discarding information that the eye doesn't see, mainly detail in the colour. The different settings, not all programs use the same measure -Photoshop even uses different measures of Jpeg quality in its Save as and Save for the Web dialogs!, delete progressively more information. Some programs offer a lossless Jpeg, but that just confuses things!

The problem is not the quality of the resulting image, a Tiff and a high quality Jpeg will look identical to the eye, it is the opportunity for further adjustments that Jpegs lack. A particular adjustment may want to make visible information that the Jpeg compression has thrown away. And also any sharpening will sharpen the invisible artifacts that even High Quality Jpegs have.

The rule I use is that if I am finished with a image and I am merely storing it to look at in the future, then I will use a Jpeg. If I intend to modify it again then I will use a tiff or psd format.

All this tiff and jpeg discussion is academic if your camera is taking Jpegs, the information has already been lost!
 
Mono said:
All this tiff and jpeg discussion is academic if your camera is taking Jpegs, the information has already been lost!
Click to expand...

I know what you're saying here, but strictly speaking this is not necessarily the case. Even with a jpeg starting point, it is good practice to save as a TIFF if there is the likelihood of much further reprocessing in the future.
As far as I'm aware (I hope someone will correct me if I'm wrong) saving as jpeg then closing/opening the file will progressively cause more and more data loss.

Although data is indeed lost in the creation of the first jpeg, this can be contained if further work is done in TIFF format - at least that's what I believe is the case!

Astrokev
 
Astrokev is right if you have taken a Jpeg and then are going to open it play around, save it, then open it again play a bit more resave etc then the intermediate saves are better done in a lossless format, I usually use psd.
 
eddwillis said:
My understanding is that it is the act of saving that applies compression,opening and closing does no harm
Click to expand...
Well, yes, that's true, but the reason some folks mention open and closing when discussing jpg quality loss is because within ONE editing session, you do NOT lose more and more quality every time you do a save.

In other words, if you open a jpg, do some editing, save it, do some more editing, save it, say 5 times total. Well, the final result is NOT an image that has taken 5 degradation hits. Only the final save (where you close the image and stop working on it) is the one that takes the hit, because the image has always been in memory from the original open, and all those intermediate save files have been written over on each subsequent save, each with only a one degradation loss.
 
Clive Watson said:
OK, no doubt this will be obvious to some people...

JPEGs lose data when saved whereas TIFFs are lossless, right?

But with a JPEG, if you go Save As, then Options, you can adjust the compression factor, the least compression (and therefore highest quality) being 1.

So if you do this with a JPEG, is it as good as a TIFF? No doubt it isn't that simple, but if so, could someone explain why?
Click to expand...

Stating the obvious, when you save off a JPEG as a TIFF you need to ensure the compression options on the TIFF, such as LZW, are turned off.

Ron
 
NoSpringChicken said:
Stating the obvious, when you save off a JPEG as a TIFF you need to ensure the compression options on the TIFF, such as LZW, are turned off.

Ron
Click to expand...
Ron, actually I do not think you have stated the obvious. In fact, I think you have stated something that is incorrect. Unlike JPG compression, TIFF compression is lossless, so it is OK to use TIFF compression. In fact, I see no reason not to.
 
RAH said:
Ron, actually I do not think you have stated the obvious. In fact, I think you have stated something that is incorrect. Unlike JPG compression, TIFF compression is lossless, so it is OK to use TIFF compression. In fact, I see no reason not to.
Click to expand...

Oops, sorry. I will start using it again and save some disk space.
 
Mono said:
Astrokev is right if you have taken a Jpeg and then are going to open it play around, save it, then open it again play a bit more resave etc then the intermediate saves are better done in a lossless format, I usually use psd.
Click to expand...

Astrokev appears to be suggesting that the mere act of opening and closing a jpeg (without a "save" stage) will have an effect.

It won't.

This is a commonly held misconception, and that's what Edd and I are commenting on.
 
When saving Tiffs Photoshop offers LZW, ZIP and Jpeg compression. LZW and ZIP are lossless ZIP compressing more than LZW, Jpeg is the usual lossy Jpeg offering high compression, but is still a Tiff so can support layers and multi page.

Many older Tiff programs will not support Zip and Jpeg compressed Tiffs. Some very old graphics programs, some DTP programs and some printer RIPS don't like LZW compression, that is why it is recommended that you turn LZW off if you are sending the image to somebody else to print. If you are using it yourself on programs you know then there is no problem.

A quick experiment on a multi-layered Tiff
plain Tiff 18.8 Mb
LZW Tiff 15.1 Mb
Zip Tiff 9.4 Mb
Jpeg 10 Tiff 9.5 Mb
Jpeg 5 Tiff 9.4 Mb but a bit bigger than the Zip!

So Zip tiff wins if you are just using a program that can handle it!
 
Just to confuse things even more I normally use EPS files for CMYK images. This purely habit as originally TIFF files wouldn't handle clipping paths reliably and Photoshop files wouldn't import into Quark picture boxes (they do now). EPS previews also display better in Quark on my Mac. Probably something I'm doing wrong. TIFF files seem a lot better now than they used to be.

Ron
 
Ron,


Nothing wrong with postscript files, especially if printing to a non-postscript printer. Create in QXD and distill in acrobat to your own setting if possible. Use jpeg (images only) for the internet, all third party printing use tif.files (eps or pdf.files) with no compression attached to any file.
 
Keith Reeder said:
Astrokev appears to be suggesting that the mere act of opening and closing a jpeg (without a "save" stage) will have an effect.

It won't.

This is a commonly held misconception, and that's what Edd and I are commenting on.
Click to expand...

Keith - perhaps I should have been more specific. I was actually referring to the act of saving an image when closing the file. I agree completely that simply opening/closing an image will have no effect on the image on disk unless it is actually re-saved.

Apologies if my initial comment was misleading.

Kev
 
It seems that a comment made at the beginning of this thread may hold a sensible suggestion as someone mentioned shooting RAW image files. If you shoot RAW images you can export them in any format without fear of losses. As long as the original RAW file is not altered any resulting files can be saved to suit the use i.e, small 72 dpi jpegs for the web or high quality 300dpi TIFFS if you are looking to have them published or printed out.

It might be handy to mention that one of the biggest stock image libraries - Alamy - now only accept 300 dpi JPEGs saved as files no less than 48mB when opened. The losses when saving as JPEGs cannot, therefore, be too big an issue as their income depends on good quality images. Previously they only took TIFFs.
 
photografix said:
i.e, small 72 dpi jpegs for the web or high quality 300dpi TIFFS if you are looking to have them published or printed out.
Click to expand...
Interesting that they now accept jpgs. Just want to mention however that the dpi setting of an image has no bearing on its web-readiness. I.e. an image that is say 800x600 can have a dpi of 72 or a dpi of 6000 and it is still the same image. It has no relevance, just as the IPTC data, EXIF data, or the caption data have no relevance. DPI is only relevant when you print an image.
 
Last edited:
I am presuming then, that to send images to Alamy I would need a professional (Canon 1 series or equivalent) camera? Because even with RAWs I can't get anywhere near 48MB with my 20D.
 
RAH I think your statement while true is misleading. Yes it represents the same amount of detail. Viewing and printing are a quite a different matter.
800 X 600 at 6000dpi will be rather small printed in inches.

I think that most of us would think more in terms of 800X 600 at 72 dpi or 800 X 600 at 300 dpi. Which is totally different.
 
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