Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Apr 28, 2004, 5:26 AM   #11
Member
 
Join Date: Feb 2004
Posts: 48
Default

PNG can be 24-bit. I can also be palletized or greyscale.

I just tested this with Paint Shop Pro. A photo which was cropped to a 592x418 67 kb JPG saved as:

726 kb BMP
454 kb PNG
668 kb TGA
460 kb TIFF (LZW)

Having been a JPG may help skew this compression test. There's also a flaw in my test. I cropped the image from a JPG to another JPG

I guess the test needs to be either

RAW -> New File Format, or
RAW -> JPG -> New File Format

I guess I did

RAW -> JPG -> JPG -> New File Format

I don't really have time right now to redo it before I leave for work. But I put the results out there anyway just FYI.
Effen is offline   Reply With Quote
Old Apr 28, 2004, 7:56 AM   #12
Senior Member
 
Join Date: Dec 2002
Posts: 5,803
Default

I guess it shouldn't surprise me that someone adapted the JPG compression idea to TIFF. Since TIFF already has a built in system of extentions for compression. I didn't realize that regular JPG would do a better job, thought. Is it much better?

I believe (but I'm not positive) that LZW is a combination of dictionary lookup and run length encoding. If that is true, it having already been a jpg would help it to a better job.

eric
eric s is offline   Reply With Quote
Old Apr 28, 2004, 4:08 PM   #13
Junior Member
 
Join Date: Apr 2004
Posts: 12
Default Re: Will ZIP compression affect image quality on TIFFs?

Quote:
Originally Posted by CheckSix
Quote:
Originally Posted by ironchef
Quote:
Originally Posted by CheckSix
Once I transfer all my JPEGs over from my camera, I batch process them as TIFFs so I will keep the image quality good without it going bad after editing them, or opening them over and over.
Why not keep the original jpeg (which is already compressed)??

I do keep the original JPEG, just like keeping a 35mm from film. However, I resave each picture as a TIFF because after someone has opened them up in Adobe PS, and resave them, the JPEG compresses more. In other words, each time the save button is pressed, the JPEG is compressed more, and it causes image quality to go from excellent to horrible.

Here's an example, with the original in the upper left corner and the final image in the lower right hand corner...

Keep in mind that is after the image was saved many, many times. JPEGs are "lossy", or the file is compressed at each save. TIFFs are lossless, so when they are saved, they are not compressed, and no image information is lost.

I save as TIFFs so I can edit them a lot without losing quality.
Ok, do you mean that you turn 75% of all your photos to TIFF and save them to your hd? Hehe, you're good, my rate is something like 5%.
I just say buy more hd-space, its almost free nowadays!
ironchef is offline   Reply With Quote
Old Apr 28, 2004, 6:42 PM   #14
Senior Member
 
CheckSix's Avatar
 
Join Date: Dec 2003
Posts: 186
Default Re: Will ZIP compression affect image quality on TIFFs?

Quote:
Originally Posted by ironchef
Quote:
Originally Posted by CheckSix
Quote:
Originally Posted by ironchef
Quote:
Originally Posted by CheckSix
Once I transfer all my JPEGs over from my camera, I batch process them as TIFFs so I will keep the image quality good without it going bad after editing them, or opening them over and over.
Why not keep the original jpeg (which is already compressed)??

I do keep the original JPEG, just like keeping a 35mm from film. However, I resave each picture as a TIFF because after someone has opened them up in Adobe PS, and resave them, the JPEG compresses more. In other words, each time the save button is pressed, the JPEG is compressed more, and it causes image quality to go from excellent to horrible.

Here's an example, with the original in the upper left corner and the final image in the lower right hand corner...

Keep in mind that is after the image was saved many, many times. JPEGs are "lossy", or the file is compressed at each save. TIFFs are lossless, so when they are saved, they are not compressed, and no image information is lost.

I save as TIFFs so I can edit them a lot without losing quality.
Ok, do you mean that you turn 75% of all your photos to TIFF and save them to your hd? Hehe, you're good, my rate is something like 5%.
I just say buy more hd-space, its almost free nowadays!
Yeah, exactly. I hate the fact that the TIFFs are so big...but it's worth it.

Your right about the cheap HDDs these days. Perhaps I'll look in the Sunday ads to see if I can pick up a 120 or something for a good price.
CheckSix is offline   Reply With Quote
Old Apr 28, 2004, 11:58 PM   #15
Member
 
Join Date: Apr 2004
Posts: 76
Default

Quote:
Originally Posted by eric s
I guess it shouldn't surprise me that someone adapted the JPG compression idea to TIFF. Since TIFF already has a built in system of extentions for compression. I didn't realize that regular JPG would do a better job, thought. Is it much better?
The final quality is the same, but the handling is inefficient. Today programs have excellent support for JPEG including setting chrominance/luminance compression, lossless rotate and great support for meta data (EXIF, IPTC).

If you have a TIFF compressed with JPEG and want to rotate it for example, the graphic programm goes via decompression, data rotate and recompression. Its lossless for lossless compressions of course, but for JPEG its different.

Quote:
Originally Posted by eric s
I believe (but I'm not positive) that LZW is a combination of dictionary lookup and run length encoding. If that is true, it having already been a jpg would help it to a better job.
LZW is arithmetic coding and most efficient. The JPEG compression is also very efficient and can have arithmetic coding for the quantized data as well.
Jurgen Eidt is offline   Reply With Quote
Old Apr 29, 2004, 1:09 AM   #16
Senior Member
 
BruceMcL's Avatar
 
Join Date: Mar 2004
Posts: 106
Default

Quote:
Originally Posted by eric s
I guess it shouldn't surprise me that someone adapted the JPG compression idea to TIFF. Since TIFF already has a built in system of extentions for compression. I didn't realize that regular JPG would do a better job, thought. Is it much better?

eric
My understanding is that Adobe owns the TIFF standard at this time. I think they were the ones who introduced JPEG compression, which means loss of data, to the TIFF standard. First seen in Photoshop 6 or 7 ??? Before then every TIFF was a lossless TIFF.
BruceMcL is offline   Reply With Quote
Old Apr 29, 2004, 11:31 AM   #17
Senior Member
 
Setiprime's Avatar
 
Join Date: Sep 2003
Posts: 484
Default

How come nobody has mentioned the JPG2000 (or JPG2 as it is known) format ??

You can save it with "Lossless" compression, although it does decrease the file size slightly, it is an excellent way to save files, instead of the larger TIF format.

It goes in your plugin folder and several versions are available FREE.
Setiprime is offline   Reply With Quote
Old Apr 29, 2004, 9:49 PM   #18
Member
 
Join Date: Apr 2004
Posts: 76
Default

Quote:
Originally Posted by Setiprime
How come nobody has mentioned the JPG2000 (or JPG2 as it is known) format ??
Or why does no camera offer JPEG2000 (J2K)?
J2K doesn't compress better than JPEG. The advantage of J2K is when using small images used for web display. There are no block artifacts using higher compression as in JPEG but the images appear softer (the softness is the J2K artifacts, compared to the 8x8 block artifacts in JPEG).

Besides this, J2K is slow and the current implementations are not very stable. Try it for yourself
Jurgen Eidt is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 11:14 AM.