Canon Digital Photography Forums  

Go Back   Canon Digital Photography Forums > 'Equipment Talk' section > Canon EOS Digital Cameras
Register Rules FAQ Members List Search Today's Posts Mark Forums Read



Reply
 
Thread Tools Display Modes
Old 29th of January 2003 (Wed)   #1
JR92
Member
 
Join Date: Jul 2002
Posts: 65
Default Best format to save a digital image without lossing quality

What is the best way to save a digital image and not lose quality over time. I know it is not JPEG, but what else, TIFF? EPS? Photoshop Doc.?
JR92 is offline   Reply With Quote
This ad block will go away when you log in as member
Old 29th of January 2003 (Wed)   #2
robertwgross
Cream of the Crop
 
robertwgross's Avatar
 
Join Date: Nov 2002
Location: California
Posts: 9,462
Default Re: Best format to save a digital image without lossing qual

Quote:
JR92 wrote:
What is the best way to save a digital image and not lose quality over time. I know it is not JPEG, but what else, TIFF? EPS? Photoshop Doc.?
I think you will get your best results with TIF. There are at least two variations of TIF. One is "straight TIF" and one is "LZW TIF". The latter does a lossless compression on the file, so it takes a little longer to save and it packs into a tighter file size. Some images will "pack tightly" in LZW TIF, and some will come out about the same as straight TIF.

We could have a debate about 8-bit-per-color TIF (24-bits) or 16-bit-per-color TIF (48-bits). Obviously the latter takes up twice as much file space, and it could be debated as to what that really buys you.

The bottom line is: It depends.

It depends on what you are trying to shoot and what you want to do with the image afterward. If you tell us that you are simply posting a small image to the web, then that means something. If you tell us that you are printing at 24x36 inches, then that means something else.

---Bob Gross---
robertwgross is offline   Reply With Quote
Old 29th of January 2003 (Wed)   #3
JR92
Member
 
Join Date: Jul 2002
Posts: 65
Default Re: Best format to save a digital image without lossing qual

Thanks for your advise Bob.
I am printing many of my images and I don't want to lose quality. Some of my wildlife shots I am having made into 20x30s. I will have my web-site up in a few weeks and probably just use JPEGs for my thumbnails.
Whta do you advise for best resolution? right now I have just been using 72. I don't know any better.
Thanks again, JR92
JR92 is offline   Reply With Quote
This ad block will go away when you log in as member
Old 30th of January 2003 (Thu)   #4
Roger_Cavanagh
Senior Member
 
Roger_Cavanagh's Avatar
 
Join Date: Sep 2001
Posts: 1,394
Default Re: Best format to save a digital image without lossing qual

If you are using Photoshop (can't speak for other editors), there are now plug-ins available for formats such as PNG and JPEG 2000 that will provide lossless compression with good results. The downside is that not all applications support these formats and the formats don't support stuff like layers and EXIF. I have been wondering about J2k, but haven't made this switch yet because I don't get thumbnails displayed in IE or ThumbsPlus. Cerious are promising better J2k support in their next version, so I will reconsider then.

As for resolution and JPGs. If you are preparing the JPGs solely for screen/web use, then DPI is irrelevant. What matters is the pixels dimensions. DPI will only affect the physical print size of an image.

Regards,
__________________
=============
Roger Cavanagh
www.rogercavanagh.com
Roger_Cavanagh is offline   Reply With Quote
Old 30th of January 2003 (Thu)   #5
Dans_D60
Member
 
Join Date: Apr 2002
Location: Temecula Ca
Posts: 592
Default Re: Re: Best format to save a digital image without lossing

Quote:
Roger_Cavanagh wrote:


As for resolution and JPGs. If you are preparing the JPGs solely for screen/web use, then DPI is irrelevant. What matters is the pixels dimensions. DPI will only affect the physical print size of an image.

Regards,
I agree that DPI depth for JPG images on the web has little effect unless you drop below 72 DPI. Display screens cannot reproduce images larger than 72-96 DPI depending on the pixel layout. So anything larger just gets lost anyway. But, larger DPI images means larger file sizes. So as a rule of thumb all my images for web reproduction are set to 72 DPI while my print resolutions are set at 240 – 300 depending on the printer selection.

Dan
http://www.pettusphoto.com
__________________
Dan
Dan Pettus Photography
BLOG
FB
Dans_D60 is offline   Reply With Quote
Old 30th of January 2003 (Thu)   #6
Roger_Cavanagh
Senior Member
 
Roger_Cavanagh's Avatar
 
Join Date: Sep 2001
Posts: 1,394
Default Re: Re: Re: Best format to save a digital image without loss

Quote:
Dans_D60 wrote:
I agree that DPI depth for JPG images on the web has little effect unless you drop below 72 DPI. Display screens cannot reproduce images larger than 72-96 DPI depending on the pixel layout. So anything larger just gets lost anyway. But, larger DPI images means larger file sizes. So as a rule of thumb all my images for web reproduction are set to 72 DPI while my print resolutions are set at 240 – 300 depending on the printer selection.

Dan
http://www.pettusphoto.com
Dan,

Nope, DPI will not change the file size just by itself. If you are using Photoshop and change with DPI with the resample box checked then the dimensions of the image in pixels will change so that the physical print size of the image remains the same at the new DPI. But you can change the DPI with resample off and the number of pixels does not change. And, broadly speaking, the file size will be related to the number of pixels (ignoring JPG compression, layers, EXIF and other stuff).

The size of the image on screen will not change NO MATTER WHAT DPI - a pixel is a pixel is a pixel. If an image is 400 x 400 pixels that is how much real estate it will take up on your screen whether DPI is 72, 240, 300 or whatever. I'd post some example, but Photoshop is tied up doing a batch conversion right now.

Regards,
__________________
=============
Roger Cavanagh
www.rogercavanagh.com
Roger_Cavanagh is offline   Reply With Quote
Old 30th of January 2003 (Thu)   #7
Dans_D60
Member
 
Join Date: Apr 2002
Location: Temecula Ca
Posts: 592
Default Re: Re: Re: Re: Best format to save a digital image without

Quote:
Roger_Cavanagh wrote:

Dan,

Nope, DPI will not change the file size just by itself. If you are using Photoshop and change with DPI with the resample box checked then the dimensions of the image in pixels will change so that the physical print size of the image remains the same at the new DPI. But you can change the DPI with resample off and the number of pixels does not change. And, broadly speaking, the file size will be related to the number of pixels (ignoring JPG compression, layers, EXIF and other stuff).

The size of the image on screen will not change NO MATTER WHAT DPI - a pixel is a pixel is a pixel. If an image is 400 x 400 pixels that is how much real estate it will take up on your screen whether DPI is 72, 240, 300 or whatever. I'd post some example, but Photoshop is tied up doing a batch conversion right now.

Regards,
I guess the use of ‘size’ with pixel dimension, document size, and file size should have been more clearly explained. By maintaining the same document size (8X10) and reducing the DPI (300 to 72) would reduce the pixel dimensions (3200X2100 to 780X520) thereby reducing the file size. I totally agree a 400 X 400 image is what it is - and basic mathematics is constant (at least I hope so!). Sorry about the confusion!
Dan
http://www.pettusphoto.com
__________________
Dan
Dan Pettus Photography
BLOG
FB
Dans_D60 is offline   Reply With Quote
Old 6th of February 2003 (Thu)   #8
chewiebakka
Junior Member
 
Join Date: Feb 2003
Posts: 16
Default Re: Best format to save a digital image without lossing qual

so lzwTIFF just try to compress the tiff file?
chewiebakka is offline   Reply With Quote
Old 6th of February 2003 (Thu)   #9
robertwgross
Cream of the Crop
 
robertwgross's Avatar
 
Join Date: Nov 2002
Location: California
Posts: 9,462
Default Re: Best format to save a digital image without lossing qual

It is hard to understand it that is a question.

TIF holds all of the data in a non-lossy method, but the file takes up a lot of storage space.

LZW TIF holds all of the data, still non-lossy, but it uses computer power to "pack" the data into a tighter file. The good news is that if you've got a fast computer, the computer power is there and it does not slow down the file saving and reading _by_very_much. Note that some people are more interesting in flat out speed, so they won't do this.

The bad news is that the degree of file space saved varies from image to image. If you have an image file with lots of repetitive information (like large areas of constant color), then the LZW TIF "packs" it tightly and you save a bunch of space. For example, an original TIF file at 10MB might get saved as LZW TIF at only 4MB. OTOH, many photo-realistic images do not have much repetitive information, so the LZW TIF ends up being 10.1MB. If I see that happen, then I simply delete the LZW TIF and stay with the straight TIF.

I have about 50GB in stored image filies, so I've been down this road before.

---Bob Gross---
robertwgross is offline   Reply With Quote
Reply


Thread Tools
Display Modes

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

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Canon Digital Rebel XT- Image Quality? Audsquad Canon EOS Digital Cameras 21 31st of August 2006 (Thu) 09:37
Save to which format? NativeCraft RAW, Post Processing and Printing 4 21st of December 2005 (Wed) 08:51
Digital Rebel image resolution quality for print Keriann RAW, Post Processing and Printing 6 21st of August 2005 (Sun) 21:03
Compromising image quality with a L lens with digital?? Kelv2888 Canon EOS Digital Cameras 20 11th of May 2005 (Wed) 13:49
Medium Format vs 35mm Image Quality?? optical RAW, Post Processing and Printing 2 27th of August 2004 (Fri) 07:04


All times are GMT -5. The time now is 07:12.


Powered by vBulletin® Version 3.6.12
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
This forum is not affiliated with Canon in any way and is run as a free user helpsite by Pekka Saarinen, Helsinki Finland. You will need to register in order to be able to post messages. Cookies are required for registering and posting. HTML in messages is not allowed, plain website addresses are automatically made active by the board.