Re: Digital Imaging, File Formats, and Color
Response below - Original Message - From: [EMAIL PROTECTED] Subject: Digital Imaging, File Formats, and Color 1) Which file format, in what type of compression, in what color space (or photometric interpretation) is the best for archiving and printing (not web use)? Brent, Jpeg is somewhat misunderstood. It is a lossy compression, but losses only occur when the file is saved. So, you've just captured the award winning image you've always wanted. You photoshop it to your liking and save as your master in jpeg format (here's where the losses occur). You now want to print it, you open it up and print (no additional losses here). If you don't save changes to the file you just printed, and simply close out it out, no further losses to your master occurs. It's the resaving that causes additional losses. In some instances I have resaved after opening but have yet to see this lead to a noticeably degraded image. Kenneth Waller
Re: Digital Imaging, File Formats, and Color
For your project, you need a color test chart, or anything that can be used as a true baseline, and have that in a picture at the begining of every session or roll. Then have one of those charts available for anyone wanting to produce an image in the future and they'll make your red the red they was there! In theory. Uncompressed TIF, but zip up your files possibly - external compression. At 01:05 PM 3/17/2004 -0500, you wrote: Back to the list after a few years of absence. I apologize if I've already missed a similar discussion. I've recently been interested in digitizing my photographic process. I'm sticking with E-6, but every slide I make I get scanned. The web-site www.josephholmes.com gave me a bit of inspiration in to what digital imaging can mean to the photographic process: overcoming, or at least managing, the limitations and variations that are introduced when we try to represent the natural world in print form or on the web. This self imposed term paper I've been doing on the web has led to more questions than answers. I came back here to get a consensus I have relied upon in the past. Here are my questions: 1) Which file format, in what type of compression, in what color space (or photometric interpretation) is the best for archiving and printing (not web use)? My feeling so far is that GIF is out b/c it is limited to 256 colors; JPEG (which is actually a compression not a format) is out because the compression is lossy; TIFF seems to be the winner. Are there there viable options to consider. Should the TIFFs be compressed in a particular way, or uncompressed? Which way? Should the file be in RGB, CMKY, XYZ, L*a*b*, or other. I know RGB is good for monitors, CMYK is good for printers, and L*a*b* has its advantages too, but what should be the bread and butter? 2) Could someone explain the Color Management process. Does this process change the information in a file, or does it merely alter it during the data process to change it for a specific use. Ex- if I have a color profile for my scanner, does it alter the raw data coming in, or provide a means of interpreting that data? Similarly, if I changed a color profile for an image in photoshop one day, and then changed it back to the original later, would the result be different from the original? And lastly, is color management based on a standard palette that all profiles look to as a baseline, or does the process happen in the absence of a standard? how? Thanks for the help and the dicussion. I'm glad to be back. Brent Roberts Florence, SC (formerly of Birmingham, AL)
Re: Digital Imaging, File Formats, and Color
- Original Message - From: Kenneth Waller Subject: Re: Digital Imaging, File Formats, and Color Response below - Original Message - From: [EMAIL PROTECTED] Subject: Digital Imaging, File Formats, and Color 1) Which file format, in what type of compression, in what color space (or photometric interpretation) is the best for archiving and printing (not web use)? Brent, Jpeg is somewhat misunderstood. It is a lossy compression, but losses only occur when the file is saved. So, you've just captured the award winning image you've always wanted. You photoshop it to your liking and save as your master in jpeg format (here's where the losses occur). You now want to print it, you open it up and print (no additional losses here). If you don't save changes to the file you just printed, and simply close out it out, no further losses to your master occurs. It's the resaving that causes additional losses. In some instances I have resaved after opening but have yet to see this lead to a noticeably degraded image. I may be mistaken, but I believe that JPEG only supports 8 bit (256 colours) colour, which is kinda limited. I'm saving my stuff as however it comes off the camera, usually RAW, so that I will have access to the full colour gamut that the camera shoots, or as 16 bit tiff. I am not overly worried about not being able to read this stuff in the future, I figure I have the software now, I can't see that changing anytime soon. William Robb
Re: Digital Imaging, File Formats, and Color
Hi, Thursday, March 18, 2004, 8:51:20 AM, Jostein wrote: - Original Message - From: Mishka [EMAIL PROTECTED] raw is *guaranteed* to be readable for as long as C complilers are available, since dcraw.c is an easily available open source program. just burn the source code together with the images once. in fact, i think, this is the only reasonable archival format for digital camera images: it keeps all the information camera captures, but no more. I trust you can give everyone who needs it a good crash course in C compilation in ten years time, then. :-) Pleas put me on the list. I agree with you that C compilers are likely to be around for 10 more years, but in a longer perspective, you will need to burn the compiler along with the image data, and archive a computer with an operating system that can run the compiler as well. all you need is the file format syntax and semantics. Then you can use whatever programming language and operating system will be the flavour of the month in 10 years time. -- Cheers, Bob
Re: Digital Imaging, File Formats, and Color
- Original Message - From: Bob W [EMAIL PROTECTED] all you need is the file format syntax and semantics. Then you can use whatever programming language and operating system will be the flavour of the month in 10 years time. That's true. Let's hope that people like John Francis still hang around by then...:-) Jostein
Re: Digital Imaging, File Formats, and Color
Hi, 2) Could someone explain the Color Management process. Does this process change the information in a file, or does it merely alter it during the data process to change it for a specific use. Ex- if I have a color profile for my scanner, does it alter the raw data coming in, or provide a means of interpreting that data? Similarly, if I changed a color profile for an image in photoshop one day, and then changed it back to the original later, would the result be different from the original? And lastly, is color management based on a standard palette that all profiles look to as a baseline, or does the process happen in the absence of a standard? how? The profile doesn't alter the raw input data. The profile is a set of numbers which describe how far away from a standard your individual scanner is. When you read the data into an editor which understands profiles it uses those numbers to map the input data to the correct corresponding colours within its own colour space, as far as possible. Colour management uses a standard reference target. When you profile a device such as a scanner you get the scanner to read a standard target whose colours correspond with the reference numbers. The profiling software reads the colours your device scanned, compares them to the reference numbers for the target, and stores the differences as the device profile. To get a successful colour workflow you need profiles for each device in the chain - usually scanner, monitor and printer. Editors like Photoshop can read the files into a device-independent colour space which acts like a hub from which it can map between the different devices in the chain. It's quite a big subject. Probably more than can reasonably be covered by email. There's some useful information here: http://www.dl-c.com/Temp/ then click 'Downloads' then 'Miscellaneous files' and scroll down. There's also some good stuff here: http://www.hutchcolor.com/CMS_notes.html -- Cheers, Bob
RE: Digital Imaging, File Formats, and Color
Hi Brent (and welcome back) I'll throw a couple thoughts out File format Tiff uncompressed (16 bit if possible) JPEG2000 looks interesting but too few programs can use it. I would consider storing RAW but there is no guarantee that it will be readable in 10 years Color space Adobe 1998. It's the closest to what can be output by ink jet and photographic printers. sRGB is too small of a gamut even though some photographic printers print to that. It's always better to have more then you need then the other way around. Unless you are printing on offset printers your file should be in RGB. Both photographic printers and ink jets use RGB not CMYK. CMYK is a very small gamut color space. Color management is a nightmare. The biggest problem is that there is no universal standard. I have found that you can do quite well just using Adobe Gamma. When I burn a CD and take it to someplace with a digital mini lab the results come out ok. I print on an Epson 2200 and use paper profiles and ICM (internal color management) and My prints match my monitor within 1-2cc's. Butch Each man had only one genuine vocation - to find the way to himself. Hermann Hesse (Demian)
Re: Digital Imaging, File Formats, and Color
Butch Black wrote: File format Tiff uncompressed (16 bit if possible) JPEG2000 looks interesting but too few programs can use it. I would consider storing RAW but there is no guarantee that it will be readable in 10 years raw is *guaranteed* to be readable for as long as C complilers are available, since dcraw.c is an easily available open source program. just burn the source code together with the images once. in fact, i think, this is the only reasonable archival format for digital camera images: it keeps all the information camera captures, but no more. consider 8 bit tiff: if your camera has 12 bit raw, instead of storing 12 bits per pixel, you'll store 24, but only 8 of them will have the real information, you store more data, and at the same time you lose some information! with 16 bit tiff the ration is 48/12, that is, raw gives 4x comression automagically (of course, i am talking to raw formats that store just the raw data, i.e. canon raw). best, mishka
Re: Digital Imaging, File Formats, and Color
On Mar 18, 2004, at 07:05, [EMAIL PROTECTED] wrote: 1) Which file format, in what type of compression, in what color space (or photometric interpretation) is the best for archiving and printing (not web use)? I'd recommend any file format that does not use lossy compression. I use TIFF for my images. I also tend to save in 16 bits per channel, which TIFF also supports. I only convert to 8-bit when I need to run a filter that doesn't support 16 bit yet (Smart Blur). For colour spaces, just save your image with your working profile embedded. My working space is Adobe RGB 1998. sRGB is very common (its the Windows default). One lab in my city uses Kodak's Pro Photo RGB which is a wide-gamut colour space. There are dozens available but I'd stick with either Adobe or sRGB unless you have specific requirements. My feeling so far is that GIF is out b/c it is limited to 256 colors; JPEG (which is actually a compression not a format) is out because the compression is lossy; TIFF seems to be the winner. I'd agree with you there. TIFF files are big but storage is cheap these days. When my files start growing I worry more about RAM than drive space. Are there there viable options to consider. Should the TIFFs be compressed in a particular way, or uncompressed? Which way? Should the file be in RGB, CMKY, XYZ, L*a*b*, or other. I know RGB is good for monitors, CMYK is good for printers, and L*a*b* has its advantages too, but what should be the bread and butter? I use RGB, as that is my working space. For inkjet printers, the driver typically converts to CMYK for you, behind the scenes. If I was sending images out to pre-press I would let them do the CMYK conversion. 2) Could someone explain the Color Management process. I used to have a couple of really good references bookmarked. One was on Adobe's website, but they seem to have removed most of the useful information since then. The other was on Barco's website but I can't find that one anymore either. I don't really know the system in enough depth to adequately explain how it works. I might be able to write a quick overview. And lastly, is color management based on a standard palette that all profiles look to as a baseline, or does the process happen in the absence of a standard? how? There is a standard format for describing colour profiles, defined by the International Color Consortium (http://www.color.org/). Colour management systems are many and varied, and each one will convert between colour spaces in a slightly different way. You also have the option of Relative Colorimetric, Absolute Colorimetric, and Perceptual conversions: http://www.creativepro.com/story/feature/12641-1.html Colour-management-aware operating systems also provide a standard location for ICC profiles. For various versions of MacOS and Windows, see this page: http://www.adobe.com/support/techdocs/1401a.htm Generally you don't need to know where the files go, unless you manually obtain a profile (eg from a print shop). If you haven't already done so I would strongly recommend calibrating your monitor. Something like Adobe Gamma, or MacOS's built-in calibrator, would be a good start. If you want to get serious you can buy hardware to get a more accurate calibration. I recently bought the Spyder Pro package from Pantone ColorVision and I'm very pleased with the result. Cheers, - Dave http://www.digistar.com/~dmann/
