Wednesday, November 10, 2010
Odd spot - The graphic arts reflected in crate labels
I was rummaging through images of vintage vegetable and fruit crate labels when I suddenly realized that a number of them reflected topics related to the graphic arts topics. Weird or what?
Sunday, November 7, 2010
Thursday, November 4, 2010
The Wayback View - Continuous tone lithography - the Collotype process
Look at any modern presswork under a loupe and you'll see those ubiquitous halftone dots. Even inkjet presses use dots to create the final image.
However, there is a printing process that eliminates halftone screening completely and renders true continuous tone lithography.
On the left is a full image of a 12" x 18" reproduction of a Mondrian painting. On the right is a close-up of just the center of the image. No halftone dots!
Collotype (a.k.a. photo-gelatin, heliotype, albertype, litchdruck, phototypie process)
Collotype is a photographic method of producing a lithographic printing surface in gelatin in which tones can be reproduced without the use of any halftone screen. This reproduction method was devised about 1860 by a Mr. Poitevin and introduced commercially in 1867 under the name "phototypie" by du Motay and Maréchal.
Although it initially became a widely used process, it was very difficult to control and not suited for long press runs. As a result, it was replaced by conventional offset lithography (with its halftone screening) and became a specialized process that was mostly used for fine art reproductions. Today, there are only a very few printers using this process (e.g. Black Box Collotype Ltd in the U.S. and Benrido in Japan).
Collotype printing
The collotype plate is made by coating a plate of glass, or sometimes metal, with a substrate composed of gelatin or other colloid and hardening it. Then it is coated with a thick coat of bichromated gelatin and dried carefully at a controlled temperature (a little over 50° C waters) so it 'reticulates' or breaks up into a finely grained pattern when washed later in approximately 16° C water. The plate is then exposed in contact with the negative using an ultraviolet (UV) light source which changes the ability of the exposed gelatine to later absorb water. The plate is developed by carefully washing out the bichromate salt and dried without heat. The plate is left in a cool dry place to cure for 24 hours before using it to print.
Exposing the film negative This view is of the back of the camera which is set at a right angle to the original art.
An artist/retoucher works on the film negative to make adjustments to the tones of the negative so that they will create a plate that accurately reproduces the original art. With a full color reproduction, all four, or more, negatives will have to be corrected.
The glass plate being exposed.
A photo-electric cell is used to test the tone and color density.
To produce prints, the plate is dampened with a glycerine/water mixture which is slightly acidic , then blotted before inking with Collotype ink using a leather or velvet roller. A hard finished paper such as Bristol, is then put on top of the plate and covered with a tympan before being printed typically using a manual proof press.
Two views of a Collotype press.
The result is a reproduction that is indistinguishable from a photographic print.
Full image and magnified to show the detail.
Collotype printing at Benrido, Japan:
Steps demonstrated include; exposing the art to film, processing and inspecting the film negative, retouching the negative, coating, drying and then exposing the plate to the negative, washing the plate to remove excess bichromate, wetting the plate and making the image level prior to inking, and finally printing the job.
The closest modern equivalent to producing continuous tone lithographic printing is 10 micron FM screening which, even under 10x magnification, appears to not have been halftone screened as in the example below:
Canadian postage stamps are an excellent example of 10 micron FM screening that results in presswork with a similar image fidelity to Collotype printing.
However, there is a printing process that eliminates halftone screening completely and renders true continuous tone lithography.
Collotype (a.k.a. photo-gelatin, heliotype, albertype, litchdruck, phototypie process)
Collotype is a photographic method of producing a lithographic printing surface in gelatin in which tones can be reproduced without the use of any halftone screen. This reproduction method was devised about 1860 by a Mr. Poitevin and introduced commercially in 1867 under the name "phototypie" by du Motay and Maréchal.
Although it initially became a widely used process, it was very difficult to control and not suited for long press runs. As a result, it was replaced by conventional offset lithography (with its halftone screening) and became a specialized process that was mostly used for fine art reproductions. Today, there are only a very few printers using this process (e.g. Black Box Collotype Ltd in the U.S. and Benrido in Japan).
Collotype printing
The collotype plate is made by coating a plate of glass, or sometimes metal, with a substrate composed of gelatin or other colloid and hardening it. Then it is coated with a thick coat of bichromated gelatin and dried carefully at a controlled temperature (a little over 50° C waters) so it 'reticulates' or breaks up into a finely grained pattern when washed later in approximately 16° C water. The plate is then exposed in contact with the negative using an ultraviolet (UV) light source which changes the ability of the exposed gelatine to later absorb water. The plate is developed by carefully washing out the bichromate salt and dried without heat. The plate is left in a cool dry place to cure for 24 hours before using it to print.
An artist/retoucher works on the film negative to make adjustments to the tones of the negative so that they will create a plate that accurately reproduces the original art. With a full color reproduction, all four, or more, negatives will have to be corrected.
The glass plate being exposed.
A photo-electric cell is used to test the tone and color density.To produce prints, the plate is dampened with a glycerine/water mixture which is slightly acidic , then blotted before inking with Collotype ink using a leather or velvet roller. A hard finished paper such as Bristol, is then put on top of the plate and covered with a tympan before being printed typically using a manual proof press.
Two views of a Collotype press.The result is a reproduction that is indistinguishable from a photographic print.
Collotype printing at Benrido, Japan:
Steps demonstrated include; exposing the art to film, processing and inspecting the film negative, retouching the negative, coating, drying and then exposing the plate to the negative, washing the plate to remove excess bichromate, wetting the plate and making the image level prior to inking, and finally printing the job.
The closest modern equivalent to producing continuous tone lithographic printing is 10 micron FM screening which, even under 10x magnification, appears to not have been halftone screened as in the example below:
Thursday, October 28, 2010
How AM and FM screening equivalencies are measured
I'm often asked about what AM/XM halftone screens are equivalent to a certain FM screen - i.e. "What AM/XM screen is equivalent to a 20 micron FM screen?"
There are two ways that this halftone screening equivalency is usually measured.
One is equivalency of detail rendering - the ability of the screening to render image detail. The other is lithographic equivalency - how they perform on press lithographically. Note that in both cases, because the respective screening technology is so different, equivalency can only be an approximation.
Equivalency of detail rendering
Since halftone dots form the printed image - more dots per linear inch translates into more detail that can be rendered.
With an AM screen the detail rendering ability is specified in lpi (or lpc) - i.e. halftone dots per inch (e.g. 175 lpi or 60 lpc).
Since an FM screen has no "lines per inch" determining the equivalent detail rendering equivalency is usually done by drawing a line through the FM screen and counting how many dots are intersected (crossed) in a distance of one inch.
The above example shows an FM screen enlarged. The distance measured is 1/16th of an inch. In that 1/16th of an inch approximately 36 dots are intersected. So, in one inch about 576 dots would be intersected (16 x 36). Put another way, there are 576 dots per linear inch - 576 lpi - to render detail, i.e. this FM screen is equivalent to a 576 lpi AM/XM screen.
Lithographic equivalency
Lithographic equivalency is a bit more complicated to figure out. It is usually measured by counting the number of edges (transitions) in a square inch.
Halftone screens with a similar number of edge transitions will have similar lithographic properties.
AM/XM equivalents of some popular FM screens.
Keep in mind, these are approximations only, however they do give a good indication as to screening performance.
Saturday, October 23, 2010
The Job Interview
One of the most challenging aspects of working at a hi-tech company is actually getting the job in the first place. When I was hired by the graphic arts company Creo, in 1997, I not only faced the usual human resources questions, but also a slew of engineer-developed questions intended to reveal the job applicant's thinking process and how they went about solving problems.
Here are a few of the questions that prospective Creo employees had to negotiate back in '97. Unfortunately, except for the one about drawing a bicycle, I haven't a clue what the answers to the other questions are. I wouldn't be surprised if the engineers asking the questions didn't have a clue either!
• What color is crab's (or shrimp's) blood and why?
• Please draw a bicycle in as much detail as you can.
Job applicants draw a bicycle - luckily they don't have to ride it.
• How do you put a giraffe into a refrigerator? Now, how do you put an elephant into a refrigerator?
• There is a square room. In each corner is a bug. Each has a mission: to walk directly towards the bug on its right. They walk at the same speed and begin at the same time. a) Do they ever meet? If yes, where? b) What is the length of the path they travel if they do meet?
• What is the sum of all numbers between 1 and 100?
• A company grows trees. Each year the tree grows, it can be cut down and sold for $1 times the square of its age in years. At that point, the money can be put into the bank and will receive 10% interest per year. To maximize profit, should the company ever cut down and sell a tree? If so, at what age?
OK, if you’ve read this far you may be scratching your head and wondering if you should have applied somewhere else. Well, let’s look closer at one of the questions – the one about putting a giraffe in a refrigerator – to see how the engineer’s subtle mind works during the interview process.
The correct answer is pretty straightforward: open the refrigerator, put in the giraffe, and close the door. Any other solution would suggest that you tend to do simple things in an overly complicated way. Now, how do you put an elephant into a refrigerator? If you said: open the refrigerator, put in the elephant, and close the door – well that would be wrong. The right answer is: open the refrigerator, take out the giraffe, put in the elephant and close the door. This tests your ability to think through the repercussions of your previous actions.
If the engineers were particularly rascally during the interview, they might follow up with another question like the one about the Lion King hosting an animal conference. Apparently all the animals attend the conference except one. So, which animal was that? Well obviously, at least for an Einstein anyway, the correct answer is the elephant since you just put him in the refrigerator!
As far as the answers to the other questions are concerned…well, if you haven’t figured them out on your own, and since this was in 1997, you'll have to wait a year for Google to be created.
Here are a few of the questions that prospective Creo employees had to negotiate back in '97. Unfortunately, except for the one about drawing a bicycle, I haven't a clue what the answers to the other questions are. I wouldn't be surprised if the engineers asking the questions didn't have a clue either!
• What color is crab's (or shrimp's) blood and why?
• Please draw a bicycle in as much detail as you can.
• How do you put a giraffe into a refrigerator? Now, how do you put an elephant into a refrigerator?
• There is a square room. In each corner is a bug. Each has a mission: to walk directly towards the bug on its right. They walk at the same speed and begin at the same time. a) Do they ever meet? If yes, where? b) What is the length of the path they travel if they do meet?
• What is the sum of all numbers between 1 and 100?
• A company grows trees. Each year the tree grows, it can be cut down and sold for $1 times the square of its age in years. At that point, the money can be put into the bank and will receive 10% interest per year. To maximize profit, should the company ever cut down and sell a tree? If so, at what age?
OK, if you’ve read this far you may be scratching your head and wondering if you should have applied somewhere else. Well, let’s look closer at one of the questions – the one about putting a giraffe in a refrigerator – to see how the engineer’s subtle mind works during the interview process.
The correct answer is pretty straightforward: open the refrigerator, put in the giraffe, and close the door. Any other solution would suggest that you tend to do simple things in an overly complicated way. Now, how do you put an elephant into a refrigerator? If you said: open the refrigerator, put in the elephant, and close the door – well that would be wrong. The right answer is: open the refrigerator, take out the giraffe, put in the elephant and close the door. This tests your ability to think through the repercussions of your previous actions.If the engineers were particularly rascally during the interview, they might follow up with another question like the one about the Lion King hosting an animal conference. Apparently all the animals attend the conference except one. So, which animal was that? Well obviously, at least for an Einstein anyway, the correct answer is the elephant since you just put him in the refrigerator!
As far as the answers to the other questions are concerned…well, if you haven’t figured them out on your own, and since this was in 1997, you'll have to wait a year for Google to be created.
Saturday, October 16, 2010
The Wayback View – 1964, The Internet imagined
1964 was the year that the Beatles first invaded America. China tested its first atomic bomb and, finally, the US Surgeon General warned against cigarette smoking.
In 1964, there were around 1.5 million people, in the US, using this mobile phone which ran on AT&T's network and was called their “Improved Mobile Telephone Service.”
IBM introduced the System/360 computer that was available with up to a whopping 8 MB of internal main memory.
And the Internet of the future was imagined:
In 1964, there were around 1.5 million people, in the US, using this mobile phone which ran on AT&T's network and was called their “Improved Mobile Telephone Service.”
IBM introduced the System/360 computer that was available with up to a whopping 8 MB of internal main memory.
And the Internet of the future was imagined:
Tuesday, October 12, 2010
Goodbye JPEG - hello WEBP?
Google is introducing a new open-source image format: "WebP" (pronounced ‘weppy’).
Google claims that images in the WebP image format will be close to 40 percent smaller than JPEG files while providing for images that are of higher quality by virtually eliminating the image artifacts associated with JPEG compression. At the present moment, WebP is still in a very early stage of development and hence, unlike the JPEG file format, WebP is not yet built into cameras, web browsers, image-editing programs, etc.
JPEG vs WebP compression at 100%
From left to right: Original image, JPEG compressed, WebP compressed. JPEG vs WebP compression enlarged
From left to right: Original image, JPEG compressed, WebP compressed.
WebP uses the Y'UV color model that is used in the NTSC, PAL, and SECAM composite color video standards. It is a bit like the LAB mode color model that is used in PhotoShop, and other imaging applications, in that the Y component, like the "L" channel, determines the lightness of the color (referred to as luminance or luma), while the U and V components, like the "a" and "b" channels, determine the color itself (the chroma).
The Y'UV color model - From left to right: Original composite image, "Y" component, "U" component, "V" component.
For image compression, WebP uses the VP8 video codec - the same methodology that is used to compress keyframes in videos. This codec uses predictive coding to encode an image by using the values in neighboring blocks of pixels to predict the values in a block, and then encodes only the difference (residual) between the actual values and the prediction. The residuals typically contain many zero values, which can be compressed much more effectively.
So far, while it is still a "lossy" compression technology, WebP compressed images certainly appear to deliver a higher level of compression (and thus smaller file size), and much higher image quality than the current standard JPEG image compression method. This is a good thing, not only for images for web application, but possibly for print application as well.
Google Chrome will likely be the first consumer application to support "weppy" compression in order to provide a faster user experience on web sites while reducing bandwidth and hosting costs.
On the other hand
Since the Y'UV color model is similar in principal to the Lab color model...why not apply the same compression methodology to an image that's in Lab mode? I've done some testing with high JPEG compression of the "a" and "b" channels of a Lab image and easily achieve file sizes that are only 20% of the original file size with no apparent image degradation. In fact they look very similar to the results obtained with the WebP image format.
Left image WebP - right image Lab compressed using very high JPEG compression for the "a" and "b" channels of an Lab image.
Left image WebP - right image Lab compressed using very high JPEG compression for the "a" and "b" channels of an Lab image.
If the Y'UV compression method could be applied to Lab images then the graphic arts industry could continue to use a color model that is well understood and in use today rather than import a new color model from another industry.
Google claims that images in the WebP image format will be close to 40 percent smaller than JPEG files while providing for images that are of higher quality by virtually eliminating the image artifacts associated with JPEG compression. At the present moment, WebP is still in a very early stage of development and hence, unlike the JPEG file format, WebP is not yet built into cameras, web browsers, image-editing programs, etc.
JPEG vs WebP compression at 100%
WebP uses the Y'UV color model that is used in the NTSC, PAL, and SECAM composite color video standards. It is a bit like the LAB mode color model that is used in PhotoShop, and other imaging applications, in that the Y component, like the "L" channel, determines the lightness of the color (referred to as luminance or luma), while the U and V components, like the "a" and "b" channels, determine the color itself (the chroma).
For image compression, WebP uses the VP8 video codec - the same methodology that is used to compress keyframes in videos. This codec uses predictive coding to encode an image by using the values in neighboring blocks of pixels to predict the values in a block, and then encodes only the difference (residual) between the actual values and the prediction. The residuals typically contain many zero values, which can be compressed much more effectively.
So far, while it is still a "lossy" compression technology, WebP compressed images certainly appear to deliver a higher level of compression (and thus smaller file size), and much higher image quality than the current standard JPEG image compression method. This is a good thing, not only for images for web application, but possibly for print application as well.
Google Chrome will likely be the first consumer application to support "weppy" compression in order to provide a faster user experience on web sites while reducing bandwidth and hosting costs.
On the other hand
Since the Y'UV color model is similar in principal to the Lab color model...why not apply the same compression methodology to an image that's in Lab mode? I've done some testing with high JPEG compression of the "a" and "b" channels of a Lab image and easily achieve file sizes that are only 20% of the original file size with no apparent image degradation. In fact they look very similar to the results obtained with the WebP image format.
If the Y'UV compression method could be applied to Lab images then the graphic arts industry could continue to use a color model that is well understood and in use today rather than import a new color model from another industry.
Friday, October 8, 2010
CtF - Computer to Foam - Printing the cloud
"FLOGOS" - flying logos - is a biodegradable foam-helium mixture. Templates form the foam into the desired shape creating small bubble clouds which then float through the air. Output rate is approximately 100-250 FLOGOS per hour, per generator.
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