I agree totally with what you say in your article. The responses show there is still confusion even over such a well written sumary. I have been scanning now 30 years. Starting on continious tone scanners that compared with todays machines, they were mamoths. To attain the optimum the 2X lpi has been the best formula for the printing industry. In Australia some printing is done at 200lpi which means scanning at 400dpi. Some other scanning tips for the printing industry can be found at www.trendsetting.com.au.
Submitted by Grant Toyer on Wed, 08/23/2000 - 23:43.
This is a good article for beginners, but some important points were missed and a correction needs to be made. You indicate that 150 line screen is the highest screen frequency used. This is not true. For process (color photographic images) work we use at least 175 line screen and depending on the nature of the subject matter will go as high as 300 lpi.
You also need to let the readers know about Effective Resolution which is related to how the image is going to be used in the page layout document (let's say Quark for example), i.e. at what percentage enlargement/reduction. If you scan a 35mm chrome which will be enlarged to 200% for a brochure which will be printing at 175 lpi, then you should scan at 525 ppi to 700 ppi (175 lpi x 1.5 min. or 2 max. x 200%) depending on the subject matter. Conversely, if you have an 8 x 10 original for that same brochure which will be used at 50% in the Quark document you can scan at 175 ppi.
Finally your readers should be aware that "resolution" is not necessarily an indication of the quality of the scan. There are quite a few desktop scanners which advertise a very high resolution, and though they are quite capable for some uses, they can not match the density range, color fidelity, and sharpness of a $250,000 drum scanner.
David Haas, ArtWorx Lithographic
a very understandable and to the point article. One note - 150 line screens are not the highest - our printer occasionally uses 175 and 200 line screens.
Much of this article is geared towards basic pricipals of scan resolution. Though great for beginers, I would love to see more detailed, useful stuff. For instance how is it that drum scans are scanned at 300 dpi. According to my calculations scanning from b/w 2.25 film to 10 x 10 would mean scanning at nearly 600dpi leaving you with a several hundred megabyte file. what gives?
Also something about the usability of desktop scanners for med to high end output. which scanners are good enough ( if any) and so on.
Thanks
Submitted by faceplant on Mon, 01/14/2002 - 18:54.
I agree with most of what you say with one exception:
I believe that you need one more column in your table:
RAW SCAN SIZE, and that your final edit should be to
drop the file size to the correct ppi. A compromise between your and
Bruce's view. I know you get cleaner Full color images by bringing
into Photoshop images scanned at higher resolutions than necessary.
I generally just add 1/3; i.e., for 200 lpi @1200 dpi final, I scan,
work, edit and convert to CYMK an image at 300 ppi. Then before
placing, seperating or printing I convert to 200 and sharpen if necessary.
It's a better place to start, and the extra storage space is only
temporary. I even start with 300 for web images, the final jpegs @ 72ppi
are noticably nicer.
I work for a company who decided to decentralize desktop publishing (I have been responsible for 95% of the company's design work for the past 12 years) by requiring all secretaries to create their own files in PageMaker for output to a Canon color copier. This article should be required reading for individuals like that, in particular, who have no concept of how everything is related and interdependent (from an idea to the software program to the output device). The article uses easily comprehended concepts to aid in the construction of professional and printable files. Well done!
Submitted by beth_pauley on Wed, 08/23/2000 - 07:24.
Since the article is meant as a primer, it would be wise to mention that the information pertains to images being reproduced at 100%, i.e., when enlarging an image to 200% of its original size you will need twice the resolution to achieve reasonable results.
Nice to read some good sense on scanning res. But high-res scans of b&w line art can become a problem if you get involved in colouring up the resulting bitmap. Just converting from b&w to colour can make the file size balloon. I know of only one product, ColorPress, that enables you to colour up using indexed colour so the resulting file is not much bigger than the original.
High-end color laser printers as a final output,which do not halftone the image at all, are left off of the table 2 above. For best results, I would scan the image to print at the resolution of the device (like the line art table). For crisp detail such as in jewelry, this would matter greatly (even for halftoning, a higher resolution yields more detail, so lpi x 2). Not so important for an impressionist painting, etc, where you can even get away with a ppi only 10% higher than the HT line screen (if desperate).
Don't forget to scan at the maximum size you might use the image. Scaling up reduces the ppi in the formula.
scanning
cool article, but the tables which are interesting are tough to print out
Please get it right
I agree totally with what you say in your article. The responses show there is still confusion even over such a well written sumary. I have been scanning now 30 years. Starting on continious tone scanners that compared with todays machines, they were mamoths. To attain the optimum the 2X lpi has been the best formula for the printing industry. In Australia some printing is done at 200lpi which means scanning at 400dpi. Some other scanning tips for the printing industry can be found at www.trendsetting.com.au.
Good, but missed some important points.
This is a good article for beginners, but some important points were missed and a correction needs to be made. You indicate that 150 line screen is the highest screen frequency used. This is not true. For process (color photographic images) work we use at least 175 line screen and depending on the nature of the subject matter will go as high as 300 lpi.
You also need to let the readers know about Effective Resolution which is related to how the image is going to be used in the page layout document (let's say Quark for example), i.e. at what percentage enlargement/reduction. If you scan a 35mm chrome which will be enlarged to 200% for a brochure which will be printing at 175 lpi, then you should scan at 525 ppi to 700 ppi (175 lpi x 1.5 min. or 2 max. x 200%) depending on the subject matter. Conversely, if you have an 8 x 10 original for that same brochure which will be used at 50% in the Quark document you can scan at 175 ppi.
Finally your readers should be aware that "resolution" is not necessarily an indication of the quality of the scan. There are quite a few desktop scanners which advertise a very high resolution, and though they are quite capable for some uses, they can not match the density range, color fidelity, and sharpness of a $250,000 drum scanner.
David Haas, ArtWorx Lithographic
very understandable and to the point
a very understandable and to the point article. One note - 150 line screens are not the highest - our printer occasionally uses 175 and 200 line screens.
Very Helpful
This was a very helpful article. It was well written and gave me a good start as I am learning to develop my scanning techniques.
Good Basic Info
This article is a very good basic guideline for those starting out in the graphic design business, or for those who need a short refresher.
great for beginners
Much of this article is geared towards basic pricipals of scan resolution. Though great for beginers, I would love to see more detailed, useful stuff. For instance how is it that drum scans are scanned at 300 dpi. According to my calculations scanning from b/w 2.25 film to 10 x 10 would mean scanning at nearly 600dpi leaving you with a several hundred megabyte file. what gives?
Also something about the usability of desktop scanners for med to high end output. which scanners are good enough ( if any) and so on.
Thanks
Useful
Very helpful to the newcomer to scanning, but would have been even better if writing had been a little clearer.
Almost
I agree with most of what you say with one exception:
I believe that you need one more column in your table:
RAW SCAN SIZE, and that your final edit should be to
drop the file size to the correct ppi. A compromise between your and
Bruce's view. I know you get cleaner Full color images by bringing
into Photoshop images scanned at higher resolutions than necessary.
I generally just add 1/3; i.e., for 200 lpi @1200 dpi final, I scan,
work, edit and convert to CYMK an image at 300 ppi. Then before
placing, seperating or printing I convert to 200 and sharpen if necessary.
It's a better place to start, and the extra storage space is only
temporary. I even start with 300 for web images, the final jpegs @ 72ppi
are noticably nicer.
This should be required reading for anyone with a scanner/printe
I work for a company who decided to decentralize desktop publishing (I have been responsible for 95% of the company's design work for the past 12 years) by requiring all secretaries to create their own files in PageMaker for output to a Canon color copier. This article should be required reading for individuals like that, in particular, who have no concept of how everything is related and interdependent (from an idea to the software program to the output device). The article uses easily comprehended concepts to aid in the construction of professional and printable files. Well done!
Don't forget output size
Since the article is meant as a primer, it would be wise to mention that the information pertains to images being reproduced at 100%, i.e., when enlarging an image to 200% of its original size you will need twice the resolution to achieve reasonable results.
Colouring up line art
Nice to read some good sense on scanning res. But high-res scans of b&w line art can become a problem if you get involved in colouring up the resulting bitmap. Just converting from b&w to colour can make the file size balloon. I know of only one product, ColorPress, that enables you to colour up using indexed colour so the resulting file is not much bigger than the original.
contone devices
High-end color laser printers as a final output,which do not halftone the image at all, are left off of the table 2 above. For best results, I would scan the image to print at the resolution of the device (like the line art table). For crisp detail such as in jewelry, this would matter greatly (even for halftoning, a higher resolution yields more detail, so lpi x 2). Not so important for an impressionist painting, etc, where you can even get away with a ppi only 10% higher than the HT line screen (if desperate).
Don't forget to scan at the maximum size you might use the image. Scaling up reduces the ppi in the formula.