when a 600ppi to 1200ppi image is sent to the RIP and outputed to even a larger line screen of 170 lpi the excess resolution is only going to slow down the RIP not improve the printed peice. I was reading some press specs on the web and some specs showed a 300 line screen, so here the 600ppi image may be used, but still a 1200ppi image seems too much. The human eye can only distinguish a little over 200 tonal values-or so I have read and it takes 2.5 of these tones just to change just 1% in screen value. I asked one presenter this question at the Adobe Cretive Suite Seminar from SkillPath. He said that the request for art above the printers max line screen is unnecessary. But that still leaves me wondering why large publications that I have submitted ad work for requested such high res images.
High Resolution for Print
- Thread starter russpears
- Start date
gordo
Well-known member
Re: High Resolution for Print
As far as scanning more contone pixels than you have halftone dots, you can look at it this way: the larger your contone pixels (the lower the resolution), the more likely it is that you'll have a sharp difference between one contone pixel and the next, as each contone pixel covers a larger area of the original image. If a pixel boundary hits inside a dot, you'll get a
jaggy in the dot itself. The bigger the difference in contone values on either side, the sharper the jaggy corresponding to the edge of the pixel will be. Large sharp features are fairly easy to notice.
On the other hand, if you have lots of contone pixels, you'll only get small steps going across the halftone dot, and so each step will be less noticeable.
The upshot is that a halftone screen can actually represent more contone pixels than the stated line frequency, which is why the "scan at 2x line frequency @ 100%" rule of thumb works. In practice, for most subject matter you can actually go to a dpi that's 1x the lpi (i.e. 150 dpi at 150 lpi) if the substrate is uncoated. However on coated substrates you may see the "jaggies" or pixelated edges, if the subject matter has sharp transitions as with architectural subject matter. 2x the lpi (i.e. 300 dpi at 150 lpi) will give you enough contone pixels so that you don't have the jaggies/pixelated edges. There is no real reason to have contone images at a higher resolution.
Many, if not most, RIPs are set by default to resample contone images to 300 dpi - as if, by default the screening would be 150 lpi. The result is that at 175 lpi the scan ends up slightly less that the 2x rule. But it usually does not cause an issue - except perhaps with FM screens that, being very high frequency will resolve the pixels in the contone image and give you jaggies/pixelation.
You can try a test on your next printed job that has some unused off-cut area on the sheet. It is much easier to understand if you can see the difference. Just add an image at different resolutions. If it's printed at 175 lpi try 125 dpi, 175 dpi, 250 dpi, 350 dpi, and 600 dpi. Make sure the RIP is set to not resample the images. If you have access to a halftone proofer you can do the same test without going to press.
best, gordo
As far as scanning more contone pixels than you have halftone dots, you can look at it this way: the larger your contone pixels (the lower the resolution), the more likely it is that you'll have a sharp difference between one contone pixel and the next, as each contone pixel covers a larger area of the original image. If a pixel boundary hits inside a dot, you'll get a
jaggy in the dot itself. The bigger the difference in contone values on either side, the sharper the jaggy corresponding to the edge of the pixel will be. Large sharp features are fairly easy to notice.
On the other hand, if you have lots of contone pixels, you'll only get small steps going across the halftone dot, and so each step will be less noticeable.
The upshot is that a halftone screen can actually represent more contone pixels than the stated line frequency, which is why the "scan at 2x line frequency @ 100%" rule of thumb works. In practice, for most subject matter you can actually go to a dpi that's 1x the lpi (i.e. 150 dpi at 150 lpi) if the substrate is uncoated. However on coated substrates you may see the "jaggies" or pixelated edges, if the subject matter has sharp transitions as with architectural subject matter. 2x the lpi (i.e. 300 dpi at 150 lpi) will give you enough contone pixels so that you don't have the jaggies/pixelated edges. There is no real reason to have contone images at a higher resolution.
Many, if not most, RIPs are set by default to resample contone images to 300 dpi - as if, by default the screening would be 150 lpi. The result is that at 175 lpi the scan ends up slightly less that the 2x rule. But it usually does not cause an issue - except perhaps with FM screens that, being very high frequency will resolve the pixels in the contone image and give you jaggies/pixelation.
You can try a test on your next printed job that has some unused off-cut area on the sheet. It is much easier to understand if you can see the difference. Just add an image at different resolutions. If it's printed at 175 lpi try 125 dpi, 175 dpi, 250 dpi, 350 dpi, and 600 dpi. Make sure the RIP is set to not resample the images. If you have access to a halftone proofer you can do the same test without going to press.
best, gordo
Re: High Resolution for Print
Gordon, your answer was really above me and I actually cannot tell if you answered my question. I will keep looking at what you wrote but the "contone pixel" language threw me and it seemed that you thought I was referring to scanning an image at one point. What I really wanted to know is why some printers will ask for higher resolution images than their line screen suggest is adequate: ex. a request for 1200ppi image for 150lpi press work. one person said that they just want more to work with but I think there has to be more to it. No doubt you answered my question, but I cannot tell. Thanks in advance for you help.
Gordon, your answer was really above me and I actually cannot tell if you answered my question. I will keep looking at what you wrote but the "contone pixel" language threw me and it seemed that you thought I was referring to scanning an image at one point. What I really wanted to know is why some printers will ask for higher resolution images than their line screen suggest is adequate: ex. a request for 1200ppi image for 150lpi press work. one person said that they just want more to work with but I think there has to be more to it. No doubt you answered my question, but I cannot tell. Thanks in advance for you help.
gordo
Well-known member
Re: High Resolution for Print
Sorry Russell,
I'm assuming that you are referring to printing on a printing press rather than printing to an ink jet proofer (or press)
I think there are may be two issues in your question.
1) the resolution of an image that will be halftone screened relative to the halftone screen frequency (lpi)
2) the resolution of the output device needed to achieve enough gray levels at the requested halftone screen frequency (lpi)
I tried to answer the first. You wrote: "when a 600ppi to 1200ppi image is sent to the RIP and outputed to even a larger line screen of 170 lpi" "He said that the request for art above the printers max line screen is unnecessary." " request for 1200ppi image for 150lpi press work"
The bottom line is that you do not need an input image (scan, digital pic) to have a resolution higher than about 2x the lpi of the halftone screen that will be used to print it. The issue is not about gray levels but about the halftone screen being able to resolve the pixels of the original image. If the image resolution is too low the halftone will resolve the pixels which you will see as jagged pixelated edges in the image. Increasing the resolution of the original image makes the pixels smaller relative to the halftone and so you don't see the pixels anymore. A resolution past 2x the lpi (i.e. more than 350 dpi for a 175 lpi screen) is, as you put it, unneeded.
If you are asking about the resolution of the output device in order to support a particular halftone screen, e.g. 1200 dpi CTP device used to image a 150 lpi halftone, then that is a different matter. Now gray levels become important. But not the gray levels in the image you are reproducing, but the number of gray levels that can be created by the halftone screen given its frequency (lpi) relative to the resolution of the CTP device (1200 or 2400 dpi).
In general, in a halftone screen, a range of 256 gray levels provides small enough tonal steps to build sharp images, moderate blends and smooth vignettes. The steps from one gray level to the next are virtually indiscernible. However, there is a special relationship between gray levels, output device resolution, and line screen ruling that is summed up in the formula: (dpi/lpi)2 +1= number of gray levels possible. Using this formula would suggest that requesting a 300 lpi screen on an output device with a resolution of 2400 dpi would result in only 65 possible levels of gray – (dpi/lpi)2 +1= 65 gray levels. In this case, with only 65 tones available, we would see visible tone step artifacts such as “shade stepping” or “contouring” where the color steps abruptly from one shade to the next without a smooth transition. When the ratio of dpi to lpi drops below 16, the number of available gray levels drops to below 256 resulting in tonal reproduction that is inaccurate and uneven, and because of this constraint, the number of available gray levels decreases as the screen ruling increases. Fortunately, in reality, the (dpi/lpi)2 +1 calculation only determines the tonal capacity of a single halftone cell and does not reflect modern screening methods.
Most modern RIPs, instead, use a halftone "supercell", which is a grouping of many halftone cells, to build screens with more accurate angles, screen rulings, and tonal gradations. Supercells contain many more pixels than an individual halftone cell and subsequently can be used to represent many more gray levels than a single halftone cell. By activating pixels in some of the neighboring halftone cells at different gray levels within the supercell, a broader range of gray levels, typically between 1024 and 4096, can be achieved.
Users of systems without this functionality must resolve gray-level issues by increasing the addressability and resolution of the output device (e.g. going to 4000 dpi), which slows down the imaging speed, or by limiting the screen ruling to a low lpi,
The optimal performance-to-quality ratio supports the popularity of devices that operate in the range of 2400 dpi. Systems using supercell screening technology to extend gray levels offer all the resolution, all the screening, and all the throughput speed that the majority of users will ever need.
I hope that's a bit clearer.
best, gordo
Sorry Russell,
I'm assuming that you are referring to printing on a printing press rather than printing to an ink jet proofer (or press)
I think there are may be two issues in your question.
1) the resolution of an image that will be halftone screened relative to the halftone screen frequency (lpi)
2) the resolution of the output device needed to achieve enough gray levels at the requested halftone screen frequency (lpi)
I tried to answer the first. You wrote: "when a 600ppi to 1200ppi image is sent to the RIP and outputed to even a larger line screen of 170 lpi" "He said that the request for art above the printers max line screen is unnecessary." " request for 1200ppi image for 150lpi press work"
The bottom line is that you do not need an input image (scan, digital pic) to have a resolution higher than about 2x the lpi of the halftone screen that will be used to print it. The issue is not about gray levels but about the halftone screen being able to resolve the pixels of the original image. If the image resolution is too low the halftone will resolve the pixels which you will see as jagged pixelated edges in the image. Increasing the resolution of the original image makes the pixels smaller relative to the halftone and so you don't see the pixels anymore. A resolution past 2x the lpi (i.e. more than 350 dpi for a 175 lpi screen) is, as you put it, unneeded.
If you are asking about the resolution of the output device in order to support a particular halftone screen, e.g. 1200 dpi CTP device used to image a 150 lpi halftone, then that is a different matter. Now gray levels become important. But not the gray levels in the image you are reproducing, but the number of gray levels that can be created by the halftone screen given its frequency (lpi) relative to the resolution of the CTP device (1200 or 2400 dpi).
In general, in a halftone screen, a range of 256 gray levels provides small enough tonal steps to build sharp images, moderate blends and smooth vignettes. The steps from one gray level to the next are virtually indiscernible. However, there is a special relationship between gray levels, output device resolution, and line screen ruling that is summed up in the formula: (dpi/lpi)2 +1= number of gray levels possible. Using this formula would suggest that requesting a 300 lpi screen on an output device with a resolution of 2400 dpi would result in only 65 possible levels of gray – (dpi/lpi)2 +1= 65 gray levels. In this case, with only 65 tones available, we would see visible tone step artifacts such as “shade stepping” or “contouring” where the color steps abruptly from one shade to the next without a smooth transition. When the ratio of dpi to lpi drops below 16, the number of available gray levels drops to below 256 resulting in tonal reproduction that is inaccurate and uneven, and because of this constraint, the number of available gray levels decreases as the screen ruling increases. Fortunately, in reality, the (dpi/lpi)2 +1 calculation only determines the tonal capacity of a single halftone cell and does not reflect modern screening methods.
Most modern RIPs, instead, use a halftone "supercell", which is a grouping of many halftone cells, to build screens with more accurate angles, screen rulings, and tonal gradations. Supercells contain many more pixels than an individual halftone cell and subsequently can be used to represent many more gray levels than a single halftone cell. By activating pixels in some of the neighboring halftone cells at different gray levels within the supercell, a broader range of gray levels, typically between 1024 and 4096, can be achieved.
Users of systems without this functionality must resolve gray-level issues by increasing the addressability and resolution of the output device (e.g. going to 4000 dpi), which slows down the imaging speed, or by limiting the screen ruling to a low lpi,
The optimal performance-to-quality ratio supports the popularity of devices that operate in the range of 2400 dpi. Systems using supercell screening technology to extend gray levels offer all the resolution, all the screening, and all the throughput speed that the majority of users will ever need.
I hope that's a bit clearer.
best, gordo
rich apollo
Well-known member
Re: High Resolution for Print
Are we talking about PDF resolution, as set in Distiller, or just the resolution of an image?
Do the images in question contain type/text?
rich
Are we talking about PDF resolution, as set in Distiller, or just the resolution of an image?
Do the images in question contain type/text?
rich
Luc St-Pierre
Well-known member
Re: High Resolution for Print
I once read and then studied and experimented a very simple resolution ratio: 1.2 times printed linescreen... and it works just fine. Why 1.2? Because 1.2 is the 45 degrees measure of a 1 (any unit) square and will therefore account for all angles a dot area might have. This number also makes most RIP's rip faster than funny and exotic numbers. High resolution is handy at time. When there is a need for retouching, manipulating etc. At other times, high resolution becomes a waste of disk space and computing power if not an outright quality-killer. When you proof a 500 ppi file on a 720 dpi inkjet and you really expect to print at 100 lpi, all you are doing is promising a rose garden. Each final dot area will average 25 pixels (5x5) !!!! Do the math.....
I once read and then studied and experimented a very simple resolution ratio: 1.2 times printed linescreen... and it works just fine. Why 1.2? Because 1.2 is the 45 degrees measure of a 1 (any unit) square and will therefore account for all angles a dot area might have. This number also makes most RIP's rip faster than funny and exotic numbers. High resolution is handy at time. When there is a need for retouching, manipulating etc. At other times, high resolution becomes a waste of disk space and computing power if not an outright quality-killer. When you proof a 500 ppi file on a 720 dpi inkjet and you really expect to print at 100 lpi, all you are doing is promising a rose garden. Each final dot area will average 25 pixels (5x5) !!!! Do the math.....
Re: High Resolution for Print
I am not familiar with much of the language your using in your responses. I appologise, but could you offer a more laymans explanation to the question "what could be the motivation for publisher's request that images be 1200ppi when their stated line screen is only 150 lpi" As a designer that wants to send better press ready files to print, I'm just wanting to understand this that seems unreasionable. As for all the posts I will continue to study them and I thank everyone for the feedback.
I am not familiar with much of the language your using in your responses. I appologise, but could you offer a more laymans explanation to the question "what could be the motivation for publisher's request that images be 1200ppi when their stated line screen is only 150 lpi" As a designer that wants to send better press ready files to print, I'm just wanting to understand this that seems unreasionable. As for all the posts I will continue to study them and I thank everyone for the feedback.
Point918
Well-known member
Re: High Resolution for Print
Russell;
Perhaps the dpi specs you are reading are not making the distinction between 8 bit art files that are halftone screened and 1 bit unscreened files which are used to reproduce line art. It has always been my understanding & experience that bitmap lineart files should be in the 1200 to 2400 dpi range to smoothly reproduce lineart images edge detail. Lineart imaged from 300dpi files always has sawtoothed edges to my eye whereas 2,400dpi files have nice crisp edges.
Don Evans
Russell;
Perhaps the dpi specs you are reading are not making the distinction between 8 bit art files that are halftone screened and 1 bit unscreened files which are used to reproduce line art. It has always been my understanding & experience that bitmap lineart files should be in the 1200 to 2400 dpi range to smoothly reproduce lineart images edge detail. Lineart imaged from 300dpi files always has sawtoothed edges to my eye whereas 2,400dpi files have nice crisp edges.
Don Evans
Re: High Resolution for Print
> {quote:title=russpears wrote:}{quote}
> when a 600ppi to 1200ppi image is sent to the RIP and outputed to even a larger line screen of 170 lpi the excess resolution is only going to slow down the RIP not improve the printed peice. I was reading some press specs on the web and some specs showed a 300 line screen, so here the 600ppi image may be used, but still a 1200ppi image seems too much. The human eye can only distinguish a little over 200 tonal values-or so I have read and it takes 2.5 of these tones just to change just 1% in screen value. I asked one presenter this question at the Adobe Cretive Suite Seminar from SkillPath. He said that the request for art above the printers max line screen is unnecessary. But that still leaves me wondering why large publications that I have submitted ad work for requested such high res images.
Most printers in their right mind would never request images above 300 ppi. There are certain types of printing that might want images at 600 ppi but not very often. I think you might be confusing what printers are asking for. If you are talking about a PDF then yes they might request it at 1200 or 2400 but that does not mean the images (pixel based) inside of it are going to be 2400 ppi. The images in the PDF will either stay their original or down sample to whatever you specify in your PDF settings but the high res text and vector information will be at 2400 to keep it high res. You definitely do not want type and vector images downsampled to 300 ppi. Once it is screened for output you want everything at 2400 ppi because it is screened as a 1 bit file meaning everything is "like vector". All pixels are either black or white. No in between.
> {quote:title=russpears wrote:}{quote}
> when a 600ppi to 1200ppi image is sent to the RIP and outputed to even a larger line screen of 170 lpi the excess resolution is only going to slow down the RIP not improve the printed peice. I was reading some press specs on the web and some specs showed a 300 line screen, so here the 600ppi image may be used, but still a 1200ppi image seems too much. The human eye can only distinguish a little over 200 tonal values-or so I have read and it takes 2.5 of these tones just to change just 1% in screen value. I asked one presenter this question at the Adobe Cretive Suite Seminar from SkillPath. He said that the request for art above the printers max line screen is unnecessary. But that still leaves me wondering why large publications that I have submitted ad work for requested such high res images.
Most printers in their right mind would never request images above 300 ppi. There are certain types of printing that might want images at 600 ppi but not very often. I think you might be confusing what printers are asking for. If you are talking about a PDF then yes they might request it at 1200 or 2400 but that does not mean the images (pixel based) inside of it are going to be 2400 ppi. The images in the PDF will either stay their original or down sample to whatever you specify in your PDF settings but the high res text and vector information will be at 2400 to keep it high res. You definitely do not want type and vector images downsampled to 300 ppi. Once it is screened for output you want everything at 2400 ppi because it is screened as a 1 bit file meaning everything is "like vector". All pixels are either black or white. No in between.
call_me_ted
New member
Re: High Resolution for Print
<<why some printers will ask for higher resolution images than their line screen suggest is adequate: ex. a request for 1200ppi image for 150lpi press work.>>
Are printers asking specifically for the IMAGES to be 1200 ppi? Or is that the resolution they wanted for the file itself?
You might re-read what were were told at about.com - the answer remains the same, irrespective of forum.
http://forums.about.com/n/pfx/forum.aspx?tsn=4&nav=messages&webtag=ab-desktoppub&tid=5293
Edited by: Ted Schulte on Apr 19, 2008 8:57 PM
<<why some printers will ask for higher resolution images than their line screen suggest is adequate: ex. a request for 1200ppi image for 150lpi press work.>>
Are printers asking specifically for the IMAGES to be 1200 ppi? Or is that the resolution they wanted for the file itself?
You might re-read what were were told at about.com - the answer remains the same, irrespective of forum.
http://forums.about.com/n/pfx/forum.aspx?tsn=4&nav=messages&webtag=ab-desktoppub&tid=5293
Edited by: Ted Schulte on Apr 19, 2008 8:57 PM
bluskool
Well-known member
Re: High Resolution for Print
Russell,
If you want the easiest solution and you are sending them PDF's, ask them for their Distiller settings. Create your art at two times the line screen and use the Distiller settings they send you to make the PDF.
If you want to understand why or get a more specific answer, you will have to ask a more specific question. You need to be more specific about what you are sending them. There will be different answers for different situations. Are you sending designs with text or vectors along with digital images? Are you sending just digital images? Are you sending line art?
If you are sending only raster stuff, then yes, the publisher is confused, but if it is not just raster stuff, then there are a few possible answers depending on the situation. Any other details would help us in giving you a better answer.
Dan R.
Russell,
If you want the easiest solution and you are sending them PDF's, ask them for their Distiller settings. Create your art at two times the line screen and use the Distiller settings they send you to make the PDF.
If you want to understand why or get a more specific answer, you will have to ask a more specific question. You need to be more specific about what you are sending them. There will be different answers for different situations. Are you sending designs with text or vectors along with digital images? Are you sending just digital images? Are you sending line art?
If you are sending only raster stuff, then yes, the publisher is confused, but if it is not just raster stuff, then there are a few possible answers depending on the situation. Any other details would help us in giving you a better answer.
Dan R.
Re: High Resolution for Print
I read and studied these replies. Someone on that forum suggested this forum, but I cannot seem to get what you say is the answer.
The only think I read the was this:
""We run a 175 line screen at 2400 dpi. Line screen IS NOT resolution. "" and ""We run a 175 line screen at 2400 dpi. Line screen IS NOT resolution. ""
Now is it possiable to do this. Im confused by this answer, because he says that line screen is not the same as resolution. Here the line the 175 lpi seems to only give 350 dpi if you take it 2 times the line screen. Now I know that all of that resolution will not give you anything better than the line screen or printing resolution. But he adds that he runs 2400 dpi? How can this work. This may be at the heart of the issue for me.
I just would like to understand better so that I can work better and provide my printed materials without issue.
I read and studied these replies. Someone on that forum suggested this forum, but I cannot seem to get what you say is the answer.
The only think I read the was this:
""We run a 175 line screen at 2400 dpi. Line screen IS NOT resolution. "" and ""We run a 175 line screen at 2400 dpi. Line screen IS NOT resolution. ""
Now is it possiable to do this. Im confused by this answer, because he says that line screen is not the same as resolution. Here the line the 175 lpi seems to only give 350 dpi if you take it 2 times the line screen. Now I know that all of that resolution will not give you anything better than the line screen or printing resolution. But he adds that he runs 2400 dpi? How can this work. This may be at the heart of the issue for me.
I just would like to understand better so that I can work better and provide my printed materials without issue.
gordo
Well-known member
Re: High Resolution for Print
2400 dpi is the resolution of the final output device - could be a computer to plate device or film. This represents the pixels that are available to be used to create the halftone dots (each made of many pixels) that will simulate the tones of your original art.
175 lpi represents the frequency of the halftone dots in lines per inch (each made up of many pixels on the 2400 dpi device) it is a measure of resolution in the sense that the finer the halftone screen the more detail it can resolve. i.e. a 175 lpi halftone will resolve more detail than a 100 lpi screen.
350 dpi at an image reproduction size of 100% is the resolution of the original image that will be halftone screened at 175 lpi using the pixels on the 2400 dpi final output device.
best, gordo
2400 dpi is the resolution of the final output device - could be a computer to plate device or film. This represents the pixels that are available to be used to create the halftone dots (each made of many pixels) that will simulate the tones of your original art.
175 lpi represents the frequency of the halftone dots in lines per inch (each made up of many pixels on the 2400 dpi device) it is a measure of resolution in the sense that the finer the halftone screen the more detail it can resolve. i.e. a 175 lpi halftone will resolve more detail than a 100 lpi screen.
350 dpi at an image reproduction size of 100% is the resolution of the original image that will be halftone screened at 175 lpi using the pixels on the 2400 dpi final output device.
best, gordo
Werby
Well-known member
Re: High Resolution for Print
Russell
As Ted asks: Are they really requesting 1200dpi for the final effective resolution? Which publications ask for this much resolution? One obvious answer why someone would ask for this much resolution is that they are going to re-purpose the image to a poster or outdoor display where it will be blown up very large. No publication would ask for this much data, and in fact several list a maximum effective resolution of 400dpi because they don't want such big files.
The statement "We run a 175 line screen at 2400 dpi" refers to the imagesetter or computer to plate system. When an imagesetter "builds" the dots for 175 lpi, each dot is made up of smaller dots. This has nothing to do with the resolution of the images that will be printed at 175lpi. It is talking about how sharp a resolution each individual 175lpi dot will be built at. Many CTP systems go up to 3600 dpi to make even 'sharper' dots.
-Todd Shirley
Russell
As Ted asks: Are they really requesting 1200dpi for the final effective resolution? Which publications ask for this much resolution? One obvious answer why someone would ask for this much resolution is that they are going to re-purpose the image to a poster or outdoor display where it will be blown up very large. No publication would ask for this much data, and in fact several list a maximum effective resolution of 400dpi because they don't want such big files.
The statement "We run a 175 line screen at 2400 dpi" refers to the imagesetter or computer to plate system. When an imagesetter "builds" the dots for 175 lpi, each dot is made up of smaller dots. This has nothing to do with the resolution of the images that will be printed at 175lpi. It is talking about how sharp a resolution each individual 175lpi dot will be built at. Many CTP systems go up to 3600 dpi to make even 'sharper' dots.
-Todd Shirley
Re: High Resolution for Print
[pdf of globes' specs|https://bostonglobe.com/advertiser/specs/specs.aspx?id=101] here is Globes specs:
Grayscale: 254 pixels per inch at 100% of final output size.
Line Art/Bitmap: 1016 dots per inch at 100% of final output size.
And I think Todd Shirley is connecting with my confusion over this. Your saying that the the half tone dot is built out of smaller dots up to 2400 dpi and higher in the image setter, NOW i CAN RE-READ THIS POST AND UNDERSTAND BETTER-THANKS!!!
but this does not seem to be what the publication is requesting here. from thie specs, do you see my further confusion? also it does not explain whay line are is requested at higher resolutions, why?
Edited by: Russell Spears on Apr 22, 2008 11:02 PM
[pdf of globes' specs|https://bostonglobe.com/advertiser/specs/specs.aspx?id=101] here is Globes specs:
Grayscale: 254 pixels per inch at 100% of final output size.
Line Art/Bitmap: 1016 dots per inch at 100% of final output size.
And I think Todd Shirley is connecting with my confusion over this. Your saying that the the half tone dot is built out of smaller dots up to 2400 dpi and higher in the image setter, NOW i CAN RE-READ THIS POST AND UNDERSTAND BETTER-THANKS!!!
but this does not seem to be what the publication is requesting here. from thie specs, do you see my further confusion? also it does not explain whay line are is requested at higher resolutions, why?
Edited by: Russell Spears on Apr 22, 2008 11:02 PM
Re: High Resolution for Print
> {quote:title=russpears wrote:}{quote}
> [pdf of globes' specs|https://bostonglobe.com/advertiser/specs/specs.aspx?id=101] here is Globes specs:
>
> Grayscale: 254 pixels per inch at 100% of final output size.
> Line Art/Bitmap: 1016 dots per inch at 100% of final output size.
>
> And I think Todd Shirley is connecting with my confusion over this. Your saying that the the half tone dot is built out of smaller dots up to 2400 dpi and higher in the image setter, NOW i CAN RE-READ THIS POST AND UNDERSTAND BETTER-THANKS!!!
>
> but this does not seem to be what the publication is requesting here. from thie specs, do you see my further confusion? also it does not explain whay line are is requested at higher resolutions, why?
>
> Edited by: Russell Spears on Apr 22, 2008 11:02 PM
They are requesting that images (like photos of people) that are pixel based be at 254 ppi. The reason they add "at 100% of final output size" is because they do not want you placing an image that is 254 ppi and scaling it 200% in your page layout application. That effectively reduces the resolution under their specs.
Lineart/Bitmap is the high resolution data like text, tint panels, vector art from Illy or something scanned as a bitmap. The old scale of thumb from my Linotype-Hell days were that the lineart should be 6 times the resolution of the images. I think Scitex used to recommend 8 times greater but you can do it at 4 times as great which is what they are requesting.
Now what you would do is make your pixel based images at 254 ppi and place them on your page in your layout app. Your text and anything else like the stuff I listed above would also go in your page layout app and when you output from there you would output the page at 1016 ppi. That would keep your high resolution data 1016 ppi but it will not upsample your images to that. If you are outputting to pdf they will stay at 254 ppi unless you specifically tell it to resample them in your PDF settings. If you are sending the file from your page layout app (InDesign or Quark) directly to the printer they will output it correctly for their device at the ppi and line screen they want to use. When the RIP converts it to one-bit data and screens it it will make the resolution of the one-bit file 1016 ppi. The higher you go with that ppi the finer the dots and the higher your LPI can go. I'm guessing from the 1016 ppi that they are currently outputting at 85 - 100 lpi? That number seems too low to me for them to be outputting at anything much higher lpi wise.
Also, the "resolution at twice the linescreen" is just a general rule of thumb. Not something written in stone.
> {quote:title=russpears wrote:}{quote}
> [pdf of globes' specs|https://bostonglobe.com/advertiser/specs/specs.aspx?id=101] here is Globes specs:
>
> Grayscale: 254 pixels per inch at 100% of final output size.
> Line Art/Bitmap: 1016 dots per inch at 100% of final output size.
>
> And I think Todd Shirley is connecting with my confusion over this. Your saying that the the half tone dot is built out of smaller dots up to 2400 dpi and higher in the image setter, NOW i CAN RE-READ THIS POST AND UNDERSTAND BETTER-THANKS!!!
>
> but this does not seem to be what the publication is requesting here. from thie specs, do you see my further confusion? also it does not explain whay line are is requested at higher resolutions, why?
>
> Edited by: Russell Spears on Apr 22, 2008 11:02 PM
They are requesting that images (like photos of people) that are pixel based be at 254 ppi. The reason they add "at 100% of final output size" is because they do not want you placing an image that is 254 ppi and scaling it 200% in your page layout application. That effectively reduces the resolution under their specs.
Lineart/Bitmap is the high resolution data like text, tint panels, vector art from Illy or something scanned as a bitmap. The old scale of thumb from my Linotype-Hell days were that the lineart should be 6 times the resolution of the images. I think Scitex used to recommend 8 times greater but you can do it at 4 times as great which is what they are requesting.
Now what you would do is make your pixel based images at 254 ppi and place them on your page in your layout app. Your text and anything else like the stuff I listed above would also go in your page layout app and when you output from there you would output the page at 1016 ppi. That would keep your high resolution data 1016 ppi but it will not upsample your images to that. If you are outputting to pdf they will stay at 254 ppi unless you specifically tell it to resample them in your PDF settings. If you are sending the file from your page layout app (InDesign or Quark) directly to the printer they will output it correctly for their device at the ppi and line screen they want to use. When the RIP converts it to one-bit data and screens it it will make the resolution of the one-bit file 1016 ppi. The higher you go with that ppi the finer the dots and the higher your LPI can go. I'm guessing from the 1016 ppi that they are currently outputting at 85 - 100 lpi? That number seems too low to me for them to be outputting at anything much higher lpi wise.
Also, the "resolution at twice the linescreen" is just a general rule of thumb. Not something written in stone.
Re: High Resolution for Print
but how can line art be output at 6-8 time the resolution of the image when the line screen is the same. Are you refering to in the RIP half tone dot creation resolution. Or are you saying that you can increase the line screen in a way that only affects vector line art not raster images.
I know everyone has give me much to think about, but getting info like this puts me back a bit where I "thought" I started to understand. I really cannot tell where the confusion comes from. Once I understand that stocastc dots are higher resolutions (2400-3000 and up) and not the halfton dots themselves, I could see how I confused the two as the same as line screen that are around 150 to 175). But this answer suggest to me that you can increase the final quality of line art in print work apart from raster images?
Again I will need to do more research into this before post more on this, but if I can be given a direction towards possiable areas of my confusion I will go there first.
but how can line art be output at 6-8 time the resolution of the image when the line screen is the same. Are you refering to in the RIP half tone dot creation resolution. Or are you saying that you can increase the line screen in a way that only affects vector line art not raster images.
I know everyone has give me much to think about, but getting info like this puts me back a bit where I "thought" I started to understand. I really cannot tell where the confusion comes from. Once I understand that stocastc dots are higher resolutions (2400-3000 and up) and not the halfton dots themselves, I could see how I confused the two as the same as line screen that are around 150 to 175). But this answer suggest to me that you can increase the final quality of line art in print work apart from raster images?
Again I will need to do more research into this before post more on this, but if I can be given a direction towards possiable areas of my confusion I will go there first.
Blair Wolfe
Active member
Re: High Resolution for Print
Not to confuse you farther, but you are just short of grasping the meaning of some of the terms you are using. The line screen ruling is a choice independent of scanner resolution or output device resolution. You can take a halftone that you scanned at 300 dpi, and print it out at 85 lines per inch on a machine that will use 2400 laser dots per inch to make those 85 lpi dots, or you can take that same halftone, and print it at 150 lpi, which is much smaller dots, since there are 150 rows of dots per inch , and still print to the same output device using 2400 dpi resolution to form each of those halftone dots. You may also send that file to a 1200 dpi device, and still get good copy, only with fewer laser dots to build each halftone dot. This would be a reason to choose a not so fine line screen, since a lower resolution printer will make better looking halftones if it has fewer rows of dots to make per inch, (maybe 106 lpi or 120)
It seems that there are a lot of folks out there that confuse the numbers thta are relevant in each step.
Not to confuse you farther, but you are just short of grasping the meaning of some of the terms you are using. The line screen ruling is a choice independent of scanner resolution or output device resolution. You can take a halftone that you scanned at 300 dpi, and print it out at 85 lines per inch on a machine that will use 2400 laser dots per inch to make those 85 lpi dots, or you can take that same halftone, and print it at 150 lpi, which is much smaller dots, since there are 150 rows of dots per inch , and still print to the same output device using 2400 dpi resolution to form each of those halftone dots. You may also send that file to a 1200 dpi device, and still get good copy, only with fewer laser dots to build each halftone dot. This would be a reason to choose a not so fine line screen, since a lower resolution printer will make better looking halftones if it has fewer rows of dots to make per inch, (maybe 106 lpi or 120)
It seems that there are a lot of folks out there that confuse the numbers thta are relevant in each step.
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