I'm working in InDesign and creating a long document with close to 100 images. I've been told that I can resize my images in InDesign (rather than doing so in Photoshop) and then export to PDF for press. Is this correct? The images I'm working with are all 2592 by 1944 at 96 ppi (27 inches wide by 20.25 high) and they will all be reduced to a final size of about 3.5 inches high at 300 ppi. Right now, they are 16-bit RGB from a microscope camera. If I resize in InDesign, will I lose quality and/or cause problems for a printer when providing a PDF that I'm assuming will be quite large? Or, am I better off resizing to 100% in Photoshop before placing in InDesign? I believe this is what a printer told me to do. Also, do I need to convert the files from 16-bit down to 8-bit for press? Thank you....I really need some concrete advise from print professionals! Karen
New at this! resizing images for pdf?
- Thread starter KarenFPL
- Start date
Colorblind
Well-known member
It really depends on what your printer can handle. Personally, I would import and scale the original images in InDesign, this way you'll preserve the images integrity (color space, bit depth, resolution) until PDF creation or ripping time. Once the document is ready, you can export it to the PDF flavor your printer prefers and choose to downsample image resolution so it doesn't exceed 300dpi which will help keeping your document to a decent size.
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If you are supplying a PDF and not the native files, definitely do it in Indesign. Then you can resample images as the PDF is made using the settings in the PDF export dialog. You can also have RGB converted to CMYK automatically without having to edit each image (if all CMYK is what you want to send). I believe 16 bit images will always be quantized to 8 bit also.
If you are sending the native files, then the size of what you send would obviously be lower if all of your image links were resampled and changed to 8 bit (and as ZIP compressed TIFF to preserve all detail, or as JPEG if you don't mind the lossy compression). This would reduce file transfer time and probably some processing time at the printer, but it probably wouldn't be worth all the extra time it would take you, unless perhaps you ran a batch automation with a Photoshop action.
If you are sending the native files, then the size of what you send would obviously be lower if all of your image links were resampled and changed to 8 bit (and as ZIP compressed TIFF to preserve all detail, or as JPEG if you don't mind the lossy compression). This would reduce file transfer time and probably some processing time at the printer, but it probably wouldn't be worth all the extra time it would take you, unless perhaps you ran a batch automation with a Photoshop action.
The result from exporting is not the same as any of the options in Photoshop. It is better for most images. If you have an image that is 500 ppi resampled to 400 ppi, then you are reducing every five columns to four and every five rows to four, or a bunch of 5x5 matrices to 4x4 matrices. For every 4x4 matrix of final pixels, the upper-left 3x3 will be kept exactly as-is from the original pixels, and the last row/column pixels will be a 50/50 averaging of the last two rows/columns from the original pixels. The lower-right pixel ends up being a 25/25/25/25 averaging of four source pixels.
This preserves sharpness almost as well as the nearest-neighbor method, without completely ignoring entire rows/columns like the nearest-neighbor method does. It expect that it would usually produce less moire than the nearest-neighbor or bilinear methods for patterned images. It is also probably the fastest algorithm second only to nearest-neighbor.
Bilinear interpolation would logically be a more space-preserving method, but consider a corner-case scenario of reducing a 1 x 1 inch image from 301 ppi to 300 ppi. If you used bilinear, the outermost pixels of the final image would be nearly identical to the outermost pixels of the source image, but the pixels in the exact center would be 180 degrees out of phase with each other, meaning the center pixels are going to be an equally weighted average of four pixels. Averaging out four pixels effectively blurs the image, so the image would be preserved on the outer edges and blurred in the center. If the source image were 302 ppi, then it would phase in and out twice instead of once. The export resampling method, however, would exactly preserve all of the pixels except for the last two rows/columns, squashing them down to a single row and column. The blurring is then limited to a single row and column instead of a large area, and the blurring is half as strong because the averaging is of two pixels instead of four. For a 302 ppi source image, there would be two rows and two columns of averaging.
In my experience, downsampling out of InDesign has created moires in my images when taken straight to PDF. I prefer to downsample in Photoshop in small increments (powered by a script or an action) reducing an image no more than, say, 250 pixels at a time. Of course, I'm taking 300 PPI images and just making them 40% of their original size, ending as another 300 PPI image. So maybe I'm misinterpreting what you're tlaking about.
gig0
Well-known member
I've heard of people downsampling (or even upsampling) images in increments before and have to wonder how much of an impact does it really make in printing. I would love to see a comparison done the same way Gordo did that JPEG mythbusting article in his blog.
The Print Guide: JPEG images for print production - the facts
Most of my images are high enough resolution that going from Tiff to JPG is not a problem. Mainly the need to resize incrementally has to do with fine patterns, rather than lossy compression as referred to in this (very good) article. For example, if you're resizing a family photo where Uncle George is wearing a fine plaid suit and Aunt Margaret is wearing a thin stripe shirt, then going from large to small in one step brings up all kinds of moirés in those patterns. Doing it little by little greatly reduces the likelihood of those moriés in my workflow.
The image stays as a TIF until the the final size is done, then saved as a JPG in the last stage. For things that don't have a lot of color variation or don't have a lot of fine detail, it doesn't change much if at all.
The image stays as a TIF until the the final size is done, then saved as a JPG in the last stage. For things that don't have a lot of color variation or don't have a lot of fine detail, it doesn't change much if at all.
Stephen Marsh
Well-known member
From my tests Photoshop bicubic and PDF bicubic resampling are slightly different. PDF bicubic resampling appears to lead to less moiré/aliasing issues than Photoshop when resizing in one single step from high resolution to lower resolution.
A PrintPlanet discussion here:
http://printplanet.com/forums/adobe/23396-very-high-image-resolution-any-quality-disadvantage
In the following topic at linkedin:
More darn Moire than I can get rid of. | LinkedIn
One can find a link to a photo of a church, here:
https://creative.adobe.com/share/63688799-ea0b-4a49-abb2-b528c7565ad2#!
and here:
TexasChurch | Flickr - Photo Sharing!
farm9.staticflickr.com/8384/8465479592_b445d26791_k.jpg - If one resizes the 2048px wide image in one step to 333px wide, there is moire.
Sometimes adding a minor blur before reduction can also be of help - just as many digital cameras have a low pass filter in front of the sensor to reduce moire. One can blur before reducing size and then smart sharpen after reducing size. If working with a raw image, you may wish to disable sharpening on the version that will be resized smaller.
So adding a 1px Gaussian blur to the 2048px image before resampling down to 333px will result in no moire.
Sometimes resizing to a similar but different size will lessen or remove moire.
There are many ways to reduce or overcome this moire effect, depending on the content of the original and the final size required. One good method is to reduce the image in steps of 50% until you get close to the final required size and then resize to the final size at the last step (too many small steps and the image may be too soft).
The 50% width/height resize results in an area 25% smaller than the original. To get to an area of 50%, use 70.7% for the resize. Resizing to 50% width/height is good for averaging out detail, which can be a blessing and a curse (blessing if the detail is noise, a curse if the detail is important). Sometimes using a value of say 66.6% is close enough to 50% without having the same pixel averaging effect.
Then there are the very minor differences in result when resampling in a linear gamma 1.0 colour space such as the 32bpc mode of Photoshop (note: linear gamma is not good for shadow detail or low key images).
Glennchan.info
and
Gamma error in picture scaling
and
PhotoAcute; How to downsample SuperResolution images to 50% size - Page 2 - Open Photography Forums
and
Gamma Correction in Computer Graphics
I do not have a DSP background, however this may technically be known as "aliasing" rather than moiré (moire is better known). Here are some more links that go into all this in more detail:
Aliasing - Wikipedia, the free encyclopedia
and
Down-sampling example 1.
and
Down sampling methods
and
Aliasing and Moire patterns
and
Downsizing and aliasing
and
Is this Aliasing?
Stephen Marsh
(Keywords for a future search: moire, moiré, aliasing)
A PrintPlanet discussion here:
http://printplanet.com/forums/adobe/23396-very-high-image-resolution-any-quality-disadvantage
In the following topic at linkedin:
More darn Moire than I can get rid of. | LinkedIn
One can find a link to a photo of a church, here:
https://creative.adobe.com/share/63688799-ea0b-4a49-abb2-b528c7565ad2#!
and here:
TexasChurch | Flickr - Photo Sharing!
farm9.staticflickr.com/8384/8465479592_b445d26791_k.jpg - If one resizes the 2048px wide image in one step to 333px wide, there is moire.
Sometimes adding a minor blur before reduction can also be of help - just as many digital cameras have a low pass filter in front of the sensor to reduce moire. One can blur before reducing size and then smart sharpen after reducing size. If working with a raw image, you may wish to disable sharpening on the version that will be resized smaller.
So adding a 1px Gaussian blur to the 2048px image before resampling down to 333px will result in no moire.
Sometimes resizing to a similar but different size will lessen or remove moire.
There are many ways to reduce or overcome this moire effect, depending on the content of the original and the final size required. One good method is to reduce the image in steps of 50% until you get close to the final required size and then resize to the final size at the last step (too many small steps and the image may be too soft).
The 50% width/height resize results in an area 25% smaller than the original. To get to an area of 50%, use 70.7% for the resize. Resizing to 50% width/height is good for averaging out detail, which can be a blessing and a curse (blessing if the detail is noise, a curse if the detail is important). Sometimes using a value of say 66.6% is close enough to 50% without having the same pixel averaging effect.
Then there are the very minor differences in result when resampling in a linear gamma 1.0 colour space such as the 32bpc mode of Photoshop (note: linear gamma is not good for shadow detail or low key images).
Glennchan.info
and
Gamma error in picture scaling
and
PhotoAcute; How to downsample SuperResolution images to 50% size - Page 2 - Open Photography Forums
and
Gamma Correction in Computer Graphics
I do not have a DSP background, however this may technically be known as "aliasing" rather than moiré (moire is better known). Here are some more links that go into all this in more detail:
Aliasing - Wikipedia, the free encyclopedia
and
Down-sampling example 1.
and
Down sampling methods
and
Aliasing and Moire patterns
and
Downsizing and aliasing
and
Is this Aliasing?
Stephen Marsh
(Keywords for a future search: moire, moiré, aliasing)
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Stephen Marsh
Well-known member
Karen,
I would first place the images in InDesign and adjust to size. This will not resample or interpolate the pixels, they will just be scaled, which will create an "effective" PPI resolution count that could be lower (enlarged size) or higher (reduced size) than 300ppi. Generally speaking, one can get away with anywhere from 225-300ppi, however this is of course image and output dependent.
Once you have the large original images linked (not embedded), you have three choices:
1. Export out a PDF using bicubic interpolation to reduce the PPI count of the images to say 300ppi if they are above say 350ppi. One can simply inspect the images in the PDF. Another option is to open the final PDF into Photoshop and elect to extract the images only (not rasterize the PDF page/s). You can then "eyeball" the images to see if you have any weird moiré/aliasing or other issues caused by the PDF image interpolation process from original high resolution to resampled smaller image. If one or more images have suffered, you could then elect to make a copy of the original and manually resize these images in Photoshop to the final print size and resolution using the "safe" techniques mentioned in this topic thread.
2. You can use a script for InDesign and Photoshop, that will dupe your InDesign file and resize/resample copies of all images in Photoshop and then relink them back to the InDesign layout. This way you can run a batch or script to sharpen or perform other edits to all of the new resized images that are linked to the new copy.
Two similar scripts are attached to this reply in a .zip archive.
3. Export out a PDF using bicubic interpolation to reduce the PPI count of the images to say 300ppi if they are above say 350ppi. Then to use PitStop Pro 12 which has a new feature to apply sharpening to images inside a PDF. For a small amount of images, one could simply use the image touch up tool and sharpen the images in Photoshop, however for 100 images it would be more productive to sharpen them directly inside the PDF using PitStop Pro 12.
Stephen Marsh
I would first place the images in InDesign and adjust to size. This will not resample or interpolate the pixels, they will just be scaled, which will create an "effective" PPI resolution count that could be lower (enlarged size) or higher (reduced size) than 300ppi. Generally speaking, one can get away with anywhere from 225-300ppi, however this is of course image and output dependent.
Once you have the large original images linked (not embedded), you have three choices:
1. Export out a PDF using bicubic interpolation to reduce the PPI count of the images to say 300ppi if they are above say 350ppi. One can simply inspect the images in the PDF. Another option is to open the final PDF into Photoshop and elect to extract the images only (not rasterize the PDF page/s). You can then "eyeball" the images to see if you have any weird moiré/aliasing or other issues caused by the PDF image interpolation process from original high resolution to resampled smaller image. If one or more images have suffered, you could then elect to make a copy of the original and manually resize these images in Photoshop to the final print size and resolution using the "safe" techniques mentioned in this topic thread.
2. You can use a script for InDesign and Photoshop, that will dupe your InDesign file and resize/resample copies of all images in Photoshop and then relink them back to the InDesign layout. This way you can run a batch or script to sharpen or perform other edits to all of the new resized images that are linked to the new copy.
Two similar scripts are attached to this reply in a .zip archive.
3. Export out a PDF using bicubic interpolation to reduce the PPI count of the images to say 300ppi if they are above say 350ppi. Then to use PitStop Pro 12 which has a new feature to apply sharpening to images inside a PDF. For a small amount of images, one could simply use the image touch up tool and sharpen the images in Photoshop, however for 100 images it would be more productive to sharpen them directly inside the PDF using PitStop Pro 12.
Stephen Marsh
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Hi, dleather.
I wonder whether there are some images resizing process which does not lose any resolution? And I think PDF image can be resized using some professional PDF processors much easier than other images.
Best regards,
Arron
mattbeals
Well-known member
I would say that you might as well do the sizing/scaling in photoshop since you're going to have to resample to 8 bit images from 16 bit. This way if you do have moire patterns you can adjust the original as necessary. I'm not sure that InDesign will convert a 16 bit image to 8 bit.
Mark Flanders
Well-known member
Greetings,
Appear to be numerous good responses here, and many opinions. for the record, here is what I would do:
1) Change the resolution in Photoshop with NO resampling...from 96 dpi to 304. (an old habit)This will do nothing at all to the images except make them much more manageable in INDesign. (yes, figure out how to batch this action if possible)
2) Then save them as RGB .jpg files with NO compression. Maximum quality. Contrary to poplular opinion, a jpg file is not lossy if it is at 100%. It simply refers to a single accurate source any time an image value is repeated. A Tiff file, in contrast, identifies each pixel even if it is exactly the same as the previous one. JPG Compression at less than 100% points more than one value in a range to a single source, but at 100% or maximum quality, there is no loss, except in file size. Also, I suggest leaving in RGB, as you cannot go back without ugly loss. Some devices want RGB, and others CMYK. Leaving in RGB allows more flexibility.
The result is that you have a reasonably sized native file with no compression, in RGB. All of your PDF options are available, and you can go back to do it differently if neccesary.
When you're ready, output PDF in print quality, or x1a, or whatever your printer desires. You can convert to CMYK at this point, and if necessary, and use image quality compression for images above 400 dpi or so.
thanks for listening!
Appear to be numerous good responses here, and many opinions. for the record, here is what I would do:
1) Change the resolution in Photoshop with NO resampling...from 96 dpi to 304. (an old habit)This will do nothing at all to the images except make them much more manageable in INDesign. (yes, figure out how to batch this action if possible)
2) Then save them as RGB .jpg files with NO compression. Maximum quality. Contrary to poplular opinion, a jpg file is not lossy if it is at 100%. It simply refers to a single accurate source any time an image value is repeated. A Tiff file, in contrast, identifies each pixel even if it is exactly the same as the previous one. JPG Compression at less than 100% points more than one value in a range to a single source, but at 100% or maximum quality, there is no loss, except in file size. Also, I suggest leaving in RGB, as you cannot go back without ugly loss. Some devices want RGB, and others CMYK. Leaving in RGB allows more flexibility.
The result is that you have a reasonably sized native file with no compression, in RGB. All of your PDF options are available, and you can go back to do it differently if neccesary.
When you're ready, output PDF in print quality, or x1a, or whatever your printer desires. You can convert to CMYK at this point, and if necessary, and use image quality compression for images above 400 dpi or so.
thanks for listening!
Stephen Marsh
Well-known member
A JPEG/JFIF image will of course be lossy, even at maximum quality/least compression. By it’s very nature it is a lossy process. Is it visually lossy? That is another very different topic.
JPEG should not be confused with JPEG2000, which does offer a truly lossless encoding method.
It is lamentable that JPEG2000 has not gained wider acceptance/use.
Stephen Marsh
Mark Flanders
Well-known member
I stand corrected. I must have been thinking of jpeg2000.
Sit, corrected, actually.
all the best,
Mark
Sit, corrected, actually.
all the best,
Mark
Mark Flanders
Well-known member
Hah! Good question!
I guess pre-press people don't ever die, we just keep posting on Print Planet!Terran Sin
New member
Because free advice on this forum is priceless for the rest of us who backed into digital printing and can't figure where or when to otherwise get the training we need to figure out those once in a blue moon problems! Thanks to all the posters contributing. You are appreciated.
mojoprime
Well-known member
And again, you just restated what colorblind said on the other page.
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