It may be a stupid question, but of all I have read and watched, people seem to use certain steps when changing the DPI resolution.
For example 240, 300, 360, 480 DPI.
In order to fill the paper sheet, I sometimes use values in between those common ones. For example 400 DPI or 200 DPI.
Is there something wrong with it? I have not seen any issues when printing but I wanted to ask anway.
Thanks
If the image has the same aspect ratio of the paper just use image size do not check resample. in the center section just enter one of the paper side sizes. Photoshop will fill in the other side and change the dpi.
If you want to crop the least amount of that you can here is how you can do it. Lets assume you have a 3:2 aspect ratio image and you have 11" x 8.5" paper.
First use Image Size on you image do not check resample in the center section set the height to 8.5". Photoshop will set the other side to 12" and set the correct dpi. Next pull out the image window frame so there is some gray area around the image. Then select the rectangle marquee tool and set the tools option bar to fixed ratio and set 11 width and 8.5 height. Next place the mouse pointer above and to the left of the image's top left hand corner in the gray area click and hold the left mouse button and drag to below ant to the right of the bottom right hand corner and release the button. This will select a 11x8.5 selection. Use the right and left arrow keys to position the selection then use menu Image>Crop. the print....
If you want to print with a border use image size do not check resample if you have a 3:2 image and 11x8.5" paper set the width to 11" Photoshop will set the other side to to 7.333" and the correct DPI. Print the image
The "standard" numbers were (are) a nice fraction of the printer dpi and that used to give a better result than oddball numbers. e.g. 240dpi is a nice 3:1 ratio of a 720dpi printer, or 6:1 ratio of a 1440 dpi printer (which are common Epson resolutions). i.e. every image pixel would be mapped to a grid of 3x3 or 6x6 printer pixels. It works out nicely. Canon printers typically worked at 600 or 1200 dpi and so 300 dpi was a good value to use for them.
If you used 500dpi on a 1200 dpi printer then every image dot would try to be mapped to a 2.4x2.4 dot grid by the printer, which cannot be done as cleanly because you cannot have 0.4 dots - just smaller dots (if the printer supports it). The printer driver would have to do a clever match-up to avoid artifacts or patterns appearing on the print.
Sometimes it pays to use more than about 360 or 400 dpi but it rarely produces a visible benefit unless the print is to be viewed from a close distance by someone with excellent eyesight. Most images do not benefit from lots of dpi because they are viewed from a reasonable distance at which our eyesight is a limiting factor (in addition to the printer/paper/ink combination). On the other hand, much less than 240 dpi offers too little detail for fine prints at typical viewing distances.
So, within reason you can fiddle the dpi and still get a good print but certain dpi values may suit your printer better than others. Beyond this, it is better to resample the image to a different pixel count and print the resampled image at an appropriate dpi.
Thanks Mr Mouse and thank you Alan, that really has helped.
How can I find out which dpi values suit my printer? I have a Epson R1800.
I used to resample always, but did not really want to print with wide borders all the time, but rather fill the paper. That's why I was asking.
Changing resolution is not the way to do it, I heard, it is better to only resample the image without changing the resolution.
So wihin reason you can fiddle with the dpi, but should not completely go to intermediate steps like 440 dpi for example?
Is it really possible to have the printer print at fewer dpi than what is native? I have the R800 and wonder if I can get more shadow detail (not to mention save ink) if the printer didn't laydown so much ink. If I chose 360dpi in photoshop which is 1/4 of 1440 is it really printing 360 dpi or is the print driver secretly going to interpolate my image back up to 1440 without me knowing?
Resampling changes the number of pixels in an image either increasing the number or decreasing the number. Any time an image is resampled some image degradation occurs.
Changing the DPI resolution does not change the image pixels no image degradation occurs only the size of the print changes. If the DPI resolution becomes too low the print may not look good be soft. The "Too low" value varies with print size and viewing distance. I had a print made 6' wide 8' hight at 100dpi and hung on stage it looked great from the audience. Still 6' by 8' at 100 dpi is 7200 x 9600 pixels I had to resample the image up in size using bi-cubic smoother.
The other reason I resample images is to reduce the dumber of pixels in an image so it fits in a web page and transfers quickly over the net.
Ink-jet printers have a maximum DPI and the can print at any DPI up to its max.
You do not need to know what DPI to set just set one print side in the Image Size Dialog with resample not checked and Photoshop will do the rest.
Mr Mouse wrote:
Resampling changes the number of pixels in an image either increasing the number or decreasing the number. Any time an image is resampled some image degradation occurs.
Changing the DPI resolution does not change the image pixels no image degradation occurs only the size of the print changes. If the DPI resolution becomes too low the print may not look good be soft. The "Too low" value varies with print size and viewing distance. I had a print made 6' wide 8' hight at 100dpi and hung on stage it looked great from the audience. Still 6' by 8' at 100 dpi is 7200 x 9600 pixels I had to resample the image up in size using bi-cubic smoother.
The other reason I resample images is to reduce the dumber of pixels in an image so it fits in a web page and transfers quickly over the net.
Ink-jet printers have a maximum DPI and the can print at any DPI up to its max.
You do not need to know what DPI to set just set one print side in the Image Size Dialog with resample not checked and Photoshop will do the rest....Show more →
I'm really wanting to know if changing the number of pixels in photoshop changes the amount of ink that is laid down by my printer.
brad_s wrote:
I'm really wanting to know if changing the number of pixels in photoshop changes the amount of ink that is laid down by my printer.
I don't know the answer for you. If you increase the number of pixels and keep the print size the same your covering the same surface area with smaller sharper pixels. However your covering the same surface area. How the printer make the larger pixels required to print the image at a lower resolution may be just how it maps its nozzles to pixels. You have a setting in your printer driver regarding print quality. In my Epson 4800 settings depending on the paper I use. I can set Print quality to 720dpi 1440dpi and 2880dpi. The 2880 setting is only available on high quality paper. I think the amount of ink laid down may have more to do with the print quality setting then the number of pixels in an image. Image I print seldom have print resolution greater the 584 DPI the lowest Print quality I can set in the driver is 720dip. I set the setting to 1440 or 2880. The is also a printer speed setting. If I set to high speed the printer prints when the print head moves in either direction. If not set to high speed printing is done when the head move in one direction but not on the return direction. I think these setting have more to do with how much ink is use then the number of pixels in an image. Of course the colors in the image influences which color inks are used.
brad_s wrote:
I'm really wanting to know if changing the number of pixels in photoshop changes the amount of ink that is laid down by my printer.
No it won't.
The ink on paper (litres per square inch) is determined mainly by the dpi set in the printer driver regardless of how many or how few image pixels are used. It may vary between printer models because of different droplet sizes but for a single printer it is the printer dpi rating that matters most. The paper and ink matter too. However, changing the number of image pixels per square inch will affect the amount of ink used to represent each pixel, because in effect you are changing the size of the image pixels. That can limit the number of colours and tones available in the print because in general each printed pixel is made up of a pattern of partially overlayed coloured ink droplets. There are only a few ink colours available in any printer.
brad_s wrote:
Is it really possible to have the printer print at fewer dpi than what is native? I have the R800 and wonder if I can get more shadow detail (not to mention save ink) if the printer didn't laydown so much ink. If I chose 360dpi in photoshop which is 1/4 of 1440 is it really printing 360 dpi or is the print driver secretly going to interpolate my image back up to 1440 without me knowing?
The printer driver will let you select any of several printer dpi settings. e.g. 1 2440 dpi printer can be set to print at 1440 dpi, 720 dpi or 360 dpi. this is the printer droplet dpi. The image pixel per inch is set in photoshop for the image and size combination that you want. e.g. that is where you tell it to print this 3000x2000 pixel image at say 300 dpi (actually ppi).
cencored wrote:
Thanks Mr Mouse and thank you Alan, that really has helped.
How can I find out which dpi values suit my printer? I have a Epson R1800.
I used to resample always, but did not really want to print with wide borders all the time, but rather fill the paper. That's why I was asking.
Changing resolution is not the way to do it, I heard, it is better to only resample the image without changing the resolution.
So wihin reason you can fiddle with the dpi, but should not completely go to intermediate steps like 440 dpi for example?
A few issues are raised here.
1. Epson printers have been multiples of 180 dpi since they were king of the heap in dot matrix printers back in the 1980s. They went from 180 to 360 to 720 to 1440 to 2880 to 5760, doubling each time. There may have been a few oddballs like 240 dpi in the early days but not with their recent printers.
Canon and HP always seemed to use 300, 600, 1200, etc. They started after the dot matrix printers were dying out.
2. Filling a page can be varied by selective cropping combined with a suitable image dpi (more accurately, ppi) setting. That way you get to control the image size and shape and also keep a whole number of printer dots to each image pixel.
3. Resampling is often incorrectly called resizing. Resampling is taking a set of pixels making an image and creating a new set of pixels to make an equivalent image with a different number of ixels, either more or less. Resampling without changing the number of pixels equals not changing the image at all.
Resizing just changes a setting that specifies the number of image pixels per inch. None of the pixels are changed by this - they will simply be printed bigger or smaller and/or with bigger or smaller gaps between them.
Resampling replaces the pixels with a different set of pixels. The new pixels are different chiefly because they don't line up with the image content shown by the original pixels. e.g. you may now have 7 pixels trying to show the same image that 5 pixels used to show.
When thinking about resampling keep in mind that every image pixel has just a single colour. There is no such thing as a partial pixel - it's all or nothing. So a change between two parts of an image can only occur at pixel boundaries. Shift those boundaries or change the number of boundaries by resampling and you need a different set of pixels that collective can only approximate the appearance of the original collection but never exactly duplicate it. Resampling always changes image quality. In general data integrity is always lost by resampling, but it can be made to look better by artificial sharpening and so on).
I think you making too big of an issue over the printers dpi specs. Think of the print drivers setting as print quality setting lower use less ink an print faster. Your images have so many optically created pixels these are the best pixels you can have. Once you resample an image these are all gone. Some commuter algorithm has massaged your optically created pixels into an image with more or fewer pixels you no longer have your cameras pixels. You can change the size an image prints by changing the images DPI resolution. No pixels are changed you still have all the optically created pixels from your camera the number of pixels are the same and the file size will be the same if save the same way. You printer can print you image at any DPI.
2. Filling a page can be varied by selective cropping combined with a suitable image dpi (more accurately, ppi) setting. That way you get to control the image size and shape and also keep a whole number of printer dots to each image pixel.
If you want to fill the paper the image must have the same aspect ratio as the paper. If it does not you have to crop the image throw away some pixels.
Once the image has the same aspect ratio as the paper you can print it and fill the paper its simple math you can divide the number of wide you have with the paper with and set the answer into the image size No resample DPI resolution or you can set the paper width in and Photoshop will do the devision and set the DPI for you.
3. Resampling is often incorrectly called resizing. Resampling is taking a set of pixels making an image and creating a new set of pixels to make an equivalent image with a different number of ixels, either more or less. Resampling without changing the number of pixels equals not changing the image at all.
Resampling always changes the number of pixels and the size of the image and file when saved. It is truly resizing. If you do not change pixels the image has not been resampled
Resizing just changes a setting that specifies the number of image pixels per inch. None of the pixels are changed by this - they will simply be printed bigger or smaller and/or with bigger or smaller gaps between them.
NOT resampling and changing the DPI resolution changes the image print size the Image and file size do not change so changing the resolution does not resize the image just the print size.
Resampling replaces the pixels with a different set of pixels. The new pixels are different chiefly because they don't line up with the image content shown by the original pixels. e.g. you may now have 7 pixels trying to show the same image that 5 pixels used to show.
Yes your original is is gone you now have a new image with more or less pixels some image quality has been lost.
When thinking about resampling keep in mind that every image pixel has just a single colour. There is no such thing as a partial pixel - it's all or nothing. So a change between two parts of an image can only occur at pixel boundaries. Shift those boundaries or change the number of boundaries by resampling and you need a different set of pixels that collective can only approximate the appearance of the original collection but never exactly duplicate it. Resampling always changes image quality. In general data integrity is always lost by resampling, but it can be made to look better by artificial sharpening and so on). ...Show more →
Once your cameras RAW mosaic image has been demosaic into a RGB image each pixel has three values a Red value a Blue value and a Green value( RGB). The resolution of the values are for the most part 8 bit or 16 bit. So in a 8 bit image each pixel has 24 bits and a 16bit image each pixel has 48 bits. When an image is resampled the algorithm used looks around at harboring pixels in order to come up the the increase or decreased pixels. There are may way the interpolation can be done.
When you look at the image size dialog the are three sections. The top section is the Image Document size. The center section the Print size. The bottom section is the control section. If in the bottom section RESAMPLE is NOT checked the top section grays out you can not change the image size just the print size.
There is a big definitional issue that has not been made clear: ppi versus dpi
The image you're working with in the editor is measured in pixels per inch (or centimeter)--ppi (or ppc). A pixel may be any one of several million colors/tones. But remember that "ppi" is the number you work with as you change the image size in Photoshop.
The printer lays downs dots of only 5 or 6 or 8 colors, so it must stipple/overlay/mix very tiny dots of color--much tinier than the pixels of the image--within the area of an image pixel to approximate the color of the pixel.
That's why the dpi of the printer must be much greater than the ppi of the image--the printer must use many dots of varying colors and densities within the same area of the pixel to approximate the pixel's color. Exactly how each printer manufacturer mixes colored dots to approximate pixel tones is a trade secret of the manufacturers. But remember that you're normally not playing with "dpi." Photoshop image resizing does not affect the printer's dpi.
The size of the pixel on the print must remain smaller than the ability of the eye to resolve it as a pixel. The average human eye at 20/20 correction can resolve around 240-300 ppi at normal reading distance. That's why you see recommendations of ppi settings of 240-360 or so. Some people say you should always choose a ppi that's a factor of the printer's dpi, as long it's within that 240-360 ppi range.
Obviously, if the picture's going to be observed at reading distance and the eye can only resolve 240-300 ppi at reading distance, then any greater resolution is wasted. Moreover, people will recommend that if the picture will be observed at greater than normal reading distance, you can use even lower ppi for larger prints because they will be viewed from greater destances. That's the theory...my experience, however, is that people get as close to a photograph as possible, so even a large print will often be viewed from reading distance. That's why I always set my ppi to 300 regardless of my image size.
Resampling changes the number of pixels in an image either increasing the number or decreasing the number. Any time an image is resampled some image degradation occurs.
Well, no, not exactly. Resampling/interpolating/"uprezzing" (which is what happens when you make the image size larger with Photoshop Image Resize) increases the number of pixels in the image by looking at each pixels and using an algorithm to guess at what color/tone an adjacent pixel should be. It doesn't take away anything, but the algorithm can't guess at micro-detail that the image doesn't contain--it can only add more area to what is already there.
So, for instance, if the original image of a human eye resolves all the eyelashes, then resampling/interpolating/"uprezzing" will result in resolving all the eyelashes, too, no matter how large you go, because eyelashes are just dark lines and the skin around them will be relatively monotone. It's easy for the algorithm to add more black line and skin surface, and nobody minds if it doesn't include skin flakes and hair mites.
That works when enough detail has been resolved in the original image, but if it hasn't, then resampling at some point will reveal that there is no detail where viewers will expect to see it. So a group portrait that's enlarged to a massive size may show dark smudges around eyes instead of eyelashes. But that's not "degradation" of the image...the detail wasn't there to begin with.
OTOH, "downrezzing" the image requires "throwing away" original image data. That's initially okay, but if you throw away image data in a downrez, you don't get it back if you then try to uprez the same image.
I'm getting up there in age been around for some time now. There use to be a TV program that only some of you will remember John Nagie paint by numbers. He sold canvas with pictures lined out inside the lines were numbers. You would fill in the outline area with a paint color with the number on it.
Ink-jet printers do exactly that they paint be numbers, The image outline is always the same square pixel. The three things vary in this image the size of the square pixel and the number in the pixel and the number of pixels.
The ink-jet printer does not have brushes the size of the pixels nor the color to match the number in the pixel, What the ink-jet printer has is some number of colored inks and a set of heads connected to these inks by a supply line. Head contain many nozzle that can squeeze out ink. What the ink-jet does is as it moves the heads across the paper is to squeeze out inks from different nozzles at different times to fill in the much larger pixels on the paper with inks that will mix together forming the correct color to fill in that square pixel.
When you change the image DPI all you are doing is changing the size of the pixels on the printed paper.
So every 6x4 300dpi image are the same 1800 x 1200 squares they only look different because the colors in the squares vary.
