I hope someone out there can please help. A friend recently asked me to take a seascape pic which she planned to have printed onto canvas. As I haven't printed any photos for many years & so pixel quality isn't something I've had to pay much attention to, I checked my camera's manual first & selected 16M as the number of recorded pixels, as this was for printing high quality images or A4 size prints (there was nothing larger). My friend has now received an email to advise:
"Unfortunately, the image you send is of same bad quality. It is only 960x552 pixel.
Could you please email us the image in good quality or replace with other one?
If possible, could you send us the images taken from camera will be in better quality to be printed. We recommend to use 3-5 Mb image in JPEG format with 150 Dpi."
I've checked the details for the pic on my PC & it shows that the size is 1.14MB & the dimensions are 3015 x 1734.
Is it possible to convert the image into a quality suitable for it is being requested &, if so, how do I go about it please?
With many thanks in advance - I really am at a loss when it comes to pixels etc.
I know it is possible to convert the images, but I don't remember how. I too am glad you asked this, because I haven't got into printing yet, but I have a feeling I will come into some similar issues.
I think it would need to be taken in a high-quality setting on a higher MP camera. My camera is 18 MP and takes pictures that are 7-8 MB each. When I process it in Photoshop, it will be 11-15 MB. A 1 MB picture will not blow up that big.
You can try to "up sample" your current image in Photoshop. Image | Image Size... and choose the pixel size you are trying for. You can also set the dpi and see how that translates into inches (choose inches instead of pixels). Use Bicubic Smoother algorithm for PS CS6, or better "Preserve Details" in CC. The trick of "Preserve Details" is that the upsizing is done in several stages, which you can emulate yourself in CS6 and before. PS does a great job of "guessing" on details, but it can only go so far of course. Nothing beats a good (raw) image to work with in 16 bits, and only convert to jpeg as the absolute final step. Good luck.
Ignore the DPI issue, it's entirely irrelevant. In fact, the e-mail that they sent you, referring to DPI, shows that they themselves have some misunderstandings themselves, which isn't a great sign in a printing company! The only thing that matters is the resolution of the file, and you have at least two issues here that you really need to figure out.
Firstly, we'll start with the file that *you* have, as everything will eventually be based off this. Your camera is 16 megapixels, but your file is only 5.2 megapixels. (You can work out how many megapixels your file is by multiplying the width and height in pixels -- in this case, your file is 3015 by 1734 pixels, 3015*1734 is roughly 5.2 million pixels, or 5.2 megapixels).
This indicates that something has gone wrong somewhere. The files that come off your camera are 4608 by 3456 pixels, and this is the size your image should be. This could indicate a few things:
* The camera wasn't correctly set to 16 megapixel mode.
* The image has been resized by your processing software, possibly without your knowledge.
* You cropped the image significantly.
This is a problem, as it means that even the file that you have is quite small, and cannot be printed at very large sizes with great quality. Ideally you need to work out why this has happened, so you can prevent it in future, and get the full 16 megapixel images from your camera, which should have the dimensions mentioned above.
The second problem is that the file that the printing company has received is even smaller than the file that you have. The file she's sent in has a resolution of just 0.5 megapixels! This means that somewhere along the line, there has been a further resize that's taken place, reducing the image size even further. How this occurred depends a lot on how your friend got the image from you. If she downloaded it from your 365project page, then the image would be very small, like this, and not the original that you have. If you e-mailed it to her, some e-mail software will automatically reduce the size of the image to make sending faster. This is usually an option that can be disabled. If all else fails, you can use a service like DropBox to share the original image file. She needs to make sure that when she receives the image, it's the same size as the image file you sent.
You don't mention how large a print she wants, but if you can get her the original image file that you have (the 5.2 megapixel one), then she should be able to get that printed at a reasonable size. Canvas is a very forgiving medium (it has a lot of texture that hides image quality issues), and your 5.2 megapixel image should be printable at a size of around 24x16 inches, provided the image itself is sharp (in focus, no motion blur) and not too noisy.
If you can get the original file off the camera, the 16 megapixel one, then you could go significantly larger, around 36x24 inches, on canvas.
I would not personally consider scaling the image up. If you can get her the file that you have, that's big enough for a reasonable-size print without any scaling. Making an image larger, especially from a compact camera which tends to have a lot of softness at the pixel level, rarely results in a file that will actually look any better when printed, and often can make things worse.
I am no expert on this but can say I have put some very old digital prints on canvas which were a fraction of that file size and they have come out fine on a fairly small canvases 20x30cm the medium is very forgiving
@abirkill First of all in retrospect I realized I confused DPI with PPI. I understand that DPI is rather irrelevant. But question for you: Although you do not specifically mention PPI in your post, it is not totally irrelevant is it? If I take a 6000px X 4000px x 300ppi image, and downsample it to 100ppi, the pixel size of the image will change to 2000px x 1333px, and the file size will drastically reduce, will it not? And conversely if I upsample from 100ppi to 300ppi the pixel dimensions will triple back up the the original 6000px x 4000px. But now if PPI doesn't matter either, then why does my print company have me send my images to them at 260ppi? (Which I've always thought was odd as I was under the impression that anything above 240ppi is practically irrelevant).
@icamera The PPI that you set in Photoshop or another editing package is just a number that's stored as metadata in the image file, in the same way as metadata stores the camera you used, or the focal length of the lens. By itself, it doesn't actually alter the image file at all.
A file that is, say, 6000x4000 pixels and has a PPI value of 1 is identical in quality to a file that is 6000x4000 pixels with a PPI value of 600, will take up the same amount of space, and will print at the same quality from any major consumer-targeted photo printing company. It's the pixel dimensions of the file that determine the quality of the final print, not the PPI value.
A lot of the confusion comes because when you alter the PPI value in Photoshop, it will also resize the image, but this resizing is not, in itself, directly related to the PPI value, it's really just trying to be helpful (albeit in a confusing manner).
If you go into the Photoshop resize dialog, you can uncheck the 'resample' box, which lets you set the PPI value without also resizing the image. If you do this, you'll see that the dimensions (in pixels) of the image stays exactly the same, regardless of what PPI value you enter -- all that changes are the physical dimensions (in inches or centimetres) that the PPI value implies. By doing this, you are just changing the PPI value, without also resizing the image.
However, by default, Photoshop checks the 'resample' box, which means that it will resize the image by determining the difference between the starting PPI value and the entered PPI value. So if you have an image with a PPI value of 150, and enter a new PPI value of 300, leaving the resample box checked, then Photoshop will both set the PPI value to 300, and resize the image to be twice as big.
The exact same result would occur if you performed the two actions separately, first resizing the image to 200%, and then altering the PPI to 300 with the 'resample' box unchecked. (Or indeed, doing those actions in the reverse order). By separating these actions out it makes it more clear what is actually happening.
So that's pretty confusing already, but then we come to what the PPI value actually implies, which if you are doing casual printing today is absolutely nothing.
Historically, and even today if you are doing professional publishing, the PPI value was very important, because it tells the printer how large to print the image. Say you need to supply an image to a magazine's artwork department, and they told you that they needed the file to be 6 inches across and that they worked at 300ppi in their publishing package. In this case, you would need to provide them with an image that 6 inches * 300 ppi = 1800 pixels across, and also had a value of 300ppi in the metadata. Both of these would be absolutely key, because their publishing software would read that PPI value in and know that the image should be sized at 6 inches across. If you accidentally gave them a file that was 1800 pixels across but with a value of 150ppi in the metadata, they'd be annoyed, because their publishing software would size that at 12 inches across! If you accidentally gave them a file that was 900 pixels across with a value of 300ppi in the metadata, their software would size that a 3 inches across. The combination of both values tells the software and printer what physical size to display the image.
The thing is, that's all very confusing if you've just bought a digital camera and want to print an image. So today, modern photo-printing companies make things much easier, in that they simply say, 'upload your file, and choose what size you want it printed'. This makes much more sense to the consumer (and indeed pretty much any photographer), because all you have to do is upload a file from your camera (no need to mess with sizing or PPI values), and choose what size you want from a list, and they do the rest.
This is why the PPI value in the file is now irrelevant, and why I said at the start that it doesn't matter if you have a file with a value of 1 ppi or 600 ppi -- this value is completely ignored by photo printing companies. They will take your file, they will take your size request, and they'll print it at the right size. In other words, they are using your size request, that you chose on their site when ordering, instead of the PPI value in the file itself, to determine how large to print the file.
So, my recommendation is that, as a photographer, don't touch any of these settings. Just save the file at the highest resolution you can (the native resolution of the camera, minus any cropping), don't worry about the PPI value in Photoshop, and upload that to the photo printing company.
(For anyone else reading who doesn't understand all that, don't worry -- here comes the important bit):
Now, what does matter is how large the photo can be printed before any fuzziness or loss of quality can be seen, because we all want to make sure that our photos look stunning, and in some cases it can be tempting to print them at larger sizes than they can really support.
This depends on a combination of viewing distance and material. If you are printing a photo at a very large size, then it's pretty rare for anyone to go and stand three inches away from it, so that can be more forgiving. If you are printing a photo on canvas, the texture makes it more forgiving than a print on paper or metal.
Confusingly, the measure of this is also referred to as PPI, but this isn't the PPI value that you change in Photoshop! Instead, you should use the native size of your file, without resizing, to work out how large it can be printed. There's a lot of personal preference, but values I find work are:
* Canvas prints or very large prints that won't be viewed up-close: 100ppi.
* Prints on photo paper or metal in a typical home environment: 150ppi.
* Prints for gallery display: At least 200ppi.
These are based on images that are pin-sharp and with effectively no noise, but equally I'm pretty picky, so these should be reasonable for most people. If you are very picky and have a camera that doesn't produce super-sharp or noise-free images, you may wish to go higher, but these are a good starting point.
So how do we use these values to determine how large we can print our file? Well, first we find the resolution of the file without any resizing -- let's take our example 24 megapixel DSLR file, which is 6000x4000 pixels, and assume we framed it perfectly, so it's not been cropped. We then find the value above for the type of print we want, and divide the file dimensions by the value. So for example, if you were printing on canvas, you could go as high as:
You then upload the image to your printing company (without any resizing), choose a print size as determined above, and wait for a stunning photo to arrive in the mail!
If you use any major photo printing service in the US (Bay Photo, WHCC, Costco, AdoramaPix, etc. etc.), UK (Loxley, Photobox, etc.), or most other large-scale printing companies anywhere in the world, this is all you need to worry about.
(End of the important bit)
Hopefully it's starting to become apparent why altering the PPI in Photoshop in the default way, that resizes the image, often leads to unnecessary complication and confusion. For example, say you started out with a file that's 2000 pixels wide, and just happens to have a PPI value of 100. (The initial PPI value in Photoshop is pretty random, and is determined by what the camera decides to write to the file if you use JPEG, or what your RAW converter uses if you shoot RAW -- with Adobe Camera Raw you can choose whatever value you like). You might then think 'Hey, I want this to be super-sharp, so I'll just change the PPI to 300'. Photoshop then 'helpfully' resizes your image to 6000 pixels across (because 300 is 3 times the initial 100 value). If you use that with the guidelines above, you'll believe that you can print that at 60 inches across, even though you only started with a 2000 pixel wide image, and the result will be extremely disappointing. In other words, when determining how large a file can be printed, only ever base the calculations off the native resolution of the image as it came off the camera.
There are a couple of exceptions to this where altering the PPI in Photoshop can be the correct thing to do:
1. At some point, the image is going to have to be scaled by something (most often upscaled), because the printer has a native print resolution (this is loosely the DPI of the printer, which should never be used in a file context, hence my concern at the quoted e-mail from the printing company mentioning DPI). Some pros believe that if they resample the image so that the number of pixels per inch in the file will match the number of dots per inch that the printer uses, they'll get better results than letting the printer software resample that automatically.
In theory, this is absolutely correct, but unless you are printing your own work, in reality it's extremely hard to achieve. Most printing companies use a variety of printers to print different sizes and on different materials, so it can be virtually impossible to determine the claimed native resolution of the printer that will actually be used to print your work. Even if you can, the claimed DPI resolution often differs from the actual resolution, because of the way the printer actually works (the actual resolution is, just to add confusion, often referred to as the LPI, or lines per inch!). If you get it wrong, then you'll have rescaled the image, and the printer will have rescaled the image a second time. This is generally a bad thing -- we want to rescale the image as few times as possible.
Additionally, resampling algorithms in printer drivers are pretty awesome these days, and can take into account printer-specific factors that aren't possible to account for when resampling yourself. If you have your own printer and want to maximise your quality when viewed under a magnifying glass, then you may want to investigate this, but if you are getting prints done by an external company, you have a greater risk of making things worse than making things better.
2. Some printing companies will still work on the old basis that the size of the print they produce is based on the combination of the file resolution and the PPI value. These are typically small volume printers that cater mainly to pros and offer specialised services. I use one printing company that does specialised work very well that insists on working this way.
There's nothing particularly wrong with this, other than it being harder to place orders, and that you are now responsible for doing the resampling, and doing it well. However, be wary of printing companies that are stuck somewhere between the two. Either a printing company should require you to set your dimensions and PPI in the file itself via Photoshop, in which case you'll just upload your files, and you won't specify the size you want them printed, or they require you to state how large you want each file printing. If they do both, then be wary -- they're asking for redundant information, which suggests someone there doesn't fully understand the process.
I can only presume that you are using a printing company like this, which is fine (if you're happy with the work!) I'm guessing the native resolution of their printers is 260 lines per inch, and they ask you to resample the image to 260 ppi so that there is no further resampling done. Bear in mind that this is quite unusual though, and generally not something that's necessary or advisable when using mainstream photo printing outlets.
@abirkill Wow! That took a while to read so I have no idea how long it took to prepare and write but man do I appreciate it! That is some really cool info. I wish there was "pin" functionality as that info should be "pinned" somewhere. Thanks much!!! Oh, and yes, the print shop I use is just as you've said, rather small and offers specialized print/framing/etc so you were spot on.
@mzzhope@howardbn09@homeschoolmom@frankhymus@abirkill@virtualbrownie@icamera many many thanks to everyone for taking the time & trouble to comment & provide such comprehensive answers. Unfortunately, after all this I fear my friend will not be able to get the image printed as try as I might the largest I can get it is 2.52MB, size 3038 x 1720. Given my camera is supposedly 16MP I'm now totally confused as to why all my images are just 2 or so MB. There's nothing at all anywhere close to 16MP now I look more closely. Just to make things worse I only use Ribbet, not Photoshop - I really am very much an amateur snapper. I tried to save a pic via Ribbet & the largest it would allow was 2.5MB, saying that this was huge & suitable for any size printing! I think I should just stick to taking pics & uploading them as printing seems to be a whole different - & difficult - subject.
@net If you can get that file to your friend at that same size, then it should be able to be printed at up to 24 inches on the long edge on canvas reasonably successfully. It's still not ideal, but it's usable if that's big enough for what she wants. You need to get the 3038x1720 version to her though, not the 960x552 version she currently has.
I've not used Ribbet, but I see that it's an online editor, which may be reducing the image size to make things faster. Looking on their support forum, it appears that you can make it use a higher-resolution file by changing the image quality setting to 'archival': http://blog.ribbet.com/?topic=changing-my-dimensions
You might want to give that a go and see if it helps.
@abirkill Alexis many thanks - I played around with Ribbet archivial & managed to get it saved as 8.58MB, dimensions 3015 x 1734, which I'm emailing as an attachment rather than via Facebook PM.
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Ignore the DPI issue, it's entirely irrelevant. In fact, the e-mail that they sent you, referring to DPI, shows that they themselves have some misunderstandings themselves, which isn't a great sign in a printing company! The only thing that matters is the resolution of the file, and you have at least two issues here that you really need to figure out.
Firstly, we'll start with the file that *you* have, as everything will eventually be based off this. Your camera is 16 megapixels, but your file is only 5.2 megapixels. (You can work out how many megapixels your file is by multiplying the width and height in pixels -- in this case, your file is 3015 by 1734 pixels, 3015*1734 is roughly 5.2 million pixels, or 5.2 megapixels).
This indicates that something has gone wrong somewhere. The files that come off your camera are 4608 by 3456 pixels, and this is the size your image should be. This could indicate a few things:
* The camera wasn't correctly set to 16 megapixel mode.
* The image has been resized by your processing software, possibly without your knowledge.
* You cropped the image significantly.
This is a problem, as it means that even the file that you have is quite small, and cannot be printed at very large sizes with great quality. Ideally you need to work out why this has happened, so you can prevent it in future, and get the full 16 megapixel images from your camera, which should have the dimensions mentioned above.
The second problem is that the file that the printing company has received is even smaller than the file that you have. The file she's sent in has a resolution of just 0.5 megapixels! This means that somewhere along the line, there has been a further resize that's taken place, reducing the image size even further. How this occurred depends a lot on how your friend got the image from you. If she downloaded it from your 365project page, then the image would be very small, like this, and not the original that you have. If you e-mailed it to her, some e-mail software will automatically reduce the size of the image to make sending faster. This is usually an option that can be disabled. If all else fails, you can use a service like DropBox to share the original image file. She needs to make sure that when she receives the image, it's the same size as the image file you sent.
You don't mention how large a print she wants, but if you can get her the original image file that you have (the 5.2 megapixel one), then she should be able to get that printed at a reasonable size. Canvas is a very forgiving medium (it has a lot of texture that hides image quality issues), and your 5.2 megapixel image should be printable at a size of around 24x16 inches, provided the image itself is sharp (in focus, no motion blur) and not too noisy.
If you can get the original file off the camera, the 16 megapixel one, then you could go significantly larger, around 36x24 inches, on canvas.
I would not personally consider scaling the image up. If you can get her the file that you have, that's big enough for a reasonable-size print without any scaling. Making an image larger, especially from a compact camera which tends to have a lot of softness at the pixel level, rarely results in a file that will actually look any better when printed, and often can make things worse.
A file that is, say, 6000x4000 pixels and has a PPI value of 1 is identical in quality to a file that is 6000x4000 pixels with a PPI value of 600, will take up the same amount of space, and will print at the same quality from any major consumer-targeted photo printing company. It's the pixel dimensions of the file that determine the quality of the final print, not the PPI value.
A lot of the confusion comes because when you alter the PPI value in Photoshop, it will also resize the image, but this resizing is not, in itself, directly related to the PPI value, it's really just trying to be helpful (albeit in a confusing manner).
If you go into the Photoshop resize dialog, you can uncheck the 'resample' box, which lets you set the PPI value without also resizing the image. If you do this, you'll see that the dimensions (in pixels) of the image stays exactly the same, regardless of what PPI value you enter -- all that changes are the physical dimensions (in inches or centimetres) that the PPI value implies. By doing this, you are just changing the PPI value, without also resizing the image.
However, by default, Photoshop checks the 'resample' box, which means that it will resize the image by determining the difference between the starting PPI value and the entered PPI value. So if you have an image with a PPI value of 150, and enter a new PPI value of 300, leaving the resample box checked, then Photoshop will both set the PPI value to 300, and resize the image to be twice as big.
The exact same result would occur if you performed the two actions separately, first resizing the image to 200%, and then altering the PPI to 300 with the 'resample' box unchecked. (Or indeed, doing those actions in the reverse order). By separating these actions out it makes it more clear what is actually happening.
So that's pretty confusing already, but then we come to what the PPI value actually implies, which if you are doing casual printing today is absolutely nothing.
Historically, and even today if you are doing professional publishing, the PPI value was very important, because it tells the printer how large to print the image. Say you need to supply an image to a magazine's artwork department, and they told you that they needed the file to be 6 inches across and that they worked at 300ppi in their publishing package. In this case, you would need to provide them with an image that 6 inches * 300 ppi = 1800 pixels across, and also had a value of 300ppi in the metadata. Both of these would be absolutely key, because their publishing software would read that PPI value in and know that the image should be sized at 6 inches across. If you accidentally gave them a file that was 1800 pixels across but with a value of 150ppi in the metadata, they'd be annoyed, because their publishing software would size that at 12 inches across! If you accidentally gave them a file that was 900 pixels across with a value of 300ppi in the metadata, their software would size that a 3 inches across. The combination of both values tells the software and printer what physical size to display the image.
The thing is, that's all very confusing if you've just bought a digital camera and want to print an image. So today, modern photo-printing companies make things much easier, in that they simply say, 'upload your file, and choose what size you want it printed'. This makes much more sense to the consumer (and indeed pretty much any photographer), because all you have to do is upload a file from your camera (no need to mess with sizing or PPI values), and choose what size you want from a list, and they do the rest.
This is why the PPI value in the file is now irrelevant, and why I said at the start that it doesn't matter if you have a file with a value of 1 ppi or 600 ppi -- this value is completely ignored by photo printing companies. They will take your file, they will take your size request, and they'll print it at the right size. In other words, they are using your size request, that you chose on their site when ordering, instead of the PPI value in the file itself, to determine how large to print the file.
So, my recommendation is that, as a photographer, don't touch any of these settings. Just save the file at the highest resolution you can (the native resolution of the camera, minus any cropping), don't worry about the PPI value in Photoshop, and upload that to the photo printing company.
(For anyone else reading who doesn't understand all that, don't worry -- here comes the important bit):
Now, what does matter is how large the photo can be printed before any fuzziness or loss of quality can be seen, because we all want to make sure that our photos look stunning, and in some cases it can be tempting to print them at larger sizes than they can really support.
This depends on a combination of viewing distance and material. If you are printing a photo at a very large size, then it's pretty rare for anyone to go and stand three inches away from it, so that can be more forgiving. If you are printing a photo on canvas, the texture makes it more forgiving than a print on paper or metal.
Confusingly, the measure of this is also referred to as PPI, but this isn't the PPI value that you change in Photoshop! Instead, you should use the native size of your file, without resizing, to work out how large it can be printed. There's a lot of personal preference, but values I find work are:
* Canvas prints or very large prints that won't be viewed up-close: 100ppi.
* Prints on photo paper or metal in a typical home environment: 150ppi.
* Prints for gallery display: At least 200ppi.
These are based on images that are pin-sharp and with effectively no noise, but equally I'm pretty picky, so these should be reasonable for most people. If you are very picky and have a camera that doesn't produce super-sharp or noise-free images, you may wish to go higher, but these are a good starting point.
So how do we use these values to determine how large we can print our file? Well, first we find the resolution of the file without any resizing -- let's take our example 24 megapixel DSLR file, which is 6000x4000 pixels, and assume we framed it perfectly, so it's not been cropped. We then find the value above for the type of print we want, and divide the file dimensions by the value. So for example, if you were printing on canvas, you could go as high as:
6000/100 = 60 inches across, 4000/100 = 40 inches tall. (Or any smaller size).
If you were printing for a gallery display that could make or break your career, then you could go as high as:
6000/200 = 30 inches across, 4000/200 = 20 inches tall. (Or any smaller size).
You then upload the image to your printing company (without any resizing), choose a print size as determined above, and wait for a stunning photo to arrive in the mail!
If you use any major photo printing service in the US (Bay Photo, WHCC, Costco, AdoramaPix, etc. etc.), UK (Loxley, Photobox, etc.), or most other large-scale printing companies anywhere in the world, this is all you need to worry about.
(End of the important bit)
Hopefully it's starting to become apparent why altering the PPI in Photoshop in the default way, that resizes the image, often leads to unnecessary complication and confusion. For example, say you started out with a file that's 2000 pixels wide, and just happens to have a PPI value of 100. (The initial PPI value in Photoshop is pretty random, and is determined by what the camera decides to write to the file if you use JPEG, or what your RAW converter uses if you shoot RAW -- with Adobe Camera Raw you can choose whatever value you like). You might then think 'Hey, I want this to be super-sharp, so I'll just change the PPI to 300'. Photoshop then 'helpfully' resizes your image to 6000 pixels across (because 300 is 3 times the initial 100 value). If you use that with the guidelines above, you'll believe that you can print that at 60 inches across, even though you only started with a 2000 pixel wide image, and the result will be extremely disappointing. In other words, when determining how large a file can be printed, only ever base the calculations off the native resolution of the image as it came off the camera.
There are a couple of exceptions to this where altering the PPI in Photoshop can be the correct thing to do:
1. At some point, the image is going to have to be scaled by something (most often upscaled), because the printer has a native print resolution (this is loosely the DPI of the printer, which should never be used in a file context, hence my concern at the quoted e-mail from the printing company mentioning DPI). Some pros believe that if they resample the image so that the number of pixels per inch in the file will match the number of dots per inch that the printer uses, they'll get better results than letting the printer software resample that automatically.
In theory, this is absolutely correct, but unless you are printing your own work, in reality it's extremely hard to achieve. Most printing companies use a variety of printers to print different sizes and on different materials, so it can be virtually impossible to determine the claimed native resolution of the printer that will actually be used to print your work. Even if you can, the claimed DPI resolution often differs from the actual resolution, because of the way the printer actually works (the actual resolution is, just to add confusion, often referred to as the LPI, or lines per inch!). If you get it wrong, then you'll have rescaled the image, and the printer will have rescaled the image a second time. This is generally a bad thing -- we want to rescale the image as few times as possible.
(Off-topic: An interesting (to me anyway) process someone went through to determine the true native resolution of an Epson printer: http://www.rags-int-inc.com/PhotoTechStuff/Epson2200/ )
Additionally, resampling algorithms in printer drivers are pretty awesome these days, and can take into account printer-specific factors that aren't possible to account for when resampling yourself. If you have your own printer and want to maximise your quality when viewed under a magnifying glass, then you may want to investigate this, but if you are getting prints done by an external company, you have a greater risk of making things worse than making things better.
2. Some printing companies will still work on the old basis that the size of the print they produce is based on the combination of the file resolution and the PPI value. These are typically small volume printers that cater mainly to pros and offer specialised services. I use one printing company that does specialised work very well that insists on working this way.
There's nothing particularly wrong with this, other than it being harder to place orders, and that you are now responsible for doing the resampling, and doing it well. However, be wary of printing companies that are stuck somewhere between the two. Either a printing company should require you to set your dimensions and PPI in the file itself via Photoshop, in which case you'll just upload your files, and you won't specify the size you want them printed, or they require you to state how large you want each file printing. If they do both, then be wary -- they're asking for redundant information, which suggests someone there doesn't fully understand the process.
I can only presume that you are using a printing company like this, which is fine (if you're happy with the work!) I'm guessing the native resolution of their printers is 260 lines per inch, and they ask you to resample the image to 260 ppi so that there is no further resampling done. Bear in mind that this is quite unusual though, and generally not something that's necessary or advisable when using mainstream photo printing outlets.
I've not used Ribbet, but I see that it's an online editor, which may be reducing the image size to make things faster. Looking on their support forum, it appears that you can make it use a higher-resolution file by changing the image quality setting to 'archival':
http://blog.ribbet.com/?topic=changing-my-dimensions
You might want to give that a go and see if it helps.