[timo]

I did a job for a company last week and they gave me a reminder that "next time i do work for them, make sure the camera settings are set to dpi of 300" so that when the image goes to print they can have the best resolution possible. where is this setting in the menu?

This is so annoying. Did they tell you how large the reproduced image was going to be? Did they tell you if it was going to be cropped? There is no way you can set anything to 300 dpi in a meaningful way in the camera. If the designer wants to sent the file to the printer resampled to 300 dpi in terms of the reproduced size (which is what matters) let him get on with it. In the absence of precise sizing/cropping information, whatever you type into the appropriate dialogue box in Photoshop will be completely meaningless.

A mobile phone will produce a file which is 300 dpi if the reproduced size is small enough. A medium-format digital camera will not achieve 300 dpi if the reproduced image is on the side of a house.

The level of ignorance among many designers and people who specify photographic requirements is amazing sometimes.

[dvest]

I work with graphic designers and can tell you that many do not understand this subject at all. I have seen them crop an individual face from a group shot of 50 people, enlarge that face to 5"x7" then wonder why it is blurry since they "made it 300dpi".

[Ron Boggs]

I too deal with this practically weekly. Fact is, graphics folks speak a different language than photographers. They think we're stupid and visa versa. Real world, graphics folks have no idea what pixels are and most photographers are clueless on dpi (at least I am). After having perhaps 1000 images paid and published, I've stopped caring what they mean by their requirements, just measure up to them, make your submission and move on. If you try to ask how a given dpi figure equates to pixels their eyes glaze over so don't even go there. I've wasted plenty of back and forth emails on this topic and have yet to hear anything from a graphics person that has any meaning to me at all...in terms of my understanding anyway.

In addition to my freelance photography, I also do lots of web work for the science center where I work and our graphics guy is always pissed that I'm uploading files (photos) that are too large even though I've downsized the pixel count to similar to the images I submit here. Gotta go through a real editing program and specify the dpi for the image to please the graphics folks.

BTW, another issue separate from dpi and pixels is file size (sure dpi and pixels factor in but less directly than most folks think) if you convert your raw images into jpegs you will get a small file size. If you want to have big file sizes for submission to publication I recommend saving as tif files. Since most of my digital work is intended for print publication rather than large fine art prints and is likely to receive little or no post processing, I almost always shoot jpegs. Take that small jpeg file and save it as a tif and it becomes 10 times larger without changing pixel or dpi count. So if the pub you are working with wants big files, send 'em tifs. Yes, I know raw is somehow better, but I only measure by the checks they send me for sold images and I hate computers with a passion (5 computers in my house and I had a PC before Windows existed so my hatred is based on familiarity not fear) so I have no reason for shooting raw. My fine art prints are generally shot on medium format film...different game with different feel. In the recent past, shooting slide film for publication taught me to shoot it right in-camera, then PP is almost irrelevant.

[tonyrodgers]

I had an experience like this when ordering a canvas print from a clueless photography franchise in Australia which I won't name. They proudly told me my default DPI was wrong (at 72) , but "Don't worry we fixed it - we printed it at 72, then scanned it at 300".... The print looked absolutely crappy. Needless to say I don't go there again

[ChrisJ]

Graphics designers no nothing of pixels, DPI is the printer resolution, PPI is the resolution when the file is on a computer and the data in the file will be arranged to in the file that you send to the printer. Different hardware, different drivers, different way of working, different standards. DPI and PPI are NOT the same thing at all.

When the file is on your computer it's in PPI, PPI works by altering the size of the pixels. You set the size you want the image to print using PPI on your computer and the printer will print it at whatever DPI it is set to.

As an example some of my images are used on the side of buses, for a double decker bus they need to be 3Mt's (10ft) tall. If I was to to interpolate the images to be that large at 300ppi the file size would be measured in Gb, there would be more interpolated (invented) pixels than genuine data, most of this would be dumped by the printer driver, so the image would be chronic.

All of my images for this use are at 50ppi, yup just 50ppi, this means that the pixels on the final print will be just 1/50th of an Inch square. not noticeable even close up.

The only constant across all hardware platforms is file-size. there is a 'rule of thumb' formula that has served me well which is 1Mb of file size for every Inch of print size on the longest edge, So for my bus pics which are 10ft (120 Inches) the file size needs to be around 120Mb, that's what the printer driver would reduce the file-size to, if I were to give it the huge file set at 300ppi, most of the data would be dumped.

So I interpolate my image in PS up to just 120Mb which is around 50ppi the actual figure depends on how many pixels you have to start with and how big you're printing, the larger you print the less ppi you need. This ensures that the minimum interpolation required is used.

Photoshop even has a tool for doing it. You go to File>New and set up a canvas for the print resolution and size, for my bus example this would be 100 Inches vertically by however much the width is (my bus images are usually in portrait and the vertical edge is the longest), you then alter the PPI so the file size is around 120Mb and click OK.

In Bridge you highlight the image your going to use and go to File>Place>In Photoshop. This will place the image in the centre of your canvas with the Transform Tool already selected, then, holding down the Shift key to maintain Aspect Ratio you drag the 'Anchor Points' to fill the canvas with the image (or part of the image) you want. Hit Enter. Sharpen to taste.

This will ensure that the minimum amount of interpolation is used, when you Flatten and Save the image the file-size will be 120Mb which I know will print perfectly. I always save as a 16bit Tiff as that can store all the data, an 8bit file might have to dump some due to the file being overfilled, 16bit can also save in the wider gamut of the Adobe Colour space, but for that the printer must have the extra red and blue cartridges required.

You send this file to the printer which will print it at whatever DPI it's set to, dpi is a compromise between ink usage, printing speed and quality, the Fuji printer the print lab uses is set to 240dpi. And they print perfectly.

Needless to say all my start images are Raw, this has never worked too well with Jpeg start images, there is just not enough data.

Chris

[Asha]

ChrisJ makes a good point--the output device is the ultimate driver for file size/resolution/dpi/ppi/whatever. Print designers usually want "300 dpi" since it works well for offset lithography. A web designer would rather have "72 ppi" since that is display resolution. All at the appropriate linear dimensions, of course.