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Resolution and The Secrets To Better Prints From Digital Images
|By Josh Austin and David Fleet|
It's time to take a look how to set resolution for images that you intend to print. This is one of those subjects that can throw people a bit, so we'll keep things nice and simple. Once again, I've recruited the help of professional photographic printer David Fleet, to help keep you on the right tracks.
We've seen (in previous articles) that there are lots of things which impact how good your photos turn out. Things like lens quality, post-processing and color management are all essential. But setting resolution is a crucial final step, determining how large and with what level of detail you can print your pictures. Let's find out more...
What Does Resolution Mean?
Low resolution/ppi (Pixilation, ughh!)
So let's start at the very beginning! Resolution is the level of detail, which is defined by the number of pixels. Pixels are the individual elements ('picture elements'), that make up a photo.
The number of pixels a photo has, its resolution, depends on how many pixels your digital camera has on its sensor. 1 million pixels is 1 Megapixel (MP).
So, obviously, the more pixels on your camera's sensor the larger its photos can be printed at an acceptable resolution (before the pixels start to become too visible: 'pixilation' - see the right hand apple).
So, how is resolution measured for prints from digital images? PPI, which stands for pixels per inch. The more pixels to every inch of photo, the higher the resolution and detail.
(If you're really interested in pixels, check out this article: What is a Megapixel?)
How Many PPI Should My Photos Have?
(This image had a resolution of 410ppi at A3)
A good rule of thumb to work to is 300ppi for professional quality prints. Anything that you're planning to sell or put up on your walls, I'd suggest printing at 300ppi or more. That will, of course, impact the size you're able to print at.
For general snaps that don't need to be absolutely top-notch, stick to a minimum of about 200ppi. Much less than this and the quality will start to become fairly disappointing.
So that's pretty simple really isn't it? But before you start thinking the higher the resolution the better, just hold up a second! There are 1 or 2 caveats that make the above guidelines a bit less rigid.
Beware The Pixel-Peepers!
You have to trust your eye when it comes to printing. If an image looks really crisp and sharp at a certain size, that's all you need to concern yourself with. Beyond a certain level of resolution it's simply impossible to tell the difference.
But also, give some thought to how an image is going to be viewed. Are you looking to print a really big poster? Worried that you can't keep above the 300ppi or 200ppi limits? Relax, because any loss of detail is likely to be unnoticeable at the viewing distance for large prints. Conversely, small prints will be viewed up close, so it's important that their resolution is kept very high.
Take it from me, if you are ever exhibiting/selling large format prints there will always be that one guy who pokes his nose right up to an image and mentions the quality! This kind of 'pixel-peeping' is totally innane, and the culprits are never going to be your customers anyway!
Native Resolution - Your Printer's Favourite!
Oh yes, there's another little caveat to add to the 300/200ppi rule of thumb: native resolution. All printers have a specific resolution at which they perform best, their native resolution. For Canon this is usually 300ppi and for Epson it is 360 ppi.
It's generally best to output files to your printer in multiples of these resolutions for absolute optimum performance. So, if an image of mine was 260ppi I would up-res (increase the resolution) the file to either 300ppi, on a Canon, or 360 ppi on an Epson.
It's really easy to do that in your post-processing software. I use Lightroom, where I just type in the required ppi number into the print resolution box on the print job tab.
For Photoshop users, simply go Image>Image Size and increase the image resolution to the desired number. I would also recommend choosing the Bicubic Smoother option from the drop down menu at the bottom when making images larger.
What to do if your image already has a resolution that is higher than the native resolution of your printer? Well, it's often best to up-res your file to the next multiple of your printer's native resolution, i.e 600ppi for Canon or 720 ppi for Epson.
Finally, Choosing Quality Settings
So, you've gone to all the trouble of ensuring your colours are perfect and of feeding files to the printer with optimum resolution. So what quality settings are you going to choose? The highest, of course!
To do this, go into your printer driver and choose the top quality setting from its menu. For Epson printers this is generally called Super Photo, or 2880x1440 dpi (dots per inch). This ensures that your printer uses the smallest possible ink droplet size to give the finest detail and smoothest transitions between colours.
You'll often see an option for printing at high-speed. In my experience this can be a tad detrimental to quality, so it's usually best to disable it. The placement of ink by the printer just seems more accurate at normal speed. But this isn't true 100% of the time. I find that my Epson Stylus Pro 7900 is just as accurate at high speed. But then, my Epson Stylus Pro 3880 doesn't perform so well. If in doubt - test!
What Else Matters? A Quick Reminder
Here's a quick re-cap of some of the other key things that impact how your photos turn out. Click the links to read the full articles:
Lens quality - The quality of glass that you use significantly affects the clarity and sharpness of printed images.
ISO speed - The lower the ISO speed, the less noise/grain will be visible in images.
Color management - A real biggy this! Everyone who creates prints from digital images should use a color manged workflow.
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