In The Desert
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Let's dispell a couple of misconceptions right away. Changing the resolution or DPI (Dots per Inch) / PPI (Pixels per Inch) will not change the size of the photograph that you view on the Internet or on your computer. It only changes the size of the photo as perceived by the printer. Other wise it's no different whether it's 72 PPI or 300 PPI. See the images below.
Another thing, some imaging programs call it DPI (Dots per Inch) and some call them PPI (Pixels per Inch) Either way it doesn't matter for anything except the size of your print. To prove this, here are 3 examples of the same photograph.
Photo on the left -- 72 PPI
Right -- 160 PPI
Photo on the left -- 300 PPI
Here's the difference. If you sent the 3 images above to the printer you'd get three different sized prints. The 72 PPI photo would be the biggest print and the 300 PPI would be the smallest print. I know, it sounds like it should be the other way around. But think of it this way -- you take this image and squeeze it to a 1 inch size -- to do that you have to squeeze the pixels closer together. Most all cameras produce an image that's 72 PPI - that's 72 pixels across a one inch space, now you take it and squeeze to 300. You've made it smaller by squeezing it. And once again this is only for the printer, as you can see above they are all the same for viewing, and in fact are the same file size 32.6 KB. Some of you are going to look at this and think it's too technical -- don't! All you need to get from this is that when you make it a higher pixel density -- say 300 your printer is going to look at it as a smaller image. Period. See the example below.
This is exaggerated to show you the difference. The small image to the left is a crop from a larger image and it's shown at a 1 x 1 inch size. Below you'll see what will happen if you try to enlarge this small crop and print it at 72 PPI (exaggerated). Now if you started off with a bigger image and changed the PPI to 300 (like the lower one) this is what your printer will see. You don't want the pixilation (jagged edges) - this is exaggerated to show what will happen if you try to make too large a print or you crop and try to make a large print. Bear with me here, this is just the basics, the good stuff is coming. We're going to show you how to avoid this and get nice prints that fit the printer
paper your using. It's easy if you print the charts we have here.
This formula will tell you how big you can print your photos safely, without the pixilation. Why do you need a formula? Because all cameras have different size sensors, starting with old ones at 2 megapixels to the new ones with sensor sizes as high as 24 megapixels. The more pixels you have the better it is for making a large print. There are other variables that will affect this, like the quality of your lenses or camera sensor quality, but we're not going to get into that. This will give you a good approximation for what size you can print a photo. And it's simple:
For this example we'll use the native size of a 6 megapixel camera -- all you have to do is substitute your camera's native image size to use this formula. On our 6 megapixel camera it takes an image that is 3072 pixels by 2048 pixels.
Back to the PPI (pixel per inch). 200 being the minimum and 300 or more being optimal. It's simple, see the figures to the right.
3072 divided by 200 = 15.36 inches
This is the largest size you should print with this pixel count from a 6 megapixel camera. An 8.5 x 11 would work nicely, or any smaller size.
3072 divided by 300 = 10.24 inches
This is the optimal size you can print from the same camera. Your print will show more detail, contrast, and you'll have a better quality print.
Once you know you camera's native pixel density, you'll know what the largest sizes are that you can safely print. Once again there are variations invovled here, printer quality, camera, lenses, etc. Be aware, the higher your PPI for a print the more ink your printer is going to use.
How big a photo can I print from my camera?
Now these are just good guidelines. I have printed large photos going as low as 150 PPI and they turned out fine, but they were not professional quality prints. It depends on what you want the prints for. Are you just showing a couple friends the photos or are you going to sell them or frame them to hang on the wall. Also keep in mind that the quality of the paper you print on matters here too. Glossy will give you more detail and also give you reflections while matte will loose a little detail but it will not be as reflective. You should know that using the right brand of printer ink can make a big difference. If you have an Epson and you want great prints, then use Epson ink. Other brands, and refills will most likely not give you the best quality. Less expensive printers may not give you as good a result as the more expensive ones.
Do you have to Resize or Crop the photos?
Not for all. It will depend on the native size ratio of the image from your camera and the size of the print you want to make. A 4 x 6 print has a ratio of 1.5. If you divide 6 by 4 you'll get 1.5. In other words the 6 inch side is 1.5 times bigger than the 4 inch side. Now we have to see how this works with your camera's native pixel size. See the chart below. You should print this out for later use.
Taking the example above -- lets make an image the right size to print an 8 x 10. If you try to divide the width (3456 pixels) by 1.25 you find it gives you 2764.8. Do this with a caculator. Now you can't do this because you only have 2304 pixels to work with on the height of the image. So start at the heighth side of the image ((2304). Now just take the 2304 and multiply it by the 1.25 and you'll come up with 2880. You have to crop the 3456 side to 2880 and you'll end up with an image that's 2880 x 2304 which will work perfectly for an 8 x 10 print size. This is not really hard or time consuming once you get used to doing this. Some printers will take an image and do the cropping for you, but they most likely won't give you the option of what to crop.Some will also leave you with white borders on the top or sides. If you crop using this method you'll either have an even white space around the edge or if you print borderless then this way it will fit perfectly. This is a much safer way to make a print -- with you controlling the output.
The other alternative, which is not a good one, would be to resize the print in your imaging program to the size you want, say a 4 x 6 and then print it. Resizing it resamples the image. What this means is that the program throws away information (pixels) to make it smaller while at the same time giving you the correct size but it'll still be at 72 PPI, so the outcome will not be very good. If your using an 6 megapixel camera or larger you could have printed it at 300 PPI or larger and this would produce a great print. The one printed at 72 PPI will be a less desirable option and the detail loss will be noticable..
To do this you'll need an imaging program that's capable of changing the resolution (PPI) of the image. Then you have to raise the PPI to get the desired size for the printer. This will take some trial and error to get the settings for your camera for different sized prints. Once you have them written down it's easy and fairly fast to get great prints.
Other Printing Options
This may be the most important part of this article, at least for those people that are just now thinking about printing their digital images. Or if you're tired of messing with all this, buying ink at an outrageous price, photo quality paper, and top of the line printers -- there are good alternatives. Online printing services!
The quality of most of these services is excellent and it's a lot less expensive than doing it yourself. If you do it yourself, you may have a little more control over the final output, but you also have to live with the ones that don't turn out. To do it yourself correctly you really need to calibrate your monitor and add the profile to your printer so you get an exact color match. The cost of the ink alone makes it undesirable. But we sometimes like to crank out a few 4 x 6's in a hurry, and the only way you can do that is with your own printer.You can get 4 x 6 prints from most places online for $.15 cents a print, and 8 x 10's for $2.99 a print. For the cost of a $100 printer you could have over 600 - 4 x 6's See the list below.
Photobucket: Prints done by Kodak, sent by mail or picked up at a Target store near you.
15 cents for 4 x 6 $2.99 for 8 x 10's - cups, mousepads, etc. available for your prints.
Also the best photo storage site on the web. We use and highly recommend Photobucket.
Shutterfly: prints, cards, photo books, calendars, and gifts. Their prices are competitive and this company has been around for a long time. Reliable, well known, and excellent quality.
Mpix: Color - B&W prints, books, greeting cards, frames, and more. A lot of options for peint papers, quality, and prices of smaller sizes are a little higher, larger sizes are less expensive.
Printing your own photos can be - fun, stimulating, irritating, and sometimes just frustrating. If you find yourself in this situation then look at having them printed on line. If you like a challenge then get a printer, a monitor color calibrator, and all the other epuipment and supplies you'll need and learn how to print them yourself. Have fun....