May 17, 2011
by posterjackcanada
Printing digital photos in large sizes is becoming increasingly popular. It’s no wonder that popularity is on the rise because when photos are printed large, the results can be spectacular. With recent advances in printers, digital cameras, and software; photo enlargement results are better than ever before. But before you dive in, if you want to get the very best results it helps if you understand the details.
First the simple stuff
First, when shooting with a digital camera you want to capture as many pixels as possible so that you have the most resolution available. While having lots of resolution will not improve your composition, focus, sharpness or clarity – if you are lacking resolution, your options for printing large photos becomes very limited.
To ensure that you are getting the most resolution, choose the highest quality setting in your camera’s menu by finding the “image quality” option and selecting Large.
Some digital SLRs allow you to shoot your photos in multiple formats at once, such as RAW and JPEG. A lot of photographers prefer to manipulate their images in RAW, but be sure to save it as a high resolution JPEG or TIFF before printing. Most photographers feel more comfortable with TIFF because of image compression. While it is true that TIFF trumps JPEG, the differences usually aren’t noticeable to the human eye when the images are printed large. You will just have to trust us on that one!
How low can you go?
So what happens when you have an amazing photo with low resolution? Can it still be enlarged? While it is possible, there are definitely a few things to keep in mind. First off, photos with soft curves, soft colours and smooth lines will work best. Photo enlargements are generally viewed from a distance, so it might not be a huge deal if there is some pixelation in a landscape shot. However, portraits should be avoided at all costs – there is nothing nice about a big pixelated face.
The 300 dpi question
The million dollar question for many photographers is whether they should digitally enlarge their photos using software tools before going to the printers. People are often taught the rule that they need 300 dpi. They treat this like some type of photo printing holy grail. The truth is that it is rare to attain 300 dpi when printing a photo in large proportions, as most cameras can’t produce an image with enough pixels. (keep reading below for a more detailed explanation on what dpi actually means)
So should you try and artificially make your image 300 dpi?
The answer is NO. First some terminology: ‘re-sizing’ generally refers to changing the set dimensions of an image, but the overall pixel count remains the same. In order to add pixels, you must ‘re-sample’ the image.
Let’s be clear – any re-sampling to add pixels will degrade your image and cause unwanted effects such as rough edges, changes in colours, pixelation, and fuzziness. However, if you must test this out for yourself, there are tools in most software packages such as Photoshop that allow for image re-sampling that anyone can experiment with. If you are serious about re-sampling and are stuck with low resolution images that need to be enlarged – you should buy a tool like AlienSkin. These special tools are designed to do the least amount of damage to the image and provide more control over the sharpening effects and the reduction of compression articles.
Not more than once
A final basic (but very important) tip about resizing images is that you should only resize an image once from the original file. Some people think they can do a series of smaller re-sampling maneuvers to lessen the negative effects. The truth is that re-sampling programs already have built in algorithms that are far superior to this approach. Re-sampling an image that has already been re-sampled will lead you down a slippery slope. If you need to create multiple re-sampled image sizes from the same digital image, start each re-sample process from the original image file.
What is this dpi you speak of?
Dpi is a term that confuses pros and amateurs alike. The major misconception stems from the double usage of the word. There is; 1) The dpi used to measure the capabilities of a printer, 2) The dpi that is used as a measurement ratio for digital photos and images. The dpi of the printer itself is not important for this conversation, so let’s concentrate on your images.
The dpi of a digital photo or image stands for ‘dots per inch’. That means that it is a useless measurement unless you know the inch part. The inch measurement denotes the print size (like a 16” x 24” print). See, isn’t it all starting to make more sense now? (so next time someone tells you their photo is 300 dpi, you can ask them – at what print dimensions sir?)
To put this in perspective, every little dot (pixel) will make up the printed image. Now imagine a line an inch long – if you could fit a three hundred little dots across that length you would be able to make an image with great detail. If you had only 10 little dots to fill in that inch, you would have a very rough sketch.
There are some detailed calculations below which you should try with your digital photos, but to start you need to be comfortable with finding the pixel length of your image. You can look at the properties of your image file from any file folder system, or you can call up the information in Photo Shop or other graphic editing tool. If you have dimensions like 3000px by 4000px you know that you have a 12 Megapixel image (3000 x 4000 = 12,000,000). If you have something like 200px by 300px, then you know you are in trouble as your image is way less than a Megapixel (or 1 million pixels). Generally you want at least a 3 Megapixel image, but today’s cameras are going to give you a much bigger image than that (if you have the image quality set to High/Large).
So how do you calculate the dpi of your image with respect to the image size you want? The following calculation shows how to compute it: (If you aren’t into this type of thing, you can upload your photo at posterjack and they will give you a quality score based on this calculation – nice and simple!)
A. Take the square root of the product from the pixel length and width of the digital image: A = SQRT(Lpx*Wpx)
B. Take the square root of the product from the length and width in inches of the desired print size: B = SQRT(L*W)
C. dpi = A/B
Lets try an example from that 12 Megapixel photo from above:
A = SQRT (3000 x 4000) -> A =3464
B = SQRT ( 24 x 32) -> B = 27.71
dpi = 3464/27.71 -> dpi = 125
The results are in
Ok, so we started with a 12 Megapixel Image and printed it at 24” x 32” and the dpi is only 125! Isn’t that going to look terrible? Actually no, the results will be VERY good. Why is that? There are three main reasons:
- When you print an image large, you look at it from farther away, so the detail looks just as crisp as when you look at a smaller image right in front of your nose.
- The RIP software that is used to tell the printer how to print your image is very advanced and does a tremendous job of enlarging the prints on paper.
- Your photo is a really high quality image taken with a quality camera and a skilled photographer. The better the photo, the better it will look at any size, especially large!
So, what is the rule of thumb for the optimal dpi when printing an enlargement? Although no hard and fast rule is available, if the photo itself is high quality, you can probably print at much less dpi than you previously thought. If you are pushing up into the 20” x 30” range and above, having 100 dpi and sometimes less is going to be just fine. Don’ t be scared!
The best thing to do is experiment; first try printing some of your favourite images in large sizes on an inexpensive medium like photo paper. When you do this, try printing the same image in three different sizes so that you see the difference and make note of where you think your personal threshold sits. Once you are more comfortable with the process, you might want to try some different mediums such as printing on canvas.
I hope that you enjoyed reading this guide. If you have more questions, be sure to contact us and we will happily answer your photo enlargement questions.
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