Recent volunteer work for an exhibition on large size printing work allowed me better understand of digital files and final print output. There’s more galleries or exhibitions today are acceptance to inkjet printing with it’s fine and flexibility output. While inkjet technology today give a huge advantage over the large-scale printing, an advanced amateur photographer who wants to make the large print may still find themselves trapped in the image size limit of what Digital SLR provide today.
The confusion laid with a traditional misconception of the DPI requirement. More often the printing house will require a 300DPI image resolution, it’s true for colour separation printing process but unnecessary for inkjet printing.
Those who shoot in digital, should know that the camera always give you the same image resolution (X pixel x Y pixel) under the same model, for example a 10 megapixel camera will always deliver you an image of 2592 x 3872 = 10,036,224 (10 million pixels, there’s where the 10 megapixels came from) with marginal different, depending on brand and camera model.
So, how big can you print if you have a 10-megapixel image (without cropping)? Here is where the DPI information steps in, DPI determine the scale of print output by how many pixels are compressed into 1-inch print out (Dots-Per-Inch). In traditional colour separation process (like a magazine, books, brochure, etc.) the minimum requirement of 300 DPI is to ensure there’s no printing dot to be seen with naked eye.
Here’s the way in Photoshop you can easily find out your print size with your image files. Under Menu > Image > Image Size, with the dialogue box, uncheck the Resample Image, enter a value in DPI and it gives you the dimension (you can choose either inch, cm, mm or other information you required under the drop-down menu). Alternatively, you can also enter the value in the dimension box and the DPI information change accordingly, they are linked respectively. The reason for you to uncheck the Resample Image is to ensure your image is not being manipulated, but only extra information is embedded and given to the printer while printing an image.
For example, if I would be required a 300 DPI output for my print requirement, 10-megapixel image files will allow me to print up to 8″ x 12″, or if I must print for 16″ x 24″, then my DPI resolution is only up to 162 DPI.
So now, what is the minimun requirement for the inkjet printing?
While you can say that the more dots get together into an inch space, the clearer your image will be, but it should depend on how the photo being presented. With large print, your audience is feet(s) away from your photo, the requirement of the DPI can be lower compared to book or magazine where the audience are inches away while reading or looking at them. Furthermore, inkjet printing using different technology compare to colour separation processing, thus the requirement shall be different.
From the experience, inkjet printing are safe to print with
162-165 180 DPI and can’t be notice by naked eye while hanging on the wall during exhibition. Of course if your image are larger, you may have more flexibility to get a higher DPI, but for an exhibition, 162 180 DPI is sufficient good enough (but not the best of course).
Now you have a better understanding of the printing requirement. So it comes with the next question, what if, you want to print something beyond your files can handle? In this case, we can’t escape from image manipulation. There’s a lot of software allowed you to do that, some claims to be better than the other and I don’t want to make a review on any of the software (there’s even some brand of the printer claims to do a better job while using the printer built-in manipulation mechanism). For sure, quality will be suffered from the image manipulation, something we need to face it realistically.
I just want to share with you about Lightroom and why we should always shoot RAW. Beside colour tweaking, change of temperature colour and retained the highest quality, there’s one most important factor that least discussed was enlarging manipulation (not that you want to do this but it’s when you need it). Because of the information amount retained in RAW format, you will benefit from it if you need to do enlarging work, you will never know when you need this, for this reason, it’s wise to always shoot in RAW format.
As for Lightroom, it allowed you to decide how big you want to export the files, anything larger than original, Lightroom will use Adobe’s algorithm to enlarge it. I found it very simple, easy to use and the result is finest. Here is the sample of images compared direct output from Lightroom and enlarged image size in Photoshop, both are double the size of original which is the 3rd image, they are all 100% crop.
Hope this information helps you and don’t just store your image on the hard drive, print it big and admire yourself for your wonderful photo :)