As a 21st century quiltmaker with a digital camera, a blog, a website and occasional publication in the print media, I find it useful to understand the difference between low and high resolution digital images. More importantly, in order to better communicate with the viewers of my quilts, it is essential to understand the optimum resolution and file size requirements of different mediums.
To understand what I am getting at, just think how offputting it can be to come across a website or blog where the photos take F__O__R__E__V__E__R to load onto the screen. Typically what has happened, is that the owner of that site has taken a bunch of photos with their new, you-beaut multi-megapixel camera and simply posted the photos with no regard to the reader (especially those on dial-up) or even their own bandwidth bill. Another common scenario is where the site owner has made up a personalised banner-image but the file size is excessive.
Multi-megapixel cameras take high resolution images with a large file size for each image. This is great if you want to make a poster size print to put on your wall but it is not so good for posting online.
Conversely, I have seen cases where quiltmakers have been disappointed to open a newsletter or magazine and to see that their beautiful quilt photos have somehow become pixellated and fuzzy in the printing process. The problem, invariably, is that the photo was not prepared at 300 dpi (dots per inch) resolution at the size it was printed.
This information sheet Understanding DPI and Pixel Dimensions prepared by www.iprintfromhome.com explains how prepare your images for print publication purposes. (This was the company I used when I needed some slide images of my quilts to take to the workshop I did with Nancy Crow. I was very happy with the results.)
This collection of online tutorials shows you show you how to rotate, crop, resize, and batch process your images for optimum use on a web page.
Kim says
72 dpi is optimal for web photos; 200-300 dpi is what you use for printing (the bigger the better for printing). I would say nothing larger than the equivalent to 460 x 460 for the photo on the web. Now, if you want it larger, put it in as a thumbnail, with the ability to click to a larger version – that way your USER gets to decide if they want to wait for the picture or not; not being forced by the owner of the website/blog. I tend to put a 300px thumbnail with a link to a 700 px larger scale photo.
Monica Johnstone says
If the discussions of pixels and dpi tends to make your head swim, it may be useful to get the hand of it with some training wheels. Try opening your high resolution photo straight out of the camera in Microsoft Office Picture Manager (which many people have whether they realize it or not) and click on Edit Pictures. The final choice in the list is Compress. Sellect Web Pages if you want to load it onto your blog or E-mail if you just want a reasonable file size to send to a friend. Then save the compressed version (I often save it with a file name that has Comp at the ned to remind myself).
Hope that helps someone!
Cheers, Monica