These days it’s rare for me to produce a print for a client; almost everything I do is sent electronically, either direct to the end user of the image or to a publisher. Downloading or uploading an image from or to the internet, sending by email as an attachment or transferring via ftp, raises the subject of size, and believe me, size matters.
In an earlier post, (click here) I explained about resolution but that’s only half the problem. Whatever the resolution, high or low, the size of the image is important for two reasons; how easy it is to transfer or send and how big an image you want to produce from the digital file. The problem was more acute before broadband but as ever higher speeds have become the accepted norm, so to have file sizes as cameras become more sophisticated and images sizes that were once the preserve of the professional camera are now commonplace on consumer models.
My first question to clients now is not “What do you want pictures of?” but “What do you want to do with the pictures?” There is no point in me sending a client digital images with a file size of over 7 megabytes if they want to use them on their website or send them to their clients as email attachments. It’s equally pointless sending them files compressed to a few hundred kilobytes (making them easy to send) if they want to use them for display prints, as the background for an exhibition stand or include them in a quality magazine.
Like most professional photographers and serious amateurs, I shoot all my pictures in RAW format. While this gives me the greatest possible latitude when it comes to making any adjustments, it also means that the files are huge (typically around 24Mb) and can only be read using specialist software. This software makes it possible to convert images to a more universal format like JPEG once (and if) any adjustments have been made. It also enables images to be saved in whatever size is required.
A RAW file (think of it as the digital negative) can be used to produce a JPEG measuring 24″ x 16″ at 300 dpi – a file size of 14.7 Mb or a 6″ x 4″ JPEG at 72 dpi – a file size of 128 Kb, no prizes for guessing which would be easiest to send as an email attachment and which would be best for a big print to hang in the reception area.
However, it doesn’t end there. The above examples are based on images being sent or used ‘uncompressed’ i.e. at the best possible quality. It is possible with some basic software (eg Photoshop Elements) to compress an image by saving it at a reduced quality level. As an example, a high resolution image, measuring 12″ x 8″ and saved at 300 dpi would have a file size of 6.46Mb at maximum quality (12). By compressing the same picture by 25% and saving at 9, the file size is reduced to 1.35Mb with little discernible loss of quality. At 75% compression, or quality level 3, the same image is only 368Kb and while the quality may be lower it would only be noticeable if the image was enlarged.
The way the software compresses an image is the subject of a more technical discussion (not here) but for practical purposes the important thing to consider is what images are going to be used for and how they are going to be delivered. For convenience, I usually give clients four options ranging from thumbnail to the full uncompressed size and they can select what they want when they download their images from the website.
If you plan on taking your own pictures or are considering engaging someone else to take them for you, take a while to think about what you’re going to do with them and remember that size does matter.