A lot of people who are serious about photography get confused about printing, you know why? Because it is confusing!
What type of file should I use to print from?
JPEG or TIFF ? To answer this question we need to look at the difference between the file types.
JPEG stands for Joint Photographic Experts Group. This group was formed in 1986 and in 1992 they released the first version of the JPEG File Format. Essentially, what the JPEG file does is compress the RAW image – it maintains a high level of detail, whilst being about 1/2 the size of the RAW file. So, a lot of photographers shoot in JPEG rather than RAW, either because they think RAW is to hard to work with or simply want to save space. So, in-camera, the image has been reduced by the JPEG algorithm (an algorithm is a set of programming rules that can be followed using different data). So, what happens when you edit a JPEG and then re-save it – if you re-save it under the original filename, it again compresses the file – making it smaller again, and a little more detail is lost. If you re-edit and save again using the same filename, again it compresses the file and more detail is lost and so on. JPEG is what is termed a “lossy” file format.
On a computer screen, this doesn’t matter so much (to a point) but when you print, you want the best quality you can get. The reason why it doesn’t matter so much on a screen is that your screen resolution, even on a large screen, is probably no more than 1920×1080 – the original image is (on a Canon 60D) is 5184×3456 – so even heavily compressed, you are still going to get a decent resolution on screen.
TIFF stands for Tagged Image File Format and was originally introduced by the Aldus Company in 1986 and was very popular for “Desk Top Publishing”. In 2009 TIFF was taken over by Adobe and has no major improvements since then. TIFF is widely supported by image-manipulation applications, by publishing and page layout applications, by scanning, faxing, word processing, optical character recognition and other applications. TIFF (generally) is a non compression file type – or “lossless”. This means that a TIFF file can be edited and re-edited without any loss in detail – making it an ideal file format for printing.
So, in answer to the original question, which is better for printing – TIFF without doubt. Most professional printing outfits will recommend a TIFF file format created with at least 240 ppi (pixels per inch)
DPI and PPI
In printing, DPI (dots per inch) refers to the output resolution of a printer or imagesetter, and PPI (pixels per inch) refers to the input resolution of a photograph or image. DPI refers to the physical dot density of an image when it is reproduction as a real physical entity, for example printed onto paper, or displayed on a monitor. A digitally stored image has no inherent physical dimensions, measured in inches or centimetres. Some digital file formats record a DPI value, or more commonly a PPI (pixels per inch) value, which is to be used when printing the image. This number lets the printer know the intended size of the image, or in the case of scanned images, the size of the original scanned object. For example, a bitmap image may measure 1,000 × 1,000 pixels, a resolution of 1 megapixels. If it is labeled as 250 PPI, that is an instruction to the printer to print it at a size of 4 × 4 inches. Changing the PPI to 100 in an image editing program would tell the printer to print it at a size of 10×10 inches. However, changing the PPI value would not change the size of the image in pixels which would still be 1,000 × 1,000. An image may also be resampled to change the number of pixels and therefore the size or resolution of the image, but this is quite different from simply setting a new PPI for the file. (source: http://en.wikipedia.org/wiki/Dots_per_inch )
This is an area that can take a lot of study to really get to understand it – needless to say, whatever the PPI your professional printer wants – give it to them!
Cropping an Image
I often hear “I sent this image away for printing and the printer cut of a part of the image!” The image size on my Canon 60D is in a 3:2 format. If I print to a 10″x8″ print, this is a 5:4 format – I either have to crop my photo to a 5:4 ratio or reduce the printed are to fit the whole image on the photograph.
The aspect ratio of an image describes the proportional relationship between its width and its height.
It is commonly expressed as two numbers separated by a colon, as in 16:9. For an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this same length unit, the height will be measured to be y units. For example, consider a group of images, all with an aspect ratio of 16:9. One image is 16 inches wide and 9 inches high. Another image is 16 centimeters wide and 9 centimeters high. A third is 8 yards wide and 4.5 yards high.
In still camera photography, the most common aspect ratios are 4:3, 3:2, and more recently being found in consumer cameras 16:9. Other aspect ratios, such as 5:3, 5:4, and 1:1 (square format), are used in photography as well, particularly in medium format and large format.
- 2:3 – 2×3, 4×6, 8×12, 16×24, etc.
- 4:5 – 4×5, 8×10, 16×20, 24×30, etc.
- 5:7 – 5×7
- 1:1 – a square. Common sizes are 5×5, 12×12, 20×20
This is obviously not an exhaustive treatise on printing, but I hope this makes it a little bit clearer. In summary, it is the Aspect Ratio of an image that determines what the best print size is. If the aspect ratio of the image doesn’t fit the aspect ratio of the print, then you have to either crop your image, print with white space around the image to fit it all in or lose some of your image.
Confused? I hope not, but if you are, then Google is a great tool!