Wednesday, 11 April 2012

Taking a picture to print: PART II – colour

It may sound silly, but when working with colour images, one of the most important things is to get the colour spot on. Nobody wants to end up with an image showing purple grass or yellow trees (with the possible exception of D.Hockney). There are different processes (both in camera and in post-production) that can have a dramatic influence on the colour of your final print/image and while it may not be in your interest to learn and understand all the related technical jargon, it's fundamental to know how they affect your image and how to control this.

In Camera

For almost all photography, the trick to creating great images is making sure that you've made each step along the way as easy and quick for yourself as possible, starting in the camera. Even before pressing the shutter, you should have gone through the menu and set the camera up for the type of shooting you want. This includes controls for choosing between jpg/RAW, metering modes and importantly, colour space and white balance.

Colour spaces are models that are used to represent colour using quantifiable values of Red, Blue and Green. There are two colour spaces available in the camera: Adobe RGB and sRGB. If you wish to know more about these, then there are some very in depth blogs and websites that will go into much greater detail. In the interest of time, here is a brief overview. The 'S' in sRGB stands for standard and as such, it has become the standard colour space for image display. Adobe RGB was designed to encompass a broader range of colours, aiming for most of those achievable on CMYK printers. So Adobe RGB has more colours, sRGB can represent finer shades of colours. This is about all you need to know. Almost all photography work is done using sRGB because it is universal and compatible around the world. Unless you have some special need for it, are controlling all post-production and are in direct contact with your printers, Adobe RGB is not for you.

Now you have your colour space sorted, it's time to correct your white balance (WB). In order to achieve the most accurate representation of the real world colours, you need to work out what the primary source of light is and it's temperature (temperature is just another word for colour –hot being redder and cold being blue). There are different types of lighting, but the three most common are tungsten (red-orange), fluorescent (blue) and daylight. To make your job easier, try not to mix different temperatures of light or you will find it very hard to balance the colour of all the elements in the image. In the event that you require another source as a fill light, try a flashgun with a complementing coloured gel. On some DSLR's, it is also possible to set your own custom white balance, and for this, you need a white surface to act as a reference colour. Generally, I just shoot on auto WB and make any small adjustments in Photoshop. In some instances, when I find that auto just isn't having the required effect, I might change it to one of the presets, but it is rare for me to need a custom WB.

Post-production

Assuming that you've been shooting in RAW/sRGB and have kept to good shooting practice, your photos should need minimal adjustments. I try to keep mine down to adjusting levels, colour balance, contrast and possibly adding a vignette. Exceptions to this include exposure comps, long exposures and HDR shots.

You may be patting yourself on the back now, thinking that you have negotiated your way through all the hurdles that have been flung in your way, but in fact there is one final test to champion. This is the part of the process when you need to work out what final output you are looking to produce and it's destination. You may want to upload your photos to a photo sharing website like flickr or 500px and have them scrutinised by your friends, enemies and total strangers. Alternatively, you may want to print them out and post them in a scrapbook or up on display for everyone to see as they walk into your room. Once you do this, you will be able to decide whether you want to export your images as CMYK or RGB.

CMYK and RGB are both colour spaces that are used to represent images in various formats. CMYK is the colour space used in printing and stands for: Cyan, Magenta, Yellow and Black. These colours are related to the process by which colour is laid down in printing. If you have the chance, try looking at a photo in a book or a magazine with a magnifying glass and you will see that it is made up of loads of little coloured dots (some colours/text may not be made up of dots, but a constant layer of colour, but these use a process called spot colours, which cost a lot more and are not appropriate for printing photos). RGB stands for...you guessed it: Red, Blue and Green. Initially, RGB was initially created to closely resemble the colour perception of the human eye, but now it is used as the standard colour space for all electronic devices, including web.

When sending images to print, always make sure your images are CMYK and 300 dpi (dots per inch – located under Image Size in Photoshop – consider whether you want to resample image, as this will change the number of pixels in the image and will affect the file size considerably). As I said in my previous post, try to export in jpg, as this will reduce file size and cause less confusion when sharing.

When editing on the computer and uploading images to the web, make sure your images are RGB and 72 dpi.

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