Keeping colour looking "reel"istic (ouch) can be tricky.

Colour is possibly the most misunderstood of all the subjects covered so far, and not an easy concept to simplify, but I’ll do my darndiddlyarndest to keep it simple.

I bet you think you know what colour is, but if you tried to explain green to a kettle, or blue to a cat, you’d struggle. And yet, when you create a colour image, your computer and your output device, be it monitor or printer, need to know what the colours are even though these devices are “blind”.

All colours, like anything else in computing, are assigned numerical values which are universally understood, by computers at least, so that when a computer receives images, they should look broadly the same as they did when they were created. As always in computing, there is a “however”.

Here it comes… However, when it comes to photos, not all colours are equal. A picture on one computer can have slightly (sometimes very noticeably) different colours on a different computer. This can be down to the set up of the computer, how the computer’s operating system handles colour, or more than likely it’ll be down to the monitor on which the image is displayed.

Think of the last time you went into a TV showroom. All those screens sitting side by side in the showroom, all displaying the same image  – perhaps of Jeremy Clarkson’s face, or a baboon’s backside (ok, same thing), but have you ever noticed that every screen has a different colour cast? This is because each TV has a different setup, different software and hardware controlling and displaying colour. They’re not all “seeing” colour in the same way, so they each display colour differently.

So it is with computers, and especially monitors and printers. Each has their own idea of what red, green and blue are.

So if you need good control of colour for a corporate print or web project, how can you minimise the colour shift from one display to another? How can you control the colour output for a print project?

Part of the answer is colour profiles. Profiles are little files of information that can be invisibly attached to the photo, and whenever a computer opens that file it will see the information, read it and assign colour values accordingly.

The colour "sail" shows the widest colour gamut, with Adobe RGB nested inside the black triangle.

There are standard profiles you can use, and the two most common ones are sRGB and Adobe RGB (1998). As a rule of thumb, use sRGB for web display. It refers to a smaller range of colours (otherwise known as gamut), and since computer displays can’t display very broad colour gamut, this has become the standard colour profile for web use. For print, a good standard profile is Adobe RGB (1998) as this references a wider colour gamut that print output can take advantage of.

Using sRGB for web images at least gives you some hope that your images will display reasonably well on a range of different monitors.

Using Adobe RGB (1998) on print projects is a good start, but I would always advise you to liaise with the photographer and the printer before pressing the button on an expensive print run. Never send a job to print without getting proofs from the printer first. You may have to pay for proofs, but the cost of a wrecked print job will be far higher.

You also need to remember that profiles alone aren’t the whole story. Your monitor needs to be correctly calibrated if you want to adjust colour in photographs, and calibration is the subject of my next blog. I can feel the excitement mounting already!

I really have had to skim over this subject in a way that would have the experts spinning in their graves (if they were dead). So I’m including some links where you can get more information, and in the case of the ICC web site, possibly more information than would sit comfortably inside a single human head.

Cambridge Colour: http://tinyurl.com/dp6d9

A colour cube thingy: http://tinyurl.com/yg5g89f

ICC – heavy-duty information: http://tinyurl.com/6f8je5

Or, as John Lennon never sang, “You say you want a resolution.”

So to continue with my series on the basics of working with digital images, I’m addressing the issue of image size and resolution. Pay attention at the back.

Let’s start by explaining DPI, which stands for Dave’s Pizza Index. Or Dots Per Inch, I forget which but no matter. What’s important is to remember that the dpi and the image dimensions (width and height) are linked when it comes to file size (the space taken up on your hard drive by the image file), while height and width on their own will only affect the printed or displayed image size. In other words, if you have a photo which is A4 in size it doesn’t matter if you print it at 72dpi or 300dpi, it will always print out at the same physical size.

Where dpi is important is when matching the image resolution to the desired output quality.

For example, images to be displayed on a web page should be set at 72 dpi because that’s the most detail a computer screen can resolve. Newspapers vary, but 200 dpi is ample, while magazines will generally require 300 dpi. Printing on a high-end ink jet printer sometimes works best when the image resolution is set to 360 dpi.

This image is displayed at 300x200 pixels, 72 dpi. A higher dpi would make no visual difference here.

For print purposes, image dimensions (height and width) are measured in inches or centimetres, while web images are measured in pixels.

A large web image might be  around 600 or 800 pixels along its longest side, while a thumbnail image might be 75-100 pixels along its longest size.

These are approximate sizes, but you can experiment to get the size which suits the purpose of your page. Some web services, including blog services like wordpress, will automatically size the image for you after you upload it, but it’s still worth ensuring the image is large enough to display decent quality, but not so large it slows upload. Upload speed and quality will also be dictated by the image compression, which I talked about in the “Jpeg – Schmapeg” article.

One temptation is to take a photo which is very small, and try to “upsize” it (otherwise known as interpolation) to something much bigger, by increasing the dpi or the physical size. All this does is add pixels which weren’t there before, so quality starts to fall off quite badly once you get beyond a certain percentage increase. It’s always best to start with a much larger image and have to scale it down, rather than the other way around. I sort of refer to this in the RAW article, when I say RAW files start out larger and with more pixel detail than jpegs.

Of course if you’re working on an important project, for example a company brochure or annual report, it’s wise to allow the photographer and printer to liaise on the best resolution. At the same time they can also liaise on the best colour space for the images to be saved and supplied in, but colour is the subject of my next blog article, so be patient my sweet, be patient…

Those of you who tuned in for my instructions on baking the perfect meringue, sorry. I ran out of space. Ask Nigella Lawson.

All the articles in this series are being adapted to pdf documents which you can download from the Free Resources section (inside Galleries) of my web site – https://timgander.co.uk/

For some years now, digital has been the default method for capturing photographic images. In fact I haven’t had a client ask me to shoot film in the last eight years, but despite this there still appears to be a lot of mystery surrounding digital.

This handy guide is part of a series I’m writing to help explain some of the processes of shooting and supplying digital images, and bust some of the jargon that might otherwise sound like the teeth-sucking obfuscation of a car mechanic.

I’ll start with an explanation of the JPEG format, which is something you should at least be familiar with even if you’re not sure what it means. You’ll probably know of jpeg as the standard image format you get when you use a compact digital camera.

So what is jpeg? Jpeg (normally seen as “.jpg” on the end of an image file name) is a data compression algorithm. Or in simple terms, it’s a way of squeezing lots of data into a smaller space on your storage device, be that a camera storage card, hard drive, CD etc. You should notice that the file size of the image on your hard drive is much smaller than the stated file size when you open the photo in Photoshop or similar other software. This is because the algorithm is designed to take data away (mostly neighbouring pixels) when the file is being closed, and put data back in when it is opened.

One way Jpeg works is by throwing away information which is repeated in the picture. A good example is a blue sky. The jpeg algorithm might say that since there is a lot of blue in one part of the picture, it can safely discard a percentage of blue pixels, but leave a little note to Photoshop saying “when you open this picture, stick some blue in here mate and it’ll look fine”. So when you re-open the file, Photoshop will see the note and know to fill in the spaces where colour information has been discarded. This system works well, but can lead to strange patterns, sometimes called artifacts, when too much compression is applied.

This image detail shows normal compression.

This version shows over-compression.

The amount of jpeg compression can be set according to different needs and preferences. You can compress a file a lot so it loads quickly within a web browser, or compress it not very much to achieve higher quality for printing.

However, there are pitfalls (such as the artifacts I already mentioned) associated with over compression. Whenever you compress a jpeg, some of the image data is lost so that the next time you open the file it won’t be as high quality as it was before you compressed it. Imagine folding an oil painting to fit it through a letter box. It will never look as good as it did before you folded it.

So used carefully, jpeg is a great way of moving images around and displaying them on web pages, but needs to be handled with care – especially when you want to reproduce images in print.

Personally I shoot all my assignments in the RAW format, which I’ll explain in my next article. Future articles will look at post production, colour reproduction and whatever else pops into my pretty little head along the way.

As with all my blogs, if you have any questions or comments you would  like to make, please feel free to contact me or post a comment here.

If you would like a copy of this article for reference, I’ll be hosting it in the Free Resource section of my web site in due course.

Article and photos © Tim Gander 2009. All rights reserved.

If you’ve read my previous blogs, you should either be starting to understand why you need unique, professionally-taken photos to market your business effectively, or regardless of the advice I give, you’ll blunder on using stock images or ones taken by Anne in accounts who got a rather nice camera for her birthday and after all it’s the camera that takes the pictures, isn’t it?

It is true that modern digital cameras, be they compact or SLR (big chunky ones with interchangeable lenses in case you’re wondering) are capable of stunning results. This has led to a problem for professional photographers who must now compete with the false perception that anything is possible with digital photography.

On the plus side for pro’s though is that while there are a lot of excellent amateurs out there, there doesn’t appear to be a greater number of good photographers than before digital existed, and the only reason amateurs make any dent at all in the professional market is through the sheer number of pictures they take. If you can’t be good, be prolific seems to be the mantra.

Look at it this way: given the number of hobby photographers there are, the amount of time they can spend on shooting any random subject they like and the lack of restraints such as who they’re shooting for, what the brief is or even the necessity to make money from their work, the “infinite monkey” principle has to kick in at some point. This is the theory that if an infinite number of monkeys were each given a typewriter and enough time, eventually they would turn out the complete works of Shakespeare.

Gorillas aren't monkeys, and they're rubbish at typing.

Of course hobby photographers don’t need to turn out anything as specific as a previously created work, or even follow a brief, plus they have more sophisticated brains than monkeys (biting my lip not to say something here…) so beyond opposable thumbs, the monkey gets left behind by the amateur.

However, my point is this. Often when I’m on assignment I get asked which camera I use (never which lens, curiously enough) and how many megapixels it has. Some people even like to tell me that if they had a camera like mine they too could take great pictures. I kid you not, a web designer said this to my face once and still I managed not to use violent force to integrate my camera with her smug face.

In fact I’m always polite in my answer, but the truth is I know I have a Canon 5D but I can’t remember, nor do I care, how many megapixels it has. I don’t care because it really doesn’t matter. What does matter is that my clients can ask me to arrive on an agreed date, at an agreed time to cover a specific job for a specific purpose and deliver great pictures as they expect. I’m not shooting randomly in the hope I get a picture worth showing someone.

So when asked about what kit I use, I’m often tempted to ponder in return what paint Leonardo da Vinci used for chapel ceilings and the like, because surely if I had the same paint I could save The Vatican a bundle on restoration works. Now if I can just train these monkeys to hold a brush…

Article and photos © Tim Gander. All rights reserved 2009