If you have followed the progress of digital cameras from their early beginnings as we have, you cannot have failed to notice that as each model is replaced with a newer one whatever else they have carried out in improvements to the new model you can guarantee that the megapixel rating of the camera will have gone up.
In the very early days of digital imaging cameras had Megapixel ratings of around one Megapixel or less, which to be honest were not really up to producing photo quality prints, but the ratings increased in the following years until photo quality prints could easily be achieved, and we have now reached the point where the latest compact cameras have ratings of around 12 Megapixels, and D-SLR cameras with ratings in excess of 16 Megapixels.
So we have now arrived at a point where most new digital cameras have larger megapixel ratings than the models they are replacing, and as we all aspire to a better-specified model it is all to easy to get caught up in the technology race thinking that more Megapixels equals better quality results. To find out if this is the case we need to look at what Megapixels are and how they effect the quality of our images.
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On digital cameras a simplified description of taking a digital image is that you press the shutter button, this allows the light from your subject to pass through the lens in sharp focus into the camera body where the image is captured on a sensor (highlighted in white on the illustration) the surface of which is covered with light sensitive image gathering elements called pixels. A modern camera sensor contains millions of these pixels and one million of them are known as one Megapixel (1 Mp). |
If you look at the two images below you will see one at normal size and the other an enlarged (x 1000) area of the sand of the same image, at this magnification the individual pixels are clearly visible. A good way of thinking of a digital image is as a mosaic of pixels and the more pixels in the mosaic the finer the image will be.
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Now still with me haven't lost the will to live yet? Then it's at about this point that you may well be thinking, all right I now know all about pixels, so exactly how many do I really need to get true photo quality prints?
Well it is widely accepted in the digital world that for every inch of your print size you will need a maximum of 300 pixels to achieve true photo quality prints, which you will see referred to as 300 ppi (pixels per inch), any more than this will be wasted as the human eye will not be able to detect a visual difference in quality above this level.
As an example the formula for a 7in x 5in print would be 7in x 300 ppi = 2100, and 5in x 300 ppi = 1500, multiply the two sums together (2100 x 1500) which gives us 3,150,000 pixels, round this up to the nearest whole megapixel number and you have approx 3 Megapixels of picture information, which would give you a true 7in x 5in photo quality print.
Don't worry to much about the mathematics used in our example as using the above formula we have produced this simple chart for you to show you how many Megapixels are required to give true photo quality at standard print sizes:-
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Looking at the chart you will see that we have shown print sizes for 200ppi as well as 300ppi, the reason for this is that 300ppi is the best option for true photo quality prints, but most people find that using around 240ppi will still give excellent results; and you will also find that 200ppi will be acceptable for very large prints because you view them from a far greater distance and this makes it very hard for your eyes to detect any loss in quality.
To use the chart first decide on what print size you want at either 200ppi or 300ppi then follow the "Blue" bar up untill it stops, then read off from the "Blue" scale on the left hand side of the chart how many Megapixels you will need. For example an 8x6 inch print at 300ppi will require 4 Megapixels for true photo quality.
Have a close look at these three images shown below they are all small sections taken from 12in x 8in prints using different compact digital cameras with ratings of 3,6 and 10 Megpixels, all of the images were enlarged in exactly the same way in Adobe Photoshop (lowering the ppi to achieve a 12in x 8in print) .
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Now you have had a good look at the images do you think you can tell which one is which, and also for saying that the images were produced by three different cameras with ratings of 3,6 & 10 megapixels can you honestly say that you can see a significant drop in quality between them all at a print size of 12in x 8in (approx A4).
If you are having problems deciding which one is which, then you are in very good company as most people will find it very difficult to spot the difference in print quality between good quality cameras with Megapixel ratings above 3Mp at print sizes up to A4.
If you only ever need standard sized prints then a good choice would be a quality camera with a rating of around 6 Megapixels from one of the well known camera manufacturers (Canon, Nikon, Sony, Panasonic etc) this will be more than good enough to produce excellent high quality prints up to A4 in size that are virtually indistinguishable from cameras with higher Megapixel ratings.
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So now for the million dollar question do more Megapixels equal better image quality, well the simple answer is that we have now long since passed the point (5 to 6 Mp) when useful increases in Megapixel ratings were required to improve image quality at print sizes up to A4, but if you need to regularly produce large poster sized prints (e.g. A3 or A2) or heavily crop your images and retain image quality you will find the extra pixels will be of benefit to you.
So if you have your eye on one of the latest high Megapixel cameras then why not treat yourself as it's only natural to want to upgrade your camera now and again, but don't expect to see a massive improvement in image quality at normal print sizes, as the only thing more Megapixels will guarantee you is the ability to produce higher quality extra large prints.