Friday, 27 October 2017

Photography: How many megapixels do you need?

Ama Dablam

When I changed from film to digital nearly fourteen years ago I asked book and magazine editors what their minimum technical requirements were. Six megapixels and an APS-C sensor was the reply from them all. I didn't then know what these terms meant but I duly went out and purchased a Canon 300D DSLR with those specifications. Since then I've stuck with the APS-C sensor but have gone through 8, 12 and 14 megapixel cameras. My current ones are 24 megapixels, four times that of the first Canon.

Do I need this many megapixels? I guess if I was producing billboard posters I might even need more though billboards are usually viewed at a distance so fine detail isn't required. But for book and magazine publication I don't. Six is still fine unless the images are cropped, when more more megapixels are useful. A quarter of one of my current pictures is roughly equivalent to a full size one from the 300D and so should have the same quality.

These thoughts were brought on by the wonderful new book Great Hiking Trails of the World, that I described here. I have four pictures in that book, all taken with the 300D. Each covers a page and a bit and measures 35 x 25.5cms. They've been reproduced well and look fine. The original raw (unprocessed) files are around 7mb each. After processing in Lightroom the TIFF files I sent the publisher are 36mb, the highest quality I can output from the raw files. I rarely use TIFF files though as they are so big, taking space to store and time to send. For magazines I usually send best quality JPEGs, which run from 2 to 15mb, depending on the camera used. Online I use much smaller JPEGs. One of my images from the book is at the head of this piece. It's 657kb, not even 1mb, which is roughly the size of all the images I post online.

That images taken with a 6 megapixel camera give such good results is pleasing. Those editors fourteen years ago are still right! And since then not one editor has asked me how many megapixels my camera has.

For those interested the technical information for the above photo is Canon EOS 300D camera with Canon EF-S18-55 f3.5-5.6 lens at 18mm, ISO 200, f8 @ 1/160. Raw file processed in Lightroom 6 with highlights reduced and contrast, clarity and vibrance increased.

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