Thank you for visiting my blog, which is usually about business writing. This off-topic post compares the 8-megapixel camera in my iPhone 4S to an 8-megapixel DSLR, my Canon 30d.
The 8-megapixel camera built into my new iPhone 4S produces the same size image as my 6-year-old Canon 30d. Only six years ago this was one of the highest-resolution DSLRs made. So now is a good time to give a practical, side-by-side comparison of cameras at either end of the 8MP spectrum. Just what, exactly, is the difference between an 8MP camera built into a phone and an 8MP camera built into a … well, camera?
Here’s how I did the test: The iPhone was mounted on a little tripod, using a Belkin grip adapter. Photos were shot using the Belkin grip’s shutter release. Aperture was f/2.4, which is wide open on the iPhone. ISO was 80. Full size on the iPhone is 3,264 pixels x 2,448 pixels = 7,990,272 pixels, or 7.99 megapixels.
The iPhone lens is an extreme wide angle, while the 50mm Canon lens is a short telephoto on my 30d. So the Canon shots were made from about 2 1/2 times the distance to get similar framing. Shots were hand-held at 1/100 second, and captured in JPEG. Aperture was f/2.5; ISO was 400. Full size on the Canon 30d is 3,504 pixels x 2,336 pixels = 8,185,344 pixels, or 8.185 megapixels.
The only bit of post-processing was to increase the brightness of the Canon file by about 1/3 stop, to match the exposure of the iPhone shot.
* Comparison #1 — 600 x 600 pixel crops from the full-size images.
* Comparison #2 — 600 x 600 reductions of square crops from the full-size images. The “full-size” square crop on the iPhone was 1,765 x 1,765 pixels. The full-size square crop on the Canon was 600 x 600 pixels.
Comparison #2 is the important one. It shows images in the form you are most likely to use them — or to see them when somebody else uses them. The simple truth is that we almost NEVER use our photos at full size. We are always shrinking them — or our computers are shrinking them automatically — for attaching to emails or uploading to social media sites.
For display on computer screens, anything over 2 megapixels is wasted data. For example, the screen on my MacBook Pro actually measures 330mm x 206mm. That’s 1,247 x 778 pixels = 970,000 pixels in area, or 0.97 megapixels. And that’s an image covering the entire screen, leaving no room for window frames, toolbars or the dock.
When you consider that more and more images are being viewed on phones, the situation is even sillier. The screen on my iPhone is only 76mm x 51mm, or 287 pixels x 193 pixels. That’s an area of 55,391 pixels, or 0.0554 megapixels.
Now before you start commenting that the iPhone 4S screen has a “resolution of 960 x 640 pixels”, understand what that means. It means that you can zoom into the image on your iPhone 4S until it is magnified to the equivalent of 960 x 640 in size — but you will only ever see 287 x 193 of it at any time.
That’s why I say the maximum useable size of an image is the size at which the entire image can be viewed on a typical device. If that device is a desktop computer, the max. size is around 1000 x 700 pixels (0.7 megapixels). If that device is a laptop computer, the max. size is around 900 x 600 pixels (0.54 megapixels). If that device is a phone, the max. size is around 300 x 200 pixels (0.06 megapixels).
In short, my 8-megapixel iPhone 4S is every bit as useable as my 8-megapixel Canon 30d DSLR for photos up to full-screen laptop size. And here they are — Canon photographed by Apple, and Apple photographed by Canon.
The next test is to use them both outdoors in strong light, and have prints made. Stay tuned.