17 June, 2012

Casio Exilim EX-ZR200 - Resolution Test

I think compact digital cameras suffer from "pixel inflation" - increasing pixel count without increasing detail. It also results in unnecessarily large file sizes. I'm testing the useful resolution of the ZR200.
This is my test setup.
5 megapixels, normal quality. Image size about 2 MB.
16 megapixels, fine quality. Image size about 10 MB. I tried to display both images at the same size.

Although the 16 MP image is slightly clearer, I don't think it's enough to justify the 5x image size, so I'll stick with 5 MP.

17 June 2012
Ok there were some uncertainties with the previous test setup, namely I didn't fix the ISO. So here's an improved attempt. This time, I'm testing the iPhone 4 as well.

These images have been cropped, so their quality is slightly reduced. Do not compare at high zoom. Cropping was only done to the bottom of the image, so the noticeboard occupies the entire width of all the images.
ZR200 16 MP fine. ISO 200 exposure 1/20 seconds. Original size 4608x3456 8.8 MB.

ZR200 5 MP normal. ISO 200 exposure 1/25 seconds. Original size 2560x1920 1.9 MB

iPhone 4 ISO 125 exposure 1/15 seconds. Original size 2592x1936 1.9 MB

Zooms of selected portions of images

These were taken from the original, uncropped images.
Since the 16 MP image has more pixels in the same area (e.g. one of the coupons), I couldn't decide whether to compare them at 1:1 pixel size or actual size. In the end I resampled the 5 MP images to twice the pixels (using nearest neighbour, so essentially making the pixels bigger). This resulted in slightly more pixels for the same area than the 16 MP image. This may not be the best way, but by stating my method I hope it lets people compare what I've done.
The comparison images were cropped to at most 800 pixels wide so they'd fit in this site, and saved at the highest quality JPG (12 in Photoshop Elements).

Comparison of coupon in the centre of the image.

Comparison of bottom right of black poster.

Although all pictures are 1:1 pixels, some pixels can be seen in the 5 MP images. This is due to the pixel doubling. The 5 MP images are also slightly larger than the 16 MP image.

The first thing to notice is the 16 MP image is the clearest, as expected. At least there's a point to using the maximum quality if necessary.
The second thing is, quite interestingly, the 5 MP image from the ZR200 is clearer than from the iPhone 4, which is also 5 MP, even though both are about the same file size. So there's an advantage to using a dedicated camera, and the iPhone's camera still has room for improvement. Also, same number of megapixels and file size doesn't mean anything.

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