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Preparing Graphics for The Web

JPEG COMPRESSION EXAMPLE

jpeg compression example JPEG Quality (1-99): Q99
Filesize: 54,124 bytes
Load Time @1.3k/sec: 41.6 sec
Load Time @2.6k/sec: 20.8 sec

This image contains subtle color gradients as well as hard-edged textures, so we'll be able to see how well these subjects fair with increased compression.

jpeg compression example JPEG Quality (1-99): Q90
Filesize: 21,868 bytes
Load Time @1.3k/sec: 16.8 sec
Load Time @2.6k/sec: 8.4 sec

Absolutely indistinguishable from the previous image, yet half the filesize. Isn't compression wonderful?

jpeg compression example JPEG Quality (1-99): Q80
Filesize: 15,054 bytes
Load Time @1.3k/sec: 11.6 sec
Load Time @2.6k/sec: 5.8 sec

Less than a third of the first image's filesize, and still indistinguishable from the first image.

jpeg compression example JPEG Quality (1-99): Q70
Filesize: 12,028 bytes
Load Time @1.3k/sec: 9.3 sec
Load Time @2.6k/sec: 4.6 sec

Still a great image, but the filesize reduction is becoming less and less significant. We could just go with this one, since experience tells us that we can't trim any more than a few more seconds off the load time before the image quality is noticeably affected, but let's remember that every bit of reduction we can squeeze out of each image can add up to something significant. Let's keep going.

jpeg compression example JPEG Quality (1-99): Q60
Filesize: 10,201 bytes
Load Time @1.3k/sec: 7.8 sec
Load Time @2.6k/sec: 3.9 sec

This is getting a little boring.

jpeg compression example JPEG Quality (1-99): Q50
Filesize: 9,096 bytes
Load Time @1.3k/sec: 7.0 sec
Load Time @2.6k/sec: 3.5 sec

Boring. When is this damn thing going to start getting ugly?

jpeg compression example JPEG Quality (1-99): Q40
Filesize: 8018 bytes
Load Time @1.3k/sec: 6.2 sec
Load Time @2.6k/sec: 3.1 sec

Highlights and shadows still smooth. Texture is still true.

jpeg compression example JPEG Quality (1-99): Q30
Filesize: 6,813 bytes
Load Time @1.3k/sec: 5.2 sec
Load Time @2.6k/sec: 2.6 sec

If you jump back a few images, you can barely make out some differences in the quality of the color gradients in the red plastic handle. But for the 1200 byte savings over the previous image, I find this image acceptable.

jpeg compression example JPEG Quality (1-99): Q20
Filesize: 5,397 bytes
Load Time @1.3k/sec: 4.2 sec
Load Time @2.6k/sec: 2.1 sec

We can now clearly see the reds breaking down even more. I think we've gone too far. At this point, I'd back up and choose the previous image.

jpeg compression example JPEG Quality (1-99): Q10
Filesize: 3,519 bytes
Load Time @1.3k/sec: 2.7 sec
Load Time @2.6k/sec: 1.4 sec

Those subtle hues are really suffering now, and the textured areas are losing definition.

jpeg compression example JPEG Quality (1-99): Q1
Filesize: 2,029 bytes
Load Time @1.3k/sec: 1.6 sec
Load Time @2.6k/sec: 0.8 sec

Nasty.

Side-by-side comparison

Shown below is a collage of samples taken from each of the 11 images above. Each sample image contains both blue and red plastic samples, as well as the placemat textures shown at 6 times normal size. They are shown at from lowest compression to highest, to allow you to directly compare the effects of the compression.

© Douglas E. Gray.


You can convert RAW, JPG, GIF images, prepare photos for the web with ReaJPEG - batch photo editing software and raw converter.
   
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