G7 RAW vs JPEG - Test

Hi Everyone,

First off, major thanks to the hard working crew responsible for the CHDK firmware. The added features this firmware brings to my G7 is just outstanding, and Canon should be ashamed of themselves for not having done this themselves. For anyone not up to date yet on what CHDK is, please have a look at the following DP Review forum:
1) http://forums.dpreview.com/forums/read.asp?forum=1010&message=24662492
and the CHDK website:
2) http://scratchpad.wikia.com/wiki/CHDK

Alrighty then. This post is about comparing the RAW mode hidden within the Canon G7 (and other related Digic II and III cameras from Canon) and its usual JPEG counterpart. Below are my test results.

• Note *

1) The RAW image had only undergone minimal processing in order to produce a standard RGB image. Only the exposure and temperature of the image was influenced to best represent the subject.
2) The JPEG image was straight off the camera, standard shooting settings.

• Camera Settings *

Environment: 2 Light sources (fairly dim), 1 incandescent, 1 halogen blue
Flash: Used, approximately 7 feet away
Mode: Aperture Priority, F/5.6
Shutter: 1/60
ISO: 80
White Balance: Auto

JPEG Size: 3.83 MB
RAW Size: 12.3 MB

Average number of JPEG photos on 4GB SDHC: 1044
Average number of RAW photos on 4GB SDHC: 325

• Overview *

RESAMPLED - Overview of the subject

1) Note the difference in colours. The RAW photo managed to completely retain the original subject's colour.

2) The JPEG image appears to have calculated an incorrect white balance. The yellow tint that stains the image is probably a result of the incandescent bulb illuminating stronger than the flash that was fired. Were this a real photo, I'd be pretty ticked about this

UP CLOSE AND PERSONAL - A look at edge quality and noise

1) The JPEG is a little sharper given that it's been worked on in the camera. I decided not to apply sharpening to the RAW because I wanted to focus more on the original quality. Had I applied a 0.5 radius unsharp mask filter to the RAW however, it would obtain a sharpness slightly better than the JPEG (finer detail).

2) The noise level between the two are identical. The one noticeable difference however is the JPEG image suffers from smearing due to compression, while the RAW image retains the original noise quality, which is finer grained. This finer grained noise allows programs like Noise Ninja or Neat Image to produce better results.

FINAL RESULT

1) Using the RAW, I passed it through Neat Image to filter out the noise, then applied a 0.5 radius unsharp mask via Gimp.

CONCLUSION

The G7 is a wonderful camera and I actually prefer to bring it with me over my 300D (slap it to my waist belt and off I go). I didn't mind the JPEG photos produced with the camera, but now having unlocked the power of RAW, I feel a little safer when taking those special moment photos. The added space taken up for the RAW + Jpeg images is well worth it too. If you have a 4GB+ SDHC card, you'll be able to store hundreds of photos.

Among other features, CHDK is truly a worthy add-on to Canon products.

Enjoy.