David B. Brooks Blog

A DEBATE ABOUT WHAT IS DIGITAL CAMERA IMAGE QUALITY Posted Sat Dec 19, 2009, 1:32 AM ET

Almost every paper and web photo publication has reported on Canon’s newest G-11 model high performance P&S camera. Some have noted that this new model has a lower megapixel count of 10 MPX, compared to the 14.7 megapixel G-10, that is still featured for sale on the Canon web site. One pundit even quoted without naming his source at Canon “They have also changed up the sensor, keeping it the same size, but making the pixels bigger. The result is a lower 10-megapixel resolution, but they claim the trade-off is better image-quality, especially in low-light situations. A Canon rep mentioned that it's because the G-11 is focused on providing the best quality in the form of a still image.”

This has come back to me from readers that Canon’s lowering the G-11 megapixel count was to improve image quality, and another assuming a similar kind of logic, that maybe the G-10 was not a very good performing camera. What comparisons of the reports of both G-10 and G-11 cameras reveals is that at the highest ISO speed rating, the G-11 produces less image deterioration at these inflated speeds, even at one stop greater ISO rating.

What is clear from the specifications is that the new G-11 captures almost 50% less image information than the the previous G-10. So if both cameras exposed the same image at a rated ISO setting of 80, wouldn’t the G-10 capture more information? And if both the G-10 and G-11 images were made in Raw format and printed to a letter-size print image wouldn’t the resulting G-10 image be based on more sensor information, with more detail in the image?

With the highest-end EOS cameras with full-frame sensor’s, isn’t the higher megapixel rating a measure of superior imaging quality?

So what is really in discussion out there between the G-10 and G-11 is maybe really about differences in image sensor quality about which camera’s processor can reproduce better images from under-exposed shots taken in low-light? So, is that a reflection of image sensor performance or how much the capture can be processed differently to get a result from inflated ISO ratings? I say this because the very first dSLR cameras I worked with did not offer much if any higher than standard ISO ratings. The camera cannot change the physical sensitivity of its sensor chip, and make it actually more sensitive to light. The image processor is just squeezing and re-interpreting the information the sensor collects when it is intentionally “under-exposed”.

In a sense it is not all that different than it was in film days. If you wanted the best image quality you loaded a standard or relatively low 64 0r 100 ISO speed rated film. If you chose a 400 or i600 ISO rated film the higher the number the more grain, excessive contrast and distorted color were usual side effects of the greater film speed. With digital it is a loss of image information and noise especially in darker areas of the image.

So , maybe if you are a photographer that shoots mostly in full daylight and want as much image information in your pictures as possible the G-10 would be a better choice if you are going to shoot at low ISO speeds. But if you are taking shots of sporting events at night the new G-11 might provide better picture information at its higher ISO speed ratings.

Don’t be misled, there is still good reason for the megapixel race, more megapixels produce more image information and better picture quality is the result. And if you want the best image quality any digital camera can reproduce, use the lowest ISO rating the camera offers.

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