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DigitalNewbie Oct 24, 2004 7:51 PM

My Canon G3 has a 7.2-28.8 mm lens, the '35mm equivalent' of 35-140mm. The PS-1 has a 7.2-50.8 mm lens, the '35mm equivalent' of 28-200 mm. I suspect that the reason 7.2mm is the '35mm equivalent'of 35mm on my G3, and 28mm on the PS-1, is the different CCD sizes: 1/1.8 inch on the G3, 2/3" on the PS-1. Am I correct?. I understand 2/3", but what's 1/1.8"? A little biggerthan 1/2"??

So how do I use CCD size and actual focal length to calculate '35mm equivalent'focal length? BTW, my '35-140' zoom lens seems more limited than the 35-135 on my old Nikkormat.

Thanks! Steve

eric s Oct 25, 2004 8:35 AM

You are correct, it has to do with the size of the sensor.

Here is a writeup which should tell you all you need to know:


DigitalNewbie Oct 28, 2004 2:46 AM

Thanks Eric, interesting article.

I'm still wondering about the size of the G3's CCD sensor, 1/1.8". Does this mean .55" (1 divided by 1.8, slightly larger than 1 divided by 2 = .50)? If so, is this a diagonal measurement? What are typical sensor sizes for various megapixel ratings? Can you tell that numbers fascinate me?.


PeterP Oct 28, 2004 7:02 PM

1 Attachment(s)
Here is another copy of theimager sizes chart recently posted by Steve,Mikefellh, and others. The 10D,20D d70,d100 have a sensor that fall in the APS size range. About 1.5x for nikon, 1.6x for Canon

Other copies can be found by entering "imager size" in the little used search box at the top of these pages

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