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[OM] Re: E-500 review and other questions

Subject: [OM] Re: E-500 review and other questions
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Sat, 22 Oct 2005 15:58:14 -0400
There are multiple possible reasons for apparent "softness".  You'll 
have to be more specific about which images you're talking about.

If it's the high ISO images (above ISO 400) you're talking about the 
Kodak CCD (charge coupled device) sensor is noisier than Canon's CMOS 
(complementary metal oxide semiconductor) sensor.  In a digital sensor 
ISO sensitivity is boosted by amplifying the signal just like the volume 
on your stereo is boosted by an amplifier.  If the signal is weak (low 
light) and the boost is high (ISO 800, 1600) then random noise generated 
in the electronics may be boosted as well and lead to false colors 
showing up on the pixels.  On the sound side, cranking up the volume on 
your amp to its maximum would likely produce some distortions in the 
sound.  Digital sensor noise has an appearance similar to film grain in 
color film except that film grains are random sized dots and false color 
noise pixels are all the same size.

Because the sensor is noisier Oly applies a fair amount of noise 
reduction processing at high ISO settings to suppress the noise.  Noise 
reduction algorithms, however, have a side effect of reducing detail in 
the image since they can't always tell a real pixel from a false color 
noise pixel.  The same thing happens when you use a film scanner and run 
the scanned image through grain (noise) reduction software.  You will 
typically soften some of the fine detail.

Canon's CMOS sensor is the undisputed leader in the noise department. 
If noise is your principal concern and you expect to do a lot of 
shooting at ISO 800 and above then a Canon DLSR is the way to go. 
Canon's CMOS sensor has noise performance typically 1 to 2 stops better 
than any of its competitors.  If you care about the zillion other 
features on the camera and/or you typically shoot at ISO 400 and below 
the noise picture doesn't make any difference.  The sensor on all 
current DSLR's have pretty much the same performance at ISO 400 or less.

Part of the reason that the 4/3 sensor is noisier than Canon's sensor 
(and it's only part of the reason) is that the 4/3 sensor is smaller 
than the Canon's "APS-C" size sensor.  The Canon sensor in the 350XT is 
22.8 x 14.8mm or 337.44 mm^2.  The 4/3 sensor is 17.3 x 13mm or 
224.9mm^2 or 2/3 the size of the Canon.  It's smaller but I'd hardly 
call it "tiny".  Tiny?  How about something in the range of 7x5mm? 
Actually that's a large sensor size for the latest crop of P&S digitals.

Olympus will counter the size argument by saying that most photographic 
images get cropped to make prints in fairly standard sizes and the 2:3 
ratio of the Canon sensor or of 35mm film is usually only found in 4x6 
prints.  If you decide to make an 8x10 or an 11x14, etc. then you end up 
cropping off a fairly significant chunk of the pixels from the APS-C 
size sensor and the effective difference in size is lessened.  If you 
were to print an 8x10 from the CMOS sensor and use all available height 
then you only be using 18.5mm of the sensors 22.8mm width or 273mm^2. 
If you did the same from a 4/3 sensor you'd be using 15.6mm of the 
available 17.3mm width or 202.8mm^2.  Now the effective difference in 
area is down to 3/4 instead of 2/3.

Gotta stop writing.  This is taking too long.  :-)

Chuck Norcutt

Ali wrote:
> Since I am embarking into the Olympus digital world...I had a few 
> questions. I read the E-500 review which had been provided by Winsor. 
> Although some of it flew over my head....I noticed the E-500 photo's 
> seemed a bit soft compared to the Rebel XT. Also many people have said 
> that the 4/3 sensor is TINY. How does this sensor compare to some of the 
> other sensors? Regarding focus points...my understanding is that 
> "multi-focus" points is typically a gimmick to attract people that might 
> otherwise buy a "point and shoot" camera. Can "multi-focus" points be 
> turned OFF or changed to single point focusing in the E-500?
> 
> I am sorry if all of this has been covered before....I never really paid 
> attention to the digital conversations.
> 
> One thing I really like about the E-500 is the dual storage slots.
> 
> - Ali
> 
> 
> 
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