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Photography Question 
Ken Henry

Sensor Size Quality

Larger films are higher quality than smaller films. As in 35mm film is higher quality than APS format 24mm size and 110 format 10mm size films.

Does this apply to digital sensors as well. Where the DP&S is about 7mm size sensors and DSLR's with APS 24mm size sensors and the full size 35mm DSLR's with 36mm size sensors.

I just learned this. Here I thought my little Canon PowerShot A540 was a 35mm size equivalent to a P&S 35mm film camera. It's sensor(7mm) is actually smaller than a 110 10mm film.

I'm now beginning to feel like the lost consumer in the world of marketing tricks. Pixels, Pixels, Pixels. The're now packing 12 megapixels in those little DP&S's.

So as a consumer why should I spend $4000+ for A 12mp DSLR versus $500 for a 12mp DP&S, unless I'm into changing lenses.

I would like to see a upper end P&S digital with a square 36mm x 36mm sensor. I really don't want to order a new swivel-ball-joint wrist.


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9/30/2007 1:35:27 PM

Bob Fately   Well, Ken, size does matter, sort of. This is because it relates, along with pixel count, to the size of the individual photosites that make up the pixels. If you have 1 million photosites on a square that's 2MM on a side, and a second sensor with 1 million photosites but 10MM on a side, you can see that the larger chip affords larger individual photosites.

This is important in that as photosites get smaller, they are more prone to picking up random photons (often heat generated by the electronics themselves) and recording them - this is the source of noise. So imaging chips with smaller photosites are more prone to noise, even at lower ISO settings.

Of course, the other imact of larger imaging surface size is shallower depth of field at a given f-stop. Where f8 might allow for 2 foot-to-infinity focus on a small format, for a 4x5 camera it is quite narrower.

On the other hand, there's that cost thing. You can get a camera with a 36x48MM CCD today - if you want to spend $20K + and put it on a medium format body. As with all electronics made with the lithographic process, due to microscopic imperfections that might ruin the entire device, as you try to produce larger sizes of chips the yield rate diminishes rapidly.

Real world, though - for P&S cameras it seems anything over about 6 MPixels is truly marketing hype - image quality is not improved and may well be lessened by noise factors. It will likely be a while, though, before similar limits are reached with the 4/3 and C-sized sensors.

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9/30/2007 2:51:58 PM

Ken Henry   Thank you Bob,

There is a limit per say, as electronics get smaller and smaller it is remarkable how they can get(cram) the info into these components.

It's like "fast cars", sell the horsepower is fine, but let's see how that little engine will do against my big ol' cubic inch Hemi with half as much horse power. And I'll do it in 1st and 2nd gear without going into 3rd and 4th gears.

Canon has already announced coming out with a 21mp 35mm DSLR. And it will use 2 sensors. It's design to compete in medium format. Hmmmmmm.....

Film scanners also. I have a Nikon Super CoolScan which can put out 24mpxls
and the pictures are better at 12mpxls. A lot less pixalation. And of course a $13,000 drum scanner will give you the most remarkable 40mpxls you've ever seen.

Well the market is Paper, Ink, Printers, and pixels. Now you kind of wonder, we save the environment from film but what about all this non-recyclable photo paper I dump into the trash. And the millions of cell phones that go to the dump with dangerous internal components. Oh, that reminds me, I have to upgrade my cellphone tomorrow.

It seems like this GreenEarth thing is very contradictory. Hmmmm....


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9/30/2007 7:26:19 PM

John G. Clifford Jr
BetterPhoto Member Since: 8/18/2005
  What you really want is enough photosite ('pixel') density, with large enough photosites so that the signal-to-noise ratio is high enough to keep noise from becoming a problem.

This is one reason why a 6 MP dSLR with an APS-sized sensor will out-resolve a 12 MP digicam with a 1/2.5"-sized sensor. The second reason is the lens; digicam lens are diffraction-limited at around f/5.6 or even lower, and the limited f-stop depends on the size of the photosite!

So, the number of pixels isn't everything when it comes to resolution and image quality. The size of the sensor, and, more important, the technology behind the sensor, are as important, if not more important. That's why a 4.3 MP Foveon-equipped Sigma SD14 can outresolve a 12 MP Canon 5D at times!

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10/1/2007 2:51:11 AM

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