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[OM] CCD's versus CMOS sensors

Subject: [OM] CCD's versus CMOS sensors
From: John Morton <loncayeway@xxxxxxxxx>
Date: Sun, 1 Apr 2007 00:28:12 -0700 (PDT)

Date: Fri, 30 Mar 2007 21:45:05 -0700
From: Moose <olymoose@xxxxxxxxx>
Subject: [OM] Re: Manual lenses to digital body - MF 1 Adapter

    
>   I am assuming that this adapter will connect a bellows to a digital 
body, although that particular option isn't mentioned...
>   
It will indeed. However, you will certainly need an additional 
extension 
tube. Most DSLRs have a forward protrusion from the prism housing (not 
E-300, 330) and the E-410/510 body is no exception. 
http://www.dpreview.com/articles/olympuse410/page3.asp

This protrusion interferes with the tab on the auto bellows that 
doubles 
as lens release and mounting tab. So you need a tube between bellows 
and 
body. A 7mm works for my 5D. It's hard to say, but it looks from the 
pictures that a longer one may be necessary with the 510. There are 
aftermarket 11mm tubes available inexpensively that would work in that 
case. The only possible drawback is that the minimum extension of the 
combined bellows and tube is greater.

Moose

                                               >>>><<<<
   
  Thanks for the heads up on that, Moose; I dug out my Auto Bellows (I tend to 
use the telescoping auto extension tube much more, for field work) and I can 
see how the tab you mention would be a problem with that overhang on the 
pentaprism housing in those photos of the 410/510.
   
  I was looking at a 10 megapixel Lumix (having bought a 5 megapixel model for 
my daughter last year, and having tried it out a few times myself) but if the 
510 has a mechanical image stabilization capability, then I am leaning toward 
that model.
   
  It is interesting to see that this unit will have a CMOS sensor; this 
technology seems to have come of age for digital imaging. Flipping through my 
copy of the 5th edition of John Russ's "The Image Processing Handbook", I note 
that the trend seems to be away from CCD's and toward CMOS sensors.
   
  The more compact pixel spacing of CCD's might tend to give a better 
resolution, but the higher energy requirements of a coupled charge sensor also 
increases the noise generated by electrical interference in the circuitry. 
While CMOS sensors have lower energy requirements, they also have more 
circuitry (the signal amplifiers, for instance) right on the chip... which 
again increases the noise from electrical interference. The added circuitry of 
the CMOS sensor increases the spacing between pixels: this decreases 
resolution, but, also serves to decrease the 'blooming' effect (trans-pixel 
contamination from strong light sources) that CCD's are sometimes prone to.
   
  So, there seem to be a number of trade-offs when choosing between the 500 (8 
megapixel CCD) and the 510 (10 megapixel CMOS); but, since CMOS sensors have 
unique registry values for each pixel (whereas CCD's offload entire rows of 
pixels to their signal amplifiers), it is apparently possible to design 
software that can (in theory) eliminate the noise characteristics of each 
individual pixel... and in the end analysis, this will give CMOS technology an 
edge over CCD's.
   
  Thus, I am now leaning toward the 510 (with its CMOS sensor); and, I am glad 
to hear that my bellows and favorite lenses will work (well enough) on that 
particular model.
   
  John M. 


John Morton 
http://OriginOfWriting.com

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