Re: Canon's new astrophoto DSLR announced [ 4x5" FILM option? ]

On Sat, 04 Jun 2005 20:35:12 GMT, Chris L Peterson
<clp@xxxxxxxxxxxxxxxxxx> wrote:

>On Sat, 04 Jun 2005 20:13:27 GMT, "David Nakamoto"
><res07oeg@xxxxxxxxxxx> wrote:
>
>>Is it necessary from a strictly technical standpoint to have a sensor the same
>>physical size as 35mm film?
>
>Not at all. But a big advantage to a sensor that size is that existing
>optics will deliver the same image scale as photographers are used to
>with film. People have a sense for what it means to use, for example, a
>300mm lens. But if you use that lens on a 20D, it is equivalent to a
>480mm lens on a 35mm camera. And a large sensor makes it easier to do
>wide angle. To get the equivalent field of a 28mm lens with a 20D, you
>need a 17mm lens- pricey.

.... and 300mm on some Canons and 390mm on others. Life would be less
confusing if certain manufacturers rationalised their ranges lol. 35mm
format is an arbitrary size, not chosen for any particular optical
requirement and focal length references based on it really ought to be
scrapped, but I don't guess they will any time soon, it's the only
real common reference point with all the different sized sensors
around.

I can't follow your point about larger sensors making wide angle
easier. The 20D has a larger sensor than the Olympus E-1 but the
latter ships with a very reasonably priced 14-54mm zoom lens of
extremely good quality and it's 14-45mm sibling is ridiculously low
cost for the (albeit lesser) quality.

>
>> Isn't what's important image size and definition,
>>and if so, couldn't this be achieved with smaller sensors with more pixel
>>density and optics to produce
>>an image that fits that sensor?
>
>The point we are at now, with 6-8MP on a 5/8 scale sensor (like the
>20D), is about the limit for pixel density. You can add more, smaller
>pixels, but the pixel size already at the resolution limit of the
>optics, so there is no point. If you want something more like the
>resolution of medium format, say 20MP, you need to build a larger
>sensor. Not as large as medium format film, but at least as large as a
>35mm frame, probably a little larger.

I disagree. The 4/3 sensor format (for example) is confidently
expected to be good up to aroung the 12-16MP area. They used to make
similar comments about processors and memory chips, we all know what
happened there (and continues to happen). Nobody _wants_ larger
sensors, the larger more expensive glass and the tank-like bodies
which accompany the 35mm format. I see nothing wrong with wanting a
small, good hand-fit body with compact lenses which provide
double-digit megapixel performance with a good dynamic range and
acceptable high-ISO native noise performance.

>
>_________________________________________________
>
>Chris L Peterson
>Cloudbait Observatory
>http://www.cloudbait.com

.

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