Re: Full-frame or 1.5 DSLR?

RichA <none@xxxxxxxx> wrote in
news:lgtdf19d7jh2tf6lisnrlmm3u3qtreg1d3@xxxxxxx:

> On Mon, 08 Aug 2005 02:10:32 -0000, Jeremy Nixon <jeremy@xxxxxxxxxxx>
> wrote:
>
>>RichA <none@xxxxxxxx> wrote:
>>
>>> How does this work, exactly? No matter what resolution you choose
>>> on the 20D, the image scale DOES NOT CHANGE like it does when you
>>> use the D2X in it's 6.8meg mode which actually REDUCES the sensor
>>> area used to produce the image.
>>
>>Cropping the image after the fact does exactly the same thing as the
>>2x crop mode on the D2x. The advantages of doing it in-camera are
>>that you can shoot faster, use less storage space, and actually see
>>the post- crop image area in the viewfinder.
>
> Oh my God!
> Then I was definitely labouring under the wrong idea.
>
> All this time I thought that a 300mm lens on a 2x sensor was truly a
> 600mm lens, it's not!

Definitely not, it just captures as narrow a field of view as a 600mm
lens would. Compared to a FF sensor with the same NUMBER of pixels, it
resolves more. But compared to a FF sensor with the same pixel pitch,
it resolves the same but captures a narrower FoV.

> It now seems apparent that the only way to fuctionally get a lens to
> provide more detail is to increase the pixel count of the sensor for a
> given area size. In other words, with a given lens, the Olympus E-300
> has the highest resolution of any DSLR on the market as far as I know.
> Cropping is simply the reduction of the area/pixel count of a given
> image.

Clearly, with a given lens and a given distance from a given subject.
If it is possible to move closer or use a longer lens then the E-300
will resolve no more than any other 8MPix camera, and less than a Nikon
12MPix or Canon 16MPix camera.

> This means that if they figure out how to keep noise down with smaller
> pixels and given excellent lenses, it might be possible to produce
> DSLRs with much higher resolution than are available now. I think
> Fuji has produced a sensor with 2um pixels. Which would mean a
> 9k x 6k or so and an image size of 54m in the same sensor space that
> we now use.

On a full frame camera you would also need bigger memory cards, more
powerful computers with more RAM and bigger HDDs. But yes you could
easily produce a FF camera with 32MPix just using the pixel pitch
currently used in the E-300.

> So if you have a 300mm lens and two sensors, one full frame and one
> 1.5, It would seem to me since the 300mm lens has a fixed focal length
> (300mm) and a specific focus point that the only difference is that
> the full frame sensor can image a wider field of view than the 1.5
> sensor. So unless it's pixels are physically smaller, the 1.5 sensor
> cannot resolve more detail than the full frame sensor because the
> 300mm lens really isn't turning "into" a 450mm lens when it's used
> with the 1.5 sensor. This means there is NO benefit (unless pixel
> pitch is smaller) to owing a sub-full frame DSLR!

This sounds correct. But note: the Canon 20D DOES have a smaller pixel
pitch than the Canon 1DsMkII, so if your lens is not long enough to
tightly frame the subject then it is possible that the 20D can out
resolve the 1DMkII. However when it is possible to move closer to the
subject or use a longer lens, then the 1DsMkII can use 16MPix to capture
the subject which is 40% more linear resolution than the 20D will give.
If you shoot portraits then the 1DsMkII is a better camera - if you
ignore the price of course.


--
Mark Heyes (New Zealand)
See my pics at www.gigatech.co.nz (last updated 25-June-05)
"There are 10 types of people, those that
understand binary and those that don't"

.

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