On Aug 23, 2005, at 11:35 PM, Tom C wrote:
... I have thought since day 1 of DSLR's, that the APS form factor
was largely a short term tactic to get consumers to buy new lenses
to go with those fancy new DSLR's. Sell APS DSLR's in the short
term and 'digital' glass to go with them. When FF sensors get low
enough in price, get all those new customers to upgrade to FF and
sell more FF lenses. ...
That seems too closely related to a conspiracy theory. ;-)
No, the challenge to manufacturers like Nikon and Canon and Pentax,
et al, is this: they had a large range of existing good lenses
designed for film's characteristics and a 24x36mm format. Digital
sensors, aside from being very expensive as the area grows, have
different characteristics. The ideal lens mount for a digital sensor,
and the ideal lens design for a digital sensor, takes into account
that the light path should be more nearly orthogonal to the sensor
even at the edges of the frame ... this implies a lens design which
"straightens" the light path, and a larger mount.
The best compromise to allow compatibility with older lenses as well
as achieve the quality and price points required by the digital
camera is to reduce the size of the format. Moving to approximately
half-frame size allowed the vast majority of existing lenses to work
well, does not increase DoF excessively, and generally allows a
photographer's kit to remain the same with the addition of one-two
additional, shorter focal length lenses. A side benefit is that those
additional lenses (and any others designed exclusively for coverage
of the half-frame format size) can be smaller, lighter, and less
expensive for their focal length and speed.
These decisions were made up to 8-9 years ago. Sensor chip technology
has been very very fast paced in the past decade. Canon, having their
own chip design/fab system, see a market advantage in being at the
cutting edge of the technology and produce new designs faster than
all the other vendors. I don't know whether they foresaw this way
back in 1985, but the EOS mount is unarguably the most suited lens
mount for 24x36 format sensors, having the largest diameter and the
shortest registration of any modern AF SLR, as well as fully
electronic coupling of all the lens controls to the body. This serves
the double purpose of fulfilling Canon's take on the backwards
compatibility game (everything in the EOS system is backwards
compatible, presuming we discount the small selection of EF-S lenses
designed specifically for the smaller format sensor cameras) and
allows them the greatest flexibility in designing larger sensors to
allow recouping the lens design/manufacturing cost investment.
That said, EOS bodies and lenses are amongst the bulkiest in the
business. The Rebel film bodies became featherweight by dint of use
of very lightweight plastic structures, pentamirrors, etc, and
they've downsized the 20D and 350D/XT bodies nicely, but that does
not reduce the size of the lenses these bodies must carry, which are
designed for 24x36mm coverage.
For me, one of my biggest priorities, once past a certain assumed
level of resolution and noise qualities, is not speed or fancy body
coverings, bazillions of features ... It's size and weight of the kit
I need to carry. My working style in the past was nearly always one
body with two/three lenses in the bag or two bodies each fitted with
a single lens. I like to walk all day with the kit and photograph the
subjects I aim for in a fluid fashion, without being too obtrusive or
constrained by fatigue. Four to six lbs is what I want the entire bag
of gear to weigh, and I don't want the bag to be overly large or
obtrusive in appearance.
The Pentax DSLRs, with a half-frame format sensor, net the quality
and the noise level I need for photographic quality, and the lenses/
bodies are compact and light. The very inexpensive yet high quality
50mm f/1.4 lens is a perfect portrait tele, the excellent and also
tiny 35/2 is a perfect normal; the excellent 14/2.8 is a superb
ultrawide at the widest FoV point that I personally find useful and,
for such a short focal length rectilinear with that speed, it is not
only small but low priced compared to the 24x36 format coverage 14s
from Nikon and Canon. I can fit two bodies, each with a lens, or one
body and three lenses into a 6lb bag.
I'm all for more resolution, lower noise, and even a larger sensor.
But I want it to fit my overall needs as the current system bits do.
As I said before, a 3:4 or 4:5 proportion format makes good sense to
me for my compositional tendencies: it uses more of the lens' image
circle and implies less wastage of pixels in cropping, and I could
easily see an 8-10Mpixel sensor at 18x24 or 20x24 (for full
compatibility with current DA series lenses) being quite attractive.
Godfrey
