Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Clayton Jones"
<cj@c...> wrote:
> Hello Jeff,
> 
> >>...if a sensor were made specifically for B&W...
> 
> >...Such sensors are made by the thousands...
> 
> I'd like to share my personal pet prediction.  This is not based on
> any technical knowledge, just pure hunch and speculation.   I've had
> this idea for over a year and it won't go away.  I predict that
> someday we'll have cameras with switchable plug-in sensors.  Here's
> why:

I'm sorry this idea "won't go away". That can be troubling. Maybe I
can help...

> To me the biggest difference from film is that we could put any film
> we wanted in our cameras - a huge range of choices.  With digi we're
> stuck with whatever we get.  That is an enormous restriction,
> especially for such expensive cameras.
> 
> Makers must constantly evolve their products to compete.  Where will
> they go?  Someone pointed out that once the MP race hits diminishing
> returns they'll turn to improving the DR and other attributes of the
> sensors themselves.  I agree, but what comes after that?
> 
> I think that someone eventually will design a plugin sensor that will
> have a standard pinout, at least within their own cameras.  They will
> make several sensors, just a few at first; color and BW.  It
> will evolve to having choices of different MP sizes with
> correspondingly different size wells, with correspondingly different
> noise and DR ratings (since all the sensors will be the same size). 
> Perhaps even different BW sensitivities such as IR and panchromatic.

Nope. Just combine the "wells" electronically on the sensor, or with
the camera's DSP, into larger wells with less noise and more dynamic
range. The Foveon X3 sensor can do this onboard the chip, and the
results can be pretty interesting.

> Each plugin sensor package will of necessity carry its own onboard
> firmware.  The camera will just have enough image processing code to
> trigger the sensor logic and transfer the data to the memory card
> (which might mean lower "body only" camera prices).  This means the
> sensor processing firmware will have a standard API.
> 
> A standard pinout and API will open up a vigorous 3rd party market for
> sensors for these cameras (think Sony, Matsushita and Kodak), and
> we'll eventually have a large range of choices.
> 
> The first company to make such a camera will likely sell tons of cams

Or fail miseralby, in very short order.

> (especially if they work behind the scenes with 3p sensor makers so
> there is a wider range of sensors out of the starting gate)  because
> the benefits will be obvious.  I predict K-M will do it because
> Minolta has always been innovative.

No, they've just been masters of creating an appearance of innovation.

> Other makers will have to folow
> suit, and it's possible the pinout and API will become industry-wide
> (that one I'm not so sure about, but what a huge difference it would
> make - the 3p sensor industry would be enormous).

Totally unfeasable. The interface requirements for different sensor
technologies are too different. So are requirements for things like
channel count.
 
> This will most likely take some years to happen, but I think it's
> inevitable.

What's inevitable is that cameras will hit a point where you no longer
look longingly at next years model, and it starts taking 5 years (and
someday, 10 years or more) before your existing camera feels "long in
the tooth".
 
> NOTE: I cringe in fear that by posting this I will start a huge thread
> in this forum.  I hope not.  I hope people will just think about it
> and put it away to wait and see if it ever happens.  Please use
> restraint and don't have a long drawn out discussion of these ideas. 
> I'm sharing this because it fascinates me and I think others here may
> appreciate it - but this is supposed to be a printing forum.

I'm very sorry, but that seems a bit "do as I say, not as I do" to me.

Now, if you're interested in why the interchangable sensor isn't going
to happen, check out items 8 and 9 ...

http://www.swissarmyfork.com/digital_photography_ifaq.htm

9) How about a DSLR with interchangeable sensors?

It's nearly impossible. You have to interchange most of the digital
camera, not just the sensor. Different sensors have different
interface voltages, different numbers of read channels, different
clocking rates. So whatever carries the sensor must also carry a
regulated power supply and the proper number and type of A/D
converters. Now, since the different sensor types have radically
different signal processing needs (Fuji diagonal matrix, Foveon
stacked color interpolation, Nikon D1X 2:1 aspect compression, etc)
you either have to put all that on the onboard processor, or make it
uploadable.

This is assuming that a processor that can do one of those algorithms
in reasonable time can do all the others in reasonable time, too. If
not, you need to make the processor bigger (more expensive, more heat,
less battery life) and waste that power when a particular sensor
doesn't need it.

Then you get into shutter requirements. Does the sensor have an
electronic shutter like Nikon D1X, D1H, Canon 1D, so the mechanical
shutter can "relax" and just serve as a between shots "blind" for the
sensor? Or does the shutter need to be a "real" shutter like in Canon
10D or D1s, Nikon D2H, Kodak 14n, etc.

Then there's details like Fuji CCDs reflect enough light so they can
be used for TTL metering, but Nikon and Canon sensors don't, so they
require preflash systems (Canon E-TTL, Nikon D-TTL).

And if your "new" sensor doesn't have the same size as the old sensor,
you need a new viewfinder mask.

8) Why aren't there digital backs for film SLRs?

Sure, it's a good question. You've got a nice film SLR, a Nikon F5,
F100, or F4, a Canon EOS 1V or EOS 3, a Minolta Maxxum 7 or 9. Why not
just slap on a digital back and shoot away? Once you actually start
looking at how you'd do it, you see that there are overwhelming
reasons why a fully integrated camera is preferable to a digital back.
Compared to a full DSLR, a film SLR and digital back has increased
cost, decreased strength (or increased weight), poor ergonomics, and a
lack of desirable features.

8.1) Size and weight

A film SLR + digital back is heavier and bulkier than an integrated
DSLR. The back of a film SLR is lightweight. It's only function is
keeping light out, and supporting the pressure plate. Neither of these
are precision functions, and the attachment mechanism between front
and back reflects this. To keep the back and front from flexing
independently of each other (destroying alignment) the back needs to
be made stronger (heavier, more expensive) than the digital section of
an integrated camera. Unlike the integrated camera, a digital back
isn't anchored to multiple points of the camera's main chassis. The
best it can do is try to grab onto the flimsy back hinge and latch
points, and go under the camera, to screw into the tripod socket.

Then there's the problem of making a weatherproof (and dust proof)
seal between a heavy, poorly anchored back and the main camera, when
the digital back is, literally, hanging off the back of the camera,
doing it's best to pull the seal apart.

8.2) No "full frame" digital backs

You cannot build a full frame 24x36mm digital back for a conventional
35mm SLR (or a medium format SLR, for that matter). The SLR is
designed to position the film at the focal plane of the lens. To do
this, the film (which is wider than 24mm) rides on polished film rails
which hold it a fraction of a mm from the back plate of the camera.
This back plate has a 24x36mm rectangular cutout leading to the
shutter and mirror box.

In a digital SLR, the silicon surface of the sensor itself must be at
the focal plane of the lens. The problem is that there are several
things in front of the surface of the sensor. First is the cover glass
of the sensor. Second is a stack of optical filters: the anti-aliasing
filter, the IR "hot mirror filter", etc. And finally, the metal frame
that holds it all together. The end result is a stack that it thicker
than the film rails.

So, in a digital back such as Leica's, the sensor is mounted to a
support structure that presses against the film rails, and the entire
sensor protrudes past the film rails into the 24mmx36mm cutout, almost
to the shutter curtains. (This is also how the Kodak digital backs for
Nikon and Canon bodies worked). The sensor's silicon "chip" is also
bigger than the "active area" that actually senses the image. The
image area is surrounded by buffers, shift registers, and the metal
leads "bonded" to the chip (that connect the chip to the outside
world), and a frame for the leads.

When you add the electronics, leads, and cover glass frame all
together, you're talking about a 4-5mm perimeter around the sensor.
The end result is that 1.36x crop sensor of the Leica back, with a
17.6x26.4mm active area, is about as big as you can cram into the
cutout and maintain that perimeter.

Now, if someone were to build a camera that had at least part of the
back plate (just past the film rails) removable, this new film camera
would be capable of being changed from film to full frame digital.
However, consider three "indicators" that no camera company will ever
build this new "digital friendly" film SLR. First, Canon say that
2003's DSLR sales have passed film SLR sales. Second, Nikon is now
launching all their "flagship" features (fastest 11 zones AF system,
fastest mirror and shutter) on a DSLR, the D2H, not on a film body.
There may not even be a film "flagship" F6 in the future. Third,
Olympus has re-entered the SLR market, with a digital only family. No
film body, and lenses that won't even cover film.

8.3) Awkward viewfinders

And, since the digital back isn't full frame, you need a viewfinder
mask. But the readouts in the viewfinder are going to stay where they
are now, so you'll have a big gap between the small, masked finder
image and the readouts. To make things worse, every integrated DSLR
launched since early 2003 (such as Nikon D2H, Olympus E-1, Canon 10D,
Pentax *ist) increases the viewfinder magnification, from a film SLR's
0.7x-0.8x, to a more comfortable 0.9x-1.0x. This offsets the "tunnel
vision" small viewfinder image of DSLRs.

8.4) Autofocus, exposure, and flash problems

Since the digital back isn't going to be full frame, you end up with
problems in the camera's auto exposure and AF systems. Modern SLRs
have metering systems with many zones distributed over the entire 35mm
frame, anywhere from the 21 zones of a Canon EOS 1V, to the 1002 zones
of a Nikon F5. Sure, you can mask off the finder, but you've also got
to "reprogram" the metering system, or it's going to meter things that
are outside the smaller "digital frame". No current film SLR has
provisions for such reprogramming.

AF is the same way. If you crop the finder, some of the AF zones are
either going to end up out of the frame, or uncomfortably close to the
edges of the frame. Neither of these are good developments.

And there's the little detail of TTL flash. Most cameras read the
flash exposure while the shutter is open, measuring the light that
reflects off the film. These sensors don't know how to read the
reflection from a CCD (and they may also be built to read an area
larger that the CCD, just like the exposure and autofocus systems
above). To counteract this, integrated DSLRs use a pre-flash based
system, where they fire reduced power pulses from the flash, before
exposure, and base the flash exposure on these readings. The Fuji S2
is the only DSLR that attempts to do "normal" TTL by looking at the
reflection from the sensor. This introduces other problems that are
beyond this discussion.

8.5) Ergonomics

Aside from the whole "bulkier and heavier" issue, the SLR + digital
back can't match the ergonomics of an integrated DSLR. There's no real
information flow between SLR and digital back, the SLR thinks it's
shooting film. So, any "digital" functions (like white balance, ISO
speed, and compression modes) have to be controlled purely by buttons
on the digital back and menus on the screen, while the "camera"
functions are operated via conventional controls.

How's this for awkward? To set the camera for ISO 400, first pull up
the ISO menu on the digital back, and set it for 400. Then "dial in"
ISO 400 on the camera's knobs so that the metering system and the
digital back will both be set to the same ISO, and you can meter. On
an integrated DSLR, one knob does it all.

A digital back won't give you any status readouts in the finder.
Integrated DSLRs typically show you how many shots are free in the
buffer and/or how many more you can get on the CF card. With a digital
back, the camera wouldn't even know that the buffer or CF card was
full: it would happily let you continue to take more pictures, which
would then be sent off into "electronic nowhere".

8.6) What about "Silicon Film"

8.7) Other "system" issues

Does the sensor have an electronic shutter like Nikon D1X, D1H, Canon
1D, so the mechanical shutter can "relax" and just serve as a between
shots "blind" for the sensor? It's wasted on a digital back. The film
SLR can't "know" that the sensor has these capabilities, and it
doesn't have controls or provisions for selecting a 1/500 sec X sync
and a 1/16,000 sec top exposure speed.

How does the digital back even know an exposure has happened? In a
DSLR, there's a sequence of events. You clear the sensor's buffers,
open the shutter, make the exposure, close the shutter, and
immediately transfer the captured image out of the sensor. It degrades
rapidly if left to sit in the sensor's storage cells. (This is the
same degradation that causes noise in long exposures on a DSLR). So
the digital back has to monitor the shutter somehow (infrared
reflections, sound, etc) to know when to clear and when to transfer an
image.

Most SLRs don't have much provision for powering a large accessory
like a digital back, so the digital back has to have its own power
source. Now we're into a system with multiple types of batteries and
chargers.

And, the last issue, which body do you make the digital back fit.
Nikon has two pro and serious amateur bodies, F5 and F100. Canon has
both EOS 3 and 1v.