Where are the BEST Point and Shoot Photos ?

Chris Malcolm writes:

You didn't hear about IMAX cinema technology until cameras became
capable of the required resolution either. It's interesting to note
that the much bigger screens in IMAX cinemas haven't been used to
accomodate more viewers by having more distant view of the larger
screen. Instead they've tried to fit in as many as possible to a much
closer view than a conventional cinema screen.

My local IMAX has way more seats than its conventional theaters, and
seating distance is comparable.

Sounds like someone realised you could make more profit if you ignored
quality.

Not at all.

The whole point of IMAX is having the screen occupy a large angle of
view at the viewer (typically 90 degrees or more for someone in the
middle of the seating area) to produce an immersive experience. The
film frame is large (10 times the area of 1.33 aspect 35 mm film, even
more for wider-aspect 35) and the projector is much steadier in order
to provide a quality image over that large angle.

To a first approximation, you get a 90 degree FOV when your distance
from the screen is 1/2 the screen width. In comparison, typical 35 mm
theatres provide decent viewing when you sit 1 screen width back or even
more. (Sometimes there are much closer seats, but the image quality is
poor that close to a 35 screen).

But it doesn't matter whether you achieve that with a really large
theatre, a large screen, and fairly normal screen-to-audience seating
distance, or a small theatre and shorter seating distance. It's the
angle occupied by the screen as seen from the audience that counts.

It sounds like Chris has seen smaller IMAX theatres, while John has seen
larger ones.

For some of the extremes: one of the first IMAX theatres is at Ontario
Place in Toronto. The theatre is inside a huge dome (though it's a flat
screen) and seats 800 people. The screening theatre inside Imax's
offices in Mississauga seats only about 40 people (sitting pretty close
to the screen!). But both provide about the right angle of view, so
both provide the "IMAX experience".

Dave

Scott W writes:

But John said the "seating distance is comparable" which I take to mean
the viewing angle of the screen is about the same as a normal theater.

I can't read minds. But here's how I interpreted what they said:
Chris said that IMAX theatres have a normal number of seats but seat
the audience closer to the screen than normal, with the unsaid
assumption that the screen was a normal size.

John countered that in his experience IMAX theatres have a
screen-to-audience distance that is comparable to ordinary theatres,
and many more seats than usual, with the unsaid assumption that the
screen is much larger than in a normal theatre.

And my point was that these are both proper IMAX theatres, just smaller
and larger ones. As long as the audience sits about half the screen
width back from the screen, you get the wide FOV - whether normal
screen and relatively fewer seats up close, or very large screen and
very many seats.

After all if this is not what John meant then he really had not point.

I think he was just saying his experience with IMAX didn't match
Chris's.

Now, should we start discussing how many pixels you would need for a
sharp IMAX image? :-)

Dave

Dave Martindale wrote:
Scott W writes:

But John said the "seating distance is comparable" which I take to mean
the viewing angle of the screen is about the same as a normal theater.

I can't read minds. But here's how I interpreted what they said:
Chris said that IMAX theatres have a normal number of seats but seat
the audience closer to the screen than normal, with the unsaid
assumption that the screen was a normal size.

John countered that in his experience IMAX theatres have a
screen-to-audience distance that is comparable to ordinary theatres,
and many more seats than usual, with the unsaid assumption that the
screen is much larger than in a normal theatre.

And my point was that these are both proper IMAX theatres, just smaller
and larger ones. As long as the audience sits about half the screen
width back from the screen, you get the wide FOV - whether normal
screen and relatively fewer seats up close, or very large screen and
very many seats.

After all if this is not what John meant then he really had not point.

I think he was just saying his experience with IMAX didn't match
Chris's.

My point about IMAX was that it's based on the fact that due to the
physiology of human vision you get a qualitatively different viewing
experience when the subtended angle of the image is much larger than
the usual standard still photograph or film theatre angle. If you want
to exploit that with a photographic print you're inevitably involved
with higher image resolutions than those which John Navas was citing
as standards. For example the diagonal of the image rectangle standard
gave us the standard 50mm lens for 35mm film which if viewed from the
same perspective gives us a subtended viewing angle of about 40
degrees, which is less than half the IMAX subtended angle of 90, which
roughly speaking will need 4 times the image pixels for the same
apparent sharpness.

So if you're producing a landscape photograph which is meant to be
viewed at a subtended angle of 90 degrees for the proper visual effect
then you'll need a camera with around 24MP to achieve the same degree
of apparent sharpness as an 8x10 print viewed at the diagonal distance
of 13 inches and produced by a 6MP camera, e.g. the Mamiya ZD.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Chris Malcolm writes:

So if you're producing a landscape photograph which is meant to be
viewed at a subtended angle of 90 degrees for the proper visual effect
then you'll need a camera with around 24MP to achieve the same degree
of apparent sharpness as an 8x10 print viewed at the diagonal distance
of 13 inches and produced by a 6MP camera, e.g. the Mamiya ZD.

Yes, those numbers all make sense. In the case of IMAX, the image is
about 3 times the dimensions (10 times the area) of 35 mm 4-perf
full-aperture, so there's potentially 3 times as much detail to spread
over a visual angle that's somewhat less than 3 times larger than
normal, resulting in an image that's actually sharper than 35 despite
the larger size.

(A lot of other things go into getting sharp images that size in a movie
system, too. IMAX cameras and projectors are all pin-registered for
image stability, most 35 cameras and essentially all 35 projectors are
not, so the 35 image wanders much more. Thankfully, still photography
doesn't have to deal with frame-to-frame registration).

Dave