Why do DSLR's still use mirrors?

David J Taylor wrote:
SMS wrote:
Alfred Molon wrote:
In article , J?rgen Exner
says...
"Roger N. Clark (change username to rnclark)"
wrote:
Why do DSLR's still use mirrors?
Because without a mirror it would be a dSL without the R.

Most people probably don't know this fine distinction and would
consider any camera with a large sensor and interchangeable lenses a
DSLR.

This is true, even though it still has some of disadvantages of a P&S,
it at least has the larger sensor. Though if someone could make a ZLR
with a larger sensor, and a wide zoom range, it'd be better than the
G1.

They did - Sony made the R1 but it ended up having less zoom range, and
being a brute of a camera becuase of the size of the sensor. Did it sell?

I think the main reason it didn't sell well is that it fell between
two large stools of marketing and public perception. Most people
couldn't the point of a non-DSLR which was as big and heavy as a
DSLR. But if all you wanted was a DSLR with a good general purpose
zoom, it was exceptionally good image quality value for money.

--
Chris Malcolm

SMS wrote:
David J Taylor wrote:

They did - Sony made the R1 but it ended up having less zoom range, and
being a brute of a camera becuase of the size of the sensor. Did it sell?

It runs into the same problems as all of these ZLRs. By the time you put
on the long lens, and in the case of the R1 the larger sensor, you're
just not saving much in manufacturing cost versus using a lens mount and
a mirror, plus you still have all the other disadvantages of the P&S to
contend with. You've saved no weight and no size, and very little money,
and you end up with decidedly inferior results compared to a D-SLR.

Sony claimed that being able to have the lens much closer to the
sensor enabled them (i.e. Zeiss) to produce a high quality zoom much
more cheaply. Some reviewers suggested so much more cheaply that to
match its quality in a DSLR zoom you'd have to pay more than the cost
of the entire R1 just for the lens.

--
Chris Malcolm

Alfred Molon wrote:
In article , Chris Malcolm says...

It's not a camera problem, it's a wide lens problem. If you want a
wide lens to operate without vignetting with standard sized filters
you have to make the lens body wide enough to take the width of filter
required. Or you can slim it down and require the use of slim filters
or step-out rings. Since polarisers don't work well with wide lenses
anyway, because they're so wide the polarisation shifts a lot over the
image, wide lenses will very often not accommodate the extra depth of a
polariser, even a slimline one.

Sure, but if you buy an A350 and care about image quality (resolution)
there are not many options out there. You'll want to buy a CZ16-80. The
only other zoom lens in this focal length range which comes close is the
Tamron 17-50, probably with less vignetting due to its wider filter
thread, but with a substantially reduced focal length range. It's a PITA
changing lenses.

Aren't you like me moving up to the Sony A350 from an R1? The CZ16-80
does sound like a remarkably good lens. I do a lot of architectural
photography, and found that the R1's 14.3mm wasn't quite enough, and
with the wide angle extension which brought it to 11.5mm, was just a
touch short of that extremely useful 90 degree field of view. So the
CZ16-80 wasn't wide enough for me.

I don't know how high your quality standards are, but mine were to
begin with lenses which at their best had as good performance as the
R1. i.e. when downsized to the R1's 10MP. The two zooms I have which
in practice I find more than fulfil that requirement are the Sigma
10-20mm and the Sony (Tamron) 18-250mm. Not as good as the R1 at 10mm
and 250mm, but IMHO as good over a larger zoom range than the R1 could
get even with its extension lenses, and at their best with the extra
detail resolution you'd expect from the 40% extra image pixels.

--
Chris Malcolm

David J Taylor wrote:
Chris Malcolm wrote:
David J Taylor

Have you compared the A350/R1/8080 taking the same scene?

I've repeated a few of my best R1 shots with an A350 plus SAL18-250mm
zoom. There's a slight loss of contrast but the extra detail you'd
expect from the 14MP is there. At first I thought the loss of contrast
was a natural consequence of the larger number of lenses in the more
complex longer zoom, but now that I've noticed the very much wider
dynamic range in the A350 images, it may be a consequence of that. I'd
say that generally speaking when compared at pixel level and when both
lenses are used at their best apertures the SAL18-250 is the effective
equal in performance of the R1's zoom when used in the same zoom range
on a 14MP sensor, and up to the extra resolution.

At its wide and long extremes the optical performance falls off a bit,
I'd guess down to about 7MP standards, since downsizing to 7MP
conceals the optical flaws.

Two improvements of the A350 over the R1 which are very obvious as you
just wander about snapping things is that the exposure is much more
accurate. Highlights are very much more rarely blown. The second is
that not only is the autofocus much faster, and operates well in worse
conditions, but it's also more often right on the nail.

Thanks for that, Chris. About what you'd expect considering that the A350
and R1 have similar-sized sensors. Would the focus difference be due to
phase-detection (A350) versus maximum-contrast (R1)?

That's what they say :-) It's *much* faster, works better in the dim
light of overcast days, and in casual fast opportunistic snapping
catches the exact sharp perfect focus more often.

The exposure
metering should be as though, shouldn't it? Or is it that the separate
focus on the A350 can offer a greater dynamic measurement range than the
on-sensor exposure metering of the R1?

The A350 meters exposure in two different ways. When using the optical
viewfinder it does the same as other DSLRs (whatever that is). When
using the separate live view sensor (smaller than the image sensor) it
used that entire LV sensor to do the exposure, and as a result catches
the tiniest highlights with very accurate exposure.

I use Picasa to organise my images and do minor snapshot type
editing. I always push the "fix exposure" button just to see what
happens. With the R1's images it nearly always made at least a slight
adjustment. With the A350 it rarely does anything. I note that I don't
have to underexpose on the A350 to avoid losing the occasional
highlight, and it has enough dynamic range in RAW that that kind of
conservative highlight exposure doesn't lose any shadow detail
compared to the R1, quite the reverse.

SAL - you have me puzzled!

SAL18-250mm is Sony's name for their rebadged and slightly modded
version of the Tamron 18-250mm.

--
Chris Malcolm

David J Taylor wrote:
Alfred Molon wrote:
In article , David J
Taylor says...

I would still be interested in a comparison between the image
quality on the Sony A350, Sony R1, and Olympus 8080 cameras which I
believe you have owned.

I still have them all, but how to do this comparison? What scene
should I shoot? An outdoor scene with everything in focus?

Alfred,

I have an indoor test scene which I usually use with new cameras as a
basic function/quality check.

But I was hoping for some more like: "If I print at A4 size, I can't tell
the difference" or "The larger sensor usually provides a better quality
image", or whatever.

I certainly couldn't tell the difference in detail between the R1 and
the A350 at A4. Probably a close look at an A2 print would be
required. More detail in the A350, less contrast (easily fixed in an
editor), much wider dynamic range, much less noise at higher ISOs, and
more latitude in all directions from the RAW image.

The R1's images usually look better in a straight ex-camera jpeg, more
vivid punch. The A350's images have about as much more detail as you'd
expect, and more detail can be brought out of the highlights and deep
shadows.

--
Chris Malcolm

Chris Malcolm wrote:
David J Taylor
[]
The exposure
metering should be as good though, shouldn't it? Or is it that the
separate meter sensors on the A350 can offer a greater dynamic
measurement
range than the on-sensor exposure metering of the R1?

The A350 meters exposure in two different ways. When using the optical
viewfinder it does the same as other DSLRs (whatever that is). When
using the separate live view sensor (smaller than the image sensor) it
used that entire LV sensor to do the exposure, and as a result catches
the tiniest highlights with very accurate exposure.

Do you notice any significant difference between exposure measured in the
standard and live-view modes?

I use Picasa to organise my images and do minor snapshot type
editing. I always push the "fix exposure" button just to see what
happens. With the R1's images it nearly always made at least a slight
adjustment. With the A350 it rarely does anything. I note that I don't
have to underexpose on the A350 to avoid losing the occasional
highlight, and it has enough dynamic range in RAW that that kind of
conservative highlight exposure doesn't lose any shadow detail
compared to the R1, quite the reverse.

I do find that I get the results I prefer with the Nikon D40 and D60 set
to -1/3 stop exposure compensation, but that might just be the way I
meter.

SAL - you have me puzzled!

SAL18-250mm is Sony's name for their rebadged and slightly modded
version of the Tamron 18-250mm.

Thanks, I saw your later post on this as well.

David

In article , Chris Malcolm says...

Aren't you like me moving up to the Sony A350 from an R1?

Yep.

The CZ16-80
does sound like a remarkably good lens. I do a lot of architectural
photography, and found that the R1's 14.3mm wasn't quite enough, and
with the wide angle extension which brought it to 11.5mm, was just a
touch short of that extremely useful 90 degree field of view. So the
CZ16-80 wasn't wide enough for me.

Well, I do a lot of panorama stitching so wideness of a lens is a non-
issue, as I can go down to whatever angle of view by stitching
individual images together. Has the advantage that all geometric
distortions are automatically corrected.
--

Alfred Molon
------------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

In article , David J
Taylor says...

But I was hoping for some more like: "If I print at A4 size, I can't tell
the difference" or "The larger sensor usually provides a better quality
image", or whatever.

Since the indoor image would be taken on a tripod at lowest ISO, the
larger sensor wouldn't give (almost) any noise advantage, only more
resolution.
--

Alfred Molon
------------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

"J. Clarke" wrote in message

David J Taylor wrote:

[...]

I appreciate that the resolution may differ, but I am thinking about
the same scene displayed at the same size, whether on a print, TV or
computer monitor. I seem to be spared significant vignetting
problems with the Nikon 16-85mm + 2nd-line polarising filter.

A side by side between the G10 and the 50D would be interesting IMO.
Both approximately 15 megapixels, same generation of technology, same
manufacturer.

What precisely are you looking for? I have a 50D with 28-80L and 100-300L
lenses, and my partner has a G10.