Another another digital camera question

The recent thread on what ISO really means in the context of digital
cameras confirmed my suspicions of how that is not really the same as film
ISO; useful enough to know, though, for both astro and terestrial use.

But (some) digital camers also allow you to set f-stops. In a "real"
camera, this has (among others) the effect of increasing the depth of
field. Not so much interest for astro, but I don't just take pictures in
the dark.

For digital cameras, are there any which actually do have a mechanical
f-stop, or is there an analogous software function to increase depth of
field? If not, I assume it's just used in the same way as the ISO setting.

SLR-type cameras excepted, of course; and if there is a software
depth-of-field it'd be *real* handy for post-processing...

On Sun, 15 Jul 2007 10:54:04 GMT, _
wrote:

For digital cameras, are there any which actually do have a mechanical
f-stop, or is there an analogous software function to increase depth of
field? If not, I assume it's just used in the same way as the ISO setting.

Digital cameras with adjustable f-stops (which isn't all of them) do it
mechanically, since there's no other way. They have electronic irises.
With these cameras, you can control your depth of focus just like any
other.

SLR-type cameras excepted, of course; and if there is a software
depth-of-field it'd be *real* handy for post-processing...

Not really. There is a camera I've read about that takes multiple
exposures very rapidly and produces a single image file that can be post
processed to select the focus distance and depth-of-field. Very
promising technology for digital cameras.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Jul 15, 6:54 am, Chris L Peterson wrote:
[...]
Not really. There is a camera I've read about that takes multiple
exposures very rapidly and produces a single image file that can be post
processed to select the focus distance and depth-of-field. Very
promising technology for digital cameras.

There's both a good and a bad part of that; the good is as you wrote.

The bad part is cameras have a finite number of shutter releases
before the mechanism needs repair -- this wasn't a real problem back
in the days of film because film cost and processing time tended to
limit the number of exposures one could/would take at a given time.

The number "50,000" often comes up as the rated number of shutter
releases for prosumer DSLRs (e.g., Nikon's D80, D70, D50, D40 and
Canon's Rebel series) and "100,000" for the higher-end cameras.

I often take 500 shots a week which, for a, say, D70, gives a 2-year
lifetime on the shutter, and bracketing (where 3 shots are taken in
automatic rapid sequence with different aperture/ISO/etc. or another
parameter) exacerbates the shutter lifetime problem if that feature
is enabled.

Something to consider.

On Sun, 15 Jul 2007 07:17:32 -0700, "
wrote:

The bad part is cameras have a finite number of shutter releases
before the mechanism needs repair -- this wasn't a real problem back
in the days of film because film cost and processing time tended to
limit the number of exposures one could/would take at a given time.

Well, I'm pretty sure the camera I mentioned doesn't use a mechanical
shutter for the subshots. Many digital cameras don't have a mechanical
shutter at all.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Jul 15, 7:21 am, Chris L Peterson wrote:
On Sun, 15 Jul 2007 07:17:32 -0700, "

wrote:
The bad part is cameras have a finite number of shutter releases
before the mechanism needs repair -- this wasn't a real problem back
in the days of film because film cost and processing time tended to
limit the number of exposures one could/would take at a given time.

Well, I'm pretty sure the camera I mentioned doesn't use a mechanical
shutter for the subshots. Many digital cameras don't have a mechanical
shutter at all.

OK; my comments pertained to DSLRs which do have a mechanical
shutter (and whose lenses typically have a mechanical iris) -- I
didn't
look back to the thread's beginning. :-)

In article ,
Chris L Peterson wrote:

On Sun, 15 Jul 2007 07:17:32 -0700, "
wrote:

The bad part is cameras have a finite number of shutter releases
before the mechanism needs repair -- this wasn't a real problem back
in the days of film because film cost and processing time tended to
limit the number of exposures one could/would take at a given time.

Well, I'm pretty sure the camera I mentioned doesn't use a mechanical
shutter for the subshots. Many digital cameras don't have a mechanical
shutter at all.

Most non-DSLR digital cameras lack mechanical shutters: if your camera
has an "electronic viewfinder", or an LCD screen where you can view your
image before you shoot it, then it has no mechanical shutter.

A lot of these cameras have quite limited f-stop settings too: quite
often you cannot set the f-stop smaller than f/8 (and here I mean
smaller aperture, not smaller f-number!). Which means the CCD chip
can get some damage if you point your camera towards the Sun. "But
why would anyone want to point their camera towards the Sun?", I
hear someone ask -- well, to photograph halo phenomena, of course!
Haloes can be relly beautiful --- anyway, I've burnt a permanent
"mark" in one corner of one of my own digital cameras, probably when
trying to photograph a halo.

So I really enjoy the shutter of a DSLR: they ensure the CCD chip
won't get any light until you really take your picture. And that,
combined with the ability to set the aperture as small as f/22 or f/32
or even smaller, and very short exposure times of 1/2000 or 1/4000
second, makes it safe to shoot a picture where the Sun is somewhere in
the image.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

"Paul Schlyter" wrote:

Most non-DSLR digital cameras lack mechanical shutters: if your camera
has an "electronic viewfinder", or an LCD screen where you can view your
image before you shoot it, then it has no mechanical shutter.

Are you sure? My Fuji DX-8 (non-DSLR) has a mechanical shutter that
sounds like an 8-track tape player changing tracks, yet it allows preview
on the LCD before and during shooting.

Having read the technical background to MER's Pancam system, I guess
image smearing is a problem that needs to be corrected for electronic
shuttering cameras.

In article . com,
wrote:

On Jul 15, 6:54 am, Chris L Peterson wrote:
[...]
Not really. There is a camera I've read about that takes multiple
exposures very rapidly and produces a single image file that can be post
processed to select the focus distance and depth-of-field. Very
promising technology for digital cameras.

There's both a good and a bad part of that; the good is as you wrote.

The bad part is cameras have a finite number of shutter releases
before the mechanism needs repair -- this wasn't a real problem back
in the days of film because film cost and processing time tended to
limit the number of exposures one could/would take at a given time.

The number "50,000" often comes up as the rated number of shutter
releases for prosumer DSLRs (e.g., Nikon's D80, D70, D50, D40 and
Canon's Rebel series) and "100,000" for the higher-end cameras.

I often take 500 shots a week which, for a, say, D70, gives a 2-year
lifetime on the shutter, and bracketing (where 3 shots are taken in
automatic rapid sequence with different aperture/ISO/etc. or another
parameter) exacerbates the shutter lifetime problem if that feature
is enabled.

Something to consider.

Please get back here in two years and report whether the shutter of
your DSLR has failed or not. Real empirical data is better than
extimates in advance.


An old story regarding how long something might work: when magnetic
tape recorders became widely available some time in the 1960's, there
were rumors that magnetic recordings would somehow "fade away" by
themselves after several decades. Recently I've been converting old
vinyl records and tape recordnings into digital formats, and I then
listened to old magnetic tapes I hadn't listened to for a very long
time. The oldest of these recordings were 38 years old -- and they
were still fine and well!

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

On Jul 17, 12:42 am, (Paul Schlyter) wrote:
In article . com,
[...]
Please get back here in two years and report whether the shutter of
your DSLR has failed or not. Real empirical data is better than
extimates in advance.

No need to wait; peoples' cameras are already experiencing the
shutter failures as reported in several Yahoo groups, and in one,
the Nikon-D70, a survey is presently ongoing collecting more data
and the 50,000 count seems definitely real (noting I haven't followed
reports in any of the Canon groups, but one person's Rebel (at work)
failed around 40,000 shutter releases per the EXIF data).

It would have been extremely rare for consumer film SLRs to have
that many shutter releases though my Dad's Contax did and it did
require shutter replacement; given the number of slides I inherited
he may have just exceeded 30,000 shutter releases (including after
the repair) some 20 years ago when he died.

[...]
An old story regarding how long something might work: when magnetic
tape recorders became widely available some time in the 1960's, there
were rumors that magnetic recordings would somehow "fade away" by
themselves after several decades. Recently I've been converting old
vinyl records and tape recordnings into digital formats, and I then
listened to old magnetic tapes I hadn't listened to for a very long
time. The oldest of these recordings were 38 years old -- and they
were still fine and well!

Same for me, including even 5-1/4" floppies from the late 1970s and
early to mid 1980s -- they still are readable.

On Jul 17, 12:42 am, (Paul Schlyter) wrote:

An old story regarding how long something might work: when magnetic
tape recorders became widely available some time in the 1960's, there
were rumors that magnetic recordings would somehow "fade away" by
themselves after several decades. Recently I've been converting old
vinyl records and tape recordnings into digital formats, and I then
listened to old magnetic tapes I hadn't listened to for a very long
time. The oldest of these recordings were 38 years old -- and they
were still fine and well!

However, the oxide on some tapes of the late 1960s and
early 1970s used a binder that soaked up water. Slowly,
over 30 or 40 years, this turned the tapes in to mush.
Apparently such tapes can be recovered by baking
them at a high enough temperature to drive out the
moisture, but not high enough to damage the tape any
further.

I've done prints from 50 year old negatives that had
not deteriorated in the slightest...it's kinda fun bringing
them back to life.

Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer