Why do DSLR's still use mirrors?

I was asked to comment on P&S versus DSLRs. I only read a few
posts to see things haven't changed much here. I didn't see
a real answer so here is one major difference between DSLRs
and P&S cameras that does not seem to have been discussed.
----

Why do DSLR's still use mirrors? One answer is simple and due
to the requirements of predictive autofocus and tracking of
moving subjects. Predictive autofocus systems provide the fastest
autofocus and fastest autofocus tracking technology currently
available in consumer and professional cameras, both film and digital.

In general, the cameras that fit in your pocket are small low-end
cameras that have slow response times. But even if you find one with
low shutter lag, it will not be of much help on subjects moving
toward or away from your camera. For such a moving subject,
the full press shutter lag is only a small part of the story
in getting a sharp picture.

Many cameras have what is called "Live View." Live view is an electronic
method of reading the "digital" sensor and displaying the result on
an LCD screen. The term "Live View" is a misnomer. It takes time
to read out the sensor, and the more pixels the sensor has, the more
time it takes. Very high speed electronics in high end cameras can
read out at rates of around 100 million pixels per second. On a
10-megapixel camera, that means the time to read out is about 1/10th
second (100 milliseconds). On lower cost cameras, slower
electronics are used, so the readout times can be longer. It also
takes time to send that data to the LCD. On some cameras, the shutter
speed can also influence the cycle time, adding another delay. All
this means that "Live View" is actually delayed view. Often this
delay is longer than 100 milliseconds, and that means when you
press the shutter the subject is in a slightly different position
than what you see on the LCD screen. This is another factor in fast
action photography and why those who do such photography usually choose
an optical viewfinder. But it is not the main factor. The main factor
is predictive autofocus.

P&S cameras, especially small cheaper ones use the sensor for autofocus
using a contrast detection method. The lens is moved, the sensor read out,
and the contrast checked, the lens moved, the sensor read out, the
contrast checked and if it is getting better keep moving in that direction,
if not, go back, hunting for best focus.

The full press shutter lag, the time from when you press the
shutter to when the camera actually takes the picture, is the best
time for a static (not moving) subject in good light. If the subject
moves, the camera gets confused because the search for the best focus
is continually moving too. That increases the lag time. You can experience
such increased lag on static subjects too if you are swaying back and forth:
the camera to subject distance is changing, confusing the camera. I
have often had P&S cameras take 2, 3 and more seconds to take the picture
when their shutter lag is rated about 1/2 second due to these effects.

For static subjects, a DSLR does what is called a phase detection: the
phase is measured which tells the camera how much the subject is out of focus.
The camera calculates how much to move the focus and does that in one step.
No second check is required. For moving subjects, put the camera in
what is called predictive autofocus and the camera monitors the phase
of the focus as the lens is moved (or not moved). The changing phase tells
the camera what direction the subject is moving and how fast, it then moves
the focus to the best position but also continually tracks it. Even more
impressive is that the camera knows its own shutter lag and predicts where
the best focus will be when the shutter actually opens and sets the lens
to that point.

When holding down the shutter on a DSLR and taking multiple frames,
each time the mirror drops, is allows you to see the subject to help
you track the subject, but the phase detection system does another
measurement of the focus. With each measurement it continually tracks
the focus, the velocity and the changing velocity. The phase detection
system in DSLRs is a set of optics and sensors behind and below the
reflex mirror. Because of the requirements of a phase detection
system design, a mirror is necessary, thus reflex mirrors are not likely
to go away. One could do this with beam splitters, but that loses
light, compromising light for the phase detection system, light metering
system and the picture you want to obtain. Again, the reflex mirror
serves a very important part of the phase detection system so is
not likely to go away.

Here is a demonstration of autofocus tracking of a DSLR:
http://www.clarkvision.com/photoinfo...with.autofocus

Test your shutter lag in your camera at:
http://www.shooting-digital.com/colu...st/default.asp

Think of this example: your baby is about to take its first step.

You grab the camera aim, and in a blink of an eye the event
is over. So did you get the picture (or several)?

P&S: Unlikely. The baby does two steps and falls; the camera finally
focuses and gets a picture of the baby on the floor. That's
assuming the camera had "instant on," otherwise the you may
have simply watched the event as the camera slowly turned on.

DSLR in single shot mode all focus point enabled: No! The camera
focused on the wall in the background. ;-)

DSLR in single shot mode, one focus point on the baby:
One frame in focus then as the baby moves forward, successive frames
are increasingly out of focus.

DSLR in predictive autofocus mode, one focus point on the baby:
All frames in focus. Many excellent pictures of the event.

The difference in "focus lock" versus predictive autofocus:
In predictive autofocus the camera fires when you press the shutter
all the way, regardless of where the focus is. If the camera
locked onto the subject and is tracking it (and its speed can
be tracked by the lens AF speed) the prediction is usually
quite good and stays in excellent focus, or, with some slower AF
consumer lenses and bodies, at least better focus than if using
single shot mode on moving subjects.

Bottom line: if you want to take photographs of things in action that
may be moving toward or away from the camera, choose a camera with
predictive autofocus. All DSLRs that I know of have predictive
autofocus. I do not know any P&S cameras with predictive autofocus.

One may use "pre-focus" on cameras without predictive autofocus.
With this method, the photographer must anticipate where the peak
action will occur, set the focus for that positions and wait.
This can work well for things like the finish line of a race.
Unfortunately if the best action occurred at a slightly
different position, you miss the best image. That is where
predictive autofocus shines.

Roger
http://www.clarkvision.com/photoinfo....and.autofocus

On Thu, 06 Nov 2008 21:16:18 -0700, "Roger N. Clark (change username
to rnclark)" wrote:


--- snip ----

Test your shutter lag in your camera at:
http://www.shooting-digital.com/colu...st/default.asp

That seems a better test of my reaction time than anything else.

--- snip ----



Eric Stevens

LOL!!! The N.Clark spamming moron is BACK spewing his ignorance and stupidity
again!!

LOL


On Thu, 06 Nov 2008 21:16:18 -0700, "Roger N. Clark (change username to
rnclark)" wrote:

I was asked to comment on P&S versus DSLRs. I only read a few
posts to see things haven't changed much here. I didn't see
a real answer so here is one major difference between DSLRs
and P&S cameras that does not seem to have been discussed.
----

Why do DSLR's still use mirrors? One answer is simple and due
to the requirements of predictive autofocus and tracking of
moving subjects. Predictive autofocus systems provide the fastest
autofocus and fastest autofocus tracking technology currently
available in consumer and professional cameras, both film and digital.

In general, the cameras that fit in your pocket are small low-end
cameras that have slow response times. But even if you find one with
low shutter lag, it will not be of much help on subjects moving
toward or away from your camera. For such a moving subject,
the full press shutter lag is only a small part of the story
in getting a sharp picture.

You're a bit late, moron. There have been quite a few threads where people
tested their P&S cameras and showed them to be much faster than your beloved and
wrongly worshipped LOW-END LOSER'S DSLR.

LOL


Many cameras have what is called "Live View." Live view is an electronic
method of reading the "digital" sensor and displaying the result on
an LCD screen. The term "Live View" is a misnomer. It takes time
to read out the sensor, and the more pixels the sensor has, the more
time it takes. Very high speed electronics in high end cameras can
read out at rates of around 100 million pixels per second. On a
10-megapixel camera, that means the time to read out is about 1/10th
second (100 milliseconds). On lower cost cameras, slower
electronics are used, so the readout times can be longer. It also
takes time to send that data to the LCD. On some cameras, the shutter
speed can also influence the cycle time, adding another delay. All
this means that "Live View" is actually delayed view. Often this
delay is longer than 100 milliseconds, and that means when you
press the shutter the subject is in a slightly different position
than what you see on the LCD screen. This is another factor in fast
action photography and why those who do such photography usually choose
an optical viewfinder. But it is not the main factor. The main factor
is predictive autofocus.

LOL!! He doesn't even know how to use live-view nor how it works. The only "lag"
is the EVF/LCD refresh rate, which is 60 to 120 fps or faster. The live-view is
accurately relaying the chosen shutter speed. But you're too amazingly stupid to
realize why that is of great benefit.

Rather than address all your ignorance and stupidity one by one with the respect
that a better person would deserve, it's much easier to just list here all the
FACTS that disprove everything you have ever said and believed in your sorry
excuse for a life. You're only worth canned replies.



1. P&S cameras can have more seamless zoom range than any DSLR glass in
existence. (E.g. 9mm f2.7 - 1248mm f/3.5.) There are now some excellent
wide-angle and telephoto (tel-extender) add-on lenses for many makes and models
of P&S cameras. Add either or both of these small additions to your photography
gear and, with some of the new super-zoom P&S cameras, you can far surpass any
range of focal-lengths and apertures that are available or will ever be made for
larger format cameras.

2. P&S cameras can have much wider apertures at longer focal lengths than any
DSLR glass in existence. (E.g. 549mm f/2.4 and 1248mm f/3.5) when used with
high-quality tel-extenders, which by the way, do not reduce the lens' original
aperture one bit. Only DSLRs suffer from that problem due to the manner in which
their tele-converters work. They can also have higher quality full-frame
180-degree circular fisheye and intermediate super-wide-angle views than any
DSLR and its glass in existence. Some excellent fish-eye adapters can be added
to your P&S camera which do not impart any chromatic-aberration nor
edge-softness. When used with a super-zoom P&S camera this allows you to
seamlessly go from as wide as a 9mm (or even wider) 35mm equivalent focal-length
up to the wide-angle setting of the camera's own lens.

3. P&S smaller sensor cameras can and do have wider dynamic range than larger
sensor cameras E.g. a 1/2.5" sized sensor can have a 10.3EV Dynamic Range vs. an
APS-C's typical 7.0-8.0EV Dynamic Range. One quick example:
http://farm4.static.flickr.com/3142/...7ceaf3a1_o.jpg

4. P&S cameras are cost efficient. Due to the smaller (but excellent) sensors
used in many of them today, the lenses for these cameras are much smaller.
Smaller lenses are easier to manufacture to exacting curvatures and are more
easily corrected for aberrations than larger glass used for DSLRs. This also
allows them to perform better at all apertures rather than DSLR glass which is
only good for one aperture setting per lens. Side by side tests prove that P&S
glass can out-resolve even the best DSLR glass ever made. After all is said and
done, you will spend 1/4th to 1/50th the price that you would have to in order
to get comparable performance in a DSLR camera. When you buy a DSLR you are
investing in a body that will require expensive lenses, hand-grips, external
flash units, heavy tripods, more expensive larger filters, etc. etc. The
outrageous costs of owning a DSLR add up fast after that initial DSLR body
purchase. Camera companies count on this, all the way to their banks.

5. P&S cameras are lightweight and convenient. With just one P&S camera plus one
small wide-angle adapter and one small telephoto adapter weighing just a couple
pounds, you have the same amount of zoom range as would require over 10 to 20
pounds of DSLR body and lenses. You can carry the whole P&S kit in one roomy
pocket of a wind-breaker or jacket. The DSLR kit would require a sturdy
backpack. You also don't require a massive tripod. Large tripods are required to
stabilize the heavy and unbalanced mass of the larger DSLR and its massive
lenses. A P&S camera, being so light, can be used on some of the most
inexpensive, compact, and lightweight tripods with excellent results.

6. P&S cameras are silent. For the more common snap-shooter/photographer, you
will not be barred from using your camera at public events, stage-performances,
and ceremonies. Or when trying to capture candid shots, you won't so easily
alert all those within a block around, from the obnoxious noise that your DSLR
is making, that you are capturing anyone's images. For the more dedicated
wildlife photographer a P&S camera will not endanger your life when
photographing potentially dangerous animals by alerting them to your presence.

7. Some P&S cameras can run the revolutionary CHDK software on them, which
allows for lightning-fast motion detection (literally, lightning fast 45ms
response time, able to capture lightning strikes automatically) so that you may
capture more elusive and shy animals (in still-frame and video) where any
evidence of your presence at all might prevent their appearance. Without the
need of carrying a tethered laptop along or any other hardware into remote
areas--which only limits your range, distance, and time allotted for bringing
back that one-of-a-kind image. It also allows for unattended time-lapse
photography for days and weeks at a time, so that you may capture those unusual
or intriguing subject-studies in nature. E.g. a rare slime-mold's propagation,
that you happened to find in a mountain-ravine, 10-days hike from the nearest
laptop or other time-lapse hardware. (The wealth of astounding new features that
CHDK brings to the creative-table of photography are too extensive to begin to
list them all here. See http://chdk.wikia.com/wiki/CHDK )

8. P&S cameras can have shutter speeds up to 1/40,000th of a second. See:
http://chdk.wikia.com/wiki/CameraFeatures Allowing you to capture fast subject
motion in nature (e.g. insect and hummingbird wings) WITHOUT the need of
artificial and image destroying flash, using available light alone. Nor will
their wing shapes be unnaturally distorted from the focal-plane shutter
distortions imparted in any fast moving objects, as when photographed with all
DSLRs. (See focal-plane-shutter-distortions example-image link in #10.)

9. P&S cameras can have full-frame flash-sync up to and including shutter-speeds
of 1/40,000th of a second. E.g.
http://chdk.wikia.com/wiki/Samples:_...%26_Flash-Sync without
the use of any expensive and specialized focal-plane shutter flash-units that
must strobe for the full duration of the shutter's curtain to pass over the
frame. The other downside to those kinds of flash units, is that the
light-output is greatly reduced the faster the shutter speed. Any shutter speed
used that is faster than your camera's X-Sync speed is cutting off some of the
flash output. Not so when using a leaf-shutter. The full intensity of the flash
is recorded no matter the shutter speed used. Unless, as in the case of CHDK
capable cameras where the camera's shutter speed can even be faster than the
lightning-fast single burst from a flash unit. E.g. If the flash's duration is
1/10,000 of a second, and your CHDK camera's shutter is set to 1/20,000 of a
second, then it will only record half of that flash output. P&S cameras also
don't require any expensive and dedicated external flash unit. Any of them may
be used with any flash unit made by using an inexpensive slave-trigger that can
compensate for any automated pre-flash conditions. Example:
http://www.adorama.com/SZ23504.html

10. P&S cameras do not suffer from focal-plane shutter drawbacks and
limitations. Causing camera shake, moving-subject image distortions
(focal-plane-shutter distortions, e.g.
http://images3.wikia.nocookie.net/ch...istortions.jpg
do note the distorted tail-rotor too and its shadow on the ground, 90-degrees
from one another), last-century-slow flash-sync, obnoxiously loud slapping
mirrors and shutter curtains, shorter mechanical life, easily damaged, expensive
repair costs, etc.

11. When doing wildlife photography in remote and rugged areas and harsh
environments, or even when the amateur snap-shooter is trying to take their
vacation photos on a beach or dusty intersection on some city street, you're not
worrying about trying to change lenses in time to get that shot (fewer missed
shots), dropping one in the mud, lake, surf, or on concrete while you do, and
not worrying about ruining all the rest of your photos that day from having
gotten dust & crud on the sensor. For the adventurous photographer you're no
longer weighed down by many many extra pounds of unneeded glass, allowing you to
carry more of the important supplies, like food and water, allowing you to trek
much further than you've ever been able to travel before with your old D/SLR
bricks.

12. Smaller sensors and the larger apertures available allow for the deep DOF
required for excellent macro-photography, WITHOUT the need of any image
destroying, subject irritating, natural-look destroying flash. No DSLR on the
planet can compare in the quality of available-light macro photography that can
be accomplished with nearly any smaller-sensor P&S camera.

13. P&S cameras include video, and some even provide for CD-quality stereo audio
recordings, so that you might capture those rare events in nature where a
still-frame alone could never prove all those "scientists" wrong. E.g. recording
the paw-drumming communication patterns of eusocial-living field-mice. With your
P&S video-capable camera in your pocket you won't miss that once-in-a-lifetime
chance to record some unexpected event, like the passage of a bright meteor in
the sky in daytime, a mid-air explosion, or any other newsworthy event. Imagine
the gaping hole in our history of the Hindenberg if there were no film cameras
there at the time. The mystery of how it exploded would have never been solved.
Or the amateur 8mm film of the shooting of President Kennedy. Your video-ready
P&S camera being with you all the time might capture something that will be a
valuable part of human history one day.

14. P&S cameras have 100% viewfinder coverage that exactly matches your final
image. No important bits lost, and no chance of ruining your composition by
trying to "guess" what will show up in the final image. With the ability to
overlay live RGB-histograms, and under/over-exposure area alerts (and dozens of
other important shooting data) directly on your electronic viewfinder display
you are also not going to guess if your exposure might be right this time. Nor
do you have to remove your eye from the view of your subject to check some
external LCD histogram display, ruining your chances of getting that perfect
shot when it happens.

15. P&S cameras can and do focus in lower-light (which is common in natural
settings) than any DSLRs in existence, due to electronic viewfinders and sensors
that can be increased in gain for framing and focusing purposes as light-levels
drop. Some P&S cameras can even take images (AND videos) in total darkness by
using IR illumination alone. (See: Sony) No other multi-purpose cameras are
capable of taking still-frame and videos of nocturnal wildlife as easily nor as
well. Shooting videos and still-frames of nocturnal animals in the total-dark,
without disturbing their natural behavior by the use of flash, from 90 ft. away
with a 549mm f/2.4 lens is not only possible, it's been done, many times, by
myself. (An interesting and true story: one wildlife photographer was nearly
stomped to death by an irate moose that attacked where it saw his camera's flash
come from.)

16. Without the need to use flash in all situations, and a P&S's nearly 100%
silent operation, you are not disturbing your wildlife, neither scaring it away
nor changing their natural behavior with your existence. Nor, as previously
mentioned, drawing its defensive behavior in your direction. You are recording
nature as it is, and should be, not some artificial human-changed distortion of
reality and nature.

17. Nature photography requires that the image be captured with the greatest
degree of accuracy possible. NO focal-plane shutter in existence, with its
inherent focal-plane-shutter distortions imparted on any moving subject will
EVER capture any moving subject in nature 100% accurately. A leaf-shutter or
electronic shutter, as is found in ALL P&S cameras, will capture your moving
subject in nature with 100% accuracy. Your P&S photography will no longer lead a
biologist nor other scientist down another DSLR-distorted path of non-reality.

18. Some P&S cameras have shutter-lag times that are even shorter than all the
popular DSLRs, due to the fact that they don't have to move those agonizingly
slow and loud mirrors and shutter curtains in time before the shot is recorded.
In the hands of an experienced photographer that will always rely on prefocusing
their camera, there is no hit & miss auto-focusing that happens on all
auto-focus systems, DSLRs included. This allows you to take advantage of the
faster shutter response times of P&S cameras. Any pro worth his salt knows that
if you really want to get every shot, you don't depend on automatic anything in
any camera.

19. An electronic viewfinder, as exists in all P&S cameras, can accurately relay
the camera's shutter-speed in real-time. Giving you a 100% accurate preview of
what your final subject is going to look like when shot at 3 seconds or
1/20,000th of a second. Your soft waterfall effects, or the crisp sharp outlines
of your stopped-motion hummingbird wings will be 100% accurately depicted in
your viewfinder before you even record the shot. What you see in a P&S camera is
truly what you get. You won't have to guess in advance at what shutter speed to
use to obtain those artistic effects or those scientifically accurate nature
studies that you require or that your client requires. When testing CHDK P&S
cameras that could have shutter speeds as fast as 1/40,000th of a second, I was
amazed that I could half-depress the shutter and watch in the viewfinder as a
Dremel-Drill's 30,000 rpm rotating disk was stopped in crisp detail in real
time, without ever having taken an example shot yet. Similarly true when
lowering shutter speeds for milky-water effects when shooting rapids and falls,
instantly seeing the effect in your viewfinder. Poor DSLR-trolls will never
realize what they are missing with their anciently slow focal-plane shutters and
wholly inaccurate optical viewfinders.

20. P&S cameras can obtain the very same bokeh (out of focus foreground and
background) as any DSLR by just increasing your focal length, through use of its
own built-in super-zoom lens or attaching a high-quality telextender on the
front. Just back up from your subject more than you usually would with a DSLR.
Framing and the included background is relative to the subject at the time and
has nothing at all to do with the kind of camera and lens in use. Your f/ratio
(which determines your depth-of-field), is a computation of focal-length divided
by aperture diameter. Increase the focal-length and you make your DOF shallower.
No different than opening up the aperture to accomplish the same. The two
methods are identically related where DOF is concerned.

21. P&S cameras will have perfectly fine noise-free images at lower ISOs with
just as much resolution as any DSLR camera. Experienced Pros grew up on ISO25
and ISO64 film all their lives. They won't even care if their P&S camera can't
go above ISO400 without noise. An added bonus is that the P&S camera can have
larger apertures at longer focal-lengths than any DSLR in existence. The time
when you really need a fast lens to prevent camera-shake that gets amplified at
those focal-lengths. Even at low ISOs you can take perfectly fine hand-held
images at super-zoom settings. Whereas the DSLR, with its very small apertures
at long focal lengths require ISOs above 3200 to obtain the same results. They
need high ISOs, you don't. If you really require low-noise high ISOs, there are
some excellent models of Fuji P&S cameras that do have noise-free images up to
ISO1600 and more.

22. Don't for one minute think that the price of your camera will in any way
determine the quality of your photography. Any of the newer cameras of around
$100 or more are plenty good for nearly any talented photographer today. IF they
have talent to begin with. A REAL pro can take an award winning photograph with
a cardboard Brownie Box camera made a century ago. If you can't take excellent
photos on a P&S camera then you won't be able to get good photos on a DSLR
either. Never blame your inability to obtain a good photograph on the kind of
camera that you own. Those who claim they NEED a DSLR are only fooling
themselves and all others. These are the same people that buy a new camera every
year, each time thinking, "Oh, if I only had the right camera, a better camera,
better lenses, faster lenses, then I will be a great photographer!" Camera
company's love these people. They'll never be able to get a camera that will
make their photography better, because they never were a good photographer to
begin with. The irony is that by them thinking that they only need to throw
money at the problem, they'll never look in the mirror to see what the real
problem is. They'll NEVER become good photographers. Perhaps this is why these
self-proclaimed "pros" hate P&S cameras so much. P&S cameras instantly reveal to
them their ****-poor photography skills.

23. Have you ever had the fun of showing some of your exceptional P&S
photography to some self-proclaimed "Pro" who uses $30,000 worth of camera gear.
They are so impressed that they must know how you did it. You smile and tell
them, "Oh, I just use a $150 P&S camera." Don't you just love the look on their
face? A half-life of self-doubt, the realization of all that lost money, and a
sadness just courses through every fiber of their being. Wondering why they
can't get photographs as good after they spent all that time and money. Get good
on your P&S camera and you too can enjoy this fun experience.

24. Did we mention portability yet? I think we did, but it is worth mentioning
the importance of this a few times. A camera in your pocket that is instantly
ready to get any shot during any part of the day will get more award-winning
photographs than that DSLR gear that's sitting back at home, collecting dust,
and waiting to be loaded up into that expensive back-pack or camera bag, hoping
that you'll lug it around again some day.

25. A good P&S camera is a good theft deterrent. When traveling you are not
advertising to the world that you are carrying $20,000 around with you. That's
like having a sign on your back saying, "PLEASE MUG ME! I'M THIS STUPID AND I
DESERVE IT!" Keep a small P&S camera in your pocket and only take it out when
needed. You'll have a better chance of returning home with all your photos. And
should you accidentally lose your P&S camera you're not out $20,000. They are
inexpensive to replace.

There are many more reasons to add to this list but this should be more than
enough for even the most unaware person to realize that P&S cameras are just
better, all around. No doubt about it.

The phenomenon of everyone yelling "You NEED a DSLR!" can be summed up in just
one short phrase:

"If even 5 billion people are saying and doing a foolish thing, it remains a
foolish thing."

On Fri, 07 Nov 2008 06:57:24 -0600, Hank Thomas
wrote:

speed can also influence the cycle time, adding another delay. All
this means that "Live View" is actually delayed view. Often this
delay is longer than 100 milliseconds, and that means when you
press the shutter the subject is in a slightly different position
than what you see on the LCD screen. This is another factor in fast
action photography and why those who do such photography usually choose
an optical viewfinder. But it is not the main factor. The main factor
is predictive autofocus.

LOL!! He doesn't even know how to use live-view nor how it works. The only "lag"
is the EVF/LCD refresh rate, which is 60 to 120 fps or faster. The live-view is

Thank you for revealing once again that when it comes to the real
facts about cameras, you have no idea what you're talking about.

You can see the effects of live view lag on high pixel count cameras
easily, and it's much greater than the LCD refresh rate. Just point
the camera at something and then move sharply and you'll see the
movement on the LCD image is delayed from when you actually moved the
camera.

This delay is so low as to be not noticable with my old 4MP P&S. But
I just tried it in Best Buy with a whole slew of 10MP P&S and even the
live view on two DSLRs and the delay is noticable to some degree or
another.

Steve

"Roger N. Clark (change username to rnclark)" wrote in
message ...

Here is a demonstration of autofocus tracking of a DSLR:
http://www.clarkvision.com/photoinfo...with.autofocus


You mentioned the possibility of autofocus shifting to the background with a
busy background. On a 20D this sometimes happens to me even with a plain
sky when tracking fast moving jets (and the AF point moved off the subject
very briefly). Even more annoyingly, with a plain sky there is nothing for
the AF to focus on and so the lens just hunts and you loose the shot.
Surely cameras now-a-days should be intelligent enough to know that if you
have been tracking a subject for a few seconds, that this is the subject you
are trying to photograph and therefore shouldn't be so quick to try and
focus on something else?

You also mentioned the AF shifting to the foreground in the case where you
came between your friend and the eagle. I have also experienced this too
and is similar to the above situation. Why should AF think that you
suddenly want to shift focus to the foreground, when you have already been
tracking the subject for a few seconds?

In the last scenario, with custom functions it is possible to change the AE
button to stop/start AF when you press the button (if for example you are
panning and know that there is a subject (such as a tree) coming up between
you and what you are photographing). Of course, this takes a bit of getting
used to and is not ideal. However, I thought that CF.20 on the 1D series
allowed you to change the sensitivity of the AI Servo tracking, so that for
sports shooters where it's not uncommon for a referee/another player to run
between you and your subject (or in the case of your friend, you coming
between the bird and him), it delays shifting focus so quickly. Maybe the
'slow' sensitivity setting should be longer than 1 second before shifting
focus? Or, maybe there should be a CF that you can turn on that tells the
camera that if you are tracking a subject for more than say a couple of
seconds, that this is what you are trying to photograph and not shift focus
to something else? With scene recognition/colour pattern tracking, surely
it is possible for the camera to recognise what you are tracking? Afterall,
if you want to focus on something else, you would let go of the button and
pick up focus again.

It would be interesting to know if Nikons 3D system prevents the above 2
mentioned problems. I've just looked on Google briefly and if appears to
use colour recognition in it's 3D focus tracking system:
http://kammagamma.com/articles/nikon...dynamic-af.php

I am also wondering if it's possible to focus and recompose with the Nikon
3D system and it will track the area that you took the initial focus from?
So for example, in a portrait you focus on an eye with the centre point,
recompose and the camera tracks where the eye is and keeps it in focus. Or
in your situation with the bird, you focus on the head with the centre point
and if you recompose whilst still tracking, it will keep focus on the head
and ignore the wings, etc.

"Hank Thomas" wrote in message
...


LOL!!! The N.Clark spamming moron is BACK spewing his ignorance and
stupidity
again!!

LOL


23. Have you ever had the fun of showing some of your exceptional P&S
photography to some self-proclaimed "Pro" who uses $30,000 worth of camera
gear.
They are so impressed that they must know how you did it.

We keep asking to see some of your photos.

Put up or shut up.

Roy G

On Fri, 07 Nov 2008 13:41:36 GMT, Steve wrote:


On Fri, 07 Nov 2008 06:57:24 -0600, Hank Thomas
wrote:

speed can also influence the cycle time, adding another delay. All
this means that "Live View" is actually delayed view. Often this
delay is longer than 100 milliseconds, and that means when you
press the shutter the subject is in a slightly different position
than what you see on the LCD screen. This is another factor in fast
action photography and why those who do such photography usually choose
an optical viewfinder. But it is not the main factor. The main factor
is predictive autofocus.

LOL!! He doesn't even know how to use live-view nor how it works. The only "lag"
is the EVF/LCD refresh rate, which is 60 to 120 fps or faster. The live-view is

Thank you for revealing once again that when it comes to the real
facts about cameras, you have no idea what you're talking about.

You can see the effects of live view lag on high pixel count cameras
easily, and it's much greater than the LCD refresh rate. Just point
the camera at something and then move sharply and you'll see the
movement on the LCD image is delayed from when you actually moved the
camera.

This delay is so low as to be not noticable with my old 4MP P&S. But
I just tried it in Best Buy with a whole slew of 10MP P&S and even the
live view on two DSLRs and the delay is noticable to some degree or
another.

Steve

LOL

Thanks for CONFIRMING that you don't know what you are talking about. Re-read
this, paying particular attention to the second paragraph. This now proves just
how unaware and unperceptive that you are. I'd hate to see your photography
after knowing this. There appears to be a mismatch between your eyes and your
brain. I'd have that checked out if I were you.

LOL

On Wed, 05 Nov 2008 23:24:20 GMT, "Dudley Hanks"
wrote:

Live View drag

This is such a huge misnomer. There really is no such thing as "live view drag"
in any camera with an EVF/LCD system these days. A true live-view delay will
never be more than about 1/60th of a second, and in many cameras much faster
than that as a minimum, far shorter than any human perception. This is the
refresh rate of the EVF/LCD display.

What you are experiencing as "live view drag" is the live-view recreating the
shutter-speed in real time. This is how an EVF/LCD viewfinder is able to
accurately represent those soft moving-water effects at slow shutter speeds and
stop-motion flapping bird wing images at high shutter speeds. The reason this
"live-view drag" has become a mantra of those with less experience is that they
test their P&S camera in the store. Never once realizing that the slower shutter
speed used indoors is what causes this perceived "live view drag".

For the experienced/advanced photographer that has come to understand the vast
benefits they wouldn't buy any camera without this feature. Having what you call
this "live view drag" is even more important to someone like me than being able
to use a bright DOF preview (as also exists on all P&S cameras). I want to
instantly see what happens to the final capture of my moving subjects as I
change shutter speeds. I enjoy having that instantaneous film-to-print preview
in real-time as I frame my shots.

D-SLR owners who have never had this great feature all their lives won't
recognize it for what it is, nor will they understand how to make use of it.
They at first, wrongly and ignorantly, consider this some kind of drawback
instead of the great asset that it is. Until they finally learn on their own.
This is why "live view" is becoming more commonplace in D-SLRs, to slowly
introduce them to the vast benefits that P&S cameras have had for a decade.

The mindless D-SLR owner/buyer/promoter will eventually figure it out, one day.
But then, come to think of it, the D-SLR owner lost use of something as simple
as having a bright DOF preview (as used to exist in better SLRs of the past, and
still exists on all P&S cameras). They don't consider that any great loss nor
even realize why its important. Some will just never figure it out.

Roger N. Clark (change username to rnclark) wrote:


Why do DSLR's still use mirrors?

Simple. If it didn't have a mirror (or surface that acts like a mirror)
it wouldn't be a single lens REFLEX. The term reflex means it has a
mirror in the viewfinding train. This is true film OR digital.

Note that a "twin lens reflex" also generally has a 45 degree folding
mirror also.

On Fri, 7 Nov 2008 13:43:22 -0000, "Paul" wrote:

"Roger N. Clark (change username to rnclark)" wrote in
message ...

Here is a demonstration of autofocus tracking of a DSLR:
http://www.spamlink.com/photoinfo/tr...with.autofocus


You mentioned the possibility of autofocus shifting to the background with a
busy background. On a 20D this sometimes happens to me even with a plain
sky when tracking fast moving jets (and the AF point moved off the subject
very briefly). Even more annoyingly, with a plain sky there is nothing for
the AF to focus on and so the lens just hunts and you loose the shot.
Surely cameras now-a-days should be intelligent enough to know that if you
have been tracking a subject for a few seconds, that this is the subject you
are trying to photograph and therefore shouldn't be so quick to try and
focus on something else?

You also mentioned the AF shifting to the foreground in the case where you
came between your friend and the eagle. I have also experienced this too
and is similar to the above situation. Why should AF think that you
suddenly want to shift focus to the foreground, when you have already been
tracking the subject for a few seconds?

In the last scenario, with custom functions it is possible to change the AE
button to stop/start AF when you press the button (if for example you are
panning and know that there is a subject (such as a tree) coming up between
you and what you are photographing). Of course, this takes a bit of getting
used to and is not ideal. However, I thought that CF.20 on the 1D series
allowed you to change the sensitivity of the AI Servo tracking, so that for
sports shooters where it's not uncommon for a referee/another player to run
between you and your subject (or in the case of your friend, you coming
between the bird and him), it delays shifting focus so quickly. Maybe the
'slow' sensitivity setting should be longer than 1 second before shifting
focus? Or, maybe there should be a CF that you can turn on that tells the
camera that if you are tracking a subject for more than say a couple of
seconds, that this is what you are trying to photograph and not shift focus
to something else? With scene recognition/colour pattern tracking, surely
it is possible for the camera to recognise what you are tracking? Afterall,
if you want to focus on something else, you would let go of the button and
pick up focus again.

It would be interesting to know if Nikons 3D system prevents the above 2
mentioned problems. I've just looked on Google briefly and if appears to
use colour recognition in it's 3D focus tracking system:
http://kammagamma.com/articles/nikon...dynamic-af.php

I am also wondering if it's possible to focus and recompose with the Nikon
3D system and it will track the area that you took the initial focus from?
So for example, in a portrait you focus on an eye with the centre point,
recompose and the camera tracks where the eye is and keeps it in focus. Or
in your situation with the bird, you focus on the head with the centre point
and if you recompose whilst still tracking, it will keep focus on the head
and ignore the wings, etc.



Thanks for giving excellent examples of why no REAL pro in the world would
depend on auto-focusing for anything on any camera. Thousands upon thousands of
missed shots in your life-time.

:-)

Those who want to rely on a point-and-shoot auto-focus feature of their DSLR and
praise what a wonderful feature it is, is only revealing their sub-amateur
status as any kind of photographer. They love to kid themselves with what they
bought. Oh, if they could only buy a camera that will do everything for them,
they might actually be a photographer one day. They can only keep hoping. LOL

"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.

jue