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I've got a really basic question: Where does the image you get in the LCD
and EVF come from ?

Does it come from the sensor ?
If so, how does the shutter speed works, do they close the shutter, discharge
the sensor, and re-open the sensor for the appropriate time ?


Thanks.

> I've got a really basic question: Where does the image you get in the LCD
> and EVF come from ?
> Does it come from the sensor ?

Usually directly from the sensor.

> If so, how does the shutter speed works, do they close the shutter, discharge
> the sensor, and re-open the sensor for the appropriate time ?

There are no more shutters in many of today's digital camera. With
electronic viewfinders, the sensor is always on. When you push the
shutter button, it saves the image to storage (simplified version).
Technically, it's a lot more complex with image stabilization
synchronization, reading out the sensor, etc. But there are generally
no more shutters . . . unles you have a digital SLR that doesn't have
full-time electronic viewfinder.

Chieh
--
Camera Hacker - http://www.CameraHacker.com/

wrote:

>> I've got a really basic question: Where does the image you get in the LCD
>> and EVF come from ?
>> Does it come from the sensor ?
>
> Usually directly from the sensor.
>
>> If so, how does the shutter speed works, do they close the shutter,
>> discharge the sensor, and re-open the sensor for the appropriate time ?
>
> There are no more shutters in many of today's digital camera. With
> electronic viewfinders, the sensor is always on. When you push the
> shutter button, it saves the image to storage (simplified version).
> Technically, it's a lot more complex with image stabilization
> synchronization, reading out the sensor, etc. But there are generally
> no more shutters . . . unles you have a digital SLR that doesn't have
> full-time electronic viewfinder.
>
> Chieh
> --
> Camera Hacker - http://www.CameraHacker.com/


This kinda brings up an interesting question, well to my mind at least.

With a DSLR you've got a mirror still, usually, at least as I understand it,
which redirects the light from the lens up into the eyepiece. This was
always seen as much better than a small compact film camera because you
were actually seeing through the lens hence had a better idea of what you'd
photograph. These days an awful lot of the compact cameras now feed their
viewscreen direct from the CCD which will actually be taking the picture.
Does this mean it will now give you a better representation of what you'll
photograph ?

Now I know that's heresy to the pro-DSLR mob, so please take it with a pinch
of salt, and if you don't even get far enough to actually read this line,
well then you're hardly worth responding to I guess.

D

D Russell wrote:
snip
>
> This kinda brings up an interesting question, well to my mind at least.
>
> With a DSLR you've got a mirror still, usually, at least as I understand it,
> which redirects the light from the lens up into the eyepiece. This was
> always seen as much better than a small compact film camera because you
> were actually seeing through the lens hence had a better idea of what you'd
> photograph. These days an awful lot of the compact cameras now feed their
> viewscreen direct from the CCD which will actually be taking the picture.
> Does this mean it will now give you a better representation of what you'll
> photograph ?
>
> Now I know that's heresy to the pro-DSLR mob, so please take it with a pinch
> of salt, and if you don't even get far enough to actually read this line,
> well then you're hardly worth responding to I guess.
>
> D

No. First of all, a good optical grade mirror produces less loss of
image quality than the eye can detect, so the reflex view is certainly
not degraded.

Secondly, the lens MAY provide a higher resolution picture (if it is a
good lens) than some of the lower resolution chips. That is, below a
given number of MP, the chip is the limit on resolution. That is
usually less than eye resolution.

Most importantly, the LCD screen is FAR lower resolution than typical
imaging chips even in low cost P&S. Most screens are well below 1MP.

I find them completely inadequate for manual focus, for instance.

Don Stauffer in Minnesota <> wrote:

> D Russell wrote:

>> With a DSLR you've got a mirror still, usually, at least as I understand it,
>> which redirects the light from the lens up into the eyepiece. This was
>> always seen as much better than a small compact film camera because you
>> were actually seeing through the lens hence had a better idea of what you'd
>> photograph. These days an awful lot of the compact cameras now feed their
>> viewscreen direct from the CCD which will actually be taking the picture.
>> Does this mean it will now give you a better representation of what you'll
>> photograph ?

This is sort of what I'm getting at, but wanted to confirm that the image on
the LCDs were indeed coming from the sensor. I still haven't got an answer
about the fact that sensors heat up, and therefore should not be exposed for
too long. Is this true or a myth ?

> Secondly, the lens MAY provide a higher resolution picture (if it is a
> good lens) than some of the lower resolution chips. That is, below a
> given number of MP, the chip is the limit on resolution. That is
> usually less than eye resolution.

> Most importantly, the LCD screen is FAR lower resolution than typical
> imaging chips even in low cost P&S. Most screens are well below 1MP.

> I find them completely inadequate for manual focus, for instance.

Hmmm... Good point. But you'd think that ultimately they'll be able to produce
really good EVF with super high resolution (same as sensor), and finally get
rid of the mirror and prism. What a saving on space and weight ! And no more
vibration from the mirror either.

I wonder how many years away we're from this.

wrote:
> > I've got a really basic question: Where does the image you get in the LCD
> > and EVF come from ?
> > Does it come from the sensor ?
>
> Usually directly from the sensor.
>
> > If so, how does the shutter speed works, do they close the shutter, discharge
> > the sensor, and re-open the sensor for the appropriate time ?
>
> There are no more shutters in many of today's digital camera.

That's not correct, unless you're writing about the absolute bottom of
the range digicam.
All digital cameras with an EVF and almost all with a LCD have a
shutter, it is just open while giving the live preview (the image
displayed on the EVF or LCD) and closes briefly to flush the sensor
before taking the exposure for a still image.
That is what gives the EVF/LCD type digicam a longer shutter lag, even
if they are set to manual focus and exposure modes.

> With electronic viewfinders, the sensor is always on. When you push the
> shutter button, it saves the image to storage (simplified version).

That may be correct for a movie mode on a digital stills camera, but
not for normal single exposures on most digicams available today.

D Russell wrote:
<snip>
>
> This kinda brings up an interesting question, well to my mind at least.
>
> With a DSLR you've got a mirror still, usually, at least as I understand it,
> which redirects the light from the lens up into the eyepiece. This was
> always seen as much better than a small compact film camera because you
> were actually seeing through the lens hence had a better idea of what you'd
> photograph. These days an awful lot of the compact cameras now feed their
> viewscreen direct from the CCD which will actually be taking the picture.
> Does this mean it will now give you a better representation of what you'll
> photograph ?
>
> Now I know that's heresy to the pro-DSLR mob, so please take it with a pinch
> of salt, and if you don't even get far enough to actually read this line,
> well then you're hardly worth responding to I guess.

The live preview in the EVF or on the LCD of a compact may give a
better idea of how the exposure will look in regards to overall
brightness and overall contrast, but the low resolution (typicaly
640x480 pixels or less) makes them totaly useless for focusing.
That explains why the upper end of the compacts that have manual
focusing also have their view magnified (usualy it's the central
portion of the live preview) when their focus control is operated, but
this can be almost useless, especialy in low light where it can look
very blotchy and low cotrast (where a SLR viewfinder could still be
quite clear and easy to focus with).

I have (and use) both a Pentax ist-Ds and a Konica-Minolta A200, so I
do have some experience in both "camps".

wrote:

> That's not correct, unless you're writing about the absolute bottom of
> the range digicam.
> All digital cameras with an EVF and almost all with a LCD have a
> shutter, it is just open while giving the live preview (the image
> displayed on the EVF or LCD) and closes briefly to flush the sensor
> before taking the exposure for a still image.
> That is what gives the EVF/LCD type digicam a longer shutter lag, even
> if they are set to manual focus and exposure modes.

That make sense I guess. So is that a mechanical shutter, or is the CCD
flushed electronically.

That definitely explains the delay that the SLR don't seem to get.

wrote:
>
> Don Stauffer in Minnesota <> wrote:

<edited, for brevity>

> > Most importantly, the LCD screen is FAR lower resolution than typical
> > imaging chips even in low cost P&S. Most screens are well below 1MP.
>
> > I find them completely inadequate for manual focus, for instance.
>
> Hmmm... Good point. But you'd think that ultimately they'll be able to produce
> really good EVF with super high resolution (same as sensor), and finally get
> rid of the mirror and prism. What a saving on space and weight ! And no more
> vibration from the mirror either.
>
> I wonder how many years away we're from this.


Hello,

I suspect that significantly better EVF's are viable, today, utilizing
OLED (organic light-emitting diode) displays. Alas, OLED technology has
been extremely slow, in attempting to gain any sort of a real foothold
in the consumer electronics industry, as a whole -- thus, I wouldn't
hold my breath, waiting for OLED-equipped digital cameras to become
commonplace.


Cordially,
John Turco <>

I do not own a digicam, but am looking - so I do not know the answer to
the question that I want to ask: If a digicam had the option of viewing
by via 'rangefinder', or LED screen, if you turned off the LCD screen,
could you avoid the sensor/screen flushing delay?

Rob in Calgary

wrote:
> wrote:
>>> I've got a really basic question: Where does the image you get in the LCD
>>> and EVF come from ?
>>> Does it come from the sensor ?
>> Usually directly from the sensor.
>>
>>> If so, how does the shutter speed works, do they close the shutter, discharge
>>> the sensor, and re-open the sensor for the appropriate time ?
>> There are no more shutters in many of today's digital camera.
>
> That's not correct, unless you're writing about the absolute bottom of
> the range digicam.
> All digital cameras with an EVF and almost all with a LCD have a
> shutter, it is just open while giving the live preview (the image
> displayed on the EVF or LCD) and closes briefly to flush the sensor
> before taking the exposure for a still image.
> That is what gives the EVF/LCD type digicam a longer shutter lag, even
> if they are set to manual focus and exposure modes.
>
>> With electronic viewfinders, the sensor is always on. When you push the
>> shutter button, it saves the image to storage (simplified version).
>
> That may be correct for a movie mode on a digital stills camera, but
> not for normal single exposures on most digicams available today.
>