Focus indicator on D70

When the D70 is set to manual focus, the little circle mark for focus still
works, and tells you when you have focused the camera according to what it
thinks.

Question - is this a function of the lens?

When I connect a 'dumb' lens (with a T adpt.) that has no data connection, the
indicator blinks on and off, as if it doesn't work... which it doesn't!

Is this normal? Does the camera need a smart lens for this function? Is there
another way to get it to work?


Another focus related question - is there any way to tell if the blur in a photo
is the result of motion blur, or focus blur? I took some blurry photos and I
need to determine if it's a motion problem or a lens/vision problem... the
camera was on a tripod at the time, but it's a long lens and low light...

1300mm f/13, 1/30 sec.

Thanks!

According to Bob :

When the D70 is set to manual focus, the little circle mark for focus still
works, and tells you when you have focused the camera according to what it
thinks.

Question - is this a function of the lens?

Not normally. With some caveats to be mentioned later.

When I connect a 'dumb' lens (with a T adpt.) that has no data connection, the
indicator blinks on and off, as if it doesn't work... which it doesn't!

The focus indicator is depending on light arriving from a fairly
wide cone. This covers everything at least down to the maximum aperture
of the kit lens (f3.5-4.5 depending on zoom position). The blinking of
the indicator may be intended to tell you that the cone of light is too
narrow to allow the focus indicator to work properly.

I have no lenses with a T adaptor at present, but I just put on
two old AI lenses (20mm f2.8 and 16mm f3.5 fisheye, and both worked
quite well with the indicator, so I would have to say that the focus
indicator works well with "dumb" lenses.

In the absence of this, I would suggest that you turn on the
grid in the viewfinder, and the zone indicator for the autofocus area to
let them serve as "anchors" for your eye's focus. When focusing, check
whether both these finder features and the image you are focusing on are
sharp at the same time. If you are on a tripod, try moving your head
from side to side slightly behind the viewfinder eyepiece, and look for
shift of position of the zone indicator or the grid relative to the
object being focused upon. If truly in focus, there should be no visible
shift, but the more out of focus it is, the greater the visible shift.
(This was used with the clear center spot in one of the Nikon F screens
for focusing things which had too small an aperture to allow any of the
focusing screens to work properly.

Is this normal? Does the camera need a smart lens for this function? Is there
another way to get it to work?


Another focus related question - is there any way to tell if the blur in a photo
is the result of motion blur, or focus blur? I took some blurry photos and I
need to determine if it's a motion problem or a lens/vision problem... the
camera was on a tripod at the time, but it's a long lens and low light...

1300mm f/13, 1/30 sec.

Is this the lens which you were using when you had trouble with
the focus indicator? If so, then I would suggest that the aperture is
too small to allow the focus indicator to work, so *that* is the
problem, not the perceived intelligence of the lens.

As for the determination of whether blur is a result of motion
or focus -- I would suggest you put the image on your computer screen
with a program which allows you to zoom into fine details. Look for tiny
bright spots. If the lens is a mirror lens, out of focus will turn into
doughnuts.

If it is a result of camera and lens motion, you should see a
bright trail indicating the direction of motion. In particular, if the
tripod is shaking (you don't say how rigid the tripod is, and some
(flimsy) tripods are sometimes worse than handheld for long lenses. If
you are jabbing at the shutter release button, instead of a gentle
increase in pressure, you are likely to wind up with 'J'-shaped trails
of the bright spots. Other shapes and directions will give clues as to
where the motion is coming from.

Also -- check whether the blur is equal throughout the image.
It could be motion of the subject.

Is the lens mounted to the tripod, or is the camera body mounted
to the tripod? It is better if the lens is mounted to the tripod. Then
take a heavy old overcoat or something similar and drape it over the
lens barrel to add damping to any vibration.

Looking through the viewfinder while mounted on the tripod,
lightly touch the camera body or the far end of the lens and see whether
there is visible motion. If so, then the tripod is not rigid enough.
Adding weight such as the old overcoat, or perhaps a leather bag filled
with lead shot will help to damp this vibration.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 19 Sep 2005 04:03:12 GMT, (DoN. Nichols) wrote:

According to Bob :

When the D70 is set to manual focus, the little circle mark for focus still
works, and tells you when you have focused the camera according to what it
thinks.

Question - is this a function of the lens?

Not normally. With some caveats to be mentioned later.

When I connect a 'dumb' lens (with a T adpt.) that has no data connection, the
indicator blinks on and off, as if it doesn't work... which it doesn't!

The focus indicator is depending on light arriving from a fairly
wide cone. This covers everything at least down to the maximum aperture
of the kit lens (f3.5-4.5 depending on zoom position). The blinking of
the indicator may be intended to tell you that the cone of light is too
narrow to allow the focus indicator to work properly.

It's odd, there is no vignetteing, so I assumed the image is large... Maybe
there wasn't enough light, I had things set a bit wrong at the time! I'm about 4
stops too dark... will try again another time in sunlight, the only control I
have is ISO setting and shutter!

I have no lenses with a T adaptor at present, but I just put on
two old AI lenses (20mm f2.8 and 16mm f3.5 fisheye, and both worked
quite well with the indicator, so I would have to say that the focus
indicator works well with "dumb" lenses.

In the absence of this, I would suggest that you turn on the
grid in the viewfinder, and the zone indicator for the autofocus area to
let them serve as "anchors" for your eye's focus. When focusing, check
whether both these finder features and the image you are focusing on are
sharp at the same time. If you are on a tripod, try moving your head
from side to side slightly behind the viewfinder eyepiece, and look for
shift of position of the zone indicator or the grid relative to the
object being focused upon. If truly in focus, there should be no visible
shift, but the more out of focus it is, the greater the visible shift.
(This was used with the clear center spot in one of the Nikon F screens
for focusing things which had too small an aperture to allow any of the
focusing screens to work properly.

Is this normal? Does the camera need a smart lens for this function? Is there
another way to get it to work?


Another focus related question - is there any way to tell if the blur in a photo
is the result of motion blur, or focus blur? I took some blurry photos and I
need to determine if it's a motion problem or a lens/vision problem... the
camera was on a tripod at the time, but it's a long lens and low light...

1300mm f/13, 1/30 sec.

Is this the lens which you were using when you had trouble with
the focus indicator? If so, then I would suggest that the aperture is
too small to allow the focus indicator to work, so *that* is the
problem, not the perceived intelligence of the lens.

It's a Mat-Cas optical tube...

As for the determination of whether blur is a result of motion
or focus -- I would suggest you put the image on your computer screen
with a program which allows you to zoom into fine details. Look for tiny
bright spots. If the lens is a mirror lens, out of focus will turn into
doughnuts.

If it is a result of camera and lens motion, you should see a
bright trail indicating the direction of motion. In particular, if the
tripod is shaking (you don't say how rigid the tripod is, and some
(flimsy) tripods are sometimes worse than handheld for long lenses. If
you are jabbing at the shutter release button, instead of a gentle
increase in pressure, you are likely to wind up with 'J'-shaped trails
of the bright spots. Other shapes and directions will give clues as to
where the motion is coming from.

Also -- check whether the blur is equal throughout the image.
It could be motion of the subject.

Is the lens mounted to the tripod, or is the camera body mounted
to the tripod? It is better if the lens is mounted to the tripod. Then
take a heavy old overcoat or something similar and drape it over the
lens barrel to add damping to any vibration.

Looking through the viewfinder while mounted on the tripod,
lightly touch the camera body or the far end of the lens and see whether
there is visible motion. If so, then the tripod is not rigid enough.
Adding weight such as the old overcoat, or perhaps a leather bag filled
with lead shot will help to damp this vibration.

Good Luck,
DoN.

The tripod is quite good - $300 ! - but there is vibration movement... I'll try
some of your tricks!

I'm wondering if there is a shutter/mirror vibration problem with the D70
shaking the thing? I've tried both the IR remote, and carefully holding the
camera still while squeezing the shutter - I'm quite good at that and get good
results with a handheld 300mm.

Thanks for all the info!

According to Bob :
On 19 Sep 2005 04:03:12 GMT, (DoN. Nichols) wrote:

According to Bob :

When the D70 is set to manual focus, the little circle mark for focus still
works, and tells you when you have focused the camera according to what it
thinks.

Question - is this a function of the lens?

Not normally. With some caveats to be mentioned later.

When I connect a 'dumb' lens (with a T adpt.) that has no data connection, the
indicator blinks on and off, as if it doesn't work... which it doesn't!

The focus indicator is depending on light arriving from a fairly
wide cone. This covers everything at least down to the maximum aperture
of the kit lens (f3.5-4.5 depending on zoom position). The blinking of
the indicator may be intended to tell you that the cone of light is too
narrow to allow the focus indicator to work properly.

It's odd, there is no vignetteing,

Vignetting is a different matter -- the cone is pointed the
other way for that, and is a cone of coverage on the film. This is
the cone if light rays to illuminate a point on the sensor for a single
spot from the image.

Let me try to do this with some ASCII art. Be sure to set your
e-mail client to a fixed pitch font (like Courier) or the proportional
pitch fonts will distort the drawing: The first one should have a 'V'
centered over the film/sensor plane.


| | normal lens wide open
\ /
\ / The light coming to a single point forms a wide cone with
\ / a large aperture
_______\/_______ - Film



|--- ---| normal lens stopped down.
||
|| The light coming to a single pont forms a very narrow cone
|| with a small aperture (hard to draw with ASCII)
_______||_______ - Film

Your very long lens with the very small aperture produces a very
narrow cone. This avoids coming in at the angles which the tiny prisms
on the focusing screen are set to accept light -- using the different
light paths to separate light coming from opposite edges of the lens, to
maximize the difference between the two beams. Without these, the
autofocus detectors (which also run the focus indicator, even with a
non-autofocus lens) can't tell the difference between in focus and out
of focus. In the old Nikon F days, the lenses with interchangeable
focusing screens (some with microprisms designed to break up the image
when out of focus) came in four different grades, for different focal
length lenses with different incoming light cone angles. And for the
ones beyond even the longest of these, or for use with a microscope, the
screen was plain ground glass with a clear center spot with a fine-lined
'+' in the center for use with the "moving your eye" trick which I
described before.

so I assumed the image is large... Maybe
there wasn't enough light, I had things set a bit wrong at the time! I'm about 4
stops too dark... will try again another time in sunlight, the only control I
have is ISO setting and shutter!

Then it is a "cat" (Catadiotric) lens? Mirror at the back, and
the front is a thin element with a central mirror mounted on it to fold
the optical path? If this is so, you will never get the focus indicator
to work with this lens. The incoming angle of the light rays will be
too narrow. Hopefully, my tricks will work for you to optimize the
focus.

I have no lenses with a T adaptor at present, but I just put on
two old AI lenses (20mm f2.8 and 16mm f3.5 fisheye, and both worked
quite well with the indicator, so I would have to say that the focus
indicator works well with "dumb" lenses.

In the absence of this, I would suggest that you turn on the
grid in the viewfinder, and the zone indicator for the autofocus area to
let them serve as "anchors" for your eye's focus. When focusing, check
whether both these finder features and the image you are focusing on are
sharp at the same time. If you are on a tripod, try moving your head
from side to side slightly behind the viewfinder eyepiece, and look for
shift of position of the zone indicator or the grid relative to the
object being focused upon. If truly in focus, there should be no visible
shift, but the more out of focus it is, the greater the visible shift.
(This was used with the clear center spot in one of the Nikon F screens
for focusing things which had too small an aperture to allow any of the
focusing screens to work properly.

Is this normal? Does the camera need a smart lens for this function? Is there
another way to get it to work?


Another focus related question - is there any way to tell if the blur in a photo
is the result of motion blur, or focus blur? I took some blurry photos and I
need to determine if it's a motion problem or a lens/vision problem... the
camera was on a tripod at the time, but it's a long lens and low light...

1300mm f/13, 1/30 sec.

Is this the lens which you were using when you had trouble with
the focus indicator? If so, then I would suggest that the aperture is
too small to allow the focus indicator to work, so *that* is the
problem, not the perceived intelligence of the lens.

It's a Mat-Cas optical tube...

I'm not familiar with that -- but the fact that you have no
aperture control suggests that it is a form of "Cat" lens. IIRC, the
focus indicator won't even work with the 500mm f8 Mirror Nikkor. I just
checked it (handheld) and I do get the same blinking indicator which you
get. Though when it is totally out of focus, I get *no* indicator.

[ ... ]

Looking through the viewfinder while mounted on the tripod,
lightly touch the camera body or the far end of the lens and see whether
there is visible motion. If so, then the tripod is not rigid enough.
Adding weight such as the old overcoat, or perhaps a leather bag filled
with lead shot will help to damp this vibration.

[ ... ]

The tripod is quite good - $300

There can be tripods which are excellent for normal lenses but
which are woefully inadequate for extreme telephotos. Some suggestions
to make the most of your tripod:

1) Have the center column down as far as possible, so there is a
minimum of single column extending above the joining point for
the legs.

2) If you don't need all of the leg sections extended, keep the
end-most (and thus the skinniest) collapsed, and use the larger
diameter sections which are somewhat more rigid.

3) If you can, take along a folding chair, and use that with the
tripod, so you can keep the legs shorter.

! - but there is vibration movement... I'll try
some of your tricks!

And there are a few more above.

I'm wondering if there is a shutter/mirror vibration problem with the D70
shaking the thing? I've tried both the IR remote, and carefully holding the
camera still while squeezing the shutter - I'm quite good at that and get good
results with a handheld 300mm.

Your handheld operation will probably damp out more vibration
from the mirror than the tripod will -- unless you add the overcoat or
the lead shot bag for damping. There is still the vibration from your
own pressing the shutter when handheld, but with practice (which it
would appear that you have), you can minimize that. However, you still
have to breathe, so timing the shot between breaths can help, too.

As for the shutter, since I believe that it is a balanced set of
"barn doors" which open before the electronic shutter allows the actual
exposure, I would think that the vibration from the shutter would be
minimal. The mirror is still part of the game -- but it is smaller than
that of a film SLR, so it should not contribute as much vibration.
However, the body is lighter, so the addition of the lead shot bag to
increase the mass should help.

Thanks for all the info!

You're welcome.

Good luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 20 Sep 2005 03:19:12 GMT, (DoN. Nichols) wrote:

According to Bob :
On 19 Sep 2005 04:03:12 GMT, (DoN. Nichols) wrote:

According to Bob :

When the D70 is set to manual focus, the little circle mark for focus still
works, and tells you when you have focused the camera according to what it
thinks.

Question - is this a function of the lens?

Not normally. With some caveats to be mentioned later.

When I connect a 'dumb' lens (with a T adpt.) that has no data connection, the
indicator blinks on and off, as if it doesn't work... which it doesn't!

The focus indicator is depending on light arriving from a fairly
wide cone. This covers everything at least down to the maximum aperture
of the kit lens (f3.5-4.5 depending on zoom position). The blinking of
the indicator may be intended to tell you that the cone of light is too
narrow to allow the focus indicator to work properly.

It's odd, there is no vignetteing,

Vignetting is a different matter -- the cone is pointed the
other way for that, and is a cone of coverage on the film. This is
the cone if light rays to illuminate a point on the sensor for a single
spot from the image.

Let me try to do this with some ASCII art. Be sure to set your
e-mail client to a fixed pitch font (like Courier) or the proportional
pitch fonts will distort the drawing: The first one should have a 'V'
centered over the film/sensor plane.


| | normal lens wide open
\ /
\ / The light coming to a single point forms a wide cone with
\ / a large aperture
_______\/_______ - Film



|--- ---| normal lens stopped down.
||
|| The light coming to a single pont forms a very narrow cone
|| with a small aperture (hard to draw with ASCII)
_______||_______ - Film

Your very long lens with the very small aperture produces a very
narrow cone. This avoids coming in at the angles which the tiny prisms
on the focusing screen are set to accept light -- using the different
light paths to separate light coming from opposite edges of the lens, to
maximize the difference between the two beams. Without these, the
autofocus detectors (which also run the focus indicator, even with a
non-autofocus lens) can't tell the difference between in focus and out
of focus. In the old Nikon F days, the lenses with interchangeable
focusing screens (some with microprisms designed to break up the image
when out of focus) came in four different grades, for different focal
length lenses with different incoming light cone angles. And for the
ones beyond even the longest of these, or for use with a microscope, the
screen was plain ground glass with a clear center spot with a fine-lined
'+' in the center for use with the "moving your eye" trick which I
described before.

so I assumed the image is large... Maybe
there wasn't enough light, I had things set a bit wrong at the time! I'm about 4
stops too dark... will try again another time in sunlight, the only control I
have is ISO setting and shutter!

Then it is a "cat" (Catadiotric) lens? Mirror at the back, and
the front is a thin element with a central mirror mounted on it to fold
the optical path? If this is so, you will never get the focus indicator
to work with this lens. The incoming angle of the light rays will be
too narrow. Hopefully, my tricks will work for you to optimize the
focus.

I have no lenses with a T adaptor at present, but I just put on
two old AI lenses (20mm f2.8 and 16mm f3.5 fisheye, and both worked
quite well with the indicator, so I would have to say that the focus
indicator works well with "dumb" lenses.

In the absence of this, I would suggest that you turn on the
grid in the viewfinder, and the zone indicator for the autofocus area to
let them serve as "anchors" for your eye's focus. When focusing, check
whether both these finder features and the image you are focusing on are
sharp at the same time. If you are on a tripod, try moving your head
from side to side slightly behind the viewfinder eyepiece, and look for
shift of position of the zone indicator or the grid relative to the
object being focused upon. If truly in focus, there should be no visible
shift, but the more out of focus it is, the greater the visible shift.
(This was used with the clear center spot in one of the Nikon F screens
for focusing things which had too small an aperture to allow any of the
focusing screens to work properly.

Is this normal? Does the camera need a smart lens for this function? Is there
another way to get it to work?


Another focus related question - is there any way to tell if the blur in a photo
is the result of motion blur, or focus blur? I took some blurry photos and I
need to determine if it's a motion problem or a lens/vision problem... the
camera was on a tripod at the time, but it's a long lens and low light...

1300mm f/13, 1/30 sec.

Is this the lens which you were using when you had trouble with
the focus indicator? If so, then I would suggest that the aperture is
too small to allow the focus indicator to work, so *that* is the
problem, not the perceived intelligence of the lens.

It's a Mat-Cas optical tube...

I'm not familiar with that -- but the fact that you have no
aperture control suggests that it is a form of "Cat" lens. IIRC, the
focus indicator won't even work with the 500mm f8 Mirror Nikkor. I just
checked it (handheld) and I do get the same blinking indicator which you
get. Though when it is totally out of focus, I get *no* indicator.

It's a Maksutov-Cassegrain, yes a folded mirror design... a 102mm 'spotting
scope'. It may prove too poor for photography. But it's way cheaper than a long
Nikkor!

[ ... ]

Looking through the viewfinder while mounted on the tripod,
lightly touch the camera body or the far end of the lens and see whether
there is visible motion. If so, then the tripod is not rigid enough.
Adding weight such as the old overcoat, or perhaps a leather bag filled
with lead shot will help to damp this vibration.

[ ... ]

The tripod is quite good - $300

There can be tripods which are excellent for normal lenses but
which are woefully inadequate for extreme telephotos. Some suggestions
to make the most of your tripod:

1) Have the center column down as far as possible, so there is a
minimum of single column extending above the joining point for
the legs.

2) If you don't need all of the leg sections extended, keep the
end-most (and thus the skinniest) collapsed, and use the larger
diameter sections which are somewhat more rigid.

3) If you can, take along a folding chair, and use that with the
tripod, so you can keep the legs shorter.

! - but there is vibration movement... I'll try
some of your tricks!

And there are a few more above.

I'm wondering if there is a shutter/mirror vibration problem with the D70
shaking the thing? I've tried both the IR remote, and carefully holding the
camera still while squeezing the shutter - I'm quite good at that and get good
results with a handheld 300mm.

Your handheld operation will probably damp out more vibration
from the mirror than the tripod will -- unless you add the overcoat or
the lead shot bag for damping. There is still the vibration from your
own pressing the shutter when handheld, but with practice (which it
would appear that you have), you can minimize that. However, you still
have to breathe, so timing the shot between breaths can help, too.

As for the shutter, since I believe that it is a balanced set of
"barn doors" which open before the electronic shutter allows the actual
exposure, I would think that the vibration from the shutter would be
minimal. The mirror is still part of the game -- but it is smaller than
that of a film SLR, so it should not contribute as much vibration.
However, the body is lighter, so the addition of the lead shot bag to
increase the mass should help.

Thanks for all the info!

You're welcome.

Good luck,
DoN.

Thanks again!