Bower 500mm f/8 Mirror lens

On 7/15/2015 6:57 PM, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off. They
are usually (always?) manual focus too ... which can be a challenge for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.


True, but few of them will work at f8

--
PeterN

On 16/07/2015 1:17 p.m., RichA wrote:
On Tuesday, 14 July 2015 04:11:48 UTC-4, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')
--

Regards,

Eric Stevens

Even with focusing aids, 500mm with an APS or m4/3rds camera is a pain to focus absolutely accurately. Also, mirror lenses were never really meant for daytime use. They started out as telescopes. Reason is that light can (even with a baffle tube coming from the primary mirror centre hole) fall in the camera sensor from outside the light cone, reducing contrast. This can be dealt with pretty well in post-processing. Also, mirror lenses of that size are susceptible to heat waves, much more so than smaller aperture camera lenses. This means close-in (100ft or less) objects are generally ok to shoot, but anything beyond that that isn't high above the ground tends to blur. Ironically, the lenses are optimized to focus at infinity which means you get a small amount of spherical aberration when focusing on things close-in, but it's better than heat waves.

Why would atmospheric refraction/shimmer affect a mirror lens more than
a normal telephoto?

On 2015-07-15 18:57, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off. They
are usually (always?) manual focus too ... which can be a challenge for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.

Does that work with a manual focus lens?

On 2015-07-16 06:46, PeterN wrote:
On 7/15/2015 6:52 PM, Alan Browne wrote:
On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off.
They
are usually (always?) manual focus too ... which can be a challenge for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.


Nope, not always. Manual Off center focusing can be a challenge.
However, if off center focusing with MF is needed, the next best thing
is to use a tripod and move the camera. Tt is rare that off center MF is
needed.

Unless you're into photography, I suppose that may be true.

On 17/07/2015 9:11 a.m., Alan Browne wrote:
On 2015-07-15 18:57, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off.
They
are usually (always?) manual focus too ... which can be a challenge
for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.

Does that work with a manual focus lens?

Yes.
The accuracy of those focus points when using small apertures may not be
very good.
OTOH there's always CDAF in LV mode. 500mm f8 with no stabilisation is
going to be a stretch unless in full daylight, unless high ISO is used,
you're probably on a tripod anyway.

In article , Alan Browne
wrote:

Modern higher level Nikons have the ability to select an off-centre
focus point.

Does that work with a manual focus lens?

sure does.

On 2015-07-16 18:05, Me wrote:
On 17/07/2015 9:11 a.m., Alan Browne wrote:
On 2015-07-15 18:57, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are
they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off.
They
are usually (always?) manual focus too ... which can be a challenge
for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus
indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.

Does that work with a manual focus lens?

Yes.
The accuracy of those focus points when using small apertures may not be
very good.
OTOH there's always CDAF in LV mode. 500mm f8 with no stabilisation is
going to be a stretch unless in full daylight, unless high ISO is used,
you're probably on a tripod anyway.

How do you know it's in focus? What is the indication?

On 17/07/2015 10:11 a.m., Alan Browne wrote:
On 2015-07-16 18:05, Me wrote:
On 17/07/2015 9:11 a.m., Alan Browne wrote:
On 2015-07-15 18:57, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are
they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off.
They
are usually (always?) manual focus too ... which can be a challenge
for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus
indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.

Does that work with a manual focus lens?

Yes.
The accuracy of those focus points when using small apertures may not be
very good.
OTOH there's always CDAF in LV mode. 500mm f8 with no stabilisation is
going to be a stretch unless in full daylight, unless high ISO is used,
you're probably on a tripod anyway.

How do you know it's in focus? What is the indication?

Left or right arrow either side of a dot - o . Arrows light up to tell
you which way to move the focus ring, dot lights up and arrows are off
when focus is achieved.

On Thu, 16 Jul 2015 06:48:42 -0400, PeterN
wrote:

On 7/15/2015 6:57 PM, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off. They
are usually (always?) manual focus too ... which can be a challenge for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.


True, but few of them will work at f8

True.
--

Regards,

Eric Stevens

On Thu, 16 Jul 2015 17:11:19 -0400, Alan Browne
wrote:

On 2015-07-15 18:57, Eric Stevens wrote:
On Wed, 15 Jul 2015 18:52:55 -0400, Alan Browne
wrote:

On 2015-07-14 19:18, PeterN wrote:
On 7/14/2015 10:52 AM, Alan Browne wrote:
On 2015-07-14 04:11, Eric Stevens wrote:
Does anyone have knowledge or experience of these? How good are they?
(For a particular value of 'good')

With some exceptions most people who buy reflex's relegate them to a
shelf at some point after the initial blush of pleasure wears off. They
are usually (always?) manual focus too ... which can be a challenge for
the wearier eyes out there.

Some cameras, at least my Nikons, have some type of in focus indicators
available in the viewfinder.

That doesn't always make focusing easy - esp. off centre.

Modern higher level Nikons have the ability to select an off-centre
focus point.

Does that work with a manual focus lens?

As PeterN has already pointed out, few of them can be relied on to
work at f/8. But still they might.
--

Regards,

Eric Stevens