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The alternative to the ultra-fast long telephoto?



 
 
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  #1  
Old June 14th 18, 01:01 PM posted to rec.photo.digital
-hh
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Posts: 660
Default The alternative to the ultra-fast long telephoto?

On Thursday, June 14, 2018 at 2:28:51 AM UTC-4, RichA wrote:
Now with cameras and their exceptional high ISO capability, these
slower but high-quality telephotos are now good and perhaps, preferable.

https://www.dpreview.com/news/7758816413/nikon-developing-compact-and-lightweight-500mm-f5-6-lens


The option has been around for "long enough", but one of the ways
that the OEMs has functionally obstructed it is through their dSLR
specifications.

Specifically, when Autofocus capability is disabled when a certain
f/stop value is exceeded. If memory serves, the common "upper limit"
value had been f/5.6, with some exceptions at f/8 (such as offered
only on higher end bodies, and/or only at the center focus point).

From a designer policy standpoint, what's needed to really enable
this is (enabled by said higher ISO sensitivity) is for the camera
to be designed & allowed to (try to) AF at f/8, f/11 and/or even f/16.

For example, if we use lens filter diameters as a convenient
surrogate, a 200mm f2.8, a 300mm f/4 and a 400mm f/5.6 all have
primary apertures of 77mm, whereas when we increment up by one
stop (eg, a 300mm f/2.8, 400mm f/4, or 500mm f/5.6) the aperture
area needs to double, which is ~120mm.

Conversely, if we 'speed up' the dSLR's Autofocus system to allow
for an even slower lens, a 500mm f/8 should drop to be only 77mm.


-hh
  #2  
Old June 14th 18, 09:41 PM posted to rec.photo.digital
Alfred Molon[_4_]
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Posts: 2,163
Default The alternative to the ultra-fast long telephoto?

In article , -hh
says...
Specifically, when Autofocus capability is disabled when a certain
f/stop value is exceeded.


Why?

If memory serves, the common "upper limit"
value had been f/5.6, with some exceptions at f/8 (such as offered
only on higher end bodies, and/or only at the center focus point).


I have the Olympus 75-300 which is F6.7 at the tele end, but autofocus
works also at the tele end.
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
https://tech.groups.yahoo.com/group/MyOlympus/
https://myolympus.org/ photo sharing site
  #3  
Old June 14th 18, 09:46 PM posted to rec.photo.digital
nospam
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Posts: 21,584
Default The alternative to the ultra-fast long telephoto?

In article , Alfred
Molon wrote:

Specifically, when Autofocus capability is disabled when a certain
f/stop value is exceeded.


Why?


because it no longer works properly, or is too slow to be useful.

If memory serves, the common "upper limit"
value had been f/5.6, with some exceptions at f/8 (such as offered
only on higher end bodies, and/or only at the center focus point).


I have the Olympus 75-300 which is F6.7 at the tele end, but autofocus
works also at the tele end.


not very well, it doesn't.
  #4  
Old June 14th 18, 11:37 PM posted to rec.photo.digital
me[_5_]
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Posts: 517
Default The alternative to the ultra-fast long telephoto?

On Thu, 14 Jun 2018 22:41:10 +0200, Alfred Molon
wrote:

In article , -hh
says...
Specifically, when Autofocus capability is disabled when a certain
f/stop value is exceeded.


Why?

If memory serves, the common "upper limit"
value had been f/5.6, with some exceptions at f/8 (such as offered
only on higher end bodies, and/or only at the center focus point).


I have the Olympus 75-300 which is F6.7 at the tele end, but autofocus
works also at the tele end.



Not saying your lens does this but there are those which mis-report
the min aperture (which is used for focusing) to the camera body to
get around this limitation. I have used a Nikon TC-20 and 1st gen
200-400 f/4 VR on D200/300/7100 and 500. D200 while accepting couldn't
hardly focus on the side of a barn. Each focus system has gotten
better, though substantially slowed compared to using a TC-14 which is
my standard go-to with this lens. Min Aperture of f/8 vs f/5.6.
  #5  
Old June 15th 18, 04:52 AM posted to rec.photo.digital
PeterN[_7_]
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Posts: 946
Default The alternative to the ultra-fast long telephoto?

On 6/14/2018 6:37 PM, me wrote:
On Thu, 14 Jun 2018 22:41:10 +0200, Alfred Molon
wrote:

In article , -hh
says...
Specifically, when Autofocus capability is disabled when a certain
f/stop value is exceeded.


Why?

If memory serves, the common "upper limit"
value had been f/5.6, with some exceptions at f/8 (such as offered
only on higher end bodies, and/or only at the center focus point).


I have the Olympus 75-300 which is F6.7 at the tele end, but autofocus
works also at the tele end.



Not saying your lens does this but there are those which mis-report
the min aperture (which is used for focusing) to the camera body to
get around this limitation. I have used a Nikon TC-20 and 1st gen
200-400 f/4 VR on D200/300/7100 and 500. D200 while accepting couldn't
hardly focus on the side of a barn. Each focus system has gotten
better, though substantially slowed compared to using a TC-14 which is
my standard go-to with this lens. Min Aperture of f/8 vs f/5.6.


With both my D800, and 500, the only usable autofocus at f8, is center
point focus. i have a lot of problems with tracking birds in flight at
f8, and have resorted to the old fashioned method, hand focus, if I have
to use f8. Have you had a similar issue?


--
PeterN
  #6  
Old June 16th 18, 07:51 PM posted to rec.photo.digital
me[_5_]
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Posts: 517
Default The alternative to the ultra-fast long telephoto?

On Thu, 14 Jun 2018 23:52:57 -0400, PeterN
wrote:

Too be honest my use with the TC-20 and 200-400 f/4 is minimal the
limitations as you have mentioned. Also makes the AF slow as molasses.
Finally, since I hand hold It's very tough to get a sharp images. I've
convinced myself it is better to stick with the TC-14 in the end.

I do miss the "nearest subject" option of the D200 though.

With both my D800, and 500, the only usable autofocus at f8, is center
point focus. i have a lot of problems with tracking birds in flight at
f8, and have resorted to the old fashioned method, hand focus, if I have
to use f8. Have you had a similar issue?


  #7  
Old June 17th 18, 04:39 AM posted to rec.photo.digital
PeterN[_7_]
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Posts: 946
Default The alternative to the ultra-fast long telephoto?

On 6/16/2018 2:51 PM, me wrote:
On Thu, 14 Jun 2018 23:52:57 -0400, PeterN
wrote:

Too be honest my use with the TC-20 and 200-400 f/4 is minimal the
limitations as you have mentioned. Also makes the AF slow as molasses.
Finally, since I hand hold It's very tough to get a sharp images. I've
convinced myself it is better to stick with the TC-14 in the end.

I do miss the "nearest subject" option of the D200 though.


I gotta say, that's one thing I do not miss at all.
You could rarely get a shot like this with closest focus. Too many weeds
in the way.
https://www.dropbox.com/s/qbknjnxve7be85n/4.jpg?dl=0





With both my D800, and 500, the only usable autofocus at f8, is center
point focus. i have a lot of problems with tracking birds in flight at
f8, and have resorted to the old fashioned method, hand focus, if I have
to use f8. Have you had a similar issue?




--
PeterN
  #8  
Old June 17th 18, 04:45 AM posted to rec.photo.digital
PeterN[_7_]
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Posts: 946
Default The alternative to the ultra-fast long telephoto?

On 6/16/2018 11:39 PM, PeterN wrote:
On 6/16/2018 2:51 PM, me wrote:
On Thu, 14 Jun 2018 23:52:57 -0400, PeterN
wrote:

Too be honest my use with the TC-20 and 200-400 f/4 is minimal the
limitations as you have mentioned. Also makes the AF slow as molasses.
Finally, since I hand hold It's very tough to get a sharp images. I've
convinced myself it is better to stick with the TC-14 in the end.

I do miss the "nearest subject" option of the D200 though.


I gotta say, that's one thing I do not miss at all.
You could rarely get a shot like this with closest focus. Too many weeds
in the way.
https://www.dropbox.com/s/qbknjnxve7be85n/4.jpg?dl=0


Sent the wrong link

https://www.dropbox.com/s/cqdavyowtoj5wi9/20180615_NickersonBeach%20Birds_7580.jpg?dl=0






With both my D800, and 500, the only usable autofocus at f8, is center
point focus. i have a lot of problems with tracking birds in flight at
f8, and have resorted to the old fashioned method, hand focus, if I have
to use f8. Have you had a similar issue?






--
PeterN
  #9  
Old June 17th 18, 07:02 PM posted to rec.photo.digital
me[_5_]
external usenet poster
 
Posts: 517
Default The alternative to the ultra-fast long telephoto?

On Sat, 16 Jun 2018 23:39:41 -0400, PeterN
wrote:

On 6/16/2018 2:51 PM, me wrote:
On Thu, 14 Jun 2018 23:52:57 -0400, PeterN
wrote:

Too be honest my use with the TC-20 and 200-400 f/4 is minimal the
limitations as you have mentioned. Also makes the AF slow as molasses.
Finally, since I hand hold It's very tough to get a sharp images. I've
convinced myself it is better to stick with the TC-14 in the end.

I do miss the "nearest subject" option of the D200 though.


I gotta say, that's one thing I do not miss at all.
You could rarely get a shot like this with closest focus. Too many weeds
in the way.
https://www.dropbox.com/s/qbknjnxve7be85n/4.jpg?dl=0


It was a selectable option, so if you didn't need it no harm.
  #10  
Old Today, 03:44 AM posted to rec.photo.digital
PeterN[_7_]
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Posts: 946
Default The alternative to the ultra-fast long telephoto?

On 6/17/2018 2:02 PM, me wrote:
On Sat, 16 Jun 2018 23:39:41 -0400, PeterN
wrote:

On 6/16/2018 2:51 PM, me wrote:
On Thu, 14 Jun 2018 23:52:57 -0400, PeterN
wrote:

Too be honest my use with the TC-20 and 200-400 f/4 is minimal the
limitations as you have mentioned. Also makes the AF slow as molasses.
Finally, since I hand hold It's very tough to get a sharp images. I've
convinced myself it is better to stick with the TC-14 in the end.

I do miss the "nearest subject" option of the D200 though.


I gotta say, that's one thing I do not miss at all.
You could rarely get a shot like this with closest focus. Too many weeds
in the way.
https://www.dropbox.com/s/qbknjnxve7be85n/4.jpg?dl=0


It was a selectable option, so if you didn't need it no harm.


I know. Since I never used it, I never missed it. OTOH, when shooting
critters through cages, the extension of the minimum focus length s
something I regularly use. It is also great for shortening the time for
focus lock. But on my cameras, it is lens function.

--
PeterN
 




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