Darren,
I don't know if you'd thought of it or not: if the effective focal length
is 2000 mm, and the crop factor is 5.64 (per Bipin), - than the actual
focal length of that glass is about 355 mm. So, that's shorter than your
500 mm (which is equivalent to 750 mm on the Pentax body).
So, the glass focal length by itself is not the factor there.
And BTW, your "disadvantage" with K-3 is not 2000/500=4, but only
2000/750=2.67.
Now, the ratio of the crop factors 5.64/1.5 = 3.76. That, divided by Sqrt
(24 MP / 16 MP) = 1.5 (assuming K3) gives us about 3.08. If I didn't make
some stupid error in my estimates, it means that the linear density of
the pixels on that P900 is 3 times higher compared to K-3. I.e. the size
of the pixel is roughly 3-times smaller (so, that's one of the
resolution-limiting factors when you make a tight crop on a larger
sensor). Of course, this matters only when the optics doesn't limit the
resolution first.
I don't know what's the optics resolution for P900, especially at the
longer end which is typically showing worse performance than the
short-end and mid-range of the superzooms. So, I don't know what is the
ultimate resolution limiting factor in this case.
Correction:
I just checked and 1/2.3" inch sensor actually has a crop factor of 5.2
( https://en.wikipedia.org/wiki/Crop_factor ). 5.64 crop factor is
fot the smallest sensor that is 1/2.5".
So, for P900 sensor, the linear pixel density is about 2.84 that of K-3,
and the actual focal length is about 385 mm.
You draw your own conclusions.
That's all about stills. For the video, that you reference, - you are not
using the full resolution of the sensor. I don't know the actual
technique, but I assume it averages the adjacent pixels. So, for the
video, the advantage of P900 would be because you cannot define the crop
while shooting video in K-3 (I have K-5 iiS, but I from what I know K-3
is the same).
Yes, the light-weight remains an advantage.
I hope these considerations are helpful.
Igor
Darren Addy Sun, 11 Oct 2015 19:11:09 -0700 wrote:
To finish my thought... my sister and I both had zooms with a 500mm
long end. The Nikon Coolpix P900 would bring things 4x as close, with
a lot less weight. Nikon sort of blew away the field with the 83x of
the P900. Even Nikon Coolpix forum members are getting sick of people
raving about it.
On Sun, Oct 11, 2015 at 8:34 PM, Darren Addy <pixelsmi...@gmail.com>
wrote:
Different tools for different purposes...
Spent an enjoyable day with my Nikon shooting birding sister. We
started the day in a Crane Trust blind before sunrise and ended at
Rowe Sanctuary near Gibbon, NE which is a great facility.
My sister is amazing at seeing birds where I'm obivious. It was great
"exercise" for me and a got a few keepers (but nothing special). We
had a pair of coyotes come into frame while shooting Great Blue Herons
on the Platte River. Unfortunately, on the opposite shore.
A middle morning visit to Fort Kearny turned up little, but good
exercise trying to capture fast-moving Ruby Throated Kinglets eating
the last elderberries on a bush/tree. Also a single cormorant keeping
his distance in the Platte River. Later, on the way to Rowe we had a
photogenic posing adult Osprey and an immature Bald Eagle enjoying
lunch at the top of a tall power pole. At Rowe we discovered some
deluxe blinds on the river and a tall above the trees blind, open to
the public (Filed for future use.) We also got a distant shot of a
Kingfisher, some black terns and our closest view of a Great Blue
Heron in the river.
Used multiple techniques (AF, MF, etc.) and learned a lot. I certainly
see the appeal of the superzooms like the Nikon P900 with its 2000mm
equiv (search YouTube for HD video from it). With the K-3 and an
extreme crop I"m only using a fraction of the sensor anyway... plus
the lightness of the P900 would be a real plus.Unfortunately, no
RAW... JPEG only... but still...
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