Nikon 50mm 1.4 AFS on Nikon D40 - Should I upgrade lens or camera?

On Tue, 6 Jan 2009 16:00:33 -0800 (PST),
wrote:

I have been using a Nikon D40 for some time with the kit lens, but
recently started using a 50mm 1.8 lens which is manual focus only on
the D40. I mostly take pictures indoors in relatively low lighting,
which makes the 1.8 lens very nice for what I take pictures of. I
actually love the clarity of the 50mm 1.8 when I can have someone stay
still enough for me to manual focus. I feel like I am missing a lot
of good shots because it takes me so long to manual focus, especially
on children who do not stay very still most of the time.

I was wondering if I should upgrade to a 50mm 1.4 AFS lens which would
have autofocus? What would be the benefits of the 1.4 vs the 1.8
(except for the autofocus on the D40)? Would it really change much
about the pictures I take (mostly of family...nothing professional,
but like to post the pictures I take)? Would upgrading camera bodies
be just as well, say to the Nikon D90 in which I can use the 1.8 in
autofocus mode?

The cheapest camera body upgrade would be to a used D50. It's
quite similar to the D40, an entry level model with the same 6mp
resolution, but it has a focusing motor that the D40 lacks. Other
than that, my preference would be for the D90. Navas' reply is
mistaken where he says :

its larger aperture would give you lower light shots, easier
focusing, and shallower depth of field

in that the aperture is much less than 1 stop larger, and the D90's
much greater high ISO performance swamps the benefit of the only
slightly larger aperture. With your current lens, the D90 would
allow you to take pictures in lower light, and they would have less
"noise" even though the D90 has a 12mp sensor. Because of the way
the optical system is designed, including the AF sensors, the larger
aperture won't make any difference in focusing unless you're talking
about lenses with fairly small maximum apertures. The design of
the lens is a factor, as is the design of the camera body, where
generally, the larger, more expensive the body, the quicker and more
accurate the focusing. Also, due to the way DSLRs are designed,
while you'd expect that the greater the maximum aperture, the
brighter the image would be in the viewfinder, this is only true up
to about f/2.8. Apertures greater than this don't produce brighter
viewfinder images, but I suspect that the D90's viewfinder produces
a larger, brighter image than the D40, whatever lens is used.

The last point Navas made is correct. The f/1.4 lens will have a
shallower depth of field at f/1.4, but at all other apertures that
the two 50mm lenses share, the DOF will be the same. You'd probably
be better off using either lens at f/2.0 or f/2.8 with the D90 than
f/1.4 with a D40, since the smaller DOF means that more of the image
will be noticeably out of focus. And if it's really dark and you
need to use f/1.4 or f/1.8, the D90 will produce better images than
the D40. It will also allow you to use any wider f/1.4 lens, and
most people find that the 30mm f/1.4 lenses are better for use
indoors, as the 50mm focal length is often too long.

Nikon's new 50mm f/1.4 AF-S lens is quite a bit more expensive
than the older lenses, making the more expensive D90 an easier
choice. It also has many additional features that may or may not be
important. Live View can be very useful, especially for macro
photography, and it was also the first DSLR to offer video, although
I suspect that that's not often used. According to Nikon, the D90's
battery life is much better than the D40, 470 shots vs 850 shots per
charge when tested with the CIPA standard, and 2,200 vs 4,200 shots
per charge when tested with Nikon's own standard. The manuals
describe the test conditions if you're interested.

Some additional differences: The D90 has a sensor cleaner and
it's LCD monitor is much improved, 3" vs 2.5", with 920k dots vs the
D40's 230k dot LCD display, and for shooting in the dark, the D90's
LCD display is off while shooting, whereas the D40 likes to make its
presence known, whether you want it to or not. IIRC, the D40 only
has a single combined (monochrome) histogram, while the D90 also
shows histograms for each of the Red, Green and Blue channels. The
D90 also has a terminal that connects with an optional GPS device,
storing latitude, longitude, altitude and Coordinated Universal Time
(UTC) in the photo's EXIF data. (I assume that's where it's stored
.. . .)

The last two I'll mention (there are probably others you can find
if you have both PDF manuals to search) are that the D40 has a
maximum continuous frame rate of 2.5 f/sec. vs 4.5 f/sec. for the
D90, and the D90's internal flash has a "free" Commander mode,
allowing it to remotely control Nikon's CLS speedlights. The only
way that the D40 can control external speedlights is to buy an
additional SB-800, SB-900 or SU-800 which is a considerable extra
expense.