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In article <. com>,
=?iso-8859-1?q?Martin_S=F8rensen?= <> wrote:
>Bummer. One of the things I like about my 105/2.5 is that it is very
>good at isolating things at f/4, and still is very sharp.

That doesn't change. The 105 will remain good at isolating things at f/4
and it will probably remain sharp even on a digital camera.

The problem is that the field of view is such that you probably don't want
to use it for portraits.

The equivalent to 105/4 on 35mm is 70/2.8 on DX.

I think that an 85 is probably the best solution.


--
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-- Douglas Adams in Dirk Gently's Holistic Detective Agency

Philip Homburg wrote:
> In article <. com>,
> =?iso-8859-1?q?Martin_S=F8rensen?= <> wrote:
>>Bummer. One of the things I like about my 105/2.5 is that it is very
>>good at isolating things at f/4, and still is very sharp.
>
> That doesn't change. The 105 will remain good at isolating things at f/4
> and it will probably remain sharp even on a digital camera.
>
> The problem is that the field of view is such that you probably don't want
> to use it for portraits.
>
> The equivalent to 105/4 on 35mm is 70/2.8 on DX.
>
> I think that an 85 is probably the best solution.
>
>

The 90mm f/2.8 (or around there) macros should also be fine for
portraits (maybe a bit too long).

Floyd L. Davidson wrote:
> "Annika1980" <> wrote:
> >Get a Canon body with the 70-200 f/2.8L IS. Yes, that lens is a bit
> >pricey but there's a good reason for that. It's probably the sharpest
> >zoom in the world.
>
> Have to admit that is pretty close to being true fact.
>
> The only lenses that seem to do better are the Nikon 70-200mm f/2.8
> and the older 80-200mm f/2.8.

Blasphemer!

"Annika1980" <> wrote:
>Floyd L. Davidson wrote:
>> "Annika1980" <> wrote:
>> >Get a Canon body with the 70-200 f/2.8L IS. Yes, that lens is a bit
>> >pricey but there's a good reason for that. It's probably the sharpest
>> >zoom in the world.
>>
>> Have to admit that is pretty close to being true fact.
>>
>> The only lenses that seem to do better are the Nikon 70-200mm f/2.8
>> and the older 80-200mm f/2.8.
>
>Blasphemer!

Isn't that pretty much a pattern though? Canon's this or that is
the best there is, excepting of course for the Nikon models.

What else is new?

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska)

"=?iso-8859-1?q?Martin_S=F8rensen?=" <> writes:

>I have seen the DOF-claim before, and I do not understand it. If you
>reduce the size of the sensor, you also reduce the size of acceptable
>out-of-focus blur, aka DOF. For geometrical reasons, I would therefore
>expect DOF to be the same for a given angle of view, ie a dSLR with a
>50mm has same DOF as a 35mm with a 75mm. If I am wrong, please show me
>why!

There are multiple ways of describing this, but here's one:

You're correct that when you reduce the size of the sensor, the
acceptable circle of confusion size is also reduced. So if you put *the
same focal length* lens on the 1.5 crop factor DSLR, you actually get only
2/3 the DOF you'd get with a full-frame camera because of that CoC size
change.

But then you'd have only about 2/3 of the field of view, which does not
give you the same shot. So, instead, you use a lens with about 2/3 the
focal length on the DSLR compared to the full-frame camera. Now, when
keeping the image size (and thus the CoC size) the same, and keeping the
f/number the same, DOF is proportional to one over the *square* of the
focal length change. For example, switching from 75 to 50 mm lens on
the same camera gives you 2.25 times the DOF, not 1.5 times as much as
you might expect.

In the comparison here, you're changing both focal length and CoC. The
reduction in focal length by a factor of 1/1.5 gives you 2.25 times the
DOF, but then a factor of 1.5 of that is taken away by the CoC change.
So they don't fully cancel, and you still get 1.5 times as much DOF
while keeping the same field of view and the same f/number.

Another way of looking at it:

DOF is inversely proportional to the size of the lens entrance pupil,
regardless of focal length, as long as you keep the overall field of
view the same (which means objects stay the same size in the print).
Suppose you use a 75 mm lens at an aperture of f/4 on a full-frame
camera; then the entrance pupil is 75/4 = 18.75 mm diameter. If you
switch to a 50 mm lens on the DSLR to keep the FOV the same, and keep
the same entrance pupil size, you will keep the same DOF. But a 18.75
mm entrance pupil on a 50 mm lens is f/2.7, not f/4.

If you set the 50 mm lens to f/4 as well, the entrance pupil drops to
12.5 mm in diameter, and then you get 1.5x greater DOF than you would
with 18.75 mm pupil.

Dave

> We are thinking of getting a dSLR, and initially cirling on Canon or
> Nikon due to availability of used fixed-length lenses.
>
> We will be looking at the lower end, 350d/400d/D50/D70s/D80 and spend a
> bit on lenses.
>
> Use is family stuff, including my son's football (soccer). I like to
> use available light, ie lenses that can be used at f/2.8 or better are
> nice.
>
> What I would like is:
> - fast autofocus
> - low shutter lag (I have given up on our Canon G3 for the 2 first
> reasons)
> - good low-light performance
>
>>From brief fondling, it seems the Nikons fit my hands better. But what
> about the more expensive Canons, perhaps 2nd-hand?
>
> Or are used dSLRs a no-no?
>

Some care has to be taken when buying second-hand of course. Check that
nothing is loose and that the sensor is clean and without too many dead
pixels. The battery may be shot, too; they have a limited lifespan so you'd
better budget for a new one.

My advice to you, given your needs as given in your original post, might be
to consider a not-too-heavily used Canon 1D. This model is definitely built
to take a licking and keep on ticking (for about 150.000 frames to be
exact), it has one of the world's finest autofocus systems, and shutter lag
is basically non-existent. The viewfinder is excellent as well, an often
overlooked point. The user interface is very good, once you get used to it -
it is somewhat different from the UI on Canon's consumer models. It is only
1.25x crop so you get better wide-angle from your lenses. And it goes for
only around 1000 Euro or even somewhat below that, here in Norway at least.
As said, the shutter is built to take 150K exposures, so even if a 1D is
sold with 50K actuations on it, it is barely broken in really.

Manual focus lenses are a problem with all Canons because the old Canon FD
lenses won't fit EOS cameras, you can use Nikkors or Pentaxes or just about
anything via an adapter but manual stop-down shooting is a pain in the neck.
It is possible, rather than practical, in my book.

The downsides to the 1D are that it is "only" 4 megapixels (but keep in mind
that this is basically enough for anything short of wallpaper size, and that
small RAW files makes for a pleasantly fast workflow on the computer) and
that high-ISO performance is no more than sufficient. Don't go above 1250
ISO except in dire emergency, at least that is my experience, and don't
underexpose. NeatImage is your friend! Battery life is not too good either;
a couple of third-party spare batteries take care of that. The rear display
is not exactly excellent either, but is good enough to check composition and
histogram and that is all you need. Oh, and the camera is big and heavy, 1.5
kilos. I'd consider this more of an advantage than a disadvantage though, as
it balances a heavy lens better and gives more stability and vibration
damping to the entire system (until your arms tire, at least). A DLSR isn't
pocketable in any case so I don't really consider size and weight much of an
issue on one.

I got mine about a year ago and have been happy as a pig in **** ever since.

>Any 3rd-party zooms worth considering as alternative to the kit lenses?
>Or are they so cheap you may as well have them?

Consider the Tamron 28-75 2.8. An absolutely excellent piece of glass,
light-weight and cheap. You'll probably want to pair it with a wide-angle
zoom though for an all-round kit, an 18-55, 20-35, 17-40 or some such beast.
28mm is sufficient for a "short normal to short tele" walkaround on a 1D,
but probably too narrow on a 1.6 crop. I'm selling mine now, but that's only
because I got a good deal on a second-hand 24-70 2.8L!

Floyd L. Davidson skrev:
> "Martin Sørensen" <> wrote:
> >OK, no religious wars, please...
>
> Ask about religious topics, and you *will* get religious wars...
>
> >We are thinking of getting a dSLR, and initially cirling on Canon or
> >Nikon due to availability of used fixed-length lenses.
> >
> >We will be looking at the lower end, 350d/400d/D50/D70s/D80 and spend a
> >bit on lenses.
>
> Add the Pentax K100D to that list. I have not used it, or even
> seen one, but it appears that it might fit your needs rather well.
>
I handled the 400d yesterday as I was waiting for prints,and that was
definately too small for my hands. Havn't tried the Pentax yet, but it
seems small too.

To me, the main problem with the small cameras is that my hands stay
the same.

/Martin

"Martin Sørensen" <> wrote in message
news: oups.com...

>> Add the Pentax K100D to that list. I have not used it, or even
>> seen one, but it appears that it might fit your needs rather well.
>>
>I handled the 400d yesterday as I was waiting for prints,and that was
>definately too small for my hands. Havn't tried the Pentax yet, but
>it
>seems small too.

I originally bought the small Canon XT because weight was going to be
an issue and I figured the small size would be beneficial when
travelling. But I have since found that ~100 grams and a few
millimeters is a small price to pay for better comfort, control, and
ease of use.

>To me, the main problem with the small cameras is that my hands stay
>the same.

An easy fix is to wrap your hands in tight linen for several years.