Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)


"Wilba" <wilba@xxxxxxxxxxxxxxxxxxx> wrote in message
news:fm9oar$rfk$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Neil Harrington wrote:
Wilba wrote:
Neil Harrington wrote:
Wilba wrote:
Neil Harrington wrote:

Greg obviously does have *some* idea about focal lengths, so
explaining the common 35mm equivalencies does not seem like
a bad idea. He's going to run into the concept sooner or later
anyway.

He does, it is, and he will, but he won't understand it from David's
explanation. :-)

I think he's better off understanding the perspective of a stated
focal length on his camera, like 100/33 = 3x, rather than 100*1.5/50 =
3x.

Not really. The "3x" in your examples tells him nothing useful.

If we accept that statement at face value, it's equally true to say that
"100mm tells him nothing useful".

Sure it does, if he's familiar with the effects of different focal
lengths and can visualize them with respect to the subject. If he's not,
he eventually will be. Presumably he already knows that magnification is
proportional to focal length, so "3x" tells him nothing new or useful.

Nice try, but let's get back to the point. (You do get it that the maths
above is only to illustrate the unnecessary complexity of thinking in
focal lengths for a format you're not using?)

For Greg, in using a camera like the D40, I believe he's better off
thinking of the view through an attached 100mm lens as a 100mm view, not a
150mm view. You seem to disagree with me (but you do agree below). Neither
of us is entirely right or wrong.

I'm saying it matters only because 35mm equivalency has become the
convention and everyone uses it. Manufacturers use it, photo magazines use
it, online sources use it, and it's used here in the newsgroups.

If Greg has one and only one camera, has not and will not own others with
different sensor size, has no previous familiarity with focal lengths in
terms of 35s, has no other reason to think in terms of 35mm equivalencies,
then I fully agree with you that he might as well just think in terms of the
actual focal lengths and never bother with any equivalencies. But those are
some big "ifs."

In my case I own many, many digital cameras with a variety of sensor sizes,
and it is not only useful but practically essential to think of them in
terms of equivalencies. Otherwise I'd have to remember that 7.8mm on my
Coolpix 7900 is about the same as 25mm on my Nikon D80, 9.6mm on my DiMage
7Hi, and so on and so on. It's far more convenient to think of all these as
equivalent to 38mm on a 35, a scale that I'm long familiar with. Nor am I
alone, obviously: My DiMage 7 series cameras all have the manual zoom ring
marked in 35mm equivalencies, not the actual focal lengths.

Again, this has no bearing on Greg's situation as long as he sticks *only*
to DX format cameras. But is there anyone interested in digital cameras who
actually does that?


What exactly do you expect him to do with the "3x"?

The same as you expect him to do with "100mm". The difference is,
with a magnification he may be able to relate it to other experience,
like looking through telescopes, binocculars, magnifiers, etc.

As I've pointed out, you are completely mistaken in trying to make that
sort of comparison. Your "3x" or any other "x" in connection with a
camera lens WILL NOT give him the same result as that power in a
telescope or binoculars.

You are completely mistaken in assuming that I did say or imply that it
would give him "the same result".

That's exactly what you said. Here's your comment again:
___________

What exactly do you expect him to do with the "3x"?

The same as you expect him to do with "100mm". The difference is, with a
magnification he may be able to relate it to other experience, like
looking through telescopes, binocculars, magnifiers, etc.
____________

If that doesn't "say or imply that it would give him 'the same result'" then
I wonder what saying or implying that might look like.


And as you know, my point is not about 3x or 50mm, but about 1.5.

You've been talking about relating all focal lengths to the 50mm "normal" or
its equivalent. That was the connection in which you went on and on about
"3x" -- as requoted above.


Are you telling me that when you think "18mm on a 1.5 factor camera",
you are thinking predominantly of an actual angle? As a number of
degrees?

Angles are measured in degrees, not millimeters.

I can't believe that anyone is genuinely stupid enough to think that "18mm
on a 1.5 factor camera" is an attempt to specify an angle!

Why'd you ask the question, then?


But just in case you are, I was implying, "18mm LENS on a 1.5 factor
camera". Blimey! :-)

That's understood. It's your question that was incoherent.


... generally speaking with short lenses one naturally thinks in terms
of field of view, while with long lenses one thinks of magnification.

Ah! That's a new and different statement from you.

OK. Is that all right, or does any "new and different statement" upset you?


So here's Greg talking about shooting birds at 510mm ... dya reckon it
might be handy for him to think about magnification? Maybe? :-)

Absolutely.


How do you think about magnification with long lenses?

That it's proportional to focal length. As I said, I believe Greg already
understands this. There's no reason to waste time dividing f.l. by some
imaginary "normal" to arrive at some cute "x" as you've been doing. A 300mm
lens will give half again the magnification of a 200mm lens, and so on. I'll
bet you dollars to donuts Greg knew this perfectly well before you tried
cluttering up his life with useless "x"s. ;-)


People have used the argument to explain why 100mm (or thereabouts) is
the ideal f.l. for portraiture (on a 35), and I can't count the number of
times I've seen someone claim that it's "most natural" because it
duplicates the magnification of the human eye, i.e. that the image in the
viewfinder looks the same size as when seen with the naked eye. It simply
isn't true, or at least it's never been true on any SLR I've tried the
comparison with.

Aha. So you're talking about lenses for portraiture. You're right, it's
complete bull***, and nothing at all to do with what I'm talking about.
I've never heard anyone argue that a 100mm lens on a 35mm camera is a good
portrait lens because it duplicates the magnification of the eye. That
sounds like someone who doesn't know what they're talking about talking
out their arse.

Yes. The same goes for anyone who says a f.l. is "normal" for the same
reason. Unity magnification in the viewfinder has nothing whatever to do
with whether a lens is "normal" or not, and as I've explained at
considerable length the notion of "normal" f.l. is a fallacy anyway.
"Normal" is in the eye of the beholder.

And again, 50mm has been long abandoned as the "normal" by makers of
fixed-lens cameras. It remained the standard lens for 35mm SLRs largely
because it's a focal length that permits making a fast but inexpensive and
compact lens that still gives the mirror enough room to swing -- not
necessarily because 50mm was regarded as the single best all-around f.l.
Earlier lenses like the Zeiss f/2 Biotar were made in 58mm for the same
reason -- not because they particularly wanted 58mm lenses.


"Normal" is almost meaningless. For head-and-shoulders portraiture a
100mm lens does provide a natural look and a 50mm would be regarded by
most people as too short. For scenery, landscapes etc. a 50 is often too
long. It's also too long by the traditional rule which says normal focal
length should be about equal to the diagonal of the negative. People got
used to the idea of 50mm being "normal" simply because most camera makers
accepted the Leica standard f.l. as their own. But there have been
rangefinder 35s with (non-interchangeable) shorter lenses for almost as
long as 35s have been popular. In the early 1950s the popular Kodak
Signet had a 44mm lens. The Bolsey I think was about the same. Most of
the Japanese RF 35s that began to flood the country had 45mm lenses. The
trend since then has been for fixed focal length lenses on compact 35s to
become shorter and shorter, various models being 42, 40 and 38mm. The
last compact 35s I owned (Konica Big Mini, Yashica T4 and Olympus Stylus
Epic) all had 35mm lenses. All of those were "normal."

Except in the sense that I learnt it, and have been discussing.

What you learned was a fallacy. There is no single, exclusive, concrete,
cosmic, metaphysical, universally desirable "normal" focal length for any
format.

[ . . . ]

I'm not sure that's the best advice. Other than compliance with
convention, why is it?

Just the fact that it *is* a convention makes it worth adhering to. You
could measure distance in stadii or room size in cubits, but few people
would grasp what you were saying since those units are not the
conventional ones nowadays.

Unless those were the units engraved on your lens ... then I'd say you're
better off working in those units, and converting them for discussion.

My Minolta DiMage 7 series cameras do have the 35mm equivalents marked on
the zoom ring, not the actual focal lengths. Some Panasonic models with
manual zoom have the same, and I suppose there may be others.

Neil


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