Why are the new DX lenses so slow?

Nikon and Canon both. I have lenses for my old F100 that are faster than
what both companies are offering. I mean f2.8 or less and a constant speed
through the zoom range. Does anybody have information about why these
digital lenses are coming out with such high and variable f-stops?

Tired of noisy pictures,


Steve

Steve wrote:

Nikon and Canon both. I have lenses for my old F100 that are faster than
what both companies are offering. I mean f2.8 or less and a constant speed
through the zoom range. Does anybody have information about why these
digital lenses are coming out with such high and variable f-stops?

Because the common consumer wants cheap, not good.

Tired of noisy pictures,

The fast lenses still work. They're not making a whole lot of new ones,
unfortunately, but a lens doesn't have to be new to be good.

--
Jeremy |

"Steve" wrote in message
...
Nikon and Canon both. I have lenses for my old F100 that are faster
than what both companies are offering. I mean f2.8 or less and a constant
speed through the zoom range. Does anybody have information about why
these digital lenses are coming out with such high and variable f-stops?

Tired of noisy pictures,


Steve



Nikon makes a 17-55mm f/2.8 DX Zoom.

Bill Crocker

"Steve" wrote in message
...
Nikon and Canon both. I have lenses for my old F100 that are faster
than what both companies are offering. I mean f2.8 or less and a constant
speed through the zoom range. Does anybody have information about why
these digital lenses are coming out with such high and variable f-stops?

Tired of noisy pictures,


Steve

I think they are trying to make inexpensive yet good lenses for the masses.
One way to do that is to make them slower. As other posters have already
said, both Nikon and Canon make some incredible lenses that will fit both a
new digital and their 35mm models. All it takes is money.

"Jeremy Nixon" wrote in message
...
Steve wrote:

Nikon and Canon both. I have lenses for my old F100 that are faster
than
what both companies are offering. I mean f2.8 or less and a constant
speed
through the zoom range. Does anybody have information about why these
digital lenses are coming out with such high and variable f-stops?


As for the variable f-stops, I would assume it's because as the focal
length changes that automatically changes what the f-stop is. The same-sized
hole is a different f-stop for 50 mm than it is for, say, 125 mm.

I was never a fan of zooms even in my film days, so I'm not that familiar
with them. You say that there are zooms where the widest f-stop is not
variable as the lens is zoomed out? Correct me if I'm wrong, but I think
that means the manufacturer was simply not telling you the truth about that
lens and not letting you know that the widest aperature opening has a
different f value based on how far out the lens is zoomed.

DP wrote:

I was never a fan of zooms even in my film days, so I'm not that familiar
with them. You say that there are zooms where the widest f-stop is not
variable as the lens is zoomed out?

Most higher-end zooms have a constant aperture.

Correct me if I'm wrong, but I think that means the manufacturer was
simply not telling you the truth about that lens and not letting you know
that the widest aperature opening has a different f value based on how
far out the lens is zoomed.

The physical size of the iris opening and the optical aperture are not
the same thing. It's cheaper to make a variable-aperture zoom, but the
good zooms are constant-aperture, for real.

--
Jeremy |

"DP" wrote:
"Jeremy Nixon" wrote:
Steve wrote:

Nikon and Canon both. I have lenses for my old F100 that are faster than
what both companies are offering. I mean f2.8 or less and a constant speed
through the zoom range. Does anybody have information about why these
digital lenses are coming out with such high and variable f-stops?

As for the variable f-stops, I would assume it's because as the focal
length changes that automatically changes what the f-stop is. The same-sized
hole is a different f-stop for 50 mm than it is for, say, 125 mm.

I was never a fan of zooms even in my film days, so I'm not that familiar
with them. You say that there are zooms where the widest f-stop is not
variable as the lens is zoomed out? Correct me if I'm wrong, but I think
that means the manufacturer was simply not telling you the truth about that
lens and not letting you know that the widest aperature opening has a
different f value based on how far out the lens is zoomed.

There is some variation, but it is relatively small. They are not
being dishonest. A 1/3rd stop or less variation is not worth the
distinction, but a 1/2 stop or more variation certainly is.

However, like all things in lense design it is a compromise. It
is possible to produce, at a lower cost, a sharper lense if it
has a variable aperture over the focal length range. A constant
maximum aperture is possible, but it either produces a less
sharp lense or costs significantly more.

It is not uncommon to target a design for low cost production,
and that is often best accomplished by allowing the maximum
aperture to vary.

It is also common to target a different design for "best
performance at whatever it costs", and that will often have a
wider maximum aperture that is constant (relatively) across the
focal range. But the lense will appeal only to those who can
justify the money spent for the best possible lenses.

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

Steve wrote:
Nikon and Canon both. I have lenses for my old F100 that are faster than
what both companies are offering.

Don't the old fast lenses work on your digital camera?

I mean f2.8 or less and a constant speed
through the zoom range. Does anybody have information about why these
digital lenses are coming out with such high and variable f-stops?

Tired of noisy pictures,

Most of the new "DX" lenses are zooms.
How many old zooms faster than f 2.8 do you have?

Steve wrote:
Nikon and Canon both. I have lenses for my old F100 that are faster than
what both companies are offering. I mean f2.8 or less and a constant speed
through the zoom range.

We lately discussed this he

The "DX" specification (i.e. small sensor only) only makes a quite short
lens smaller, cheaper and lighter. With tele lenses it does not help
much and so it does not make sense to build long "DX" lenses. The ones
already used for 35mm are still the best price/performance compromise
you can construct here. So they are continued to be sold.

-Michael

Supposedly the D80 will make the D200 a more "prof"-choice and less
interesting for discounters.

But regarding the experiences we had with the D100 and D70, I'm glad we
have a D200 and would rather buy another D200 than a D80 for backup.

-Michael