Digital F Stop question

Archived from groups: rec.photo.digital (More info?)

In article <m2Y%d.1158$z.1067@newsread2.news.atl.earthlink.net>,
bchastain@XNOSPAMXhyperfeed.com says...
> I'm been looking at the Nikon D70 and have been surprised at the offered
> standard lens, Zoom-Nikkor 18-70mm f/3.5-4.5.
>
> I'm aware of the multiplication factor one must to use to convert the mm to
> 35 mm camera equivalent because of the sensor size, but is there also some
> sort of conversion for f-stops as well?
>
> In other words, assuming ASA-100 for both a 35 mm film camera and the Nikon
> D70, would the Nikon f/3.5 lens be as slow as it sounds, and so
> inappropriate for low light level photography?

No, the F-stop is a factor of the focal length and aperture
size, so it doesn't change with the size of the film or
sensor.

Yeah, f3.5 is kind of slow, but sufficient for general
photography. To get something significantly faster, you'd
need to go to a single focal length lens. I picked up the
Nikkor 50mm/f1.8 at the same time that I bought my D70;
that's an extremely sharp and inexpensive lens that happens
to be a good portrait length for digital.

Diane

Archived from groups: rec.photo.digital (More info?)

"Diane Wilson" <diane@firelily.com> wrote in message
news:MPG.1caa1af04910fb4d989a81@news-server...
> No, the F-stop is a factor of the focal length and aperture
> size, so it doesn't change with the size of the film or
> sensor.

Ok, thanks for the information.

> Yeah, f3.5 is kind of slow, but sufficient for general
> photography. To get something significantly faster, you'd
> need to go to a single focal length lens. I picked up the
> Nikkor 50mm/f1.8 at the same time that I bought my D70;
> that's an extremely sharp and inexpensive lens that happens
> to be a good portrait length for digital.

And thanks for the suggestion!

Bruce.

Archived from groups: rec.photo.digital (More info?)

Bruce Chastain wrote:
> I'm been looking at the Nikon D70 and have been surprised at the offered
> standard lens, Zoom-Nikkor 18-70mm f/3.5-4.5.
>
> I'm aware of the multiplication factor one must to use to convert the mm to
> 35 mm camera equivalent because of the sensor size, but is there also some
> sort of conversion for f-stops as well?
>
> In other words, assuming ASA-100 for both a 35 mm film camera and the Nikon
> D70, would the Nikon f/3.5 lens be as slow as it sounds, and so
> inappropriate for low light level photography?


There is no conversion for f-stop but digital does have less noise
(grain) and you can up the ISO for low light shooting more than film.
You might say there should be an ISO conversion factor where maybe ISO
800 digital is equal to ISO 100 film in terms of visible noise/grain
(I'm just throwing random numbers but I believe there is a difference).
BTW the D70 starts at ISO 200, no lower.

So f/3.5 in digital with ISO 1600 (max) will probably do better than
film in low light, you just won't have the blurry backgrounds. Also you
will have problems with autofocus in low light & there is no focusing
screen on the smaller viewfinder.

You can get the 50mm f/1.8 for another $100 & that's supposed to be
really an excellent lens. You will definitely want the kit lens unless
you plan to spend a lot on a super wide angle.

Archived from groups: rec.photo.digital (More info?)

Bruce Chastain wrote:

> I'm been looking at the Nikon D70 and have been surprised at the offered
> standard lens, Zoom-Nikkor 18-70mm f/3.5-4.5.
>
> I'm aware of the multiplication factor one must to use to convert the mm to
> 35 mm camera equivalent because of the sensor size, but is there also some
> sort of conversion for f-stops as well?
>
> In other words, assuming ASA-100 for both a 35 mm film camera and the Nikon
> D70, would the Nikon f/3.5 lens be as slow as it sounds, and so
> inappropriate for low light level photography?

yes: it's 3.5

If you want something faster, go for the 17-55mm/f2.8, or for the
50mm/f1.4, or any other fast lens.

--
chidalgo

Archived from groups: rec.photo.digital (More info?)

"Bubbabob" <rnorton@_remove_this_thuntek.net> wrote in message
news:Xns96219ED6DEAEEdilfjelfoiwepofujsdk@216.168.3.30...
> "Bruce Chastain" <bchastain@XNOSPAMXhyperfeed.com> wrote:
>
> > In other words, assuming ASA-100 for both a 35 mm film camera and the
> > Nikon D70, would the Nikon f/3.5 lens be as slow as it sounds, and so
> > inappropriate for low light level photography?
> >
>
> The D70 doesn't have a 100 ISO sensitivity. ASA? Where you been the last
30
> years? <g>.

Watch it, Bub. I still use descriptive notation for chess, as well as ASA
for film. :-)

Archived from groups: rec.photo.digital (More info?)

Bruce Chastain wrote:

> I'm been looking at the Nikon D70 and have been surprised at the offered
> standard lens, Zoom-Nikkor 18-70mm f/3.5-4.5.
>
> I'm aware of the multiplication factor one must to use to convert the mm to
> 35 mm camera equivalent because of the sensor size, but is there also some
> sort of conversion for f-stops as well?
>
> In other words, assuming ASA-100 for both a 35 mm film camera and the Nikon
> D70, would the Nikon f/3.5 lens be as slow as it sounds, and so
> inappropriate for low light level photography?
>
> Thanks,
> Bruce.
>
>
Basically yes. Making low f/# lenses is expensive, especially low f/#
ZOOM lenses.

Archived from groups: rec.photo.digital (More info?)

In article <Uof0e.1904$z.1304@newsread2.news.atl.earthlink.net>, Bruce
Chastain <bchastain@XNOSPAMXhyperfeed.com> wrote:

> > The D70 doesn't have a 100 ISO sensitivity. ASA? Where you been the last
> > 30
> > years? <g>.
>
> Whoops, sorry. I clearly gave away my age and history with film cameras.
> :-)

It will always be ASA to me too.

Archived from groups: rec.photo.digital (More info?)

"Dave Martindale" <davem@cs.ubc.ca> wrote in message
news1ut3d$s2v$2@mughi.cs.ubc.ca...
> In terms of setting exposure, f/3.5 is always f/3.5, so it is a slow
> lens. You can get faster lenses, but fast zooms are expensive.

I knew the money part would be in there somewhere. :-)

> On the other hand, you also use aperture to control depth of field. At
> f/3.5, this lens will have about 1.5 times *more* depth of field than a
> full-frame 35 mm camera shooting at f/3.5 with a lens that gives the
> same angle of view (i.e. about 2/3 the focal length). If you like
> large apertures for their shallow depth of field, then you need about
> one stop *faster* lens on the D70 than on the full-frame SLR.

Thanks for pointing that out. I hadn't thought about the depth of field.

Bruce.