Digital F Stop question

Discussion in 'Digital Photography' started by Bruce Chastain, Mar 22, 2005.

  1. 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.
     
    Bruce Chastain, Mar 22, 2005
    #1
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  2. Bruce Chastain

    Diane Wilson Guest

    In article <m2Y%d.1158$>,
    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
     
    Diane Wilson, Mar 22, 2005
    #2
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  3. Bruce Chastain

    Jim Guest

    "Bruce Chastain" <> wrote in message
    news:m2Y%d.1158$...
    > 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?

    No. The 35mm equivalent refers to the angle of view which is caused by the
    smaller image size of the digital camera.
    >
    > 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?

    It is as slow as it sounds (but, the minimum ISO for the D70 is 200).
    However, as the fastest lenses in that range only have f2.8 maximum
    aperature, the kit lens is not much of a handicap.
    Jim
     
    Jim, Mar 22, 2005
    #3
  4. "Diane Wilson" <> 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.
     
    Bruce Chastain, Mar 22, 2005
    #4
  5. "Bruce Chastain" <> wrote in message
    news:m2Y%d.1158$...

    > 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?


    Nope. f/3.5 is f/3.5.

    > 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?


    You cannot even get the D70 to give you ISO 100 -- 200 is the slowest
    setting. Moreover, though I don't personally own a D70, sample images
    suggest that ISO 800 gives more than adequate results. So the f/3.5-f/4.5
    range is at least as useful as it would be for a film camera, where it is
    quite common for zoom lenses these days.
     
    Andrew Koenig, Mar 22, 2005
    #5
  6. Bruce Chastain

    paul Guest

    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.
     
    paul, Mar 22, 2005
    #6
  7. Bruce Chastain

    Diane Wilson Guest

    In article <>, says...
    > 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.


    The D70 does have an auto-focus assist light, so low-light focusing
    doesn't seem to be a problem. Unless you need to maintain absolute
    darkness for your subject matter, at which case it might be better
    anyway to go to manual focus and focus by measuring the distance.

    Diane
     
    Diane Wilson, Mar 22, 2005
    #7
  8. Bruce Chastain

    chidalgo Guest

    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
     
    chidalgo, Mar 22, 2005
    #8
  9. Bruce Chastain

    Bubbabob Guest

    "Bruce Chastain" <> 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>.
     
    Bubbabob, Mar 22, 2005
    #9
  10. Bruce Chastain

    C J Campbell Guest

    "Bubbabob" <rnorton@_remove_this_thuntek.net> wrote in message
    news:Xns96219ED6DEAEEdilfjelfoiwepofujsdk@216.168.3.30...
    > "Bruce Chastain" <> 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. :)
     
    C J Campbell, Mar 23, 2005
    #10
  11. > 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.
    :)

    Bruce,
     
    Bruce Chastain, Mar 23, 2005
    #11
  12. 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.
     
    Don Stauffer in Minneapolis, Mar 23, 2005
    #12
  13. Bruce Chastain

    Bubbabob Guest

    "Bruce Chastain" <> 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.
    >:)
    >
    > Bruce,
    >
    >
    >


    So did I, by knowing what you were talking about <g>.
     
    Bubbabob, Mar 24, 2005
    #13
  14. In article <Uof0e.1904$>, Bruce
    Chastain <> 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.
     
    Randall Ainsworth, Mar 24, 2005
    #14
  15. "Bruce Chastain" <> writes:

    >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?


    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.

    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.

    Dave
     
    Dave Martindale, Mar 24, 2005
    #15
  16. "Dave Martindale" <> wrote in message
    news:d1ut3d$s2v$...
    > 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.
     
    Bruce Chastain, Mar 24, 2005
    #16
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