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Equivalent focal lengths - Photography

Michelle Steiner wrote: > I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will > also be a Nikon so I can interchange the lenses between the cameras. > I'm pretty much settled on the D70. > My question is, if I put my current 50mm on a D7, what would its > equivalent focal length to a 35mm camera be? 75 mm (roughly, as the multiplier is not exactly but very close to 1.5 x) Juergen...

  1. #1

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will
    > also be a Nikon so I can interchange the lenses between the cameras.
    > I'm pretty much settled on the D70.
    > My question is, if I put my current 50mm on a D7, what would its
    > equivalent focal length to a 35mm camera be?
    75 mm (roughly, as the multiplier is not exactly
    but very close to 1.5 x)


    Juergen
    Juergen . Guest

  2. #2

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will
    > also be a Nikon so I can interchange the lenses between the cameras.
    > I'm pretty much settled on the D70.
    >
    > My question is, if I put my current 50mm on a D7, what would its
    > equivalent focal length to a 35mm camera be?
    >
    It'd be equal to a 75mm lens.

    --
    John McWilliams
    John McWilliams Guest

  3. #3

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > John McWilliams <jpmcwcomcast.net> wrote:
    > > > My question is, if I put my current 50mm on a D7, what would its
    > > > equivalent focal length to a 35mm camera be?
    > > It'd be equal to a 75mm lens.
    > Thanks.
    > Does that 1.5 : 1 ratio hold true for all focal lengths? Would my 85 mm
    > lens be equivalent to a 127.5 mm lens?
    Yes.


    Juergen
    Juergen . Guest

  4. #4

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will
    > also be a Nikon so I can interchange the lenses between the cameras.
    > I'm pretty much settled on the D70.
    >
    > My question is, if I put my current 50mm on a D7, what would its
    > equivalent focal length to a 35mm camera be?
    For the D70:

    In x the multiplier would be 36mm /23.7mm, or about 1.52.
    In y the multiplier would be 24mm /15.5mm, or about 1.55.

    Split that and you get 1.53.

    Just multiply the FL of the lens by that number to get the 'equivalent'.

    50 x 1.53 = 76.5mm
    100 x 1.53 = 153mm

    and so on.

    Cheers,
    Alan

    --
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    Alan Browne Guest

  5. #5

    Default Re: Equivalent focal lengths

    >> > My question is, if I put my current 50mm on a D7, what would its
    >> > equivalent focal length to a 35mm camera be?
    >> >
    >> It'd be equal to a 75mm lens.
    >
    >Thanks.
    >
    >Does that 1.5 : 1 ratio hold true for all focal lengths? Would my 85 mm
    >lens be equivalent to a 127.5 mm lens?
    Yes, it's always x1.5, but you should also know that a 50mm lens on
    your digital Nikon will not behave exactly the same way a 75mm does on
    a film camera. The way to think of it is this: you're still shooting
    with a 50mm lens, but you're always cropping to end up just using the
    middle part of the picture.

    -Joel

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    Dr. Joel M. Hoffman Guest

  6. #6

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > In article <xpIwd.3027$4n4.2273fe11.lga>,
    > [email]joelexc.com[/email] (Dr. Joel M. Hoffman) wrote:
    >
    >> Yes, it's always x1.5, but you should also know that a 50mm lens on
    >> your digital Nikon will not behave exactly the same way a 75mm does
    >> on a film camera. The way to think of it is this: you're still
    >> shooting with a 50mm lens, but you're always cropping to end up just
    >> using the middle part of the picture.
    >
    > But the cropping is optical, before the image is captured; that's not
    > the same as cropping with an enlarger (film) or with software
    > (digital).
    Why not?


    David J Taylor Guest

  7. #7

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > In article <32ig4eF3mhh96U1individual.net>,
    > "David J Taylor" <david-taylorinvalid.com> wrote:
    >
    >>> But the cropping is optical, before the image is captured; that's
    >>> not the same as cropping with an enlarger (film) or with software
    >>> (digital).
    >>
    >> Why not?
    >
    > Because when you crop the captured image, you're increasing the pixel
    > size, thus reducing the sharpness.
    If a CCD sensor is smaller than a full 35mm frome (36 x 24mm), then the
    area which the sensor sees is just the same as cropping the 35mm negative
    in an enlarger, or cropping a full-frame CCD sensor image in software.

    David


    David J Taylor Guest

  8. #8

    Default Re: Equivalent focal lengths

    Michelle Steiner <michellemichelle.org> writes:
    > In article <32ig4eF3mhh96U1individual.net>,
    > "David J Taylor" <david-taylorinvalid.com> wrote:
    >
    > > > But the cropping is optical, before the image is captured; that's
    > > > not the same as cropping with an enlarger (film) or with software
    > > > (digital).
    > >
    > > Why not?
    >
    > Because when you crop the captured image, you're increasing the pixel
    > size, thus reducing the sharpness.
    "increasing pixel size" ? Not unless you decide to, post-crop, change
    the output area over which those pixels are projected.

    If you take a CCD which is less than a 35mm frame and print it out at,
    say 12"x8", the output projections of those pixels are going to be
    larger than if you had the same sized sensor elements spread over a
    whole 35mm frame (and thus if you had more of them).

    So, in effect, the digital case is identical.

    I suggest you try being a little clearer about precisely what you mean
    by 'pixel size' because it appears than you're confusing yourself.

    B>
    Bruce Murphy Guest

  9. #9

    Default Re: Equivalent focal lengths

    Bruce Murphy wrote:
    > Michelle Steiner <michellemichelle.org> writes:
    >
    >
    >>In article <32ig4eF3mhh96U1individual.net>,
    >> "David J Taylor" <david-taylorinvalid.com> wrote:
    >>
    >>
    >>>>But the cropping is optical, before the image is captured; that's
    >>>>not the same as cropping with an enlarger (film) or with software
    >>>>(digital).
    >>>
    >>>Why not?
    >>
    >>Because when you crop the captured image, you're increasing the pixel
    >>size, thus reducing the sharpness.
    >
    >
    > "increasing pixel size" ? Not unless you decide to, post-crop, change
    > the output area over which those pixels are projected.
    >
    > If you take a CCD which is less than a 35mm frame and print it out at,
    > say 12"x8", the output projections of those pixels are going to be
    > larger than if you had the same sized sensor elements spread over a
    > whole 35mm frame (and thus if you had more of them).
    >
    > So, in effect, the digital case is identical.
    >
    > I suggest you try being a little clearer about precisely what you mean
    > by 'pixel size' because it appears than you're confusing yourself.
    >
    Relax, Bruce. The OP's original point, lost recently, was that there's a
    difference between the cropping that can occur in the *viewfinder* vs.
    post production, if you will, cropping. That's true of both pixels and
    grains.

    --
    John McWilliams
    John McWilliams Guest

  10. #10

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > I'm not comparing the same focal length on different sensor or film
    > sizes; I'm comparing different focal lengths on the same film or sensor
    > size.
    This sub thread is in a semantic tangle over the word "crop". Don't worry about it.

    For the D70 the effective multiplier is approx. 1.53 for every lens FL.

    Thus 50mm -> 76.5mm effective. (1.5 is close enough as few lenses stated to be
    a specific FL are actually that specific FL ... a couple mm either way is common).

    Cheers,
    Alan.

    --
    -- r.p.e.35mm user resource: [url]http://www.aliasimages.com/rpe35mmur.htm[/url]
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    Alan Browne Guest

  11. #11

    Default Re: Equivalent focal lengths


    "Michelle Steiner" <michellemichelle.org> wrote in message
    news:michelle-97EDB1.13341318122004news.west.cox.net...
    > In article <32imm0F3ncbm8U1individual.net>,
    > "David J Taylor" <david-taylorinvalid.com> wrote:
    >
    > > > Because when you crop the captured image, you're increasing the
    > > > pixel size, thus reducing the sharpness.
    > >
    > > If a CCD sensor is smaller than a full 35mm frome (36 x 24mm), then
    > > the area which the sensor sees is just the same as cropping the 35mm
    > > negative in an enlarger, or cropping a full-frame CCD sensor image in
    > > software.
    >
    > I'm not comparing the same focal length on different sensor or film
    > sizes; I'm comparing different focal lengths on the same film or sensor
    > size.
    Exactly. Different film and sensor sizes are just that, different. It's
    senseless to call it a crop or a magnification.

    Greg


    G.T. Guest

  12. #12

    Default Re: Equivalent focal lengths

    G.T. wrote:
    >
    > Exactly. Different film and sensor sizes are just that, different. It's
    > senseless to call it a crop or a magnification.
    One way or another, for comparative reasons or anything else, it is useful to
    know the 'crop' factor or 'magnification' value between the standard 35mm format
    and whatever smaller format digital sensor is used.

    Most exp. for those who use the same lens on both film and DSLR's.

    Cheers,
    Alan.


    --
    -- r.p.e.35mm user resource: [url]http://www.aliasimages.com/rpe35mmur.htm[/url]
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    Alan Browne Guest

  13. #13

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > In article <cq25ti$4m3$1inews.gazeta.pl>,
    > Alan Browne <alan.brownefreelunchVideotron.ca> wrote:
    >
    >
    >>This sub thread is in a semantic tangle over the word "crop". Don't
    >>worry about it.
    >
    >
    > Do you mean that I should be anti-semantic?
    As long as you're not anti-semitic.


    --
    -- r.p.e.35mm user resource: [url]http://www.aliasimages.com/rpe35mmur.htm[/url]
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    Alan Browne Guest

  14. #14

    Default Re: Equivalent focal lengths


    "Alan Browne" <alan.brownefreelunchVideotron.ca> wrote in message
    news:cq2705$951$1inews.gazeta.pl...
    > G.T. wrote:
    >
    > >
    > > Exactly. Different film and sensor sizes are just that, different.
    It's
    > > senseless to call it a crop or a magnification.
    >
    > One way or another, for comparative reasons or anything else, it is useful
    to
    > know the 'crop' factor or 'magnification' value between the standard 35mm
    format
    > and whatever smaller format digital sensor is used.
    >
    Yes, knowing the conversion factor helps film SLR users pick lenses for
    their digital SLRs.
    > Most exp. for those who use the same lens on both film and DSLR's.
    >
    My film SLR experience is limited so the conversion factor is meaningless to
    me. To me there is no crop or magnification. I take a picture with my
    Digital Rebel and it is what it is.

    Greg


    G.T. Guest

  15. #15

    Default Re: Equivalent focal lengths

    Dr. Joel M. Hoffman wrote:
    >>>>My question is, if I put my current 50mm on a D7, what would its
    >>>>equivalent focal length to a 35mm camera be?
    >>>>
    >>>
    >>>It'd be equal to a 75mm lens.
    >>
    >>Thanks.
    >>
    >>Does that 1.5 : 1 ratio hold true for all focal lengths? Would my 85 mm
    >>lens be equivalent to a 127.5 mm lens?
    >
    >
    > Yes, it's always x1.5, but you should also know that a 50mm lens on
    > your digital Nikon will not behave exactly the same way a 75mm does on
    > a film camera. The way to think of it is this: you're still shooting
    > with a 50mm lens, but you're always cropping to end up just using the
    > middle part of the picture.
    In almost all cases, using a cropped sensor DSLR will use the best part of the
    lens where there is the best resolution and the least linear distortion as well
    as clearly avoidng vignetting from additional filters such as circ-pols. Given
    the overall 'inconvenience' of using 35mm format lenses on cropped DSLR bodies,
    these are considerable countervailing benefits.

    In most cases, the 'cropped' performance of a specific lens will be better
    performance than the 'equivalent FL' lens would be at comparable aperture and price.

    A case in point. My 50 f/1.7 will become a 75 (ish) f/1.7. So for US$80 I get
    a lens with useability and performance that is close to an 85 f/1.4 which costs
    8x as much.

    My 300 f/2.8 becomes a 450 f/2.8 or a 630 f/4 with the 1.4TC! Talk about going
    up market real fast (with the TC, the res won't be as good as the 600 f/4 of
    course, but damned good IAC). With the 2TC, it's a 900 f/5.6!!

    My 80-200 goes to 120 - 300 f/8. Great for sports/nature.

    In all cases above, of course, the sweetest part of the lens is used.

    A minor negative is, that for the narrower FOV of the lens on a cropped sensor,
    an excess of glass is presented which increases susceptibility to flare. This
    is manageable of course by careful photographers.

    Cheers,
    Alan.


    --
    -- r.p.e.35mm user resource: [url]http://www.aliasimages.com/rpe35mmur.htm[/url]
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    Alan Browne Guest

  16. #16

    Default Re: Equivalent focal lengths

    Michelle Steiner <michellemichelle.org> writes:
    > In article <32imm0F3ncbm8U1individual.net>,
    > "David J Taylor" <david-taylorinvalid.com> wrote:
    >
    > > > Because when you crop the captured image, you're increasing the
    > > > pixel size, thus reducing the sharpness.
    > >
    > > If a CCD sensor is smaller than a full 35mm frome (36 x 24mm), then
    > > the area which the sensor sees is just the same as cropping the 35mm
    > > negative in an enlarger, or cropping a full-frame CCD sensor image in
    > > software.
    >
    > I'm not comparing the same focal length on different sensor or film
    > sizes; I'm comparing different focal lengths on the same film or sensor
    > size.
    Actually, yes you are. The post to which you replied (wrongly) was
    comparing 50 and 75mm lenses between film and cropped DSLR bodies. You
    appear to be confused enough to start going on about 'optical
    cropping'.

    B>
    Bruce Murphy Guest

  17. #17

    Default Re: Equivalent focal lengths

    Michelle Steiner wrote:
    > In article <32imm0F3ncbm8U1individual.net>,
    > "David J Taylor" <david-taylorinvalid.com> wrote:
    >
    >>> Because when you crop the captured image, you're increasing the
    >>> pixel size, thus reducing the sharpness.
    >>
    >> If a CCD sensor is smaller than a full 35mm frome (36 x 24mm), then
    >> the area which the sensor sees is just the same as cropping the 35mm
    >> negative in an enlarger, or cropping a full-frame CCD sensor image in
    >> software.
    >
    > I'm not comparing the same focal length on different sensor or film
    > sizes; I'm comparing different focal lengths on the same film or
    > sensor size.
    OK, I wasn't. To me, crop refers to a cutting of the image, not a change
    of focal length.

    David


    David J Taylor Guest

  18. #18

    Default Re: Equivalent focal lengths

    Alan Browne wrote:
    []
    > A case in point. My 50 f/1.7 will become a 75 (ish) f/1.7. So for
    > US$80 I get a lens with useability and performance that is close to an
    > 85 f/1.4
    > which costs 8x as much.
    []
    > Cheers,
    > Alan.
    Not really - you have just the same picture as if you just used the
    central part of a full-frame sensor with the 50 f/1.7 lens. By magnifying
    and only using the central part you will magnify the any defects as well
    (as a fraction of the total image), and make them more visible. Of
    course, exactly /how/ visible they are will depend on the lens and sensor.

    Cheers,
    David


    David J Taylor Guest

  19. #19

    Default Re: Equivalent focal lengths


    "David J Taylor" <david-taylorinvalid.com> wrote in message
    news:32l1i7F1a8i0sU1individual.net...
    >
    > Not really - you have just the same picture as if you just used the
    > central part of a full-frame sensor with the 50 f/1.7 lens. By magnifying
    > and only using the central part you will magnify the any defects as well
    > (as a fraction of the total image), and make them more visible. Of
    > course, exactly /how/ visible they are will depend on the lens and sensor.
    >
    > Cheers,
    > David
    >
    The crop factor is pretty confusing stuff when you are used to a portrait
    lens being 90/100mm. The crop factor of a 50mm lens makes it "look" the same
    size as an 80mm would but with the perspective of a 50mm lens! It is this
    perspective thing which gives traditional photographers the biggest amount
    of drama. There is not the same opportunity for focus depth with a DSLR
    using a 50mm lens as there is with a 35mm camera using a 90 or 100 mm lens.
    When was the last time you saw a 65mm portrait lens?

    I used to pull focus on an eye with f2.0. The cheek or nose would soften and
    conceal skin blemishes. Even at f1.4, a 50mm lens has too much DOF to pull
    this off. I find now that to obtain the same results as I used to get, I
    have to frame a shot using the same lens as I did with film but with greater
    distance between me and the subject.

    Doug


    Ryadia Guest

  20. #20

    Default Re: Equivalent focal lengths

    Ryadia wrote:
    []
    > The crop factor is pretty confusing stuff when you are used to a
    > portrait lens being 90/100mm. The crop factor of a 50mm lens makes it
    > "look" the same size as an 80mm would but with the perspective of a
    > 50mm lens! It is this perspective thing which gives traditional
    > photographers the biggest amount of drama. There is not the same
    > opportunity for focus depth with a DSLR using a 50mm lens as there is
    > with a 35mm camera using a 90 or 100 mm lens. When was the last time
    > you saw a 65mm portrait lens?
    >
    > I used to pull focus on an eye with f2.0. The cheek or nose would
    > soften and conceal skin blemishes. Even at f1.4, a 50mm lens has too
    > much DOF to pull this off. I find now that to obtain the same results
    > as I used to get, I have to frame a shot using the same lens as I did
    > with film but with greater distance between me and the subject.
    >
    > Doug
    Interesting, Doug. So for portraits....

    - you want the same perspective as a 90mm lens (say), so that defines your
    viewpoint.

    - you now want the same FOV, so that defines the new focal length required
    as 1.5 x 90mm, i.e. 60mm.

    - you want the same DOF as your 90mm f/2.0, so you need an aperture of
    what? f/1.3? (I'm unsure about this).

    - so you need a 60mm f/1.3 lens on digital (crop) to get the same results
    as you 90mm f/2.0 on film?

    Back of the envelope agrees with what you say....

    What are the implications of going the other way? Is 6 x 6cm an "easier"
    format for portraiture?

    Cheers,
    David


    David J Taylor Guest

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