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Is the difference between F1.8 and F2.8 noticeable?

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  • Is the difference between F1.8 and F2.8 noticeable?

    Hey,
    I've been eyeing a purchase of a 50mm F1.8 lens for my Sony Alpha. I'd like to know if the difference of the amount of light that enters at the setting, in comparison for example with a F2.8 lens. Is the difference noticeable? Currenty I'm stuck with the basic 18-70mm F3.8 lens that came with the camera, so I'm sure more light is going to enter the lens, but I want to be sure if the F1.8 is worth the extra dollars (specially since it's a a fixed 50mm portrait lens, no zooming). I tend to take shots in dark environments, with low intensity light sources (like concerts, theater, etc).

    Thanks for the help!

    GRINGO.
    "Nihil est in intellectu quod non prius in sensu" | Portfolio | Soņando Despierto (visual blog)

  • #2
    quote

    Your F 1.8 lens lets in twice as much light as a 2.8-I stop difference,and four times as much light as your F3.8-2 stops difference.Regards.Ken

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    • #3
      I have a 10.5mm 2.8 fisheye and the 50mm 1.8 lens and there is a noticable difference when is comes to low light shooting. And the 50mm 1.8 is great for concert, theater, and portraits expecially for the price.
      Jacob Fales Photography

      Flickr

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      • #4
        Yes but the question is do you need it, especially if money is a concern. You can boost the ISO from 200 to 400 which is equivalent to that one f-stop.
        Nikon D800e, D300, D5000, NIKON GLASS 85mm F/1.8 D, 105mm f/2.8 Micro AF-S VR, 70-200 AF-S VR f/2.8, 28-300 AF-S VRII,10.5mm Fisheye, 24-70 AF-S f/2.8, TC-20E III AF-S, Sigma 12-24 HSM, Sigma 30mm f/1.4 HSM, Sigma 150-500 OS, 2 SB-600 Speedlights, SB-900 speedlight, 4 YN-622N transceivers, Manfrotto 190MF3 tripod & 322RC2 ball grip head. - NJ, USA
        Flickr Photobucket
        Ok to edit and repost my shots on DPS forums

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        • #5
          Just to be anal-retentive (and yes, I spell it with a hyphen), the difference between f/2.8 and f/1.8 is one-and-a-third stop.

          f/2 would be twice the light. (1 stop)
          f/1.8 is 2.5 times the light. (1.33 stops)
          f/1.4 would be 3 times the light. (1.66 stops)
          f/1.2 would be 4 times the light. (2 stops)

          It's a power-of-two thang.
          I shoot with a Canon 5DmkII, 50D, and S90, and Pansonic GX-7. flickr stream and equipment list

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          • #6
            And perhaps equally important for actual portrait work. Wide open, a 2.8 lens at 5 feet has a depth of field of roughly four inches. A 1.8 lens at 5 feet has a depth of field of just over an inch.

            Whether you WANT to be able to control depth of field that much is something to consider, and doing it by accident and having the tip of the nose in focus and the eyes and ears fading out is a real possibility.

            It's not quite what you asked, but it is a difference!

            But Mom, Pentax IS rebellious
            Pentax K-7, K20D
            Pentax SMCP-FA 35mm f/2.0 AL -- Pentax SMC 50mm f/1.7 -- Pentax DA 50-200mm f/4-5.6 ED -- Sigma 28-70mm f/2.8 EX DG IF Aspherical -- Pentax DA 18-55mm f/3.5-5.6 WR

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            • #7
              Originally posted by inkista View Post
              Just to be anal-retentive (and yes, I spell it with a hyphen), the difference between f/2.8 and f/1.8 is one-and-a-third stop.

              f/2 would be twice the light. (1 stop)
              f/1.8 is 2.5 times the light. (1.33 stops)
              f/1.4 would be 3 times the light. (1.66 stops)
              f/1.2 would be 4 times the light. (2 stops)

              It's a power-of-two thang.
              I was approximating, but,Whatever blows your dress up! Ken

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              • #8
                Originally posted by inkista View Post
                Just to be anal-retentive (and yes, I spell it with a hyphen), the difference between f/2.8 and f/1.8 is one-and-a-third stop.

                f/2 would be twice the light. (1 stop)
                f/1.8 is 2.5 times the light. (1.33 stops)
                f/1.4 would be 3 times the light. (1.66 stops)
                f/1.2 would be 4 times the light. (2 stops)

                It's a power-of-two thang.
                Sorry inkista, I'm the same.

                The "1.4" in f/1.4 is approx sqrt(2), which is a whole stop number. So the list is:

                f/2 would be twice the light as f/2.8. (1 stop)
                f/1.8 is 2.5 times the light. (1.33 stops)
                f/1.6 would be 3.2 times the light. (1.67 stops)
                f/1.4 would be 4 times the light. (2 stops)
                f/1.3 would be 5 times the light. (2.33 stops)
                f/1.1 would be 6.4 times the light. (2.67 stops)
                f/1 would be 8 times the light. (3 stops)

                f/1.2 is a half-stop, so that would be 5.7 times more light than f/2.8 (2.5 stops).
                Last edited by crunch; 11-20-2008, 07:32 PM. Reason: correction on f/1.2

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                • #9
                  Originally posted by Mr Guy View Post
                  And perhaps equally important for actual portrait work. Wide open, a 2.8 lens at 5 feet has a depth of field of roughly four inches. A 1.8 lens at 5 feet has a depth of field of just over an inch.

                  Whether you WANT to be able to control depth of field that much is something to consider, and doing it by accident and having the tip of the nose in focus and the eyes and ears fading out is a real possibility.

                  It's not quite what you asked, but it is a difference!

                  May be a silly question but what happens at lets say 10 feet? Would the depth of field be larger? Like if your shooting a concert and you can't get 5 feet away, would you be safer at a further distance from getting a sharp nose and blury eyes?
                  Nikon D700, Nikon D200, 50mm f1.8, 28-80mm, 28-75mm f2.8, 70-300mm 5 speedlights, some stands, umbrellas etc.
                  My flickr
                  My Website

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                  • #10
                    Originally posted by sarahgirl777 View Post
                    May be a silly question but what happens at lets say 10 feet? Would the depth of field be larger? Like if your shooting a concert and you can't get 5 feet away, would you be safer at a further distance from getting a sharp nose and blury eyes?
                    The further the lens is focused (10 ft vs 5 ft), the greater the DoF (more will be in focus), for a given aperture.

                    So yes.

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                    • #11
                      If you are in a low light, fast action situation, it is the difference between getting motion blur and stopping the action.
                      I don't make photographs, I find photographs

                      Nikon D90
                      Nikkor 18-105, 50mm 1.8,50-300,28mm
                      Fujifilm Finepix s5000

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                      • #12
                        Originally posted by crunch View Post
                        Sorry inkista, I'm the same.
                        ...

                        f/1.2 is a half-stop, so that would be 5.7 times more light than f/2.8 (2.5 stops).
                        Thank god someone caught that. I have GOT to stop trying to do the math in my head...
                        I shoot with a Canon 5DmkII, 50D, and S90, and Pansonic GX-7. flickr stream and equipment list

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                        • #13
                          Originally posted by sarahgirl777 View Post
                          May be a silly question but what happens at lets say 10 feet? Would the depth of field be larger? Like if your shooting a concert and you can't get 5 feet away, would you be safer at a further distance from getting a sharp nose and blury eyes?
                          See this site: http://www.dofmaster.com/dofjs.html
                          Mark

                          My Photo Blog
                          Druziak Photography

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                          • #14
                            Great Website

                            Originally posted by mdruziak View Post
                            Thanks for sharing that link, that can definately come in handy.
                            Nikon D700, Nikon D200, 50mm f1.8, 28-80mm, 28-75mm f2.8, 70-300mm 5 speedlights, some stands, umbrellas etc.
                            My flickr
                            My Website

                            Comment


                            • #15
                              woah, thanks for the replies everyone! lots of technical words, but pretty helpful none the less. So to sum it up, it is worth it to buy one. I have been trying to break in the realm of concert/theatre photography (as a minor side - hobby - job) kind of thing, and the low light situations have been very hard. Good practice though. I want to keep the ISO as low as possible (the noise is also frustrating, and much more difficult to eliminate later on). Once again, thanks everyone!
                              "Nihil est in intellectu quod non prius in sensu" | Portfolio | Soņando Despierto (visual blog)

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