85mm 1.8 - A few questions

Discussion in 'Photography Equipment & Products' started by keith204, Feb 22, 2008.

  1. keith204

    keith204 No longer a newbie, moving up!

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    Alllright, race season is coming up, and I am looking for a way to take better pictures. Primarily, faster pictures would be nice! At the track, flash is hard to use, becasue it lights up the dirt floating through the air. So, max aperture is critical. I currently ONLY shoot with my 70-200 2.8, at 2.8. Currently, I also shoot at the wider end of that focall ength, between 70-100mm primarily. So, 85mm would be a fine focal length. Another fact...I use AI servo a LOT, so I need a good, accurate, fast-focusing lens.

    Questions:
    • Does the 85mm 1.8 have a fast, accurate focus?
    • Has anyone used the 85mm 1.8 for action photos?
    • What type of shutter speed increase would I be looking at? For instance... if the ambient light provided 1/60 at f/2.8, ISO 1600... whatabouts would the shutter speed be at f/1.8 and ISO 1600?
    • Is the 85mm sharp at 1.8?
    If you have experience, let me know! Thanks!
     
  2. newrmdmike

    newrmdmike TPF Noob!

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    my nikon 85 1.8 doesn't have that fast of focus i feel like, at a distance its reliable, up close its less accurate, but its easy to focus manual, and to tell when its not perfectly focused.

    if at 2.8 ur getting 1/60 then at 1.8 you would get 1/250th (is that right? or is it not a full stop from 2 to 1.8?)

    i would shoot f/2 its not as shart at 1.8

    i love my 85 1.8
     
  3. keith204

    keith204 No longer a newbie, moving up!

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    1/250th? That's amazing! For reals? I'm not totally sure how stops work.
     
  4. kundalini

    kundalini Been spending a lot of time on here!

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    I have the Nikkor 85mm f/1.8 and am very pleased with the color and contrast it gives. 9 blades and gives nice bokeh. I haven't tried to use in action situations, but the focus speed works well enough for me. I tend to use it at f/2 to f/2.8 more often because I find it sharper than at f/1.8. One more advantage is the smaller size and lighter weight than lunking a zoom around.
     
  5. ThomThomsk

    ThomThomsk TPF Noob!

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    f/1.8 and f/2.8 are one and a third stops apart. f/2 and f/2.8 are a whole stop. So 1/60th at f/2.8 gives you a theoretical 1/170th at f/1.8.
     
  6. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    It is a USM lens, so the focus should be pretty good. I couldn't tell if it's 'Ring USM' (the good type of USM) though.

    Focus speed also has a lot to do with the camera, since it's the camera that tells the lens what to do.
     
  7. newrmdmike

    newrmdmike TPF Noob!

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    thoms right, i knew it wasn't quite 2, but didn't know exactly how much.
     
  8. dipstick

    dipstick TPF Noob!

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    I don't know what kind of races you shoot, but what about DOF? 1.8 will give you a pretty shallow depth of field, not always suited for action shots.

    A prime can also be limiting in terms of getting the compositions you want when you are unable to change your distance from your subjects.
     
  9. Deadeye008

    Deadeye008 TPF Noob!

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    Are we talking about Nikon or Canon here. The canon 85mm 1.8 has the "ring USM" so it should be very fast. Just as fast as your 70-200 2.8 USM(if it's canon) I would imagine.
     
  10. schumionbike

    schumionbike TPF Noob!

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    If you get the 85 mm 1.4 then you'll get the 1/250 shutterspeed. 1.4 and 2.8 are two full stop apart.
     
  11. DSLR noob

    DSLR noob TPF Noob!

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  12. JerryPH

    JerryPH No longer a newbie, moving up!

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    The concept is simple... every time you open a full stop, it doubles the light so you can half the speed.

    If at F/2.8 you were shooting at 1/60th, then at F/1.8 you would be at 1.5 stops faster... so, from 2.8 at 1/60th you go to 2.0 and 1/120th... and to 1.8 you go to 180th, since thats a 1/2 stop. The full stop is an F/1.4 and thats where you would get 1/250th.

    Full stops are:
    1.4, 2.0, 2.8, 4, 5.6, 8, 11, 16, 22, etc...
     

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