Nikon 85 mm f/1.8 D Softness Question

Discussion in 'Digital Photography' started by Music_Producer, Apr 26, 2006.

  1. Music_Producer macrumors 68000

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    Sep 25, 2004
    #1
    I'm relatively new to photography, so I had a question regarding this lens..

    I just bought it for my Nikon D50.. to take some good portrait pictures. I was testing it out all day today, and the pictures are beautiful. I love that out-of-focus blur it gives at f/1.8.

    Now, the puzzling part is.. are the pictures supposed to be soft at 1.8? Or sharp? I took some pictures of my wife's cat (in the garage.. ISO 400 and shutter speed of 160) .. and the pix looked terrible.. very soft. Almost as if, I didn't focus right.

    When I used my sb-600 flash, and moved the shutter speed to 500.. the pictures were much better. All this, at f/1.8.

    So are the pictures always soft at f/1.8? I mean, the whole point of using a lens like this in low light situations is the f/1.8 thing.. but if the image comes out soft.. I'll have to go to f/3.0 and above.. which kinda beats the whole purpose. Sheesh I'm confused! Please help.. thanks! :)
     
  2. Linkjeniero macrumors 6502

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    #2
    I'm not the most knowledgeable person on the topic here, but for what's worth: I had similar problems with my new Nikkor 50mm f/1.4, and for what I read, the softness problems happen when the aperture is big and the subject is too close to the lens. So if you want sharp shots at a hight aperture, you have to take the shot from a distance. (I tried it, and it really helped).
     
  3. Clix Pix macrumors demi-goddess

    Clix Pix

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    #3
    When you have a fast lens wide open at, say, f/1.4 or f/1.8, this lets in a lot of light, which is great. It also reduces the depth of field so that not much is actually in sharp focus. You point the lens at a baby's eyes and face....the sharpest point of that image is going to be where the lens was aimed: ie, the eyes, and the rest of it is not going to be sharp. Going in the other direction, if you were to have the lens aperture set at f/22, everything will be in sharp focus. Depending upon what you're trying to do this may or may not be desirable, just as it may not be desirable to have only a small portion of your image in sharp focus. In doing a landscape photo, you probably would like to have everything in sharp, clear focus. In shooting a portrait of someone, you probably would just as soon have the background and stuff around them softened so that it is less distracting and the subject of your photo really stands out.

    So, those photos taken of the cat in the garage were not sharp because you had the lens wide open at f/1.8. Look again at the images and maybe you'll find the one area which actually is in focus. Try shooting the cat again, this time choosing several different apertures so that you can note the differences.

    Another potential issue is how close you were to the subject. Each lens has a specific focusing distance and if you're too close you will not get a correctly focused image. Be sure that you aren't getting so close to the subject that the lens cannot focus correctly.

    You might want to look online for some basic photography info which will explain things and next time you're at the library or in a bookstore pick up a book or two about the technical aspects of photography.

    Hope this helps!
     
  4. Music_Producer thread starter macrumors 68000

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    #4
    Thanks for the reply Clix Pix and LinkJeniero! I'll try that out and see if it works.. shooting the same object at f/1.8 from varying distances.

    Clix pix.. yup I know that a wide aperture throws everything out of focus.. I just didn't want it to throw the main subject out of focus! ;-) Its probably the distance thing.. or maybe its the cat!
     
  5. Music_Producer thread starter macrumors 68000

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    Sep 25, 2004
    #5
    Check these out..

    This one, taken in the backyard.. looks super sharp.. because the shutter speed was way high.. somewhere around 3200 with f/1.8. I focused on the leaf and its sharp..


    [​IMG]

    Now, the one with the cat.. without a flash.. at f/1.8 but shutter speed was 160.. which I assume, s houldn't blur because of no tripod, etc..

    [​IMG]


    This one, with a flash (and actually closer to the cat) at f/1.8.. the SB 600 was bounced off the ceiling.. shutter speed was somewhere around 500:

    This one's so sharp!

    [​IMG]

    :confused: it seems like the shutter speed eliminates the 'softness' But i'll keep trying and playing with it.
     
  6. PBGPowerbook macrumors regular

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    Jan 6, 2004
    #6
    on that 'soft' one, i think you just missed focus - the ear of the cat looks sharp. and are you sure that your flash auto settings arent stopping down the lens, because that last one doesnt look like 1.8...dunno though
     
  7. Music_Producer thread starter macrumors 68000

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    #7
    Hmm.. I just noticed the ear part, the funny thing was though.. that I took quite a few pics - 9 to 10.. and all of them are soft.. and I focused on his nose/eyes..so i'm not sure how the ear got sharp instead!

    Yup, the flash one is at f/1.8 .. shutter speed 500. Although I am not quite sure why its so sharp.. at 1.8 it should have that bokeh bit. Ahh, I need to get back to that photography book
     
  8. Music_Producer thread starter macrumors 68000

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    #8
    Oh wait, another newbie question. When you say .. that I "missed" the focus.. this cat was moving, as in.. yawning, stretching, etc.

    If I lock on to his nose (pressing the shutter half way..and keeping it pressed) and he moves, and then I click.. won't that 'follow' his nose? A rather retarded way of asking, but you know what I mean. I forget what its called..

    My DX 18-55 mm lens does that.. the 85mm lens isn't digital.. :confused:
     
  9. Linkjeniero macrumors 6502

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    Jan 6, 2005
    #9
    That deppends on the camera settings. If you're using the presets (macro, portrait, etc), only the Sports mode has it. If you're shooting manually, you can select the autofocusing in the menu (I forgot how to do it exactly, look it up in the manual).
     
  10. Abstract macrumors Penryn

    Abstract

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    #10
    Not sure if you missed the point of what Clix Pix was trying to say. He's saying that although your new lens can provide you with a very short depth of field, taking photos with a very small region of focus may be causing the blurriness you see in your cat photo.

    If you take a photo of a bug at f/1.8, then great. It's small, so it's very easy to get the entire bug into focus. Only the bug will be in focus, and everything else is either slightly blurred, or very blurry, depending on how far away the surroundings are away from the bug.

    If you're taking a photo of a cat that's 18 inches long, and you focus on your cat's nose, yes his nose will be perfectly in focus, but since the depth of field is so narrow (lets say 1 inch in front and behind the nose), the rest of the cat is going to be blurry. If you're taking a photo of something large like a cat, and it's body is behind his head like in your photos, it may be a better if you don't use f/1.8 and use f/8 instead (for example). If you're taking a photo of your cat's face straight on, and his body isn't in the shot, then it's a portrait and the subject has no depth information, so setting the aperture to f/1.8 is okay since the cat appears to be 2D anyway. There's nothing blurry behind or in front of the subject if your subject appears "flat."
     
  11. Abstract macrumors Penryn

    Abstract

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    #11
    Well as long as he isn't moving very fast, and the shutter speed is sufficiently fast, the focus won't have to "follow his nose" as you said. Why? Because the distance from his nose to the camera isn't going to change. If the distance from your camera to the cat's nose was 4 feet, and then your cat moves a little bit so that your cat's nose is 4.5 feet away, every part of your cat that's exactly 4 feet away from your camera will be perfectly in focus, but his nose might not be since it's 4.5 feet distance, not 4 feet.

    Oh, and if your depth of field is 0.2 inches (ie 0.1 inches in front, and 0.1 inches behind the point where your camera is focusing), then technically, everything at a distance between 3.9 and 4.1 feet will be in focus. Everything outside of this distance will be slightly blurry.

    Oversimplified (and probably slightly wrong.....it's 2:22 am here :eek: ), but I hope you at least get the point.
     
  12. ChrisA macrumors G4

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    #12
    The depth if field on a llens like this at f/1.8 is so narrow that you most decide on what part of the cat or person to focus. Most photographers will want the eyes to be sharp because

    Technically any lens, not just yours can only focus to one distance. Parts of the subject not at that exact distance will not be in focaus. However there is an area near the plane of focus that will be acceptably sharp at f/1.8 that area may be only inches from the plane but at f/16 it could be many feet.

    What you need to learn to do, is use this to your advantage. Use the narow depth of focus to draw attention to some part of the photo and let the rest blur out. If everything needs to be in sharp focus then shoot at f/8 or so.
     
  13. ChrisA macrumors G4

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    #13
    (1) the nose is a poor focus target. use the eyes.

    (2) No. If the focus is locked. it's locked. Well I think there is an AF mode where the camera is suposed to follow focus. But don't expect it to work very well in low light and close subjects and I'm not sure about the lens. I don't think the one you have has a fest focus motor in it. The system wuld work better outdoors in sunlight with some subject 15 feet away. You can always use the manual focus ring on the lens.
     
  14. Music_Producer thread starter macrumors 68000

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    Sep 25, 2004
    #14
    Got it! Thanks everyone for your replies.. really appreciate it. The same lens at f/2.2 produces absolutely sharp pics.. I guess you were all right about the narrow range of sharpness it gives at f/1.8. Ahh, I'm in love with this lens..

    :)
     
  15. Abstract macrumors Penryn

    Abstract

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    #15
    f/2.2 is better? That isn't much of a different at all. Try something above f/5.6 at least.
     
  16. Chip NoVaMac macrumors G3

    Chip NoVaMac

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    #16
    Do you have a place to post full resolution images. You may have front/back focus issue, not common - but does happen.
     

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