When to use diopter correction?

Discussion in '35mm Cameras and Accessories' started by semi-ambivalent, Jun 12, 2011.

  1. semi-ambivalent

    semi-ambivalent Subscriber

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    I use glasses when I'm at a computer. The screen is about 18-24" away, and I use a pair of cheap +1.25 reading glasses. If I'm reading a book I usually hold the book about a foot or so away and I can see better using some +1.5 glasses. (They're both worn and the diopter mark is rubbed away but that is a good guess at the numbers.)

    I'm wondering if I need correction for my F3's viewfinder. If I use it with the glasses it is almost immediately "not right". Things look OK if I don't wear them but I've seen some focus issues in negatives that make me wonder if I need/should use correction at the eyepiece.

    How does one determine this? How "far away" is the focusing screen in an F3?

    sa
     
  2. budrichard

    budrichard Member

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    Make an appointment with an Ophthalmologist and have an eye exam. Bring your camera and explain what your needs are.
    An alternative is an Optometrist but they are not Medical Physicians.
    Only by starting with a known base line of your eyes, can you determine what your requirements are.-Dick
     
  3. dxqcanada

    dxqcanada Member

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    When viewing through the viewfinder the lines on the focusing screen should be in focus/clear.
    If they are not ... then you need a diopter.
     
  4. PhotoJim

    PhotoJim Member

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    If you're not sure, borrow a camera with built-in diopter correction and set it to the neutral position (there is usually a little click stop here). Then adjust the diopter to see if you can make it better. Look at the viewfinder lines or the exposure readout. If you can sharpen the image this way, then a diopter would help you.

    The viewfinder in most cameras is at about one metre effective focus distance, so if you need focusing assistance at this distance, a diopter will help.

    Bear in mind that if you're new to reading glasses, this might gradually shift so the diopter value might change.

    You can also use your reading glasses, potentially. I can use my cameras through my glasses fine (I have progressive lenses so there is a sweet spot at the appropriate distance), but more and more I'm finding it convenient to use my naked eye with diopter adjustment (I haven't bought any diopter lenses, but most of my SLRs have built-in correction).
     
  5. Ian C

    Ian C Member

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    If you require eyeglasses to correct your distance vision you’ll likely need your glasses to see the viewing screen image sharply.

    On eyepiece viewing cameras the eyeglasses prevent you from getting your eye in the proper position. The rubbing of the eyeglass lens against the (sometimes metal) bezel surrounding the eyepiece sometimes abrades the eyeglass lens or coatings.

    To see the eyepiece image clearly without glasses requires the proper eyepiece diopter lens so that eyeglasses aren’t necessary. This “customizes” the eyepiece view for the owner, but makes it difficult to focus for most others.

    People who need reading glasses, like the relatively weak 1.25 dipoter reading glasses, don’t usually need an eyepiece diopter. Eyepeice diopters are needed by folks who require eyeglasses to correct DISTANCE VISION, because that’s what we see in a viewfinder. We're not focusing on something at arm's length.
     
  6. Bob-D659

    Bob-D659 Member

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    From your description, it sounds as if your eyes are losing their ability to focus on close objects, pretty common as they get older. The F3 viewfinder is set for viewing at 1 meter. So you would need slightly less correction that the +1.25 you use for reading. Take your camera shopping and try on a pair of +1 reading glasses and see if they work. I bought some dollar store +1.25 glasses and cut the lenses down to make a couple of screw in diopter lenses as that is what I needed to see clearly while wearing my normal "distance" vision glasses.
     
  7. jeffreyg

    jeffreyg Subscriber

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    I'm not familiar with the F3 viewfinder but my FM2 viewfinder unscrews and I believe there are other power (+/-) viewfinders may be available. Additionally when I bought my Hasselblads I sent them my eyeglass Rx and I was able to purchase the appropriate viewfinder eliminating the need for glasses to focus. I also got rubber clip-on eyecups which eliminate glare and I can wear non Rx sunglasses.

    http://www.jeffreyglasser.com/
     
  8. tkamiya

    tkamiya Member

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    I just went through this with my F-100.

    If your camera has a diopter adjustment, use it to see if you can get all the indicators (like shutter speed, etc) into a sharp focus. Then take the lens off and see if split prism (if you have it) area, and the texture of ground glass is sharp in focus. I suggest you take the lens off so that these things are clearly and only visible without distracting images.

    If you cannot bring them into sharp focus, you will need the diopter lens.

    If you wear bi-focal eye glasses, be careful because as you look down to see indicators at bottom of the view finder (if you have any), it will be using the corrected portion of the glasses and you will be using the center portion of the glasses to see the split prism.
     
  9. Chan Tran

    Chan Tran Member

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    The screen is supposed to appear 1 meter from the eyepiece. Use the glasses that you can see best at a 1 meter distance. Or estimating your eye condition based on what you said I think if you install the 0 eyepiece from Nikon it would be right to use without glasses. The 0 eyepiece is actually +1 diopter because the stock camera is -1.
     
  10. PhotoJim

    PhotoJim Member

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    Ahh, but you're not focusing on the subject. You're focusing on the focusing screen.

    Analogy: Project a slide. Go a metre away from it. If you're farsighted it will be blurry, even though the slide might be of mountains many kilometres away, because the image on which you are focusing is only one metre away.

    A focusing screen is essentially the same thing. It is a projected image of the field of view of the lens and it is a flat field. Everything in that field appears to be the same distance away, as far as your eye's focusing is concerned, and that distance is 1 metre (on most cameras).
     
  11. Diapositivo

    Diapositivo Subscriber

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    I am a glass wearer (around -2 dioptres, myopic vision). When you are shortsighted, you normally wear your glasses. If you then put dioptres on the viewfinder, you are supposed, to avoid strain, to take your glasses away, and put them again, any time you bring the camera to the eyes.

    Besides contact lenses, the solution is to just keep the glasses on. I can see information on the viewfinder, if needed I just tilt very slightly my eye on one side. I basically see all.

    So my advice for short-sighted people is to buy some rubber washer for the viewfinder ocular in case there isn't any, and just keep your glasses as usual. After a while you get used to it.

    If I get it right, my lens + camera cannot serve as a dioptre, so there is no risk, in principle, that I focus on the wrong plane. But if you don't see clearly the viewfinder image the difference between in-focus and out-of-focus is harder to detect.