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  1. #1

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    Nikon FM2 prism problem

    I'm new here, so you'll have to excuse me if this is the wrong forum to post this in or this sort of thing isn't dealt with at all here.

    I bought a nikon fm2 online a couple days ago and it arrived today. The camera seems to be in excellent condition wtih a nice, tight mechanical feeling overall, but there seems to be a problem with the prism.I don't know much about this.. i'm pretty new to the whole camera thing and especially manual analog ones, so while i believe it is the prism that is the culprit, i don't know for sure.

    My problem is that when i try to focus, the two halves of the circle will not align (excuse my lack of proper camera lingo here ). Say if i focus on a vertical line, what im focusing on will align, but the circle in the prism stays the same.

    So.. to my questions.

    - Is this a problem with the prism? Is it perhaps misaligned?
    - If so, is this something your average camera and optics store could fix or do i have to send it to Nikon?
    - In either case, how much would aligning the prism cost?
    - Considering that the mechanics of the camera seem to be in very good condition, all moving parts i've tried seem to be very clean and tight, how much would it cost to have it completely refurbished (aprox. ofcourse.. say cleaning and perhaps some replacement parts on the winder)?

    Again.. if this in the wrong forum to post this in, i'm sorry. Any links you have would be appreciated

  2. #2

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    The focusing aids in the middle of the viewfinder screen on the FM2 or any camera for that matter, are dependent on the lens for functioning. If the lens is too slow in maximum aperture, then you may find that one or more of the focusing aids will just not work. Also, if your eye is not centered in the eyepiece, this can affect the working.

    Also, if the Fm2 has removable focusing screens, it is quite possible that the screen has not been "seated" completely. This is a user-removable part. It could have been bumped in transit. You could remove and replace it, and see if that makes a difference. The smooth side of the screen goes towards the prism, the rough side goes towards the mirror.

  3. #3

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    The focusing aids in the middle of the viewfinder screen on the FM2 or any camera for that matter, are dependent on the lens for functioning. If the lens is too slow in maximum aperture, then you may find that one or more of the focusing aids will just not work. Also, if your eye is not centered in the eyepiece, this can affect the working.
    'If the lens is too slow in maximum aperture, .. ' What do you mean by that? How can the aperture be "slow"?

    And yes, i noticed that moving my eye in relation to the eyepiece changed the appearance of the focus. This isn't what im experiencing though. No matter how i move my head, the focus ring stays the same. What changes is the alignment of the image. The focus aid ring does not move, nor does it when i try to adjust the focus on the lens.

    Also, if the Fm2 has removable focusing screens, it is quite possible that the screen has not been "seated" completely. This is a user-removable part. It could have been bumped in transit. You could remove and replace it, and see if that makes a difference. The smooth side of the screen goes towards the prism, the rough side goes towards the mirror.
    If by removabel focusing screens you mean removable prisms, no, they're not intended as user removable.
    Last edited by Degenetron; 03-23-2007 at 02:12 PM. Click to view previous post history.

  4. #4

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    Degenotron:

    The maximum aperture of the lens is often referred to as slow or fast. Generally any lens with a maximum aperture larger than f2.8 is fast and anything smaller is slow. This originates in the fact you can use a faster shutter speed at a given light level with a larger aperture.

    I think you also have the prism and focusing screen confused. The prism is the big hunk of glass on top of the camera between the focusing screen and the eyepiece, it's fixed and is only there to transmit light from the focusing screen to the eyepiece. The focusing screen is what the image from the lens is displayed on by the reflex mirror, as well as what contains the focusing aids (if any) that you see in the viewfinder. The confusion may occur due to the fact that the focusing screen often contains a split-prism focus aid (the split circle at the centre).

    On the FM2 (like all the FM/FE/FA series except the original FM) the focusing screens are user-replacable. You likely have an improperly installed focusing screen. Try reinstalling it. Note also that if the max aperture of the lens is slower than f4 or so you will get the split-prism on the focusing screen blacking out when you try and focus.

  5. #5

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    I think you also have the prism and focusing screen confused. The prism is the big hunk of glass on top of the camera between the focusing screen and the eyepiece, it's fixed and is only there to transmit light from the focusing screen to the eyepiece. The focusing screen is what the image from the lens is displayed on by the reflex mirror, as well as what contains the focusing aids (if any) that you see in the viewfinder. The confusion may occur due to the fact that the focusing screen often contains a split-prism focus aid (the split circle at the centre).
    You're right. i did have those confised, or rather, merged. I thought what i saw in the eyepiece was directly linked to the prism.. guess i need to read up on my camera mechanics. Anyone got a link to some schematics?

    On the FM2 (like all the FM/FE/FA series except the original FM) the focusing screens are user-replacable. You likely have an improperly installed focusing screen. Try reinstalling it. Note also that if the max aperture of the lens is slower than f4 or so you will get the split-prism on the focusing screen blacking out when you try and focus.
    Hmm.. the screen mght be user replaceable, but i have no idea how to reinstall it. As for the aperture of my lens (the only one i got for this cam atm), it seems to be 3.5 to 22 ? the ring around the lens that has the info on it, is gone, so i don't know manufacturer and such, but the rings on it allow 35-70mm and i the aperture ring has number ranging from 3.5 to22.. as i said earlier.. im a n00b ;p No matter how i set t up though, the split-prism focus aid (learned a new term there ) does not change.

  6. #6

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    Perhaps I should have been more detailed. The focusing screen is likely where your "issues" lie. The focusing screen is accessed thru the front of the camera, when you take the lens off. It is situated directly above the mirror in the top of the "mirror box". To remove you normally might want to use a pair of tweezers or small needle nose pliers to grip onto a little tab. IIRC, you pull downward on the screen towards the mirror and it should pop out. While out, you should clean it. To re-install, you insert the back end first then raise the side closest to the front up and it snaps in place. The focusing screen itself contains a pair of micro-wedges in the center that provide the split-image line-up-the-vertical-lines type of focusing aid, and these are sometimes called micro-prisms. But....they are not the reflex viewing prism which is between the viewing screen and the eyepiece and in your camera is fixed into the camera body permanently.

    Some focusing screens do not work with some lenses. That is why Nikon provided a variety of different screens, so you could customize the camera to your lens choices, and shooting style.

  7. #7
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    Degenotron:

    In an SLR like the FM-2, the only thing that happens when you rotate the focusing ring is that you change the optics of the lens. If the camera focusing screen has a split image spot, half if the image that appears in will move as you rotate the focusing ring.

    As Mavrz noted, the focusing screens in the MF-2 are replaceable - if you remove the lens, you can see the bottom of the focusing screen at the top of the box under the prism. There is a release at the front edge of the screen that you can readily see with the lens removed, and I there is a special tweezer tool that you get when you purchase a replacement screen that is used to release the catch to remove the screen. It's possible that the screen was not installed properly. However, having changed screens in a Nikon, my experience was that it would have been quite an undertaking to get it wrong, so I think I would not put that explanation high on the list of possibilities.

    There were (are) three focusing screens that fit the FM-2. The standard K screen has a split image focusing spot surrounded by a circular microprism spot. These concentric spots are in the middle of the overall matte field.. The split in the split-image spot is horizontal when the camera is held in the 'landscape' position, so it can only be used to focus on vertical lines.

    I use an f3.3 lens as my standard workhorse lens, and the split image function works fine with it. But it doesn't work well at all with an f4.5 lens. So as Mavrz pointed out, the problem could be the aperture of your lens.

    But I wonder if perhaps the camera you purchased as the B screen instead of the K screen. The B also has a circular spot in the center of the focusing screen, but it is not a split image spot. Instead, of two concentric circles in the viewfinder, you see only one circle, and it is NOT a split image.

    So - when you look through the viewfinder of your FM-2, do you see one circle, or two concentric circles. If you see only one, then you have a B screen that doesn't allow split image focusing.

    I've sent my FM-2 back to its maker a couple of times. About 15 years ago I had the shutter assembly replaced - that cost about US$150 at the time. The FM-2 was an active model until 4-5 years ago, and Nikon tends to maintain parts and service for a while after they retire a model, so it's possible that they could still do a CLA on your. If you are into traditional photography, the FM-2 is one of the best traditional cameras around, so it might be worth the investment.

    But I don't think your problem is more likely something other than prism alignment.
    Louie

  8. #8
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    Quote Originally Posted by Degenetron View Post
    I

    Say if i focus on a vertical line, what im focusing on will align, but the circle in the prism stays the same.
    You don't say whether you have taken any photos with this camera and lens yet, so although the vertical line will align in the viewfinder, we don't really know if this is focussing accurately or not. I'd say shoot a roll of film where you are focussing on objects at a variety of distances, and if they all turn out to be focussed correctly then I wouldn't worry too much about the two halves of the circle. If the focus is off, however, you'll definitely need to explore the suggestions given here.

  9. #9

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    You don't say whether you have taken any photos with this camera and lens yet, so although the vertical line will align in the viewfinder, we don't really know if this is focussing accurately or not. I'd say shoot a roll of film where you are focussing on objects at a variety of distances, and if they all turn out to be focussed correctly then I wouldn't worry too much about the two halves of the circle. If the focus is off, however, you'll definitely need to explore the suggestions given here.
    Yeah, as i said, i got this cam today. I've shot some images today, and i'll spend the rest of the film when i get daylight, at different ranges. As for not caring too much about the focus ring though.. i dunno.. i want this camera to work. I, unfortunately, paid well over the going rate for a half decent fm2 for it.. believeing it was near mint.. i'll shoot up a couple rolls tomorrow though and have them developed. I'll see how it goes.. but either way, it not working correctly will need to be fixed.

    A big thanks to the others that posted replies too. It, apparently, doesn't take much to educate someone like me on this subject, and i did actually learn quite a bit here.

    To sum things up.. My problem is likely cused by either an incompatible lens or a problem with the lens itself. Would that be a probable interpretation?

    Monophoto:
    As for your wondering if my camera has a B or K screen.. it has a single circle composed of two halves that will (or should) allign. there is one circle.

    And thanks all of you for providing me with info on the cam It is greatly appreciated.

    I'll get back to this post once i've taken some more pics and had them developed.

    If you are into traditional photography, the FM-2 is one of the best traditional cameras around, so it might be worth the investment.
    So i've gathered, I was recommended to get this cam by a professional photographer who used this in his non pro years and continues to use it as a backup. After reading up on it i had a hard time justifying getting any other camera.
    It needs to be working though.. and mine doesnt' seem to be.. Since i am rather impressed by the mechanical state of it,i would like to keep it. Returning it is the last option. I just need it to work like it should
    Last edited by Degenetron; 03-23-2007 at 08:56 PM. Click to view previous post history.

  10. #10
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    Degenetron,

    Hi.

    First of all, welcome to the world of traditional photography. At some point you might want to post a thread on the "Intro to APUG" forum.

    You do not mention whether or not you have the user's manual for your "new to you" FM2.

    If so, then many of the helpful hints above will make sense. If not, you should certainly get one.

    I've found that a good source for manuals is: http://www.craigcamera.com/

    I have no connection to this fellow except as a satisfied customer and find he's a great resource.

    BTW: The split-image circle acts m/l as a rangefinder and upon coming together you should be in focus. I would concur with the suggestion that it screen is not seated properly if is likely not adjusting as you move the focus ring on the lens.

    But it is not necessary to rely on the circle to make an in-focus pic. It is an aid. Your eye is your best tool for ensuring focus on a manual SLR!

    Good luck. Take pics. Post to Gallery!

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