Nikon F4 focusing screens: is there an option for F1.4 depth of field?

Discussion in '35mm Cameras and Accessories' started by j.c.denton, Feb 2, 2018.

  1. j.c.denton

    j.c.denton Member

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    For the FE and FM seriens, there are several posts on the net about which focusing screens show the real depth of field up to f/1.2, e.g. the K2 screen. But I cannot find that kind of information regarding the focusing screen options on the F4.

    Does anybody know which Nikon F4 focusing screen shows the real DOF for at least f/1.4 or faster?

    I've heard conflicting opinions with respect to troublefree focusing over different focal lengths when adapting F3 screens, so I'd rather avoid that route for the moment.

    Best wishes,
    Chris
     
  2. shutterfinger

    shutterfinger Member

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    From the instruction manual supplied with my F4s purchased new in 1991.
    page 90.jpg page 91.jpg
     
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    j.c.denton

    j.c.denton Member

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    Yes, but what is the visible depth of field of these screens?
     
  4. sepiareverb

    sepiareverb Subscriber

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    I have a big Nikon F4 press information binder, everything F4 is in it. Neither the technical features press info nor the technical information brochure mention DOF for focusing screens.
     
  5. shutterfinger

    shutterfinger Member

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    The only other piece of documentation that may be of help.
    img001.jpg
    in segments for easier viewing
    img002.jpg img003.jpg img004.jpg img005.jpg
    And the accompanying text in 4 languages
    img006.jpg img007.jpg img008.jpg img009.jpg
     
    Last edited: Feb 2, 2018
  6. tedr1

    tedr1 Member

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    If I understand correctly, it is not possible for any screen to change the DOF, that is created by the lens only. Blur caused by the screen may change the appearance of sharpness, however this blur is added equally to all of the image and has no effect on the DOF.
     
  7. E. von Hoegh

    E. von Hoegh Member

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    I was wondering about that, dof vs max aperture as affecting the screen made no sense, but I thought maybe I had missed someting anent these newfangled cameras...
     
  8. wiltw

    wiltw Subscriber

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    But it is possible that the fine texture of a focusing screen HIDES the apparent lack of focus...like dSLR focusing screens are fine for improved brightness, since some of the light is diverted by the half-silvered reflex mirror downward to the AF sensor. The typical dSLR screen is better for f/2.8 lenses, but you need a coarser textured screen for improving the precision of focus presented in the viewfinder, if you want to manually focus faster fixed focal length lenses.
     
  9. dmtnkl

    dmtnkl Member

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  10. tedr1

    tedr1 Member

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    That thread suggests that some bright screens may cause a subjective change in the perception of DOF in the viewfinder. This seems like something that is quantifiable by making test exposures and then making prints, which show the actual DOF. With the camera set up duplicated and a print located where it can be seen from the camera position, the actual DOF as shown in the print, may be compared with the DOF shown in the viewfinder. This allows a conclusion to be reached about whether the screen is causing a subjective change in perceived DOF in the viewfinder.
     
  11. wiltw

    wiltw Subscriber

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    A coarse textured focusing screen shows you more readily (than a fine textured focusing screen) when something is in or out of focus, ergo it will better depict things 'within the DOF'.

    But since 8x10" print is assumed for DOF calculations, and also since most DOF calculations wrongly assume the viewer has 'manufacturer standard' vision (and not the more acute visual acuity to which the optometrist strives to correct vision, 20/20) viewfinders (which are only 24mm x 36mm in our 135 format film cameras) are a pretty poor assessment of DOF regardless of the focusing screen which is used!

    I challenge anyone with an SLR and f/1.4 50mm lens to focus at a distance of 60"...can you tell that something at 59" or 61" is in or out of focus (without rocking the focus ring to determine the best focus for the item at 59"?!
    Using a 1964 vintage film SLR I can detect 1" change of distance if I use the fine focus surround ring and go for 'best focus', but determining if something is within DOF while focused at 60" is subjective and difficult. Now stop down to f/4 and have a look.
     
    Last edited: Feb 2, 2018
  12. dmtnkl

    dmtnkl Member

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    I mostly post the thread link to show some users' experience, claiming you may adapt screens between an F3 and an F4 by disassembling them and swapping their frames, which the OP might find useful.

    In my experience, the best screens for getting a feel of the dof are screens with random grain, like the B, B* screens for the F3 or the B, B2 for the FE/FM series. As was linked in that thread, the following also shows how coarseness/randomness of the screen texture influences the viewfinder image.

    https://hakkarainen.kuvat.fi/tempo/thedeathofviewfinder/

    Brightness optimized screens may be good for slow lenses where dof is not critical anyway, but one problem i find very annoying is that their etching patterns sometimes produce moire/aliasing with fine detail.

    Ideally, we would have a film camera with a digital sensor instead of a focusing screen and an EVF of high quality. All EVFs i have seen to date produce a high contrast image and are no much for a real optical viewfinder.
     
    Last edited: Feb 2, 2018
  13. MattKing

    MattKing Subscriber

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    Depth of Field is calculated (and realized) based on a bunch of criteria and assumptions relating to Circles of Confusion, viewing distance and visual acuity of the viewer.
    Focusing screens are designed to deal with a whole bunch of different criteria and assumptions relating mostly to getting an image in focus at the correct distance, and relating secondly to the brightness and general visibility of the entire scene.
    The coarseness or fineness of the viewing screen would no doubt have an affect on how slightly out of focus parts of the image might appear.
    I have no doubt that some screens might give more of an indication than others about how depth of field might present itself in a print.
    But I've never relied heavily on that.
     
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    j.c.denton

    j.c.denton Member

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    Thanks dmtnkl, that link was extremely helpful! I missed the last updates, it looks like I don't get informed by mail when new replies are posted.

    In the meantime a lot has happend. I bought a F3 with a red-dot K screen and an additional K-screen without red-dot. In addition I had the chance to buy a F4 with an F4 K-screen. In essence, I am able to run the same comparison as linked to at kuvat.fi , but taking the viewfinder pictures with my mobile did not deliver a sufficient quality to do a valid comparison. I can definitly approve the different appreance of bokeh between the F4 K screen and the F3 screens, including the rainbow effect that has been mentioned, plus the split-prism on the F4 K screen seems to be unsharp as well until one gets near to perfect focus whereas with both F3 screens, both partial images within the split prism are always sharp on their own. This is also visible in the samples shown at the link dmtnkl posted.

    I could also see that the orignal F3 K-screen without the red-dot is darker than the newer variant with the red-dot. I just wasn't sure whether I see a difference in dof between both versions, but the samples shown at the link show the original one to display lesser dof, provided a fast lens is attached to.
     
  15. apoglass

    apoglass Member

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    Focus screens that are intended for use with autofocus lenses typically increase viewfinder brightness, but as a result do not necessarily show the image that reaches the film when the aperture diaphragm opening is wide.

    For example, the screen may effectively vignette the peripheral light so that the maximum aperture as shown in the viewfinder image may be f/2 or f/2.8, even if the lens is actually faster and wider open than that. In such cases, the viewfinder seen image shows the reduced brightness and increased depth of field of the lens when stopped down somewhat, even though the lens is actually wide open, so the film records the brightness and depth of field of the wide open lens and not what is depicted in the viewfinder. That is the reason for focus difficulty when the lens is wide open with such bright screens.

    For cameras that focus with the lens wide open (as is usual with modern cameras), it can be quite confusing that the lens created image while manually focusing often matches neither what is shown in the viewfinder with the bright screen, nor the image as it will be with the diaphragm stopped down for exposure in brightness, depth of field, or focus.

    It gets even more confusing if the lens also exhibits focus shift, as the diaphragm is stopped down due to progressive decrease in spherical aberration with reduced aperture.

    An easy way to check for focus screen vignetting is to see if the viewfinder image continues to get brighter as the (preview stopped down) lens aperture is opened. If, for example, the viewfinder image gets brighter as the lens aperture is opened from f/5.6 to f/2, but does not get any brighter from f/2 to f/1.4, then you can conclude that the focus screen is not appropriate for attempting to focus at f/1.4 because it is hiding the light from the periphery of the lens.
     
  16. Neil Grant

    Neil Grant Member

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    ..yes that's true: bright screens suggest more depth-of-field. Your eye can partially 'focus though'. Totally clear screens are possible for photo-mic. But there you focus by 'parallax'. The vf can only show an approximation of the depth of field because the screen cannot direct all the light beams pssing through it to your eye. However, all the light beams will reach the film and contribute to image formation. This difference is the key. Try to get the coarsest screen you can.
     
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