Pentax Digital Spotmeter EV readings

Discussion in 'Classic Manual Cameras' started by jim_gardner|4, Jan 12, 2010.

  1. This may be the wrong forum but I cant find one for light measurements and guessed people here may use a Pentax spotmeter.
    Anyway I have just dug out my late fathers Pentax spotmeter. It's simple enough to use, just point and dial in the ev number to the dials on the meter to get a reading after setting the film speed. The slightly confusing part is that the ev display does not change with the film speed i.e. the wall here measures 7 ev regardless of film speed set. If I then set 7ev on a Hasselblad lens the resulting combination of shutter speed/aperture could be way out because the meter reads the same at all film speeds and the lens has no way of knowing what film speed is being used.
    I am fairly sure the meter is working correctly so should I assume the meter ev readings are always for a set film speed and if so does anyone know what it is? or am I way off the mark?
    Many thanks, Jim.
  2. Jim,
    Your meter is working correctly. When you change the ISO (film speed) in the calculator dial, it changes the f-stop/shutter speed combination(s) to match the EV reading from the viewfinder display. The dial where you set the film speed has no connection to the meter readings at all. It is just a dial to calculate f-stop / shutter speed combinations at a given film speed at the light level indicated by the LED display in the viewfinder.
    There are other spot meters that do this calculating electronically and show an f-stop in the viewfinder display. The Pentax is not one of them, and is the better because of this.
    I don't understand your question about the Hasselblad lens. There is no EV dial on a lens. Just f-stop and maybe shutter speed if there's a shutter in the lens.
    The tricky part of using a spot meter is knowing what to aim it at, and how to interpret the reading. I would suggest a google search on how to expose film and how to use light meter articles.
  3. BG, Thank you for your quick response. I almost always use a spot meter (Sekonic L508) which gives direct readings of f stop/shutter speeds so no problem there, it is the ev values that is confusing me.
    The Hasselblad lenses have an orange scale on them which I am pretty sure is an ev scale. If the Pentax meter ev reading is not directly linked to the film speed set, I can not see how exposures can be correct if the ev dial on the lens is used.
    I hope that explains my question a little clearer.
    Regards, Jim.
  4. If the Pentax meter ev reading is not directly linked to the film speed set, I can not see how exposures can be correct if the ev dial on the lens is used.
    I hope that explains my question a little clearer.
    Regards, Jim.​
    I have an old Kodak Retina with an EV scale on the lens. There's a little lightmeter on top of the camera that has a film speed setting that corrects the reading in EV to be input to the lens. If I remember correctly, the numbers will only match the raw readout when the ISO is set to 100 and the shutter speed is set to 1/100 second.
    All this is kind of irrelevant to your Pentax spot meter as you just read the choice of shutter speeds and f-stops from the calculator dial and set them on the camera. Just ignore the EV markings on the lens.
    The beauty of the Pentax dial is that it allows one (me actually :) ) to visualize the range of tones that I'm reading and determine the proper exposure quickly. For example, if I'm shooting someone in a white shirt (and the white shirt has the same light as the face), and the reading says EV 9 off the shirt, for example, I put the EV 9 on the calculator dial and then open up two stops for the correct exposure. IE. setting the dial to EV 7 to see the choices of shutter speeds and f-stops that will give that exposure.
    I find it confusing to have a spot meter that reads out f-stops, especially if I'm reading shadow areas that fall below f-1.4 and I'm shooting at an f-2.0. If white is EV 8 1/3, then black is EV 3 and I set the lens to the f-stop associated with EV6. Hope this makes sense!
    Good luck with your new meter and please enjoy it.
  5. There was a long thread on this, a couple of months ago.
    The gist of it: Manufacturers have used the abbreviation "EV" to connote two fundamentally different things: (1) "Exposure value" on the Spotmeter (in the sense of "absolute light value", independent of camera settings), and (2) "Equivalent value" on those old manual lenses with coupled aperture and speed rings (in the sense of "equivalent camera settings", independent of the actual level of incident or reflected light).
    The thread is here:
  6. Jim - you are correct. Your meters scale can be used as a direct EV readout only when using 100 speed film or rating film at 100. Other meters will give direct EV readouts at any desired ISO - my Sekonic L- 308B for example.
  7. Thanks all. As mentioned I mostly use my Sekonic which reads different EVs depending on film speed set. Actually I donโ€™t use the EV readings but wanted to get my head round it anyway. The main reason for wanting to know about the Pentax meter is that I have inherited it and wanted to take it out and use it now and then as my father would have wanted me to do. Thanks again, Jim.

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