Anyone with a Konica Minolta Flashmeter VI?

Discussion in 'Lighting Equipment' started by BeBu Lamar, Jul 5, 2022.

  1. I found something strange with my KM Flashmeter VI. In spot mode and I measure a white area on my monitor the reading is lowered by about 0.6 EV if I turn the meter 90 degrees. Or if I turn the monitor into portrait orientation. I wonder if this only with my meter? If this with all the KM Flashmeter VI?
     
  2. Monitors are polarized, and your meter will be sensitive to that.
     
  3. For the meter to be sensitive to that it should have a polarizer as well. Which I am surprised.
     
  4. A reflective surface in its optical path will do.
    But anyway, you just found it is sensitive to polarisation convincingly.
     
  5. The acid test would be to rotate a polarising filter in front of the meter (filter facing backwards if a CPL).

    In any case, I'm a skeptic when it comes to the benefits of spot metering. Unless you're also going to be carrying a grey or white card to stick somewhere in the scene and meter from. Otherwise you're just pointing a meter at a small area of unknown reflectivity and guessing that it should turn out mid grey in the final image. With no guarantee that the overall flare factor of the spotmeter matches that of your camera body and selected lens.
     
  6. The screen reflects very little light as the room light is off the room is almost totally dark. I just want to check the light intensity of the screen. I don't know if I have a polarizer. I would have to do some more tests. I suspect it only happens with that model of the monitors.
     
  7. It (the polarisation) happens with all liquid crystal displays. They consist of a liquid crystals between to crossed polariser sheets, and a light source behind that.
    So the light coming from the screen itself is always polarised. And your meter turns out to be sensitive to the direction of polarisation.
     
  8. In that case; why not just put a wide area reflectance meter right up against the screen? No need for a spot meter with its image-splitter viewfinder.

    Incidentally, if you're trying to verify the maker's claim of a 5,000:1 contrast range, or similar daft figure - you're wasting your time.
     
  9. I wanted to see if the white point is 100 cd/m^2 like I calibrated and measured with the calibration sensor. Any way measuring normally with my NEC monitors (old S-PVA panels) when holding the meter in normal fashion and the monitor in landscape mode the reading is correct but read lower by 0.6EV when either is turned by 90 degree.
    Checking my laptop screen I found the reverse is true that is I have higher reading holding the meter 90 from the normal way. My Nikon Df give similar readings as well.
     
  10. And now you know why that is not strange.
     
  11. Now that is weird.
    I just tested quite a few DSLRs with both linear and circular polarising filters and found almost no difference in the metering or AF response between filter types. Except that the CPL was obviously visually denser than the linear filter, and the camera metering reflected that.
     
  12. You didn't test the Df. There is no general rule your test would provide proof for.
     
    Last edited: Jul 9, 2022
  13. Note that I use no polarizer. Just the meter or camera and the LCD screen. I didn't test the Df in liveview mode. In liveview it use the imaging sensor for metering and there is no reflective surface in the optical path. In viewfinder mode the meter sensor is in the viewfinder and the light must reflect from the mirror before reaching it.
     
  14. The screen is the polarizer.
     
  15. I know but Joe said he tested with polarizer. If you put a polarizer in front of the lens you would lose some light but the amount of loss doesn't change as you turn the camera or the polarizer. The intensity of the light would change only at the part of the scene that the light is polarized.
    If you use a linear polarizer and an LCD screen he would have a much pronouced effect than 0.6EV. Could be a couple of stops.
     
    Last edited: Jul 9, 2022
  16. I didn't test a Df. I don't see why it would be any different from other Nikon DSLRs, but you never know until you test it practically.

    As I said before, the acid test would be to use a known polariser filter and check any variation in metering with rotation angle. First finding a non-polarised evenly lit surface of course. A sheet of matt card or white copier paper under overcast daylight should fit the bill.

    Also, remember to blind the eyepiece. All Nikon SLRs/DSLRs have metering that's in the prism-housing and sensitive to light entering through the viewfinder. Usually your eye and head perform that function.
     
  17. Yes I have one, but its just for show. It conked out on me years ago and was replaced with Sekonic...
     
  18. And knowing that now helps how in deciding if the OP's meter is "strange" in what he observed?
     

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