Light Meter

[denny_rane]

<p>Anybody have a schematic for the light meter in a Nikon F2.?<br>

Thank You</p>

[jim_momary]

<p>One spot here ...<br>

<a href="http://www.street-photo.fr/fr/images/docs/Nikon_F2_Finder_DP-1_Adjustment.pdf">http://www.street-photo.fr/fr/images/docs/Nikon_F2_Finder_DP-1_Adjustment.pdf</a></p>

<p>Unsure of its accuracy, take it for what it is worth.</p>

<p>Jim M.</p>

[Dieter Schaefer]

<p>Is this a trick question? There's no light meter in the F2; there's only five different Photomic finders that meter - which one are you interested in?</p>

[denny_rane]

<p>Awesome.....Thank You.<br>

I cannot believe how small the trimmer pots are.<br>

Thanks Again Jim</p>

[denny_rane]

<p>Dieter -<br>

Which one do YOU have a schem for.?<br>

Thank You</p>

[Dieter Schaefer]

<p>As it turns out only the same as in the link above. Saw a couple different ones on ebay recently.</p>

[denny_rane]

<p>Wow...I did not even think to look on Ebay.<br>

I am glad Jim had this. My Amprobe DMM outs more Current/Voltage than the meter is designed for. 16 micro-amps is real small.!<br>

Thanks Again...I appreciate it.</p>

 

[rodeo_joe1]

<p>Just a thought on calibration. The procedure described in Glen Walpert's article is flawed. He says to <em>focus</em> on a grey card and calibrate to that. Unfortunately, most lenses will change effective aperture when focused close enough to cover a grey card - unless you have a <em>really big</em> grey card. It also assumes that the grey card has an accurate 18% reflectance - not a given if the card is old, dirty or faded.</p>

<p>My suggestion is to amend the calibration instructions and focus the lens on infinity while filling the frame with a large sheet of white copier paper. It doesn't matter if the paper is out of focus, but the loss of effective aperture in focusing close can lead to a difference of half-a-stop or more. And obviously this will have an effect on calibration accuracy.<br /> <br /> The use of white paper has the advantage that copier paper is readily available in pristine condition, has a reflectance as close to 100% Lambertian as you can get outside of a laboratory, and comes in sizes that can easily fill the frame of the camera and fill the acceptance angle of a handheld light meter. BTW, double up the paper thickness to ensure you get a true 100% reflectance. The reflectance of thinner paper can be affected by a dark background.</p>

<p>If you want to compare the white paper reading to an incident meter then you simply subtract 2.5 stops from the reflected reading of the paper.</p>

<p>Edit: I also think Glen's assessment of the meter sensitivity is a bit off. The battery test circuit shows 3 volts passing through a 155K variable resistor (likely 150K nominal value). That makes the meter half-scale close to 20 microamps at very minimum. It seems likely therefore that the meter movement is 50 uA full scale - a fairly common value.</p>