Fear – to a great extent – is born of a story we tell ourselves.

light meter calibration.

So I realize I am getting ahead of myself cos I am still writing out a bunch of random thoughts about the purchase a month or so ago of an old beautiful cherry wood field view camera and what I have been going through in order to get up to speed using such an incredible instrument. More on that eventually.

But part of that getting up to speed included breaking out some of my old film equipment stuffed in scratched Pelican cases one of which was my Soligor Spot Sensor II (analog version) light meter. I took it and some Polaroids and the Westa camera to K's parent's place in eastern Washington over the fourth to test.

The Polaroids were coming out blank.

Unsure of whether or not it was a bad lot of expired Polaroids (I've now tried two separate packages though both dated the same so likely from the same batch) or my inexperience at operating a view camera (although a precision photographic instrument it's not really rocket science) or ... the light meter misreading the reflected light.

So I started digging on the interwebs and found some random but very little help on calibration of old analog spot meters (thank God it is analog though ... I'm not sure what it would take to calibrate a digital meter - surely more than the tools I employed for this little bit of surgery I'll explain below). Of the two pieces of information I found amongst the many more numerous posts of people inquiring as to calibrating these particular meters (with no real answers) the first was that there is apparently only one guy somewhere in Vermont who does these kind of repairs and the second was buried in replies to one of the posts about how - unbeknownst to many I can only assume - hidden under the logo of the meter are three teeny tiny pan pots that the guy assumed were used for calibration (but said he was scared to touch them so left them alone).

I however ... am not. Armed with a utility knife to pry off the little metal decal (glued on most likely with a drop of super glue on either side - exactly how I will reattach it) and a small safety pin I went to work -

A close-up above showing the three pan pots which I discovered roughly as such: the left one is a trim dial that fine-tunes the calibration (i.e. barely changes the reading of the meter), the middle one is the roughest dial while the right pot is in between the two. Simply using the end of the pin I was able to dial these around to adjust the sensitivity of the meter.

Not really visible in the first picture is my masking tape mockup of the Zone System on the lens barrel (I can't believe you can actually pay money for what amounts to a small piece of masking tape marked in permanent pen with the eleven zones from 0 to X that then align with the various EV readouts - on the Soligor the EV scale runs from 2 to 18).

So not really being terribly scientific at this point - I just knew the meter was mis-calibrated and was overexposing by two to three stops (two at lower light levels; three at brighter levels) - I took my trusty 7D and found the  grey house across the street to be close to an 18% grey.

Purposely throwing the image out of focus I set the 7D's light meter to the spot mode (which has about 1.5% coverage area dead-center - the Soligor has 1% coverage but close enough) - the lens (although not a prime lens unfortunately but again - not really being too scientific here) zoomed to roughly 50mm or a 1:1 ratio - taking the camera away from my eye the proportions across the street were about the same) - and aperture priority of f/5.6

I got a reading of 1/125th of a second at an ISO of 100.

So setting the Soligor similarly to ASA 100 I aimed it at the house - it was a bit low (reading an EV of 10 which - with an exposure of f/5.6 and 1/125th - would place the grey two stops above middle grey - i.e. two stops overexposed). I wanted an EV reading of 12 which would put the grey of the house at roughly 18% and match the exposure reading of the Canon (although I know Canon's meters tend to run a smidge hot - again - this is hardly scientific until I get to the next step).

A few little adjustments to the pan pots and boom -

In order to test at least a little validity of this crazy setup I brought the resulting files into Photoshop.

Now I am fully aware of the gamma correction in Adobe Camera Raw vs. another application like Canon's Digital Photo Professional utility (thus - the huge disparity of gamma corrections between applications and the multitude of RGB profile spaces like ACR's ProPhoto or Canon's fairly arbitrary and highly-generic 'Wide Gamut' color space and the gammas of each) and how that certainly affects the rendering of values (as does the bit-depth and so on).

I probably should have stressed at the start how this is hardly scientific as I seem to continue to repeat that mantra - and that if you did choose to pay some guy in Vermont a hundred clams (I'm too cheap and always assume I can do whatever myself) to calibrate your light meter he probably has some more - umm - professional standards ... or maybe not haha.

But anyway - I used ACR and converted the blurry image of the house to the sRGB color space (roughly a gamma of 2.1 I believe). I cropped in and then introduced yet another variable by having Photoshop's behind-the-scenes-unknown-to-me-and-everyone-else-besides-Thomas-Knoll algorithm convert to greyscale (20% dot gain).

Dropped an eye dropper on the image and ...

Pretty darn close (theoretically an RGB value of 128 is middle grey - i.e. 18% grey - but it depends on the gamma curve and color space - with a gamma correction of 2.2 and sRGB I believe it is supposedly somewhere closer to 114 ... ). But after the 3.5 million other variables introduced in this highly arbitrary calibration exercise a value of 123 is pretty incredible. Which tells me - albeit somewhat roughly - that f/5.6 125th/second at ISO 100 was the correct exposure to capture what I wanted and place it at a value equal to middle grey (highly important with Zone exposure!).

I'm feeling much better.

Now - all of that of course is completely useless because I do not plan on somehow incorporating my 7D into the mix when photographing on sheets of 4x5" film with an old wooden camera. So the real calibration is of course the combination of dialing in the meter to my specific film (ADOX ASA 25 panchromatic) and developer (ADOX Adonal)-slash-development (temperature of the developer/how much agitation/total development time) combination. Using that combination after shooting an image of an 18% grey card (which I think I have but I'll have to dig ... ) under fairly controlled lighting (a shady spot outside) and developing the film and then subsequent print - I'll be able to judge just how calibrated it all is by how close the print looks like the 18% grey card.

And that actually is a really good reason for figuring out how to calibrate my light meter myself.

So that test will come later tonight when it's dark out and I can develop some film ... but for now the meter is likely quite close in calibration and I am feeling much better about taking it (and the Westa!) to the Sierras ...

the violent bear it away.

Maybe the best song in to which to go running.

Or standing alone in the middle of crazy wild spectacular beauty.

Or driving through granite vistas eternal.

Endless.

Or just lying under a birch tree looking up at lazy clouds hanging in pale blue skies.