How to calibrate camera, the film, and the Sekonic?

[rob_caswell1]

<p>I prefer to use my Sekonic 508 when metering. It's such an amazing tool, and especially helpful measuring off camera flash, the flash delay mode is helpful, the spot meter, and now I'm delving into some of the other advanced functions.</p>

<p>Because I have a variety of cameras, my logic is to have one meter and not 5, but now I'm rethinking the issue.</p>

<p>I've been using off camera flash much more, so I'm using the L508 and trying to be more precise. Something I noticed across the range of cameras. After developing and scanning B+W on my Epson my images seem to be about a half stop off to a full stop. It could be the scannning, it could be the subject moving around (it was a 2 year old), it could be the shutter speeds of the cameras differing.</p>

<p>Shooting cheap Fuji color and having it developed at CVS, the tech told me he adjusted a roll almost a stop. I have a feeling it has more to do with the 40 year old SLR's than the meter. When testing, I sometimes use a Canon 10d in conjunction with the Sekonic to gat a "polaroid" and I'm pretty close to spot on give or take a half stop... but again there could be some slight variables... being outdoors for example.</p>

<p>I will likely sell off the the 40 year old SLR bodies and just roll with a Nikon F100 body. I wish to try and calibrate the camera to the ISO of the film. That way I would know roughly where to compensate with the Sekonic on a particular camera.</p>

<p>So the geek in me is trying to develop a definative test. How do I calibrate the camera (any camera), the lens, and the film and apply it to the Sekonic? How to I factor in development times?</p>

<p>Is there someplace that will do a densitometer reading?</p>

[SCL]

<p>Too many variables to start with. You need to narrow them down. I'd start with the meter..do you take incident or reflective readings? Personally I'd go with incident, but if going with reflected, I'd get a gray card, folllow the instructions (for angle of light, etc) and make sure my meter readings were consistent. Then, once I nailed that, I'd work on the film and development. I'd use only 1 film. I'd decide what ISO to use (box speed or whatever...and I'd stick with it throughout testing. Let's say box speed for example. I'd shoot the gray card, exposing per meter and bracket each side of the indicated exposure by 1/2 stops. Then I'd go to the development part of testing. I'd use my standard developer, standard times and temps, and find the optimally exposed negatives. That would give me the standard ISO for this combination. Then I'd repeat the process for changes in development concentration, times, temps. And so on and so on. Needless to say, with film latitudes being what they are, personally I'd skip most of this process just do a roll of test shots and go with what looks (or scans) best...not very scientific, but I don't have the patience to do all the other testing.</p>

[dave_wilson1]

You're saying half to full off how? Over

exposd, old camera, shutter is probably

slow needs adjustment. Five cameras,

one metering system yes

inconsistencies will likely show it's

head. Just take notes and adjust or

have your cameras calibrated $$$.

[SteveH]

<p>The old B&W photographer in me empathizes with your dilemma. This is the question that Ansel Adams attempted to answer with his Zone System. The camera/lens/shutter/meter/enlarger/paper/print are actually a unit that need to be coordinated. Zone system methods can help. Try finding some old books on the subject. Consider Ansel Adams series on the Negative, Camera, Print; David Vestal - The Craft of Black and White Photography; Minor White on the Zone System and the "BTZS" (Beyond the Zone System) writings. Have fun. </p>

[lex_jenkins]

<p>Unless you're using large format sheet film or medium format in a camera with interchangeable backs, you'll end up chasing your tail trying to apply the Zone System.</p>

<p>In most cases with b&w film in 35mm and medium format you'll get excellent results by rating, exposing and developing the film to suit the predominant lighting and subject contrast range on the roll.</p>

<p>And if you're scanning rather than making optical enlargements, try to avoid excessively contrasty negatives. Try giving the film around 10% to as much as 25% less development than the suggested starting times, unless the manufacturer's data includes times for use with condenser enlargers - that's usually pretty close to the right CI for scanning as well.</p>

[thirteenthumbs]

<p>The film speed test explained in "The Negative" can be used on roll film cameras. Set up a continuous tone subject such as an 18% gray card in open shade, meter it for the base reading, shoot the series, process normal, and evaluate the result. Any B&W film and developer can be used. The attached pdf is the test series.</p>

<p>Another approach will be to build a simple shutter speed tester such as the ones explained in this thread:<br>

http://www.photo.net/large-format-photography-forum/0044cW?start=10<br>

Skip to page 2 for currently available parts and upgraded tips. Some newer cameras such as Nikon's with vertical travel shutters recommend not tripping the shutter with the back open but older cameras with horizontal travel shutters will not be a problem. The tester accuracy starts to read slow at 1/500 and faster. </p>

 

[john_shriver]

<p>If you're getting exposure accuracy problems with flash, it means that your lens apertures aren't accurate. (Or the lenses have different T-stops.)<br>

If you're getting exposure accuracy problems without flash, it's much more likely shutter speed accuracy. Even when new, they were only accurate to say 15%, and more like 30% and 1/500 and over. (Those were JCII inspection tolerances.) On a 30 year old film camera, it's quite likely the shutter needs a full clean/lube/adjust to be accurate.<br>

Ideally, if you have a T-mount lens that can be adapted to all the cameras, you can do tests with that one lens to eliminate it as a variable.</p>

[rob_caswell1]

<p>Well... the system I'm using is Leica R glass, a Leicaflex SL, and a Leica R4s. The SL seems to be underexposing a stop. The R4s seems to be pretty close , because my adjustments were either a half stop under exposed to spot on.</p>

<p>I'm waiting on a Leitex adapter to try one of the Leica R lens on the F100.</p>

<p>Age could be an issue</p>

[SCL]

<p>Rob - it's possible that your SL, given its age, might need a short trip to the camera doctor to bring its shutter times within tolerance. I remember when I had one, as well as an SL2, that each needed a tweak (the SL2 needed one specifically at 1/2000). The R4s, as I recall, is an electronic shutter rather than a mechanical one and less subject to falling out of tolerance.</p>

[ian_gordon_bilson]

<p>Other,more rigorous forums,have tied themself in knots about this problem.<br>

You are not wrong -my L408 Sekonic gave under-expopsure of close to 2/3 F out of the box.<br>

I suspect most Sekonics are the same. It has to do with the "Calibration Constant",which is 12.5 for the Sekonics. <br>

My advice-get into the calibration setting of your meter and set it to under-read by 2/3F.<br>

Put another way -if you read F16 ,the corect reading will be more like F11 minus.<br>

Duck & Cover,but it works for me.</p>

[randy_johnson5]

I would use your Canon 10D as a benchmark for exposure and then match your Seconic to yield the same shutter speed

and f stop. You could just adjust the film speed on the Seconic to yield the same shutter speed and f stop you got on the

correct exposure with the Canon.

[john_shriver]

<p>The Leicaflex SL has a classic "low tension, low speed" Leica focal plane shutter, derived from the design of the Leica M shutter. It is very quiet, but the spring tension is very slow, so when the lubrication goes gummy or dirty, the shutter speeds go "off". There isn't enough "power" behind the curtains to power through dirty lube in the bearings. If you're seeing exposure errors with the SL without flash, it's time for a clean/lube/adjust.<br>

Any camera repairer who still works on film cameras should be able to check the shutter speeds in an instant.</p>

[mark_l6]

<p>Well I use a 508 and performed all the rigorous testing as described by others here and ended up adjusting exposure compensation setting to give +2/3 stop exactly as Ian suggested. Now that I know it's right, if I have any problems I have to look elsewhere, and it usually turns out to be either a thermometer or a shutter.</p>