Nikon F Apollo

[ColColt]

My Luna Pro SBC takes 9v batteries so, I lucked out with that one. the only meters I have that require 1.35v are the FTN's and my MR-4 meter. That one is on it's way to George for a CLA and I asked him to recalibrate so I can use standard 1.5v batteries.

 

[leicarfcam]

But it won't be good for every meter you need to check in bright sun and in dim indoors against a known good meter.

The way to test a meter is with an 18% reflectance gray card in direct sunlight.. But even that does not give you factory correct readings. Meters are calibrated to luminance not reflectance.. If the meter is correctly calibrated, you should get approx 100asa 125th @ f/16 minus 1/2 stop or f/11 v f/16 off a gray card in direct sunlight or what would be equal to approx 12% reflectance..

 

[ColColt]

Meters are calibrated to luminance not reflectance

Yep, and camera manufacturers calibrate to ANSI standards(whatever that is as it's not published). I always read and experimented myself, about the so called substitute metering such as grass, dirt, weathered concrete, palm of your hand and open one stop, and of course the grey card, etc. and it's always worked out well to the point that on a standard run of the mill digital camera those readings will give the histogram a bell curve that right in the middle.

Maybe cameras are rather calibrated for 12% rather than 18% grey.

 

[Xmas]

The way to test a meter is with an 18% reflectance gray card in direct sunlight.. But even that does not give you factory correct readings. Meters are calibrated to luminance not reflectance.. If the meter is correctly calibrated, you should get approx 100asa 125th @ f/16 minus 1/2 stop or f/11 v f/16 off a gray card in direct sunlight or what would be equal to approx 12% reflectance..

No good at all you need to do at least two tests

Sunlight levels
Available darkness levels

The battery voltage, the cells and the galvanometer need to be matched close to factory tolerances

 

[leicarfcam]

No good at all you need to do at least two tests

Sunlight levels
Available darkness levels

The battery voltage, the cells and the galvanometer need to be matched close to factory tolerances

Some meters do in fact have a bright and dim adjustment but unless either has been tampered with, you shouldn't have to worry about them and beside that....do you have the proper equipment to calibrate those 2 settings?? You can try hit or miss adjusting but most likely miss it.

If you have the proper battery or modification, voltage is a no brainer..

The metering cells are automatically adjusted by resistors..

The galvanometer cannot be adjusted other than is zeroing it out..

If the above have not been tampered with the below is all you should need to do..

Normal calibration of an otherwise working meter should only require adjusting the sensitivity pot then possibly adjusting the battery test if your camera has a test button....

 

[leicarfcam]

Yep, and camera manufacturers calibrate to ANSI standards(whatever that is as it's not published).

True...and each maker has their own version of the ANSI standards. During the many years I was a camera repair tech I found out a couple of them. For example Nikon is approx 12% while Sekonic states theirs is closer to 14%..

I always read and experimented myself, about the so called substitute metering such as grass, dirt, weathered concrete, palm of your hand and open one stop, and of course the grey card, etc. and it's always worked out well to the point that on a standard run of the mill digital camera those readings will give the histogram a bell curve that right in the middle.

Just because a meter is calibrated to factory standards does not mean it is right for all situations. That's why substitute readings as you say work fairly well..but you should bracket if the images are important..

Maybe cameras are rather calibrated for 12% rather than 18% grey.

Regardless of the makers standards 18% is a pretty good starting point then adjust according to your preferred readings.
Back in the early days of the Nikon F and into the F2 era, many pros preferred to modify the readings to their own taste and Nikon made it easy to do so by one single adjustment. Just peel back the top leather to expose the sensitivity pot and adjust to your liking...

 

[leicarfcam]

Here is an article I just came across that is related to the current discussion.

http://www.bythom.com/graycards.htm

 

[ColColt]

That was a good read. If 18% was good enough for Ansel, it's good enough for me. Actually, I could probably count the times I've used a grey card on one hand. If I was in doubt about exposure I'd use substitute metering, usually in the form of dirt or grass and sometimes I'd use my spot meter, meter off flesh if taking a portrait, and open one stop. It seemed to work 99% of the time.

 

[leicarfcam]

That was a good read. If 18% was good enough for Ansel, it's good enough for me. Actually, I could probably count the times I've used a grey card on one hand. If I was in doubt about exposure I'd use substitute metering, usually in the form of dirt or grass and sometimes I'd use my spot meter, meter off flesh if taking a portrait, and open one stop. It seemed to work 99% of the time.

Ansel Adams didn't much use 18%. He preferred the zone system which is 1 stop open from the meter reading. One of his favorites was the Weston Ranger 9 meter which he made a zone dial for it..

In truth there is no such thing as a 100% accurate meter. That's why 18% is a good starting point. I've metered off a gray card many times and set my exposure accordingly...and I usually open up 1/2 to 1 stop from the indicated reading..

 

[ColColt]

Ansel Adams didn't much use 18%.

What I had in reference to was the link above and the latter part of it toward the bottom...

"Bob's book even quotes a Kodak veteran who says that Adams was so vehement about the issue, that he apparently spent a "whole day and most of a night" at Kodak arguing for 18% gray. Still, no one I talk to at Kodak can tell me why Adams wanted 18%."

Knowing he used the Zone System made me scratch my head a little after reading that.

 

[Xmas]

Some meters do in fact have a bright and dim adjustment but unless either has been tampered with, you shouldn't have to worry about them and beside that....do you have the proper equipment to calibrate those 2 settings?? You can try hit or miss adjusting but most likely miss it.

If you have the proper battery or modification, voltage is a no brainer..

The metering cells are automatically adjusted by resistors..

The galvanometer cannot be adjusted other than is zeroing it out..

If the above have not been tampered with the below is all you should need to do..

Normal calibration of an otherwise working meter should only require adjusting the sensitivity pot then possibly adjusting the battery test if your camera has a test button....

'otherwise working meter' is a nice thing to start with.


If you are instead starting with a eBay or charity shop find and a Wein cell then before you try a film you need to try bright and dark readings against a known good meter.

If both are the same you are ok

The CdS cells can age
The meter can be of zero or lose sensitivity
The cordage may be offset or the variable resistors noisy

If they are not the same 1/3 stop you can't treat the meter as working for E6 it is a necessary pass fail test

Some people don't use grey cards or the zone system

 

[leicarfcam]

'otherwise working meter' is a nice thing to start with.

If you are instead starting with a eBay or charity shop find and a Wein cell then before you try a film you need to try bright and dark readings against a known good meter.

It's obvious you don't know how meters are calibrated at the factory or after service.

If both are the same you are ok

Meters that do have a high and low calibration are done so with voltage. And BTW: this voltage is too low for over the counter volt/ohm meters to measure. This is where specialized equipment comes in. Each one is adjusted to output a certain voltage which is different for each setting. Once done you then isolate one of the cells and measure the output voltage. If it is out of tolorance, you replace that cell. You then isolate that cell and do the same with the other cell. If the meter only has a single cell then checking is easier.
Once you have proper voltage with the 2 settings and proper voltage off the cells then you make the final adjustment. Again proper adjustment is done by measuring voltage but since most end users don't have the specialized equipment, it's done by a gray card.

The CdS cells can age

This is why voltage is measured by a tech..

The meter can be of zero or lose sensitivity

You have a zero adjust to bring it back to zero. The only way a galvanometer is out is if it goes open circuit. If that happens, you trash it and replace with a new one..

The cordage may be offset or the variable resistors noisy

Most meters don't use cordage and resistors are cleaned before trying to adjust..

If they are not the same 1/3 stop you can't treat the meter as working for E6 it is a necessary pass fail test

Some people don't use grey cards or the zone system

In the end many meters do not use a high/low circuit. This part is handled by a simple series circuit which delivers accurate readings with a simple easy to manufacture meter..