Testing the lightmeter accuracy on a 35mm camera

Chan Tran said:

I use an enlarger dichroic color head as light source. My 4x5 enlarger head has about a 6" round evenly light surface. I use a color analyzer with fiber optic probe inserted in the color head to monitor color balance. Set the filter to get a color temp approximately 4700K (I don't think this is very critical. Checking the color temp with a digital camera). Use the spot meter (I use a Minolta Flashmeter VI and Minolta Spot meter M both have spot mode) checking the brightness. Dial in more filtration, monitoring it with the color analyzer to have the same reading on 3 channel so the color temp doesn't change as the light intensity changes. I was able to get the light level of EV15 and EV9 @ ISO 100 doing this. Verifiying using the spotmeter.

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This is a great idea!

Cholentpot said:

Related the the whatchamacallit.



Maybe you're thinking of the Thagomizer named after the late Thag Simmons.

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No. I'm thinking of a Dongle when I talk about a Dongle

https://www.wordnik.com/words/dongle
https://www.merriam-webster.com/dictionary/dongle
https://en.wikipedia.org/wiki/Dongle
https://dictionary.cambridge.org/dictionary/english/dongle

Moose22 said:

No. I'm thinking of a Dongle when I talk about a Dongle

https://www.wordnik.com/words/dongle
https://www.merriam-webster.com/dictionary/dongle
https://en.wikipedia.org/wiki/Dongle
https://dictionary.cambridge.org/dictionary/english/dongle

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Don Gall is the brother-in-law of Thag Simmons.

Cholentpot said:

Related the the whatchamacallit.



Maybe you're thinking of the Thagomizer named after the late Thag Simmons.

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Do not forget the "thingie" aka "thingy".

Sirius Glass said:

Do not forget the "thingie" aka "thingy".

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Named after Carlos Thingo I presume.

Little update, I found something. FILM CAMERA TESTER. The Tester also get sold through eBay for international shipping but for germany its 100 euros more including import fees and shipping cost. Maybe I pull the trigger next month.

Testing the lightmeter accuracy on a 35mm camera

How does your light meter know how you are going to develop the film? At what dilution? Time? Temperature? Agitation? Printing on a Diffuser? Condenser? Point source? Your interpretation of the scene?

unwantedfocus said:

Little update, I found something. FILM CAMERA TESTER. The Tester also get sold through eBay for international shipping but for germany its 100 euros more including import fees and shipping cost. Maybe I pull the trigger next month.

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The camera tester you're buying only test the shutter speed and not the meter. The light source is not a standard known value light source.

cliveh said:

Testing the lightmeter accuracy on a 35mm camera

How does your light meter know how you are going to develop the film? At what dilution? Time? Temperature? Agitation? Printing on a Diffuser? Condenser? Point source? Your interpretation of the scene?

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This is what you do to allow for all those variables: take a bracketed series of exposures of a front lit scene when the light is not going to change for a while. Develop the film keeping notes about developer, dilution, agitation, all that stuff. Pick the negative that is going to work well in your enlarger to realise your interpretation of the scene.
Check your notes to discover what this ideal exposure was. Now go back to the scene (the light hasn't changed) and point the camera at it. Adjust the camera's meter until it reads out the exposure the film already told you was correct. Calibration done. That's as accurate as things go.

If you change the variables, developer, dilution, enlarger, etc, just re-calibrate the camera's meter the same way as before. The calibration may well be different but it will be accurate.

cliveh said:

Testing the lightmeter accuracy on a 35mm camera

How does your light meter know how you are going to develop the film? At what dilution? Time? Temperature? Agitation? Printing on a Diffuser? Condenser? Point source? Your interpretation of the scene?

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A CLA will allow the exposure to be accurate. Then one can develop normally.

cliveh does not endorse the use of light meters... he has the experience to know the proper exposure without them.
If Leica had meant for us to use light meters they would have built one in the M2 - not as an ugly add-on wart.

To the question: How does your light meter know how you are going to develop the film? At what dilution? Time? Temperature? Agitation? Printing on a Diffuser? Condenser? Point source? Your interpretation of the scene?

I would give a long-winded answer:

Fresh film has an ISO/ASA/DIN speed. Manufacturer tells you this speed. It is the film's real speed (unless data sheet says otherwise). If you plan to use the film normally, set that value for the Exposure Index (EI) on your meter's calculator dial (e.g, where the setting is labeled "Film Speed", "Exposure Index", ASA/ISO/DIN).

When you intend to use the film in your own special way, then choose an EI to fit your personal answers to the questions: "how you are going to develop the film? At what dilution? Time? Temperature? Agitation? Printing on a Diffuser? Condenser? Point source?"
Some developer data sheets will tell you the EI to expect. I remember Panatomic-X (normally 32) is to be exposed at EI 80 when developing in Kodak Reversal Processing Kit. So the developer can make a difference. If you don't test yourself, you can ask around here to get a good ballpark EI to use for a different developer. You may want to push the film as far as you can, go for it.

To the final part of cliveh's question "Your interpretation of the scene?" Here you take a meter reading and decide whether to use the reading as-is or shift the emphasis. You can use Zone System to take a spotmeter reading of a part of the subject and place it on an appropriate Zone, e.g., a shadow reading placed on Zone III. Or you can follow any folklore about how much exposure compensation to give a backlit scene, "black cat in a coal mine" or other special case.

As a final thought, many times you will read where people suggest EI of half box speed or 2/3 stop less than box speed. "To get better shadow detail" and/or "To agree with Zone System". I often mention both reasons but only recently started thinking about them separately and independently. Better shadow detail is a good thing and I like to go for it. And Zone System speed can be proven to be 2/3 stop less than box speed. I like to use Zone System metering techniques. Also add into the mix that flare will help shadows. In practice, I set my most accurate meter to 2/3 stop towards greater exposure than tested speed and I use that whether calculating by spotmeter with Zone System placement or by incident meter. When it gets darker and I want to handhold, I consider whether I want to switch to the film's rated speed or maybe even 2/3 stop the other way towards decreased exposure. I like to get good prints, so I usually hold it there. You can push further with increased development, but I think "nothing" of a 2/3 stop push and will develop that roll of film without any change in plan.

For those who are interested. I received the other 3 SRT 101's as mentioned in an earlier post, here is what happened in the meantime.

SRT no.1 shutter speeds were all the same, the gears on the bottom were just dirty with gunk and with a little lighter fluid, everything works again.
SRT no. 2 One pulley was loose and disconnected from the aperture ring and a little round part which guides the pulley was loose laying in the viewfinder, iso dial pulley was unwound, attached everything works again.
SRT no. 3 lightmeter cable on the bottom was disconnected and had to be resoldered. Works now again

I cleaned every camera, while it was open removed prism blew away the dust and bits.

I tested all 3 cameras against my iMac screen and they all had the same value f5.6 500th of a sec.

On some models the CDS cell wiring is different. Also one had a white pulley string. (attached some images they are slight out of focus im sleep deprived in the middle of finals at the moment)
Side note when i pressed the shutter on 1 second, the SRT no. 1 was still struggling a little bit, very small but compared to a clean one it was noticeable.

So I'm assuming they all work fine.

That's so cool. Glad you got them working. I fixed an SRT for my niece once by replacing a pulley string with whatever I could get my hands on. Later on I bought a length of coated steel cable "for the next time".