Meter calibration.

[Stealth3kpl]

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Lenses have different transmissions. On my Nikon D700, my Zeiss 35 f2 would result in a different shutter speed to my Nikon 35 f1.4 at a given f stop. So it follows that a hand held incidence meter will give a different exposure result for at least one of these lenses. So, how can I go about establishing a relationship between readings on the meter and readings with, say, my 35 summicron on the M6/MP? In a post somewhere on the forum someone suggests a method of establishing the true iso of a film by taking exposures of a grey card (or perhaps that was a black card?) and finding the iso for a given exposure setting to achieve a clear frame on the black and white film. This is essentially the same thing.

Any thoughts?

Pete

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[Xmas]

Hi

 

If you were shooting transparency (i.e. film like Kodachrome) then you might want to calibrate the exp meter and camera shutter, cause you would be annoyed by 1/3 stop errors, upon projection.

 

But with C41 color or conventional monochrome it is probably not worth bothering.

 

If you don't have the shadow detail or it is not a nice color then you probably need to rate films a bit slower then the box speed.

 

You always need to look at the negatives even if you have proof prints or scans.

 

The meter only works for average scenes, if you are shooting very contrasty scenes then you may have to use specialist developers or lose high light or shadows, you need to be aware of this. Low contrast sceanes you can reduce exposure obtained from a average meter reading.

 

Noel

[Clearlight]

Does this suggest that, for a given f-stop, light admitted by the lens can vary between individual specimens - that the actual f-stop varies (one is inaccurate)?

[Stealth3kpl]

I suppose in theory there may be a difference in transmission by different specimens of a particular model. I doubt there'd be any practical difference.

Pete

[Michael Geschlecht]

Hello Cleasrlight,

 

Welcome to the Forum.

 

F stop is the purely mathematical relationship between a lens's opening & the distance from its theoretical second nodal point to the film or sensor plane. F stop does not always accurately define transmission as those above have already said.

 

Actual transmission is measured in T stops. These are used in places like the movie industry where it is necessary to splice together segments done w/ different lenses to make a whole & the continuity of exposure is critical segment to segment.

 

BTL meters automatically compensate for this w/ F stopped lenses & make them defacto T stop lenses. This is done in a more complex manner w/ some digital camera programs which do this & compensate for unevenness of exposure, etc.

 

If you use a separate metering system (ie: handheld) you may w/ some lens/film compensations have to adjust exposure. Not often though.

 

Best Regards,

 

Michael

[tobey bilek]

You can empirically detirmine film speed, but do not use the largest stop Keep to 2.8 to 11 .

 

Nikon cheats on transmission at widest stop by at least 1/3 stop, sometimes more.

 

I find a typical 18% reflectance subject , take a photo and check the histogram. Then you can compare the incident reading and put a correction on the camera. The D40, D200, D700, and D3 are all different. People can brag over Nikons fancy color matrix, but I think it sucks just like every other in camera reflective meter.

 

My Sekonic Studio Delux selenium never fails on a film camera, Digitals I have to put a compensation factor in depending on one of the 4 digitals I am using. It is pasted on each of the four bodies.

 

Usually the Nikon works ok for sun, but overcast I use the the spot meter and put the spot on the brightest spot in the sky and then overexpose it 1.7 stops so it does not blow or expose as grey. The land is then -1.7. Or measure them separately and split the difference. But if you go at it like joe schmo, you will overexpose every overcast scene.

[JBA]

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If you were shooting transparency (i.e. film like Kodachrome) then you might want to calibrate the exp meter and camera shutter, cause you would be annoyed by 1/3 stop errors, upon projection.

 

I regularly shoot PKM 25 in my Nikon Fs incident metering with a Gossen Digisix and largely ignore 1/3 stop increments, and have yet to over or underexpose a photo by an unacceptable margin. Then again, I haven't projected slides in nearly 30 years and no longer even get my Kodachromes mounted.

 

People are always going on about how slide films have such narrow exposure latitudes, but in my experience this is mostly limited to Velvia 50, which is quite intolerant of underexposure. In my experience, Kodachome has a very wide latitude and is very forgiving.