Sunny 16 calculation for ISO160 film

benjiboy said:

I think guestimating exposures when good light meters are available so cheaply on the second hand market is ill-advised because any cost of buying a meter will soon be recouped by the increased percentage of accurate exposures, and to avoid the wast of time, effort and materials taking the pictures and processing them.

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Occasionally, I will guestimate and then meter for two reasons: keep up my guestimating skill and as a sanity check that the meter is operating correctly vis-à-vis Sunny 16.

Steve

I'd probably just treat it as 100 ISO film, and be half a stop over exposed, which for negative film, is rarely a bad thing.

Many of us rate 160 color negative film at 125 anyway. I suggest you try 1/125 second at f/16. If the shadows are the least bit fuzzy drop to f/11. I have taken incident meter readings and in every case I get 1/ASA at f/16, to the point where I do not bother metering in those conditions. However, for any other I use an incident light meter.

It has been decades since I last used slide film, Sunny/16 never worked for it, unless you are happy with 3-4 correct exposures per 36x roll. Negative film has at least a stop of latitude over and under the ISO rating, and usually more than that, so Sunny 16 or Sunny 11 (I always found that to give sightly more printable negtives) works OK.

graywolf said:

Many of us rate 160 color negative film at 125 anyway. I suggest you try 1/125 second at f/16. If the shadows are the least bit fuzzy drop to f/11. I have taken incident meter readings and in every case I get 1/ASA at f/16, to the point where I do not bother metering in those conditions. However, for any other I use an incident light meter.

It has been decades since I last used slide film, Sunny/16 never worked for it, unless you are happy with 3-4 correct exposures per 36x roll. Negative film has at least a stop of latitude over and under the ISO rating, and usually more than that, so Sunny 16 or Sunny 11 (I always found that to give sightly more printable negtives) works OK.

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once you do it for a while you get even better than a light meter ..
the last few rollss of slides i shot ( 120, 35mm and some sheets )
came out perfect ... sans meter

I remember ideal conditions for sunny 16 as a front-lit subject, clear skies, at sea-level, between 10 a.m. and 2 p.m. Some of the brightest, harshest and worst conditions for making interesting pictures in terms of lighting qualities. Good conditions for testing light meter readings versus "box speed" of film, but not much else. Tests performed under these lighting conditions will help you calibrate equipment and exposure. Using transparency film is the key. Negative film involves too many variables to easily pin it down using this method. Too much latitude in the processing and printing.

Peter Gomena

Graham_Martin said:

I live in Florida where the sun is very bright. When I use an exposure meter the readings indicate that Sunny 16 applies here.

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I live in the mountains of southern Oregon, which has even brighter skies than Florida due not only to very low humidity but higher altitude. I don't go by meter readings--I go by what the photos look like. Extensive tests, especially with transparency, indicate that the rule should be more like sunny f11.3.

"Sunny 16" may apply to extreme conditions, such as snow or white sand, but for scanning purposes I've found it produces underexposure. F16 was more appropriate for slide projection (on a screen you see saturated colors, but not noise), but it doesn't work so well for scanners

f11.3? Or do you mean f11 = 1/3 stop?


Steve.

A couple days ago I took pictures for most of the sunny hours (from 12:00 to 18:00 which means solar 11:00 to 17:00 due to summer daylight saving time or what's that called) and my Gossen Multisix with incident light gave me readings there were substantially EV 14.5 with very boring predictability ("sunny 16" corresponds to EV 15). I was taking pictures in the city centre of Rome and I suppose that asphalt and cobblestones were pretty much bouncing sun light (more than grass or bare earth). The instruction manual shows, and use confirms, that with my lightmeter the direction of the light is not a big factor. Front sun or sun at 30° give basically the same reading. I suspect this is also due to the "reflective" behaviour of cobblestone, asphalt, or other buildings (which in Rome are often whitish, when they are cleaned from pollution deposits that is).
The sun was either unshielded, or very slightly veiled by thin clouds, which gave a slightly different appearance but did not seem to alter the reading. I suppose low-altitude clouds always have this merely diffusing effect.

Good morning, Graham;

One point to consider is the accuracy of the shutter assembly in your camera. Under the old ASA specifications, the shutter speeds were considered to be correct if they were within plus or minus 20 percent of the nominal speed rating for speeds of more than 1/500 of a second. At shorter shutter speeds, the tolerance was plus or minus 40 percent. That meant that a shutter that was set to 1/1000 of a second could be considered to be "in specification" if it was anywhere from 0.6 milliseconds to 1.4 milliseconds. That 1.4 ms would give you 1/600 of a second. 0.6 ms is 1/1,667 of a second. That is the normal limit of the specification. And this is more than 1/3 of a stop.

Then there is the amusing case of the old "Copal Square" Vertical Travel Metal Focal Plane shutter. This was listed as having the fastest focal plane "X" synchronization back in the 1960s at 1/125 second. That 1/125 second is 80 ms, but when you put it onto the camera shutter tester, almost every single one of them comes out to remarkably close to 95 ms or 96 ms or about 1/100 second, not 1/125 second. However, please note that this is at the plus or minus 20 percent tolerance of the specification, so it is "in spec."

What is all of this coming down to? Test your camera. Have a shop actually measure the shutter speeds for you, and give a report to you of the actual timing of your shutter. When you know where your shutter really is, then you can make some good decisions on where to go with your camera to make an adjustment. In some cases, you may not need to make an adjustment. The shutter may have that "adjustment" already built into it.

Can you get the same information just by exposing a roll of slide film at all of your shutter speeds with the appropriate corresponding lens aperture settings? Yes, you can. If that is your preferred way to do it, then use it. A critical eye with a magnifier looking at the highlights and at the shadows can also make the determination of which way to go and by how much with each shutter speed/lens aperture combination. With a standard light source and light sensor, you can also measure the aperture settings of your lenses. It is just that with my own training and experience in engineering, I like to measure each of the pieces and then work with those records of the individual variations to determine the actual exposure values I have with my camera bodies and lenses. And I also hope that the guys in the film factory are consistent in their work.

The actual sequence of hand-hand shutter speeds should actually be marked: 1/30, 1/60, 1/120, 1/240, 1/480, 1/960.

Light meters measure exposure values. When they say 1/1000 at f/4 they mean 1/960 at f/4. They do not "compensate" for the "non-linear" progression (actually, non-linear on a logarithmic scale) of what is printed on the shutter selector.

Producers mark 1/1000 but when one measures the exact performance of a shutter one would ideally want a perfect shutter to give 1/960 of exposure. If it does it's not a 4% mistake, it's fine. By the same token, if the shutter exposes for 1/860 it's not a 14% overexposure, it's a 10% overexposure.

Testing shutter precision by making several exposures at different shutter speeds with uniform light, compensating with a varying lens aperture, gives indications only about that particular diaphragm/shutter speed combination, not about shutter precision, as lenses tend to introduce an error also, the actual f/value is not be what it appears on the barrel (to say it more properly, the f/value does not coincide with the t/value).

Aperture "mistakes" are particularly strong at the extreme of the aperture range. Also, vignetting will be more pronounced while a lens is used at full aperture so one should consider only the centre of the image.

If one wants to know the exact speed of a focal-plane shutter there are electric devices which are relatively cheap (search on APUG for shutter tester, shutter accuracy etc.).

The problem with those is that they give proper measurements only with focal plane shutters, not with leaf shutters. Use of those testers with leaf shutters is probably at the base of the common (mis)belief about 1/500 in central leaf shutters to be something like 1/250 or 1/300 in reality.

I also, like Ralph, like to know exactly how a certain piece of machinery performs. I have had all my SLRs tested by a guy who gave me the exact time for each shutter position of each camera. I would have already bought a shutter tester if I had found a model which would work also with leaf shutters.