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Step 2Switchable Automatic / Manual Apertures
Historically, switchable automatic / manual aperture controls came next. They have a single aperture ring, a separate "AUTO/MAN" switch, and a little pin on the rear (camera side) of the lens. The photo here shows a Pentax Super Takumar 28mm f/3.5 lens which is of this type.
The "Automatic" operation is the automatic closure of the lens to the set aperture when the shutter is pressed -- the lens is intended to remain wide open for focus until that moment. The aperture ring is usually set close to the camera body because closing of the aperture needs to be able to be triggered by the body pressing in the little pin protruding from the back of the lens. Incidentally, this has to happen fast with little force, so the number of blades in the aperture is typically 6-8 to reduce friction, unfortunately making the stopped-down aperture not exactly circular.
The "Manual" mode is available largely to support older bodies that cannot press the pin. An external slide switch selects "AUTO" or "MAN" operation. This also can serve as a "depth of field preview" button, in which case the switch may be spring loaded to return to the "AUTO" position.
To use this type of lens on a modern DSLR, which also cannot press the pin, the lens is simply put in "MAN" mode and the aperture ring is used rather like the second ring on a preset. There is no first ring and hence no preset stop. The best way to get around this is to get used to knowing how many detents you pass to go from wide open to each of the other f/ numbers. For example, if f/5.6 is 5 detents away from wide open, you would focus wide open and then turn the aperture ring 5 detents to take the photo at f/5.6. This is a little confusing at first if you have multiple lenses with different detent intervals, etc., but it really works well with practice.
Unfortunately, the "AUTO/MAN" switch typically is a little piece of plastic sticking out on the side of a solid metal lens barrel, so it is not unusual to find the switch broken off, leaving the lens permanently in "AUTO" mode. If that's the case, try to switch it one last time into "MAN" mode. Failing that, you essentially have the third type of lens....
The "Automatic" operation is the automatic closure of the lens to the set aperture when the shutter is pressed -- the lens is intended to remain wide open for focus until that moment. The aperture ring is usually set close to the camera body because closing of the aperture needs to be able to be triggered by the body pressing in the little pin protruding from the back of the lens. Incidentally, this has to happen fast with little force, so the number of blades in the aperture is typically 6-8 to reduce friction, unfortunately making the stopped-down aperture not exactly circular.
The "Manual" mode is available largely to support older bodies that cannot press the pin. An external slide switch selects "AUTO" or "MAN" operation. This also can serve as a "depth of field preview" button, in which case the switch may be spring loaded to return to the "AUTO" position.
To use this type of lens on a modern DSLR, which also cannot press the pin, the lens is simply put in "MAN" mode and the aperture ring is used rather like the second ring on a preset. There is no first ring and hence no preset stop. The best way to get around this is to get used to knowing how many detents you pass to go from wide open to each of the other f/ numbers. For example, if f/5.6 is 5 detents away from wide open, you would focus wide open and then turn the aperture ring 5 detents to take the photo at f/5.6. This is a little confusing at first if you have multiple lenses with different detent intervals, etc., but it really works well with practice.
Unfortunately, the "AUTO/MAN" switch typically is a little piece of plastic sticking out on the side of a solid metal lens barrel, so it is not unusual to find the switch broken off, leaving the lens permanently in "AUTO" mode. If that's the case, try to switch it one last time into "MAN" mode. Failing that, you essentially have the third type of lens....
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