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Author Topic: what does Stopped Down mean???  (Read 3795 times)
Prismpic
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« on: January 23, 2006, 01:16:46 PM »
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Excuse the dumb question but What does stopped down mean? I am determined to get all this SLR info in my head to get the best out of my Canon t-70. Your feedback is appreciated.
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boku
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« Reply #1 on: January 23, 2006, 01:25:16 PM »
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"Stopping down" mean making the aperture smaller.

For example: f/2 is a larger aperture; f/8 is a smaller aperture. It is smaller by 4-f/stops (f/2.8, f/4, f/5.6, f/8). To go from f/2 to f/8 means you are "stopping down" the aperture by 4 stops.

The term "stop" comes from the old design of lenses where the area of the aperture was controlled by a rotating ring that had click "stops" for setting the aperture. Each click let in twice as much or half as much light depending on which direction you went. Light is proportional to area. f/stops are give in diameters of the aperture to the focal length of the lens. Area has a squared relationship to diameter.
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Bob Kulon

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Play it Straight and Play it True, my Brother.
framah
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« Reply #2 on: January 23, 2006, 02:27:45 PM »
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Very good, Bob!!!  You get an "A" !!    

It brought back long lost memories of my first classes in photography.  

 Of course my main problem is that the short term memories are going quicker!
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« Reply #3 on: January 23, 2006, 04:19:29 PM »
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Gotcha! Thatís understandable. Thanks.

My first assignment: Break out manual.

What made this confusing? The specifications for exposure modes lists 3 auto modes (which Iím not getting into because I'm interested in MANUAL). But after the 3 autos are listed it reads:

"manual, stopped down AE (only for lenses without AE signal pins), program flash AE and electronic flash AE

What Iím understanding from your description is "stopped down" IS manual correct? Why would that not logically be included in "manual" instead of coining another term???
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Ed Jack
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« Reply #4 on: January 25, 2006, 01:20:53 PM »
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Quote
Gotcha! Thatís understandable. Thanks.

My first assignment: Break out manual.

What made this confusing? The specifications for exposure modes lists 3 auto modes (which Iím not getting into because I'm interested in MANUAL). But after the 3 autos are listed it reads:

"manual, stopped down AE (only for lenses without AE signal pins), program flash AE and electronic flash AE

What Iím understanding from your description is "stopped down" IS manual correct? Why would that not logically be included in "manual" instead of coining another term???
[a href=\"index.php?act=findpost&pid=56633\"][{POST_SNAPBACK}][/a]

OK, I think to fully answer your question one more thing needs to be said.

All modern camers have electronic apertures. This allows for the aperture to be held wide open all the time. Only when you click the shutter to take a picture does the aperture close to the assigned "F-stop" for that particular exposure just before the shutter fires. This is to allow the brightest view finder possible. DOF preview is sometimes refered to stoping down as a means to get the image in the viewfinder that is set for that cameras aperture when "stopped down" i.e. as it is when the shutter fires.

Ofcourse origionally stopping down meant - still means what the others said.
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dbell
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« Reply #5 on: January 26, 2006, 04:05:00 PM »
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Gotcha! Thatís understandable. Thanks.

My first assignment: Break out manual.

What made this confusing? The specifications for exposure modes lists 3 auto modes (which Iím not getting into because I'm interested in MANUAL). But after the 3 autos are listed it reads:

"manual, stopped down AE (only for lenses without AE signal pins), program flash AE and electronic flash AE

What Iím understanding from your description is "stopped down" IS manual correct? Why would that not logically be included in "manual" instead of coining another term???
[a href=\"index.php?act=findpost&pid=56633\"][{POST_SNAPBACK}][/a]

The T-70 has a wide-open (full-aperture) manual mode, in which you set all of the camera's controls manually, but the lens aperture remains all the way open until you release the shutter. This is the way just about all modern cameras work. It ALSO has a mode (stopped-down AE) in which the meter is engaged with the lens stopped-down to the selected aperture. This is for use with lenses that aren't capable of wide-open metering.

If you can help it, you don't want to meter with the lens stopped down because with a small aperture, the viewfinder will get very dark. In the early days of TTL metering, the meters ONLY worked with the lens stopped down (my Pentax Spotmatic was that way). Wide-open metering was a big advance in usability because it meant that you always got to focus (with the meter on) in a nice bright viewfinder.

Hope this helps,


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