Canon A-1

[david_77]

I'm an uber beginner at this. I've bought a Canon A-1 and lots of B&W film and have several questions concerning the device and terminology (please be patient with me, I have NO idea what I'm doing at the moment...)

1. What are f/stops?
2. What is aperture?
3. How does the amount of exposure affect a picture?
4. How does shutter speed affect a photo?
And also, everytime I twist my lense to the green "a" for ae priority, the viewfinder blinks the error display...

 

[tirediron]

Welcome to the forum! First, go over here and download a free .pdf file of your camera's manual. It will answer most of your questions.

Briefly, "f stops" are the units that describe how large the aperture is for any given exposure. It's a fractional measurement, so the numbers may not make sense, just remember the large the number (f16, f22) the smaller the aperture and the less light the lens will admit to your film. This also affects depth of field and other factors as well. The aperture is a physical device inside the lens exactly like the iris of your eye which is adjustable via the aperture ring, or f-stop ring on the lens.

For exposure, too much light will produce a dark to opaque negative which will render as a white, detailless print. Too little will be the opposite.

Shutter speed affects the photo in many ways, by controlling the amount of light that can reach the film, and short shutter speeds will allow you to stop movement, longer ones to enhance it (think of the soft, feathery water you see in some pictures of streams and waterfalls).

Not sure on the error, refer to the manual.

 

[gsgary]

Read these
http://www.cameramanuals.org/canon_pdf/canon_ae-1_pt1.pdf

http://www.cameramanuals.org/canon_pdf/canon_ae-1_pt11.pdf

 

[dxqcanada]

You can also read up in our Tutorial Thread: http://www.thephotoforum.com/forum/...rum-photo-gallery/123160-tutorial-thread.html

... I do have a question for you ... I am curious on why you picked up an older film SLR and lots of B&W film, when you do not know how to use such a camera and basic camera controls ? I am not hacking on you for doing so ... I just want to know why this occurs.

 

[KmH]

The lens aperture numbers (f-stops) make a lot of sense if you have an understanding of the math involved.

The little f, in f/8, f/16, or f/11, represents the lens focal length, or the focal length a zoom lens is adjusted to, so that little f is a number that changes depending on the focal length of the lens.
The number under the little f tells us what fraction the size of the lens opening (aperture) is according to the focal length of the lens.

In short, the f-stops describes the lens aperture size as a ratio (fraction) of the lens focal length.

Lets assume you have a 50 mm focal length non-zoom lens on the A-1, so the little f = 50 mm.

Now we have the fractions - 50/8, 50/16, and 50/11. So if we do the math: 50 mm divided by 8 = 6.25 mm. In other words a 50 mm focal length lens set to f/8 has a lens opening that is 6.25 mm wide.
By the same math: 50 mm divided by 16 = 3.125 mm. In other words a 50 mm focal length lens set to f/16 has a lens opening that is 3.125 mm wide.

Now here is where it gets tricky - it would be easy to suppose that a 6.25 mm wide lens opening would let in 2x's as much light as 3.125 mm lens opening would, but it doesn't. 6.25 mm lets in 4x's as much light as a 3.125 mm lens opening because the area of he lens opening has increased 4 times.

So to calculate what f-stop lets in twice a much, or 1/2 as much if you want less light, light we have multiply using the square root of 2, or 1.4142.

So if we multiply f/8 times 1.4142 we get = 11.3, or rounded off f/11. In other words f/8 lets in twice as much light as f/11 does, or we can turn that around and say f/11 lets in half as much light as f/8 does.

If we now assume that we have a 100 mm lens on the camerathe little f is then 100/8, 100/16, 100/11, such that at a lens aperture setting of f/8 the lens opening is now 12.5 mm wide, not 6.25 mm wide as it is for the 50 mm lens.

You may or may not have already heard the expression 'a fast lens' or someone discussing 'lens speed'. They are referring to how the size of the lens opening effects what shutter speed can be effectively used.
Letting more light in with a larger lens opening lets the photographer use a shutter speed that leaves the shutter open for a shorter time (a fast shutter speed).

Lenses that can be opened to lens apertures of f/2.8 or more, like f/2, f/1.8, f/1.4, are known as 'fast' lenses.