But what you're describing is basically sorta true of any full aperture metering camera. That is, the camera "knows" how far it's supposed to stop down the lens and that the lens isn't stopped down until the moment of exposure. Actually with an FD lens, you have a lever that is moved as the aperture ring is rotated and a corresponding lever inside the body (visible on the right side of the camera's mount opening) is moved in turn so the camera knows at what aperture the lens is set to (even though it's still wide open). There are no sensors!
CoolTouch,
Note: For reference througout my post please open:
This image
This is exactly what i am describing, we are just using other words. The "lever that is moved as the aperture ring is rotated" is what I am referring to (Canon's slang: "Aperture signal lever") , this one couples to the corresponding lever inside the camera ("aperture signal coupling lever"), and in the A-1 and AE-1
this lever DOES have a position sensor or "encoder" in the camera. This sensor is a wiper with a gray code pattern which gives the camera's CPU the instantaneous position of the lever, digitally. When shooting at shutter priority mode, this lever falls down, and when the instantaneous position is what the camera desires, then this aperture signal lever's movement is frozen and the rest of the exposure cycle is triggered, which includes moving the "lever that actually stops down the lens" (Canon's slang: "Automatic aperture lever").
And, at any rate, what you're describing isn't what happens with an FD camera when it's set to shutter priority. In shutter priority, the lens is set to "A" (or sometimes a small circle), which tells the camera by means of that same "preset" lever that moves when the aperture ring moves that the camera has auto control of the lens and can set the aperture wherever it wants. This "preset" lever can move back and forth for the complete range of the lens's aperture values. Because the aperture is set to "A" it has complete freedom of movement. When the lens is not set to "A" this lever can still move freely in one direction, but it is stopped cold in the other direction, which indicates the aperture setting on the lens. But there's no such restriction to its movements when the lens is set to "A". It has to be this way so that the camera can move it to wherever it thinks it should be so that it will control the degree of iris closure, which is still done by the stop down levers in the camera and the lens during exposure.
Yes, I know, there is no contradiction with what I wrote. But the part i'm adding is the following:
The aperture signal lever is operated on the camera by the "aperture signal coupling lever". On the AE and AE-1, all this mechanism is spring powered so if the "aperture signal coupling lever" is moved outside the initial position (like, for example, when switching the lens out of the A position, setting an aperture value on the lens and then stopping down the lens), there is no way for the camera to reset the position of the "aperture signal coupling lever" by its own means.
So what does this mean? This will be more evident below, in my next replies.
Wrong again. The stop down lever on the exterior of the camera body "charges" the stop down lever on the base of the lens, not the lever that's telling the camera what the aperture is set to. And AE is impossible (on the AE-1 at least) because the lens cannot be set to "A" in stop-down mode.
You're not getting my point. And part in bold is wrong -- more on this later.
But first, What I am trying to explain?
I'm trying to explain:
Why, on the A-1 and AE-1, Canon chose not to implement a decent manual exposure mode. "Decent" as in "the camera knows what aperture are you selecting, and thus can compare it with the meter's preferred aperture and tell you if you're OK or not.
Read on, more follows.
You know, I've been using the A-1 on and off for about 35 years, and I have never once been able to get it to display this EEEEE you're talking about. And I just gave mine a workout right now to see if I could. Shoot. No luck!
1. Set the camera to manual mode
2. Set LENS aperture to a value (i.e. f5.6)
3. Stop down the lens by using the stop down button on the A-1
4. Now set LENS aperture to A
5. Set camera to Program or Tv mode
If you try to shoot, or meter, the LED display should display EEEEE.
Why? Because the "aperture signal coupling lever" is not on its required position for AE, which is fully up. And thus you need to perform a procedure to reset it manually: Press the double-exposure lever, wind the camera again. This procedure is in the manual!!
Well, I'll take your word for it with respect to the New F-1, but it's a completely different animal from the A-series Canons. Oh and by the way! I need to mention this, since you've given your reasons why the A-series Canons don't have the aperture connected to a meter readout
I just gave you the reason. above. But i will ellaborate:
If you wanted the aperture connected to a meter readout on the A-1 (or AE-1), this means that on manual mode the "aperture signal coupling lever" should be left loose to follow the position of the "aperture signal lever" [like on the FTb, AT-1 and F-1s]. This means that, if you change to Tv mode afterwards (step #5 on my above list), the "aperture signal coupling lever" will not be on its required position for AE, and thus you will
always get an EEEEE display/error whenever you want to switch to AE. And Canon didn't want to have this awkward user experience. Period. QED.
Also, this explains the reason the New F-1 requires a motor drive for Tv operation -- to govern the "aperture signal coupling lever" at will.
It is complex to explain, but I think I have done everything to explain it. BTW I also have extensive experience with the A-series cameras as well.
the Canon AT-1, which debuted in 1978, if I'm not mistaken (same year as the A-1) is a totally completely manual exposure only camera. Canon decided to put together this little gem so that film students would buy it instead of an AE-1 and then get all frustrated because of its "crippled" nature when in manual mode. The AT-1 is, in fact, the ONLY amateur-orientated Canon FD camera since the FTb that has a meter that responds to aperture settings (ignoring stop down metering of course). The AV-1 doesn't count because it has no manual mode and the user has no control over shutter speeds at all. So it was possible for Canon to add this feature into at least one of its A-series cameras.
Again, if you read my post above, you'll see there is no contradiction: The AT-1 has no Tv mode and thus the "aperture signal coupling lever" can follow the "aperture signal lever" all the time, with no problems.
I don't think the manual went far enough. All it does is explain how to use that button on the side of the mount for an instant sort of exposure compensation -- and you better hope it's enough.
You have a different A-1 manual then. Mine has the bearded man pics, it tells you which exposure compensation dial setting to use depending on the situation. See manual on butkus' website.
Well it does have exposure compensation settings on that dial on the left, but honestly, when's the last time you used exposure compensation?
I used them all the time for AE photography in dimly lit jazz clubs.
I still think that Canon's metering method found on the original F-1 and the FTb was just about perfect. You have a central rectangle that occupies about 12% of the image area
I agree.
You know, Nikon came up with just about a perfect averaging method with most all of their cameras' meters that were made from the mid-70s onward. 60-40 metering, with 60% emphasis occurring inside a largish circle visible in the viewfinder and 40% outside of it. Nikon stuck with that for years.They tightened it up on the F3 to 80-20 though. My reasoning as to why they did was they figured pros who were shooting slide film, with its very narrow exposure latitude, would get a greater percentage of correctly exposed shots than if they went with their 60-40 pattern. I don't know if that was their actual motive behind it,
The motive is really technical. The F3 wanted to dispense with the meter-inside-prism concept. They could go the F-1 route with split prism but I guess they didn't because of patents or perhaps some other technical issue.
So they chose to put the meter cell at the bottom of the mirror box. See this image of F3 system:
http://camerajunky.files.wordpress.com/2013/06/metering.jpg
The way the cell is positioned, it would have been damn difficult to achieve any other pattern than spot metering, due to optical reasons.
This is also why the F3 requires a translucent mirror, and this is why the F3 finder brightness isn't any better than the F2 cameras.
but based on personal experience with the F3 and shooting slides with the camera set to "A" I had very few shots where perfect exposure was missed.
Yet me, with the F-1N and a screen for the 'bottom centerweighted averaging' pattern that you hate so much, also got perfect Provia 100F exposed slides on my last trip, all exposures, all situations. It depends on just knowing the meter.
Just as people using the most primitive TTL meter, the averaging meter on the Spotmatic, can also get perfectly exposed slides. I still agree Partial method is the best, only because it requires less effort, less thinking needed. Same for the F3 meter.