BetterPhoto Q&A
Category: New Questions

Photography Question 
Chris Jacko

Aperture Priority

I have a Canon AE-1 Program, which is an old film SLR that I picked up second hand a few weeks ago.

I have played with the camera, everything is working well and it all seems in very good condition. After playing with the settings, and seeing that the light meter is accurate, I have come to the conclusion that Aperture Priority is the main setting I will use, for the convenience yet still maintaining control of DOF (and have been told since that this is a wise move) though, having started my photographic journey on digital and having all the shot info recorded automatically by the camera, I am wondering how do I find what Shutter speed the camera decides to use for the shot, to make record of it?


To love this question, log in above
9/17/2005 1:47:56 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  Nice old camera. I have one. If you don't have it, download the user manual at
The AE-1 Program is designed to be used in full Program (lens set on "A" and shutter set to "Program") and Shutter-priority (lens set on "A" and manually selected shutter speed) autoexposure modes. The standard work-around is to leave the lens on "A" and adjust the shutter speed until you get the desired aperture. Otherwise, you can set the shutter speed and aperture manually.

You can use stop-down metering with non-FD lenses. Set the desired aperture, push in the Depth of Field Preview button, adjust the shutter speed so that the meter needle in the viewfinder aligns with the mark next to "5.6". This method cannot be used with FD lenses.

To love this comment, log in above
9/17/2005 6:02:20 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  Forgot to mention (though it might be inferred from my previous answer) - The AE-1P does not have Aperture-priority autoexposure mode.

To love this comment, log in above
9/17/2005 6:09:43 AM

Chris Jacko   When you do not have the aperture on the A setting, so setting it manually, and then having the shutter speed set to Program, is that not Aperture Priority?
And the AE-1P doesn't have a needle for light meter, it has LED's, though the AE-1 has the needle and lacks Aperture Priority - maybe you are confusing the two?

To love this comment, log in above
9/17/2005 6:17:21 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  No. With the aperture set manually (not on "A") and the shutter dial set to "Program," the AE-1P will give inconsistent metering. The viewfinder display will be the aperture it wants to set, not the actual setting. It is not capable of Aperture-priority.

Sorry, your are correct, there is no meter needle. The aperture value (and M and flash ready symbol) lights up on the right side. For stop-down metering you still match need to match "5.6" rather than the actual aperture set.

To love this comment, log in above
9/17/2005 6:47:38 AM

Chris Jacko   Excuse my ignorance, but what is 'stop down metering'?

I am also not quite sure what you mean by not capable of Aperture Priority - when setting the aperture manually and leaving the camera to set the shutter speed, isn't that Aperture Priority?

Again, sorry for my ignorance, but thank you have helping me out! :)

To love this comment, log in above
9/17/2005 6:57:31 AM

George Anderson   I think reading the manual will help you out a lot. See also: companies/canon/fdresources/SLRs/ae1pgrm/

To love this comment, log in above
9/17/2005 8:18:07 AM

Chris Jacko   1. Thank you for the link, though I already knew of the site, it is indeed very useful.
2. The manual does not mention Aperture Priority, however;
3. The AE-1P works in an Aperture Priority mode.
I google'd "aperture priority" - - to make sure my definition of 'aperture priority' was not somehow distorted. The first link, , stated this;
"Under the aperture-priority mode, you select an aperture and the camera chooses an appropriate shutter speed."

By setting your Canon AE-1P shutter speed to PROGRAM and your aperture ring manual you can achieve Aperture-Priority with it, as I said before. AND even if the manual doesn't mention it.
Trust me. I picked up the camera and started clicking away. I put a test roll in and did just that, test to see if it was all working fine. Using those settings not only worked, but worked well - not to mention convinience.

So, I again thank you for your concern, though, even being a young and *relatively* new (1 year) photographer, this isn't the issue I initially intended to discuss and is also an issue that I know I do not have to look further into - maybe you should play with your camera and get back to me if it works, or even more so if it doesn't.
However, I am still wondering how I can, if at all possible, find out what shutter speed the camera chooses when in Aperture Priority mode.

To love this comment, log in above
9/17/2005 8:54:18 AM

George Anderson   Good for you. I don't own any old Canon A-series cameras, and I certainly don't feel any desire to play with them or find out why they didn't proudly advertise aperture priority for the AE1-P in the first place as Nikon did, rather than offering so many one-off models with differing combinations of automated exposure (AE-1, AE-1P, A-1, AV-1, etc, etc.), rather than just settle on one and offer something else truly useful, like TTL flash and a fast vertical shutter.

But I promise, in future if I ever feel the need to purchase a 20-year old A-series Canon, I'll consult you first.

To love this comment, log in above
9/17/2005 10:56:26 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  Chris, with all due respect, the AE-1 Program does NOT have Aperture-priority autoexposure as a feature, undocumented or otherwise. The earlier A-1 and AV-1 did have Aperture priority. There is no reason that Canon would have kept such a feature secret if the AE-1P had it.

When the shutter dial is set to Program, the camera’s metering algorithms select a single shutter speed and aperture combination. The aperture setting the camera has chosen is displayed in the viewfinder, there is no direct way to read the shutter speed selected. One can figure it out by changing the shutter speed (while leaving the lens on A) until that same f/stop is displayed in the viewfinder.

The AE-1 Program cannot read the current aperture setting from the lens. Note that moving the aperture ring off of "A" does not change the f-value displayed in the viewfinder, but the signal light in the upper right changes from P (full Program) to M (manual exposure). Moving the lens off of “A” will not change the shutter speed that Program selects. The camera will use that same speed regardless of the aperture setting on the lens.

You can test this yourself (I actually did this with my AE-1 Program this afternoon). In dim indoors, select Program and A on the lens. Note the f-stop displayed (eg. f/4). Next, leaving the lens on A, select a shutter speed that gives f/4 (eg. 1/30). So in this example Program + A have set f/4 and 1/30. Now, change the aperture to f/22, but leave the shutter dial set to Program. If the AE-1P is capable of Aperture priority, then it should set the shutter speed to 1 second (f/22 at 1 sec. is the same expsoure as f/4 at 1/30). Press the shutter. You'll see that the shutter speed has not changed.

The fact that you got acceptible results using the camera with manually selected aperture and "Program" shutter speed is simply a result of coincidence (choosing an aperture close to what the camera would have) or the generous exposure latitude of the print film you used.

To love this comment, log in above
9/17/2005 2:35:03 PM

Chris Jacko   OK, I am sitting infront of my computer, in Australia, with my camera, a few rolls of film a packet of developed photographs and a cup of tea.
When I did the test roll of film, which is the roll I am looking at now, I encountered a beuatiful flower next to the road, it being the start of Spring here, so I decided to photograph it. I made a note to use f/1.8, 1. to test the outter limits of my 50/1.8 lens and 2. because the DOF is beuatiful.
I took these photographs, three of them, and turned to walk down the rest of the hill to the Brisbane River - my initial destination. When I turned and looked I saw a a cloudy sky, tree line, a gastly bright yellow crane and the water - very reflective. So I decided to shoot it, the reflection was too beutiful to pass up, not to mention the hidious yellow crane.
For this shot I decided to turn the aperture all the way to f/22 (the other extreme on the lens, again to test it as I had only recently got them) I left the shutter speed on PROGRAM and proceeded to snap two shots of this scene.
(Lighting for both were practically identical due to cloud cover)

These shots were correctly exposed.
If what your saying is correct, then the photographes of the flower should be vastly over exposed and the crane to be exposed correctly, OR the flower to be correctly exposed and the crane vastly under exposed (or neither to be exposed correctly)
This came into my mind when I woke up, so I checked it, and sure enough both are correctly exposed.
I then also checked the negatives, to see if the photolab had done some drastic adjustments, but sure enough, the negatives also looked correct (no all black or all clear)

Now, I don't know how you can explain this, and still be correct?
If the camera isnt possible of it, why do I have a stip of (100 ISO, out of interest - so exposure compensation for the cloud cover was made at the time, correctly) negatives sitting infront of me. Acorrding to you, they do not exist?

So please do me a favour, put a roll of film into your camera and try it. I'm sure I don't just have a 'special model' so if it works for me, which I can asure you it DOES, then it will work for you also.

Also, I just testing this, because I don't like your test - 1. it doesn't my sence to me at the moment and 2. because you are not actually testing for Aperture Priority, if I am understanding it even remotely correctly.

OK, it is 12:40PM here in Australia, and I'm sitting next to a window. Its a bright sunny day. I picked up my camera. The settings it was on were f/1.8 and PROGRAM. I didn't change these. (play along at home by setting it the same)
I then pointed the camera out the window into the bright sunshine and took the photo. Then I pointed the camera under the desk that I'm sitting at, fairly dark, and shot. Very noticable difference in shutter speed. For outside I am guessing (and it is truely only a guess) around 250th, under the desk it would have had to have been 15th or slower. Now, PLEASE do this yourself and see! IT WORKS.
(I just did it again, in case - exact same result)

Regarding my initial question - I'm guessing the answer is NO. However, please feel free to email me on and leave this space for anyone that can answer my question, even if the answer is a simple NO.

Have a nice day and I hope to hear from you via email,

To love this comment, log in above
9/17/2005 7:43:45 PM

Jon Close
BetterPhoto Member Since: 5/18/2000
  Hi Chris.
Hi Chris,
Re flower v. cloudline and window v. desk, yes the camera will chose a higher shutter speed for a brighter scene and a slower shutter speed for less light. But it is NOT computing that shutter speed with respect to the aperture you've set. It is computing it with respect to the aperture it has calculated - the value it displays in the viewfinder.

Re the flower v. the cloud line. The flower was not as bright a scene. Program probably determined 1/125 and f/4. Setting f/1.8 was +2 stops overexposed, within the latitude of print film (generally about -2 to +3), so the negatives and prints looked fine. Same when you turned and took the much brighter scene with the crane and reflective water. Program probably computed something like 1/250 f/11. Setting f/22 is -2 stops, again within the film's exposure latitude. "Good enough for government work," but it is not Aperture priority autoexposure.

As I tried to illustrate in my test, if the camera is working in Aperture priority - metering THE SAME SCENE - it should change the shutter speed when you change the aperture setting on the lens. The AE-1P does not do this.

To love this comment, log in above
9/18/2005 8:17:50 AM

Chris Jacko   Well I am yet to notice any problems with doing it this way, and, as you said, if the camera is adjusting the shutter speed according to the amount of light to within the films own 'margin for error', than it is effective.
Not ideal, but effective.

After I wrote that message I put film into the camera and took some photos, so I cannot test your method at this stage, unfortunatly.

However, in light of what you have said, I have managed to confuse myself about setting shutter speed and aperture manually.
In the AE-1, which I had a brief play with, correct exposure is achieved when the needle is in the middle, at 5.6
With the AE-1P, however, there isn't a need, but LED's. The manual says that the exposure is incorrect when the lowest or highest f stop number is blinking. Does this mean that when it is not blinking it is correct? Does the f/5.6 (and the little line next to it in the viewfinder) mean anything?
Generally I am sitting here, at 2AM, confused and wishing that there wasn't undeveloped film in the camera...
I hope you can help me, and a appologise for any hostilities I have show towards you.

To love this comment, log in above
9/18/2005 8:58:47 AM

Glen Taylor   "..if the camera is adjusting the shutter speed according to the amount of light to within the films own 'margin for error', than it is effective. Not ideal, but effective."

Hah! Wait til you try reversal (slide) film. I've ruined photos that were 1/2 stop over.

This whole thread seems like a fine rebuttal to arguments that heavily automated cameras are great for beginners. Never did understand how anyone trying to master exposure, DOF, etc. could benefit from turning their camera into a very large point & shoot (program or AE mode) unless that's as far as they wished to go in terms of photography.

I started with a simple camera that metered FULLY in manual mode without any additional manipulation. That was a big help. I mastered f/stops and aperture. Then, and only then, I tried automated modes, and only to solve specific problems (just like Peter Burian said the pros did in his NGS book). Great advice, btw.

To love this comment, log in above
9/18/2005 9:55:46 AM

Chris Jacko   I decided to read the manual, again, and read more about Stop-Down Metering. I came upon this.

"CAUTION: NEVER attempt to do stopped-down metering with an FD lens unless there are close-up accessories between it and the camera. If you do stopped-down with an FD lens attached, erroreous exposure may result."

I have FD lenses and therefore stop-down metering is irrelivent to me, at this time.

A question I have, now, is when the manual says change the aperture and/or shutter speed until the maximum or minimum aperture on the lens does not flash for correct exposure, I am sitting here with one aperture and going through server different shutter speeds that are not making the LEDs blink. How can all these different shutter speeds, with the same aperture and same subject under same lighting, all create correct exposure?

To love this comment, log in above
9/18/2005 10:45:04 PM

Jon Close
BetterPhoto Member Since: 5/18/2000
  Hi Chris,
No need to apologize, I understand the frustration. So much for Canon's old tag-line "So advanced, it's simple." Well, only if you've never used another SLR. ;-) If one comes from Nikon, Minolta, Pentax, or even Canon's F- or previous A- models it can be confusing.

Pared down:
Full Program autoexposure - set the lens to A and the shutter to Program. The viewfinder displays "P" at the top and the aperture the program has chosen.

Shutter priority autoexposure - set the lens to A and select the desired shutter speed. Viewfinder will display the aperture value the program has chosen (no P or M in the top right). Blinks if it cannot set the aperture wide enough or small enough for the shutter speed chosen. Change the shutter speed to get desired aperture.

Manual with FD lenses (including Vivitar, Sigma, etc. with "A" setting on the aperture ring) - Similar to Shutter priority. Start with the shutter speed desired, the viewfinder will display suggested aperture value. Then set that value (or other if applying exposure compensation to the meter reading) on the lens. The viewfinder will display M and the suggested aperture value, not necessarily the value actually set.

Manual with FL lenses and similar without "A" setting, or other lenses attached with an adapter - Use stop-down metering.

To love this comment, log in above
9/19/2005 5:56:50 AM

Chris Jacko   OK, just to check that I am understand this properly.

I pick up my AE1P.
I flick the switch to A to turn it on.
I take the lens cap off. (important one :P)
I point it at what I want to photography.
I focus.
I put my aperture ring, for example, to 8.
Do I then wish to see the LED corresponding to 8 lit up in the viewfinder for idea exposure? (doing it a different way to what you said, just making sure)

Thank you for all your help, and thank you for putting up with me and my ignorance!

To love this comment, log in above
9/19/2005 6:43:30 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  Yes, you can set the aperture first, then turn the shutter speed dial until the same f-number lights in the viewfinder.

But it's a bit simpler if you can get used to leaving the lens on A and simply turn the shutter dial until the aperture you want lights in the viewfinder. That way you don't have to remember what the lens was set for, or pull the camera down from your eye to check. Only set the lens aperture ring manually if you purposely want to apply exposure compensation to the metered reading, or to bracket exposures.

To love this comment, log in above
9/19/2005 8:10:15 AM

Chris Jacko   :D

It has taken me a while, but I finally understand what you mean.

By putting it into Shutter Priority and, for example seeing 5.6 in the viewfinder, when I want 8, I would decrease the shutter speed until 8 is displayed, and that way I also know all the info about the shot to write down.


Thank you!
As I said, it has taken me a while to get to that point of understanding, but it just clicked in my head! :)

To love this comment, log in above
9/19/2005 3:55:00 PM

Log in to respond or ask your own question.