Stopped Down Metering - Totally Confused (Canon AE-1 Program)

<p>Hello everyone! long time, no see! I'm back since my first post 5 months ago. I finally realized that Photo.net might be an awesome place to ask my photography questions, as Google always brings up forum posts from this site whenever I type something in. The responses are always well thought out, easy to understand, and unlike many a Flickr discussion, actually clean and unoffending.</p>

<p>My question is about stopped-down metering, specifically on a Canon AE-1 Program with a 50mm Canon FD lens.</p>

<p>By design, the camera always shows the preferred aperture that it calculates to be the best for producing a balanced exposure with its center-weighted, open-aperture metering. For instance, I pointed the camera at my bottle of lens cleaning under my desk lamp. I chose a shutter speed of 1/15, and the camera showed / recommended an aperture of f/5.6.</p>

<p>Now, I just discovered the stop-down lever on the side, and am actually amazed at its ability to show the depth of field I would be working with but for this forum post, I am asking about how it measures, and if this metering has any benefits over it's default.</p>

<p>With the lens stopped down, yet wide-open at f/1.8, I get the same reading. The meter on the right show f/5.6, with the shutter speed at 1/15. What confuses me is that when I move the ring to f/5.6, the meter shows a dropped preferred aperture of f/2. I move the shutter speed dial to 1/2 sec, and it shows f/5.6.</p>

<p>What am I missing? Am I doing something wrong? How can one metering mode result in a significantly slower shutter speed than the other? Is the metering system on the right changed, so that the values no longer represent what they originally did?</p>

<p>Am I to assume that the stopped down metering is right, and that the open aperture metering is wrong, which in this case would result in a vastly under exposed image considering the open-aperture specs were f/5.6 at 1/15 sec, and the stopped-down specs were f/5.6 at 1/2 sec.? Or is it the opposite, with the stopped-down metering resulting in an overexposed image?</p>

<p>I am unable to answer your question about that DOF button on your camera, although I have one too I have found it the most useless piece of plastic ever invented. I would however like to clear something up about metering issues, not to insult you by any means, but as extra information that you should be aware of. The camera always lies about metering. It never gives a correct metering ever. This is the first golden rule that a photographer learns. Why? Because it seeks to reduce everything to neutral grey. OK, take a complete white piece of paper or card. Take a photograph of that white, let it fill the viewfinder, But make sure you take a photograph at the camera's suggested exposure. Now look at it, or the histogram. The image will be grey, not white, and the histogram will not be in the middle as the camera told you, but it will be to the left of middle. If you do this for black, everything above will be reversed. So whenever you meter something, say something that is bright, you know that to get a better exposure you should over-expose by at least one stop, sometimes two stops. The same goes with the dark shadows, if you are metering for something here and there is a lack of brightness about your scene then whatever the camera suggests as the correct exposure, pull back maybe two thirds to 1 stop exposure to a correctly exposed black. However, as far as blacks are concerned, if you have 16 bit raw processing then this part of photography is no longer that important, it still is in film photography, but not digital. But the highlight issue is. The only thing I can say about the DOF button is that when you press the DOF button it physically changes the aperture size in the camera, and the camera interprets this as just another exposure, so I would suggest that this mertering that you see is nothing, just ignore it, because as I understand things, the DOF has to stop down everything so that you can see whatever it is you are supposed to see. However, I found this thing ridiculously infuriating because I have never seen any DOF, just a blackened gunge of an image that makes no sense whatsoever, and certainly gives you no sense of what is in focus and what is out of focus. </p>

<p>The Canon AE-1P is a film camera, which does not produce a histogram so Mr. Watts answer is not relevant to th OP's question.</p>

<p> </p>

The stop down "mode" is not for metering the scene. Your AE-1 properly meters with the lens wide open. The lever you

speak of is to preview the depth of field, nothing more. The lever stops down the lens to the taking aperture. Use any

settings from this mode at your own risk.

 

 

The term "stop down metering" is used when attaching a lens to a camera that cannot control or read the aperture of the

lens. Often used when attaching, say, a Minolta lens to a Canon body with an adapter.

<p>Well, I saw canon AE 1 program, and that made me think he was using AE program on a digital. However, Mr.Watts's answer about the camera's metering methods is Correct, this applies to both film and digital, except in wfilm you expose for the shadows, digital other way around. And again, with film, the camera always lies about exposure readings is also true. His shadows will always read an over exposure making black less black as the camera attempts to reach grey. So Bob, you could have supplied more help to our colleague other than simply saying that my answer was not applicable.</p>

<p>The first thing you need to do, if you haven't already, is to read the manual. You can download a copy from the following site:</p>

<p><a href="http://www.butkus.org/chinon/canon.htm">http://www.butkus.org/chinon/canon.htm</a></p>

<p>The following thread from the Canon FD forum may also be of some interest:</p>

<p><a href="../canon-fd-camera-forum/00VDFw">http://www.photo.net/canon-fd-camera-forum/00VDFw</a></p>

<p>On the AE-1P, stopped down metering only works with non-FD lenses, i.e., lenses that do not have the full compliment of levers and signal pins needed for full aperture metering. With FD lenses, you can only meter at full aperture on the AE-1P. Non-FD lenses include Canon's FL and R breech lock lenses, and lenses with pre-set or fully manual apertures.</p>

<blockquote>

<p> with film, the camera always lies about exposure readings is also true</p>

</blockquote>

<p>Not really. The reflected meter of the Canon AE-1 Program, or any camera, film or digital, is designed to read average scenes of average tonality accurately. It's only when the scene is not average such as scenes containing overall dark or light tones that the exposure will require compensation. That compensation will vary with the degree the scene deviates from "average". This does not mean the meter is "lying". It means that you need to understand how a reflective meter works and how to use it to obtain correct exposure. The manual will explain this. <br>

Gordon explains the stop-down process well when using non-FD lenses. With Canon FD lenses, you don't need to use stopped-down metering. You meter with the lens wide open. Again, the manual will explain this.</p>

<p>Hi Louis, Ok, should have been more precise, it's true, for example when you meter a grey card, it's pretty good at an accurate exposure. I guess it's obvious I don't mean "lies" but this is the word that stuck with me ever since I was in college in the darkroom, "the camera lies" was just one of those flippant expressions that we all understood.</p>

<p>I was called away to breakfast when I started posting my reply, I couldn't add more at the time, I just wanted the OP to know digital discussions re his film camera question did not relate. Since others have replied, I guess all is now OK.</p>

 

<p>One thing that should probably be added is that there is no advantage in using stop down metering, that is stop down metering is not any more or less accurate than open aperture metering. With any camera/lens combination that allows open aperture metering, you might as well use it, because it is definitely more convenient. Also, with some camera/lens combinations that are designed for open aperture metering, it might not easily be possible to use stop down metering, but for camera lens combinations that allow both metering methods, the results should be identical.</p>

<p><br />Stop down metering isn't a "mode" like centre weighted, spot, average etc, it's an obsolete system which was used in earlier SLR's. In the early days of through-the-lens metering, when viewing and focussing were done with the lens at full aperture, there was no way of "telling" the metering system in the camera body what taking aperture the lens was set on, i.e what aperture it would stop down to when the picture was taken. This meant that you had to manually stop the lens down from full aperture to the taking aperture, to enable the metering to do its job - this was usually achieved by a button or lever which also served as the depth of field preview.<br>

"Modern" film SLR's like the AE1P have a system called meter coupling. whereby the aperture set on the lens is transmitted by an extra linkage back to the camera body. This then makes a calculation to work out the exposure based on the reading at full aperture, but taking into account the difference between the full viewing aperture, and the taking aperture. Its more accurate because more light is available to the meter, and obviously simpler to do – so the depth of field preview on these cameras is just that, and was not intended to be used for metering – at least with meter coupled lenses such as the FD series. You don't need to worry about stop down metering at all unless you are using older lenses such as the FL series which didn't have this feature.</p>

 

<p>So stopped-down metering doesn't work on my FD lens and that is why I am getting drastically different exposure reading? Or do I not know how to use either metering now?</p>

<p>There is a lever in your lens that tells the body to what aperture the lens is set to. The camera uses this information to calculate the exposure, it does this with the lens wide open so it is easier to focus and compose. Older Cameras with a built in meter often had a lever on the side of the lens mount that you pressed and it stopped the lens down and took a reading, this is stop down metering. Your Canon does not need to do this. When you stop the lens down, you are reducing the amount of light passing through the lens thus affecting the meter. The meter still sees what lens is set to and takes that into account. Your camera is not made to meter this way with the standard lenses. If you had an older FD lens that is a preset or something similar, then you would stop down to meter. A preset lens is one that you set the aperture and the lens closes down, you have another ring that you twist back to wide open so you can focus and compose, right before you press the shutter button, you twist the ring back and it stops at the setting that you chose previously, the preset.</p>

<p>Alright, so even though my 50mm FD lens has a stop-down LEVER, that does NOT mean the lens is capable of flawless stopped-down METERING? All that means is that I have the ability to preview the depth of field? <br>

ot </p>

<p>Yes. Stop down metering is for lenses that don't communicate with the camera. You set the aperture and stop down and see what the meter reads. If it needs more light then you either open the aperture more or slow the shutter down. If it needs less light then you need to close the aperture down or speed up the shutter. All of this is done with the aperture closed down to the specified setting.<br>

The aperture lever is on the mount side of the lens, one adjusts the aperture and the other holds the aperture open until the mirror flips up out of the way, then it closes the lens down to the setting on the lens.</p>

<p>On your Canon AE-1P stop down metering doesn't work with your FD lens. On some cameras you could do either especially the Nikons.<br>

As you asked what's the advantages and disadvantages compared to full aperture metering? Advantages is small is any. Full aperture metering is convienient as you don't have to push the stop down level to meter and release it to focus. Full aperture use maximum aperture of the lens to feed the light sensor and thus it can meter at lower light level than stop down. When it's rather dark, stop down metering may not feed sufficient light to the sensor for accurate measurement. Stop down metering does have an advantage (but it's nil if everything is well made) that the meter measures the actual amount of light that will reach the film while full aperture metering the meter will have to make a subtraction based on the amount of movement the aperture coupling is telling the meter. If the aperture diaphram and this coupling are not made precisely there is possilby some error. However, in my experience this error if any is very small and not important.<br>

Many Nikons you could do the stop down metering even with lenses designed for full aperture metering by defeating the aperture coupling. For example you could do this with Nikon F2A, F2AS, F3, FM and FE.</p>

That lens and that camera are both capable of accurate stopped down metering.

 

What you have to do is push in the stop down lever/dof preview lever, and put you aperture to where you want it, you then

adjust your shutter speed (and or iso) until the small red square lines up with the 5.6 number, the midpoint, on the

aperture range in the viewfinder, this gives you an accurate midtone reading. The key to understanding this is that the

aperture numbers in the viewfinder become irrelevant, they are no longer aperture readings as the meter scale is now

different, all it is is a needle that needs to point horizontally for a correct midtone exposure.

 

There is no advantage to using the camera like this though, however the meter is just as accurate, all it allows you to do

is use older lenses that didn't have the same level of automation, it also helps with dof preview but it makes accurate

focusing more difficult and the viewfinder brightness is much lower.

<p>As Scott pointed out, the OP did not understand the metering needle correctly in stopped down:</p>

<blockquote>

<p>The key to understanding this is that the aperture numbers in the viewfinder become irrelevant, ... the needle ... needs to point horizontally for a correct midtone exposure</p>

</blockquote>

<p>Then, there is nothing wrong with what the OP observed:<br>

With the lens stopped down, yet wide-open at f/1.8, ... The meter on the right show f/5.6,(this means the needle is horizontal, pointing at the specified position. This means the correct aperture is 1.8) with the shutter speed at 1/15. What confuses me is that when I move the ring to f/5.6(now you chose a little more than 3 stops smaller aperture), the meter shows a dropped preferred aperture of f/2(this means the needle is not horizontal, i.e underexposed situation). I move the shutter speed dial to 1/2 sec,(now you have about 3 stops more of exposure time) and it shows f/5.6.(meaning the needle is horizontal and the exposure should be fine)<br>

However, like many already said, the manuals warned not to use FD lenses with AE-1, AE-1P in stopped down because of some mechanical issues. The T90 handles this well, check out manuals for the A-1 </p>

<p>The camera is not made to take into account stop down metering with a normal lens. When you stop the lens down, it will change the reading of the meter because there is less light getting in. Page 52 of the manual states "NEVER take a shot before releasing the stop down lever or exposure may be incorrect." I never did see in the manual about any mechanical issues with stopping down an FD Lens.</p>

<p>I have, or had, an AE-1P and thought it was a wonderful, full featured SLR w/ a very bright focusing screen, AE lock, and a terrific shutter sound. "Snick". Wonderful camera that could also mount, and meter, w LOTS of lenses w/ an adapter. It's perfectly capable of manual metering, as well as stop down metering (only w/ non Canon lenses used w/ an adapter). You're out of luck w/ the DOF preview. Oh sure, it's allegedly there by the lens mount, but it's so convoluted to use it isn't worth the trouble.</p>

<p>To manually meter in stop down mode (again, not possible w/ a FD lens), you'll need an FL lens or a non OEM lens w/ an adapter. You first focus, stop the lens down to working aperture, and adjust your shutter speeds and/or lens aperture until you get the 5.6 LED to light up in the viewfinder. This can be confusuing until you figure it out. On this camera, used in manual stop down mode, 5.6 does not mean that the aperture is at 5.6. It means that your exposure is now correct. You can light up the LEDs above or below it to intentionally over or under expose your shot. 5.6 is just your reference point. It's an LED equivalent of the center mark in match needle metering. If you're using the camera in A or P modes w/ an FD lens, then 5.6, as well as all the other LED info in the viewfinder, indicates the actual aperture that the camera has chosen. This is confusing even after you've read the manual, but that's how it works. </p>