Please read this in the context of “the user being able to control the exposure with Aperture”. Everything then falls in the place. Please read previous comments too.

Of the three elements of the exposure triangle (ISO, Aperture and Shutter Speed), ISO is the property of the film (or the sensor in case of dslr) which when considered a constant (since high ISO is not recommended in any case), Aperture forms half of the equation in terms of exposure.

If you have noticed, in fully manual mode, you cannot choose the exposure setting, the exposure is defined by the values you choose for ISO, Aperture and Shutter Speed. In aperture priority mode the camera chooses a corresponding shutter speed to get the perfect exposure.

Set your camera in Shutter Priority mode and then what will the camera use for the right exposure? Answer is Aperture.

Shutter Speed is a property of the camera body while Aperture is a property of the lens and Aperture ranges are usually limited by the cost and type of the lens. But that doesn’t make the statement “aperture is not used to control the exposure” any correct.

“Aperture Is Not Used For Exposure”

This is so wrong I’m simply stunned. You might choose not to use aperture to control exposure, however to say that it is not used for it is simply not true and misleading.

My basic problem with this article is that it will mislead some photographers into thinking that there is not a relationship between exposure and aperture, from the beginning of the article: “So the next time you use a wide or a small aperture, know that you are not changing the exposure.” If you are using a manual mode, yes, you are. Speaking of being lawyerly, such a statement clearly assumes that the photographer is not using manual mode and in fact does not know what changes exposure (else they would not need be told such a basic, if misleading, piece of information).

As I said – there is no less complicated way of thinking about exposure than in terms of what it actually means. Some of the actual effects of changing aperture are as you describe but others (chromatic aberration once again) are dead wrong.

I do not think it a credit to the community to assume people can’t understand the relationships between aperture and exposure. Even the camera makers help nudge people in this direction by labeling control some control screens on basic DSLRs. Even if they didn’t, though, “the entry level people” are certainly not being helped if the “powers that be” who try to guide them through the process of learning…think it’s not worth trying to teach them properly!

I think the comment that I am being lawyerly is indefensible when it does seem that in the face of solid info that contradicts the article it has not been amended and instead the focus is on appearances, rather than substance. That is the very essence of a rhetorical device.

“CA is not an aperture effect”… simply means aperture is not the root of the problem, the glass is. I do not and cannot lead people into thinking what they or what they can’t do, I only mention the obvious scientific findings.

The problem with photographers is that they blow exposure our of proportion. And the entry level people find it just too difficult to cope with the complications of the exposure. Here’s my tip: use the auto mode. You shouldn’t need to worry about exposure in 2011 in 90% of the situations.

Half the world believes they are controlling exposure in Av/A-priority or the Tv/S-priority mode. They simply fail to read the camera manual.

An article of this level assumes that the reader and the author are on the same page whereas the basic definitions of aperture, exposure etc. are concerned. So if they want to read about what aperture-priority does, they can read my previous articles discussing camera modes https://www.apnphotographyschool.com/digital-camera-modes/. We’ve discussed the exposure model in detail in one of our previous articles too. So an article which talks about aperture effects does not have to be all inclusive of the definitions of these terms and by no means needs to quote scientific equations and defend oneself like a lawyer. You agree that you do not use aperture-priority (or aperture) to control the exposure (bar the M mode). What you’ve stated about exposure is obvious, established and covered in our article on exposure https://www.apnphotographyschool.com/secrets-exposure/. So we are not working without the actual model or trying to hide it, we are trying to say what it is and what it is not. We’ve also covered the effects of varying aperture, shutter-speed and ISO in various articles previously so this article has been built on already covered and established framework and must be interpreted in that context.

I hope you enjoy being a part of the APN community, we have readers of all levels of knowledge and we try to keep topics uncomplicated and focus on one thing at a time. Hope you’d agree with this approach. Our past articles stand testimony to the fact that the information is thoroughly researched upon and is open to constructive discussions. Thanks for the tip in your last comment.

Wish you all the best!

Onto your second point, let me explain myself more clearly. Here is the equation, universally recognized by optic scientists and serious photographers worldwide, for exposure:

H = Et

H is defined as the exposure (the total quantity of illuminated light), E is the illumination coming into the image plane (at any given point of time), and t is, of course, time. Lux * seconds = Lux-seconds (or esposure).

A fun but surprisingly accurate analogy: When we say somebody died of exposure, we don’t say they died because they stood in the door of an igloo for a few hours. We say they died because they were exposed to the cold for those few hours – the aperture of their dwelling is vitally important in this case! (On the other hand, the people on the Space Shuttle will get very hot very quickly if there is no way to radiate the heat they generate outwards at the rate it is generated – sort of like a big, white, spacefaring igloo with no door at all – as there usually is when you are surrounded by a fluid e.g. Earth’s Atmosphere, but since that gets into radiant heat I’ll stop there.)

Let me repeat: Exposure is the combination of the amount of light, which is controlled by your aperture, multiplied by the time you expose your medium to that light. When I open up the aperture, I’m allowing more light to fall onto the sensor. For the same amount of time, the image gets more exposed.

I kind of get what you’re trying to say here but it is simpler to work with the actual model, rather than trying to protect people from what that actual model is.

About camera modes I will simply say that, in practice (again, this isn’t at all incompatible with the real world), with fixed sensitivity film (or sensors) you often have to make a tradeoff between shutter speed and depth of field effects (I caught myself writing “brightness,” which of course is instead a function of the total exposure). When the image comes out under- or over- exposed, you still do have control over aperture in Tv mode, and you still have control over shutter speed in Av mode, by using exposure compensation. Then, to avoid high ISO noise you can push brightness up in your post-production.

As a parting comment – yes, cameras can hide a lot of the actual workings of photography from the novice. But, as your article attempts to illustrate, the actual effects of varying aperture and shutter speed are very different, so for a photographer to really gain control over their photographs they have to understand that those two elements work together and they have to understand that you cannot just use one.

My personal method is simply, when possible, to decide what I want to prioritize: Aperture (either a smaller aperture for increased sharpness and decreasing other unwelcome effects of the lens – yes, including CA, or a larger aperture for depth of field effects) or shutter speed. If the other value gets too far out of balance from where I need it to be, I typically use Exposure Compensation to adjust the camera’s target exposure – either lighter or darker than it normally attempts to expose. Is this “direct” control over the other value? No. Does this matter? No, because otherwise you’re, as you say, using Manual and not taking advantage of the camera’s specific autoexposure features.

And on that note, here’s my own tip: When you want to isolate and highlight a white object in a busy scene (say a somewhat dark forest) you can simply set the camera to one of the priority modes, and then dial exposure compensation down. The surroundings get darker, but white tends to stay white. Simple!

Best of luck!

Also I’ve substantiated the theory behind the use of Aperture in point number 3, which must be read in its entirety. Unless one is using the fully manual M mode, Aperture does not affect the exposure. That’s because today’s cameras use an inbuilt light-meter and have automatic exposure calculation. Exposure is controlled by using the exposure-compensation button, unless you want to experiment with the full “Manual” mode. See http://www.kenrockwell.com/tech/modern-exposure.htm. Also see point 7 at https://www.apnphotographyschool.com/exposure-revisited-10-exposure-myths-truths/ and https://www.apnphotographyschool.com/control-exposure/.

So depending on which auto-semi-auto mode you use on your camera, you really take control of the aperture only in two modes:
1) Aperture Priority (A mode in Nikon or Av in Canon: You vary the aperture and the camera can get the correct exposure by adjusting the shutter-speed automatically. So you are not setting the exposure.
2) Full manual (the M mode on the dial): You control the exposure by setting the aperture AND the shutter-speed. Camera will not make an adjustment to either and you’ll get what you set. (You’ll have to make sure that the camera doesn’t boost the ISO automatically either.)

In this day many photographers still believe that they are controlling the exposure with the aperture. This cannot be farther from the truth (unless the camera is set to M mode). A simple reference to the camera manual shall clarify this. Aperture is for depth-of-field, bokeh and must be used as such.

If someone starts off thinking that, they’re completely upside-down on aperture. (The article ought to get that straightened out since it has it backwards throughout.) It’d be more useful to say “chromatic aberration is not a side effect of a LARGE aperture,” which hints at the situation that CA is usually seen in, where you have a “small” f-number (which means a large aperture). Technically it’s true either way, but CAs are usually reduced significantly on stopping down (to a smaller aperture).

“Aperture is not used for exposure” …seriously, how do you think exposure is controlled then? Exposure is not defined as the length of time, but the total amount of light falling into the sensor plane (as our handy reference Wikipedia tells us). Discounting ISO (which isn’t actually changing exposure, though it seems to have the same effect), aperture is one half of the method used for varying exposure, along with the time your sensor is exposed.