What advantages does manual mode have over aperture priority mode?

Question

I'm wondering what are the most compelling reasons to switch to manual mode on my DSLR. I mostly just use aperture priority mode so I have good control over the depth of field combined with an awareness of the shutter speed that goes with it. My photography is mostly done wandering about with camera in hand, or occasionally on a tripod. I don't do studio photography and I just use the natural light.

I did learn how to take photos manually (with an Olympus OM-1) so I know how to do it, but I enjoy the extra convenience of aperture mode, particularly being able to take the photo quickly and capturing the moment rather than fiddling with dials and missing the shot.

So what would be some key advantages of using manual mode for my sort of photography that are worth the (small amount of) extra hassle involved?

And do you have any tips to minimise the downside (other than practicing to be quick)?

Answer 1

I typically use aperture priority as well, but I also work a fair bit in manual mode. The typical case for me is if I am in an environment where the lighting situation is quite static, but the subject may have a lot of contrast. Here I switch to manual mode and shoot a few test frames to pinpoint the exposure (typically I try to spot meter on a white surface, and then overexpose that reading by 1.5-2 steps as a first guess).

The main advantage is that you are in full control, and the camera will not be "fooled" by unexpected contrasts in the frame. The downside is that it is a bit slower to change exposure in case the lighting situation changes.

Answer 2

The biggest benefit I can think of is consistency between shots.

This is normally not much of an issue, but when you are wanting to capture the changing light in a scene for time lapse or do panorama stitching the consistency becomes really important.

Answer 3

Aperture priority can be ideal for a walkaround mode, especially when combined with exposure compensation.

I only tend to flip to manual mode when I'm shooting a lot with the same lighting, or rapidly changing lighting -- so things like food photography (where dark meat or glistening glazes can trick the metering), or fireworks where the automatic metering may pick up a previous shot, or not understand why you're taking a photo of a blank scene.

Answer 4

Manual mode can give you more consistent metering when you're taking several photos in a scene. For example, suppose that you're photographing a person whose body is fully illuminated but whose face is partly in shade. If you take a full-body image and then a head and shoulders portrait, the metering could end up different because the percentage of the frame that its brightly illuminated will change. But if you're in manual mode, you can select the "right" exposure and then both will be consistent.

Answer 5

If your subjects stay the same but your background changes in luminosity greatly. I was shooting sports indoor with a door to the outside open, so my subjects would have gotten real dark if they went by of the door.

Also, if you want to maintain a certain shutter speed (freeze action) and aperture (for subject isolation), and you don't have TAv mode or equivalent, you would use manual mode. You can increase ISO through software (essentially it is the same as hardware ISO), although if you need to change the ISO significantly, you need to use RAW or the JPEG tone curve will eat the data in the shadows.

Manual everything makes it a lot easier if you are doing shoots for stuff like events, sports, portraits, etc. Often, you want to post-process the first picture and copy all of the settings to the following ones. If your camera is changing the exposure or WB between shots, it makes it harder.

Lastly, manual mode is great for flash photography when and mixing ambient with flash. There are some cases where aperture priority can work better, with auto ISO off.

Answer 6

I prefer manual mode for a few areas:

1) stage fotografie. Usually, on stages the light has very high contrast. Any automatic mode most of the time will blow the faces because it is trying to get all the dark background to 18% grey.

2) panoramic fotos. Having inconsistent exposure for the frames is a real pain in stitching them together, so I'll use manual mode for these.

3) other high contrast scenes (person in front of window). The automatic mode does not know if I want the background properly exposed or the person in front of it, usually the person is too dark and the window too light. Using manual mode I decide which one is important for me.

4) manual wireless flash. I use non-TTL strobist flash a lot, and in these cases the automatic modes do not know about the extra light from the flash, so I need to go manual.

I use automatic modes when I just want to make a quick picture to show on twitpic or facebook.

Answer 7

Sometimes the amount of exposure compensation available (ie +/- 2 stops) in Aperture priority mode might simply not be enough.

Answer 8

Reading through this article about the zone system (found from this answer) made me see how using the zone system would be useful and require manual mode. Basically using a spot meter (for me, the one built into the camera) to find the exposure for the part of the photo you want to appear with a particular brightness, and setting the exposure accordingly.

Of course, you could make a fair guess and use exposure compensation. Or suck it and see with viewing the result on the back of the camera, adjusting and retaking the photo (for static subjects). But that did seem interesting.

Answer 9

The main reason I switch into manual mode is to create shots that I know aperture priority won't do.

Silhouettes or intentionally over/under exposed shots for example. Aperture priority is great for 'normal' or 'properly exposed' shots, but not so great once you want to start experimenting a bit.

A recent favourite of mine is a very high contrast shot I took from inside a tunnel looking out into the bright sunlight. This was well outside what the aperture priority mode on my Canon 400D would be happy doing.

Answer 10

As well as the reasons of consistency between shots (either for high-contrast photos in fairly consistent lighting or for stitching shots together), I also use Manual when I'm using a flash indoors.

Might be just due to lack of effort to learn how to shoot Av + flash on my part, but I find it much easier just setting it in full manual with f/4, 1/100 ISO 400 (or thereabouts) and letting the E-TTL flash metering do its thing.

(this is for shooting events indoors)

I also find that shooting indoors in a location with large windows makes it worth being in Manual mode as well. Otherwise whenever there's a window in the frame, you'll have the meter under-expose (in the day) or over-expose (at night) depending on the brightness outside. This seems to be more important with wider lenses (with a long telephoto I guess you're getting much more subject than background anyway most of the time, so the frame is more likely to be more consistent).

Answer 11

Full manual control is also necessary where you are taking shots, for example inside a building, where you perhaps need to bracket exposures for HDR where there is a high dynamic range, or where there is just inadequate lighting. In these circumstances exposures longer than 30s may very well be needed, and most cameras under aperature priority will only time a shot for a maximum of 30s. Use manual exposure and the bulb setting, using a timing device to time the shot.

Answer 12

I find the question similar to "what advantages does shutter priority mode have over automatic mode?"

The answer is, plenty! For example, this picture was taken with shutter priority mode to capture motion blur:

I wanted motion blur so I selected 1/20 s exposure. I also wanted the background to be sharp. Fortunately, I have a 18-55mm f/3.5-5.6 IS lens. At this 33mm focal length, the maximum aperture is f/4.5. I knew the camera will select an F-number of at least f/4.5 because nothing else is physically possible (it selected f/5 automatically). If I had an extremely fast zoom lens with much wider maximum aperture, I would probably have used manual mode instead of shutter priority mode so that there's no danger of the camera automatically selecting an aperture that would blur the background. Ok, given the sheer amount of light in the scene, and given that the lowest ISO my camera supports is 100, there was no danger of automatically selecting a wide aperture (it selected ISO 125 as the ISO, only slightly larger than the minimum ISO 100), but if there's a lower amount of light, that's a potential danger.

The tractor was probably about 10 meters away (hard to say, because I can't know if the focus is on the tractor or on the house behind the tractor). Hyperfocal distance at the automatically selected aperture is 11.4 meters. If I had a fast F/1.8 zoom, the depth of field would be only 7 meters behind the subject at F/1.8, so the background would appear blurred if the focus was at the tractor and not at the background (at the high speed of the tractor, it's hard to select which object to focus on!)

If you're taking images of quickly moving objects in the dark and DON'T want motion blur, or using a long lens without image stabilization with its maximum aperture in the dark, you may have a constraint for both the aperture (the largest the lens supports) and the exposure time (the longest acceptable so that the photo won't be shaken and the moving objects appear sharp).

In such a scenario, you will adjust the exposure by changing the ISO level, using manual mode with specified aperture and exposure time, and auto-ISO.

Also, sometimes, you may want to capture a certain pre-defined amount of motion blur, either blur of the background or blur of the moving object. Then you'll have to set the exposure time to a certain number. Now, if in such a situation, you also want precise control of the depth of field, you have a constraint for both the aperture and for the exposure time. Then you'll use auto-ISO to adjust the exposure.

So, as a summary, I find the manual mode with auto-ISO extremely useful. The auto-ISO is useful on my camera from 100 to 3200 (well, you can set it to allow 6400 as well, but there will be so much noise that it may be better to manually choose 6400 if needed, or temporarily adjust the maximum allowed auto-ISO to 6400 before shooting and setting it back to 3200 after shooting). This 100..3200 is 32 times difference, or 5 exposure values. That's plenty for many situations.

Manual mode without auto-ISO is usually the mode of choice for astrophotography.

Answer 13

TLDR summary: so the photographer can be intentional about exposure, rather than having camera software engineers decide for you.

With anything other than manual, you are relying on the algorithm of your camera to decide your exposure. Even in Aperture Priority mode. This is bad because 99.9% of the time it doesn't match what you intended as a photographer.

Don't believe me? In aperture priority mode, recompose (e.g. reframe) your scene with your camera without changing the lighting or moving your subject(s), and you'll get a different exposure value from the camera even though the light from the subject(s) reaching your camera has not changed. The only thing that changed is your camera's best guess of what to do, according to the data from all those metering sensors, the metering mode and a host of other parameters processed by a black-box algorithm only the engineers truly understand -- so it's unpredictable to you and me.

The camera has no idea of what your intent is or what part of the image is important. Its best guess is that the subject is usually in the center, which is a good first order prediction for casual photography, but also often not how we compose (rule of thirds?)

Then there's the fact that all camera meters are looking to normalize for D65 gray. Even if what you are shooting is white. Or black. Or any other luminosity that isn't D65 gray. So point your camera at a white wall, and it will try to expose to make it D65 gray. It won't give you the exposure that matches what you are trying to show with your photograph (your intent), even if you spot meter.

The reason to use manual is so you can be intentional about your exposure. Blacks can be black. Whites can be white. And so on. The alternative is to fight the algorithm using exposure compensation, changing metering mode, moving the focus point etc, which I would argue is not faster because it's mostly trial and error.

That's why we use manual. Because only we know what image we're trying to make and how it should be exposed. So just dial that in using manual exposure, rather than having the camera do guesswork and then trying to game the camera's algorithms.

Answer 14

Manual exposure is necessary whenever you are using neutral density filters, or any other filters which significantly darken or limit the amount of light coming into the sensor. You don't need to set manually with a polarizer or other filters which only lessen ight by a stop or so. But If you don't set exposure yourself with darker ND filters Ii.e. Lee's Big Stopper), the camera will almost always not correctly compensate, and it's difficult to gain control over any changes you make to the settings.

Answer 15

A reason I use it, is because setting only the aperture often is not enough.

Assume I am in a fairly dim room taking photos of my son. I want to use aperture f/1.8 because of that nice blurry background (and of course because I need any light I can get). If I am in AV, then the camera might come up with settings like [ISO 200, 1/40th]

Because he is moving alot, a shutterspeed of 1/40th is not fast enough and will result in many unsharp pictures. (Which can be a desired look, but I do not want that most of the time).

Of course I can use TV instead, but this might change the aperture depending on the brightness.

So I choose M and select my aperture and a shutterspeed that I think is fast enough (say 1/160th). I set the ISO to auto, and in the example above it would select it to be 800. This is fine by me, and i do not care too much about the ISO. (of course lower would be better .. but if I do want to use a given aperture and shutterspeed .. that is how it is)

So basically like this I have an "ATV" Mode where only the ISO is varied by the camera. This of course is not as flexible as AV or TV, as the mentioned setting (1.8 @ 1/160th) in bright sunlight will result in overexposed pictures even at ISO 100. So you may have to adjust those settings when the light changes - but you do not have the change the ISO/any setting every photo.

Answer 16

Also, if one is using any kind of external meter (eg an incident light meter, or a flash meter, or a spot meter if using a camera that has none), manual mode is easier for dialling in the values from that meter than arguing with exposure compensation....

Since it bears repeating: Manual flash by guide number (where you set the camera to calculated values, period), and also use of old-school flashes that do autonomous flash metering (aka telecomputer) but need the camera set to predefined values.