- Gallery
- Blog
- Digital Photo Decal
- Home | News
- Assignments/Lessons
- Course Information
- Fall 2009 Archive
forums for photodecal.org
You are not logged in.
Today we talked about the different exposure programs available on the camera.
They're listed here as a quick refresher (as an added note - this is the wiki! Feel free to add/edit all the content)
http://www.photodecal.org/wiki/index.ph … e_programs
Answer the following questions:
What are the advantages of each exposure program? Disadvantages? In what kind of situation would you use or avoid each?
Automatic
Program
Shutter priority
Aperture priority
Manual
As you can tell from this list, there are more permutations for auto/manual control of the four parameters (how many? 2^4 = 16, actually) than what we actually have access to. Think of a new program mode, define whether each of the parameters (Shutter speed, Aperture, ISO, exposure) are automatic or manually defined, and talk about what advantages it has and how it might be used.
Feel free to comment on other students' posts as well.
Automatic-
Advantage: Allows you to take a picture without worrying about the settings.
Disadvantage: Have no control of how the image will turn out. It's all based on the automatic settings.
Use: Basic shooting
Avoid: Pictures with thought that require certain settings to be manipulated
Program-
Advantage: Useful when ISO is all you want control of.
Disadvantage: Again, you lose full control of the picture.
Use: Most pictures
Avoid: Maybe in low-light settings?
Shutter priority-
Advantage: Was useful for getting sharper pictures during the day and (sometimes) at night.
Disadvantage: It was difficult to find the right speed on the first try.
Use: When you need to control the sharpness of a picture, say taking a fountain
Avoid: Fast-paced photography where the right speed needs to be found
Aperture priority-
Advantage: You have full control of what the main focus of the image will be
Disadvantage: With the lens set on automatic, it's sometimes difficult to get the lens to focus on the right thing
Use: When wanting to focus on a main part of an image
Avoid: When you want the whole picture to be sharp
Manual-
Advantage: Complete control over the image.
Disadvantage: It takes longer to get an image
Use: When you want to manipulate all aspects of your image
Avoid: When you care to change only one setting or none at all
A program that allows you to control Shutter Speed, ISO, and Aperture while leaving exposure automatic. This would be advantageous because it would allow you to focus on one part of the picture, control the noise of the picture as a whole, and sharpen (to a degree) what is being focused on.
I think there may be a bit of a misconception about aperture priority - aperture priority simply lets you *choose* which aperture you want to set it at. You could set it at f/2.8 or f/3.5, and have a very shallow depth of field (not everything is in focus). However, you could just as well use it to set the aperture to f/16, so everything will be in focus.
Now here's a question for your proposed exposure program J.P. : if shutter speed, ISO, and aperture are controlled manually, how can exposure be automatic?
So I didn't know if we were all supposed to write up a post or add on to the previous so this is my take
Automatic
Adv - Easy (just point and click)
Disadv - No control over settings
Use - Simple Shots (nothing fancy)
Avoid - When you want to control some aspect of the image
Program
Adv - Allows you to control ISO
Disadv - Creating noise by overusing
Use - To brighten images without flash
Avoid - Abusing the ISO which may create noise
Shutter priority
Adv - Allows control over shutter speed
Disadv - Difficult to set the right speed with enough exposure
Use - For fast movement, like water
Avoid - Setting it too fast in low light (ending up with a black image)
Aperture priority
Adv - Allows one to adjust the depth of field
Disadv - Small aperture results in slow shutter speed creating blur
Use - Capture an image at the highest speed after setting a specific depth of field
Avoid - Setting at such a low aperture so that camera must compensate with a long exposure time
Manual
Adv - Allows for complete control over exposure
Disadv - Takes a long time to configure
Use - To get a very specific/precise type of image
Avoid - Quick shots that need to be taken immediately
New Program: Manual control over both shutter speed and aperture with ISO and Exposure automatic. This would allow for the best exposure while still being able to control for shutter speed and aperture (so I could photograph a single raindrop or something - focusing only on a specific thing at a fast speed)
What are the advantages of each exposure program? Disadvantages? In what kind of situation would you use or avoid each?
Automatic: The best analogue to a point-and-shoot camera, this mode allows you to take a picture with minimal configuration time. It doesn't allow you to set anything of interest, which is generally the reason you bought your SLR (e.g. depth of field, high shutter speed, etc.). It's useful to use this mode when you're just trying to take pictures fast, or you're letting your younger brother take random shots.
Program: Traditionally in this mode one can manually set the ISO film speed here. However, in many DSLRs, this may be set to either Auto or set manually in all modes. Therefore, this mode is similar to 'auto' mode except that one manually sets the ISO, usually to diminish or increase noise depending on the lighting or effect (however, noise can always be increased in post-processing, but it is in general very difficult to remove).
Shutter priority: Manually setting the shutter speed hasn't often proven very useful for me, however it could help in requiring a certain speed for clarity while always having enough light out. For instance, in a fast sports game, depth of field may not be a priority to set as much as making sure you can see the ventilation holes in a player's jersey.
Aperture priority: Extremely useful for low light in my opinion, this mode allows one to manually set the f-stop while having the shutter speed automatically set. Coupled with EV offset, this mode will give a fair trade off of time spent adjusting and qualities we wish to control. It can also be useful for portraits, or other places where we want to deterministically control the depth-of-field.
Manual: Full control over ISO, Aperture, and shutter speed allows extends the range of exposure beyond the EV scale and also allows some portions of your image to be overexposed for either effect or out of necessity. This can take a while to get used to, as it can take a bit of time to get all the settings correct for a balanced shot. It is helpful especially if you're taking pictures of still objects or in certain, more "artistic" scenarios.
My own exposure program would probably take advantage of the flash. Flash output can be varied, and most lenses have digital rangefinders on them. It would be trivial to calculate the output light of the flash at a certain distance from the source, and determine the correct settings of ISO, Aperture, and Shutter speed accordingly. It would be pretty useless in certain situations though, such as when the light could be dissipated or reflected (e.g. in foggy conditions or behind glass).
The flash mode is an interesting one, Christoffer - it doesn't have so much to do with the exposure as it does with how the camera does the metering. Currently this is done purely by "metering sensors" that just take the available light, and using different algorithms (you may have seen evaluative, center average, spot, etc.), calculate an exposure.
Using preflashes would certainly have applications when doing flash photography, where the amount of the flash that is going to reflect back isn't necessarily represented by the existing available light, and I'm actually somewhat surprised we don't see the use of this, or at least the option (although constantly firing preflashes to meter would get somewhat annoying).
In very dark situations, you will notice your flash fire some preflashes, but this is for the autofocus rather than the metering.
Also, just as a note, you can comment on the posts by other students, as I might imagine the responses will get repetitive after the first few. I am fairly impressed by the wide variety of uses most of you are finding for the different modes, however, especially among the shutter/aperture/manual priority modes.
Program mode seems a pretty solid choice for when you're on the go and want to snap pictures quickly under a variety of lighting conditions, but still want an overall level of control on the noise and are willing to sacrifice a fast shutter speed. If you're in low light in automatic mode, the camera will probably go for the widest aperture and whatever ISO it takes to give a somewhat reasonable shutter speed, but if you're in Program mode you can take the hit with a slower shutter speed and thus minimize noise...plus, if you've got a tripod, there's now no problem at all (automatic, however, wouldn't realize that shutter speed isn't an issue).
Re: flash exposure program, isn't that what some of the E-TTL stuff is? I don't know anything about it as I don't have an external flash.
My idea is maybe in the spirit of A-dep. Instead of specifying the desired DOF range and letting the camera figure it out, I think it would be useful to specify a level of motion blur (including none) and have the camera figure out the necessary settings (mainly exp time/aperture) to achieve that level of motion blur.
Obviously not the easiest thing to do. You would have to assume a stationary/tripod setup. You would need to know distance to target, which some lens' can already do? Or autofocus can be used for ranging? You would also need to know how fast your subjects might be moving perpendicular to the frame. Hopefully this could be determined by the camera or maybe just dialed in. I was thinking of your indoor track runners picture as something that could benefit - automatically pick necessary ISO for instance to prevent blur.
What are the advantages of each exposure program? Disadvantages? In what kind of situation would you use or avoid each?
Automatic
adv: Ease of use, no need for knowledge
dis: Cannot make specific changes
use: When you do not know much about photography
avoid: When you want a picture to look a specific way,as it may not take the picture with the correct focus, depth that you want
Program
adv: It is the easiest to use after Automatic.
dis: You cannot control blur or depth of field really.
use: When you do not have time to change both the shutter speed and the aperture, when you only want to change the ISO.
avoid: Maybe is you were taking pictures in low light where the subject was moving quickly, you would want to use either Shutter or Aperture priority to get control over the aperture and shutter speed so the picture takes quickly.
Shutter priority
adv: Lets you determine how long you want the shutter open.
dis: Cannot control aperture, so you can't really control depth of field.
use: If you are taking a picture of running water and you wanted the blur effect you could use it. Similarly if taking pictures of lights or stars you would use shutter priority to keep the shutter open for longer periods of time.
avoid: When you want to control the aperture to control what part of the picture is in focus.
Aperture priority
adv: You can control the depth of field, so you can control how much of the picture is in focus.
dis: You cannot control the shutter speed, so the shutter may be open too long or too short.
use: When you want a certain part of the picture more in focus than the rest, you can set it to the largest aperture to get the smallest shutter speed possible.
avoid: When you want to control the shutter speed to a specific amount.
Manual
adv: You have complete control.
dis: It is much harder to use, takes a longer time to set up.
use: When you want complete control of everything and when you want to control the exposure.
avoid: When you are working in a quick environment, when you do not care about contorlling the exposure and only want to control ISO, aperture and/or shutter speed.
I think an interesting program to use would be where you could control only Shutter Speed and Exposure, and the ISO and Aperture would be controlled for you. In this circumstance you could control how exposed your picture would be and how long the shutter stays open. It would be good for taking pictures of running water, moving lights and general low-light photography. However you could not control how much the picture is in focus, which I think would be the worst part of this program. I feel as though not being able to change the ISO would not be as big of a deal (although still problematic, especially for professionals and people who are actually good at photography) as most people I see shoot rarely change the ISO.
dylannelson wrote:
Re: flash exposure program, isn't that what some of the E-TTL stuff is? I don't know anything about it as I don't have an external flash.
Somewhat - TTL is what the flash uses to meter and determine what flash output it should have. I think the suggestion was more along the lines of firing preflashes to get a better idea of the scene, rather than just relying on natural light.
dylannelson wrote:
My idea is maybe in the spirit of A-dep. Instead of specifying the desired DOF range and letting the camera figure it out, I think it would be useful to specify a level of motion blur (including none) and have the camera figure out the necessary settings (mainly exp time/aperture) to achieve that level of motion blur.
Obviously not the easiest thing to do. You would have to assume a stationary/tripod setup. You would need to know distance to target, which some lens' can already do? Or autofocus can be used for ranging? You would also need to know how fast your subjects might be moving perpendicular to the frame. Hopefully this could be determined by the camera or maybe just dialed in. I was thinking of your indoor track runners picture as something that could benefit - automatically pick necessary ISO for instance to prevent blur.
This is a very interesting one - to date there's nothing like it, but there are ways that it could be implemented. Currently, on just about every camera but Canon, you can set an auto-ISO mode with a minimum shutter speed - say 1/200s. Everytime the shutter speed dips *below* that minimum, the camera will boost the ISO (and/or aperture, depending on the mode), to ensure that your shutter speed will always have that as a minimum.
There's not really a way to automatically calculate what shutter speed you need, although as explained here, you can do this yourself:
http://photodecal.org/wiki/index.php?ti … speed_rule
An interesting idea might be to install the motion-sensing gyroscopes used for image stabilization to calculate your rotational speed, and combined with the focal length of the lens, figure out a minimum shutter speed.
Subject motion is a bit trickier, since subjects are fairly unpredictable in their movement. We would probably need to see a shift away from using dedicated AF and metering sensors and exclusively using the "Live View" mode (using the actual image sensor, like most consumer digicams but few DSLRs do).
AV mode = all you need. (sometimes TV).
Shutter speed changes commensurately to aperture. Why use manual mode when you have +/- exposure compensation?
pt wrote:
AV mode = all you need. (sometimes TV).
Shutter speed changes commensurately to aperture. Why use manual mode when you have +/- exposure compensation?
To be perfectly honest, I probably spend 95% of the time shooting in Av mode myself. In most cases the aperture is the most important element to control, and the shutter speed justs sort of follows from that.
However I find even Av to be far from perfect - ISO is still somewhat static (depending on your camera), and I might argue that it's the most irrelevant exposure parameter of all, and is the one that should be left to float while shutter and aperture are controlled.
Manual mode brings up an important point, and there is a rather large anti-automatic sentiment from new beginners and oldies who regard manual as superior - this applies to both focusing and metering. Coming from an engineering/computer science background, I don't really worry about leaving the camera on automatic and "not having control". One of the themes in this class is that it's perfectly OK to leave your camera on automatic modes (aperture priority, shutter priority, auto-ISO, etc.). As long as you know *how* these algorithms work, you still know exactly what your camera is doing and can adjust it at will (with +/- compensation as you mentioned), in which case an "automatic" program mode like Aperture priority still gives you complete manual control, while processing and being faster and more accurate than any human could ever be.