What is the point of Av and Tv mode, when there is Program Shift?

[Jackofknives]

What is the point of switching to Av (aperture priority) or Tv (shutter priority), when you have Program mode where you can directly shift (Program Shift) your aperture or shutter number and the other options will change accordingly, just like in the Av and Tv mode. You can also change exposure compensation accordingly. So what is the point of using Av and Tv mode then, especially that in P mode you can change both simultaneously make it more convenient and faster (doing everything that Av and Tv can do), it’s like having Av AND Tv mode in the same function.

Thanks

 

[tecboy]

Tv mode is for motion blur, and Av mode is for DOF.

 

[CAP]

WTF?

Tv mode is for motion blur, and Av mode is for DOF.

Never hard that one before.

 

[Jackofknives]

I understand, but, for example, in the Canon MarkII P mode, you can change the Aperture (just like in the Av mode) and then shutter changes automatically according to your exposure compensation, just like how it works in Av mode. And similarly, in P mode, you can change the Shutter speed (just like in the Tv mode), and aperture changes automatically according to your exposure compensation. So there it seems that P mode can do both Av and Tv mode.

PS. I double check the mode. It seems in P mode it's more difficult to go into extremes, like shutter speed 4000. You have to increase your ISO alot first, whereas in Tv mode, you can go shutter 8000 first, then aperture flashes, then you can adjust accordingly. P mode locks you down so you're restricted in your exposure.

 

[Derrel]

Yeah, Tv mode is EXCELLENT for situations when the Time Value (aka the shutter speed) is a critical factor. Good examples include when one wants to do panning shots, and a specific shutter speed is the critical factor. Same thing when showing moving water or waterfalls or whatever; set the desired Time Value, then let the camera adjust the aperture.

In Av or Aperture Value automatic mode, the user determines the needed or desired f/stop. At times, that is the widest f/stop, like f/1.8; at times, a medium aperture; at other times, it is a smaller aperture, like say f/11, which will give deep depth of field. Many times a SPECIFIC aperture is desired, so Av has been a long-time mode offered since the late 1960's or early 1970's in many SLR type cameras.

Programmed Auto appeared in the later part of the 1970's, and has continued to evolve. It can work quite well, as long as the user understands how it works, and what types of settings are critical, or non-critical. The biggest issue in some systems is that once the exposure is shifted, that the camera REVERTS BACK TO BASELINE exposures after every exposure is made, or after each sequence of Continuous motor-driven frames have been shot, or after the camera is switched OFF, any of which can make Programmed mode more of a pain in the azz than just going to Av or Tv mode, and setting the camera the way the shooter wants or needs it to be.

In a system where the camera's automatic metering will automatically revert to the "baseline" pairing of speed and f/stop, the automation must be continually overridden, which can result in a lot of wasted effort, or ruined shots, or highly inconsistent shots.

 

[Jackofknives]

Yeah, Tv mode is EXCELLENT for situations when the Time Value (aka the shutter speed) is a critical factor. Good examples include when one wants to do panning shots, and a specific shutter speed is the critical factor. Same thing when showing moving water or waterfalls or whatever; set the desired Time Value, then let the camera adjust the aperture.

In Av or Aperture Value automatic mode, the user determines the needed or desired f/stop. At times, that is the widest f/stop, like f/1.8; at times, a medium aperture; at other times, it is a smaller aperture, like say f/11, which will give deep depth of field. Many times a SPECIFIC aperture is desired, so Av has been a long-time mode offered since the late 1960's or early 1970's in many SLR type cameras.

Programmed Auto appeared in the later part of the 1970's, and has continued to evolve. It can work quite well, as long as the user understands how it works, and what types of settings are critical, or non-critical. The biggest issue in some systems is that once the exposure is shifted, that the camera REVERTS BACK TO BASELINE exposures after every exposure is made, or after each sequence of Continuous motor-driven frames have been shot, or after the camera is switched OFF, any of which can make Programmed mode more of a pain in the azz than just going to Av or Tv mode, and setting the camera the way the shooter wants or needs it to be.

In a system where the camera's automatic metering will automatically revert to the "baseline" pairing of speed and f/stop, the automation must be continually overridden, which can result in a lot of wasted effort, or ruined shots, or highly inconsistent shots.

Thanks, that was very helpful.

 

[Big Mike]

What is the point of switching to Av (aperture priority) or Tv (shutter priority), when you have Program mode where you can directly shift (Program Shift) your aperture or shutter number and the other options will change accordingly, just like in the Av and Tv mode. You can also change exposure compensation accordingly. So what is the point of using Av and Tv mode then, especially that in P mode you can change both simultaneously make it more convenient and faster (doing everything that Av and Tv can do), it’s like having Av AND Tv mode in the same function.

Thanks

Your intuition is correct, it doesn't matter what mode you are in, if you end up at the same settings, the photo will be the same.
P, Av or Tv are just different ways of getting to the settings that work for you. And of course, using Manual mode is just another way of getting to the settings you want.


In my DSLR/Photography 101 course, after I teach the students about aperture and shutter speed priority modes....I then ask them why 80% of photographers prefer aperture priority over shutter speed priority, even when shutter speed is the more important settings (for freezing or allowing motion blur).

The simple answer...is that when using shutter speed priority, you are much more likely to run into the limits of your lens's aperture....the camera will then flash the number at you and either refuse to shoot, or it will shoot and not give you the exposure you want. But if you use Av mode, the camera has a wider range of shutter speeds that it can give you, reducing the likelihood of running into a limit.

 

[TCampbell]

Program mode follows something called the "Program Line" to establish it's initial setting.

Suppose it's very dark... in such a situation the camera can only open the f-stop on the lens as much as the limit that the lens allows. From there it has no choice but to extend shutter duration. But if you give it more light, it picks an initial setting that offers some wiggle room on both aperture and shutter (splitting the difference). That's the "program line" and it varies for each lens you attach. E.g. A 50mm f/1.4 lens will have a different "program line" than, say, the EF-S 18-55mm f/3.5-5.6 lens at the 50mm focal length (where it would be limited to f/5.6 or above).

You can read more about it here: Canon Professional Network - Shooting modes

Program mode will pick an initial exposure setting based on the program line, but allow you to perform a program shift. But if you know you want... say, a shallower depth of field, then you'd be program-shifting ever shutter exposure and that will get tiring. So it's much easier to just use Av mode and dial in the aperture you know you want, and let the camera pick the shutter speed. Conversely... if it's the shutters speed you want to control, then you can use Tv mode.

The difference is how long it takes to get the camera set to the exposure settings you want to use.