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According to the Pentax K50 and K10D manuals, in P mode, if I select aperture, then program will choose a corresponding shutter speed, and if I specify shutter speed, then camera will select a corresponding aperture.

To me it's unclear: what is the point of Av and Tv modes, if P mode does the same and give me easy access to aperture and shutter speed adjustment at the same time? Is it just that one of the dials is disabled in Av or Tv mode, or something else?

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It is a different camera model, but it is the same question/answer. –  Michael Clark Jan 29 at 1:55
    
This question introduces P mode and assumes settings (like aperture and shutter) can be changed, which it can't. –  BBking Jan 29 at 3:41
    
The question is not about difference between Av and Tv. My point is what the difference with the P mode. As to me with in P more I have Av and Tv at the same time. Just need to turn front or back dial. –  tigran Jan 29 at 7:53
    
@BBking - Are you 100% sure? You can adjust the shutter/aperture balance in Nikon cameras in P. Might be worth checking the manual... –  James Snell Jan 29 at 10:44

7 Answers 7

up vote 4 down vote accepted

In my experience (with a Canon, not Pentax, but it's probably similar), P mode is part-way between Auto and Av/Tv modes.

The difference between P and full auto is that you are given the option of making creative adjustments, if you want. The camera will use its auto algorithm (or something like it) to choose an aperture and shutter speed, and you can then (optionally) adjust these. Your adjustments are temporary, and intended for that shot (or maybe a few similar shots one after the other). If you leave the camera alone for a while (say 30 seconds), it'll forget your adjustments.

P-mode is essentially Auto Mode with optional/temporary Av/Tv control.

If you think of P-mode as the same as Av/Tv mode, it's probably because you are always wanting to make those Av/Tv adjustments. In which case, P-mode is not for you.

P mode is good for:

  • People who want auto mode, with the option of manual tweaking
  • People who only sometimes want to make aperture/shutter adjustments
  • Novices who have only limited technical knowledge of shutter speed & aperture (e.g. a rough idea of what higher/lower do, but not a good sense of what value to pick)
  • Shooting a wide range of subjects in highly variable lighting conditions (it may mean less dialling through widely varying aperture or shutter settings, though often I find Tv more suitable for this if Av is proving too fiddly)

Av/Tv modes are good for:

  • People who want manual mode, without having to adjust both aperture & shutter each time
  • People with a good knowledge of aperture & shutter speeds, who know what they want in each shot
  • People who always want to control the shutter speed & aperture
  • Shooting reasonably consistent subjects and/or in reasonably consistent lighting conditions, with a reasonably consistent variation from what the camera's auto algorithm would choose (i.e. avoiding having to repeatedly make the same optional/temporary adjustment in P mode)

I've really focussed just on the exposure settings, but as @StanRogers points out there may be some other automated features in P-mode that aren't in Av/Tv, like popping up the flash (apparently a Canon thing, not a Pentax thing). As a "more auto" mode, you can expect some other features may also be simplified or act like they do in full auto modes.

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1  
Might I recommend adding that P(rogram) generally leaves the "to flash, or not to flash" question in your hands (when compared to Auto)? –  user2719 Mar 6 at 2:15
1  
At least on Pentax, you have to pop flash manually in any mode. –  tigran Mar 6 at 8:14

According to the Pentax K50 and K10D manuals, in P mode, if I select aperture, then program will choose a corresponding shutter speed, and if I specify shutter speed, then camera will select a corresponding aperture.

Not entirely true. After reading the manual, you can't set values other than ISO.

Av & Tv lets you set the aperture & shutter speed (accordingly) and adjusts other settings around it for correct exposure (according to manufacture specifications).

P mode, you can not actually set the aperture or shutter. The camera chooses it all by itself and the wheel dials change the ISO.

Pentax K50, p.87

However, you can customise these wheel dials, even in P mode:

Pentax K50, p.164

Personally, this is just messy and it's much easier to use either P, Av or Tv.

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Still, to me looks like P is a supper set of Av and Tv and I can control aperture with rare dial and shutter speed with front dial. I don't see ISO to be changed. –  tigran Jan 29 at 8:01
    
Try resetting your camera. –  BBking Jan 29 at 10:30
1  
Pentax camera has this (nice IMHO) ability... you are in P and the camera choose whatever it wants, but if you move the dials the camera switches to Av or Tv automatically --- a kind-of program shift on steroids. I think that pressing the green key you go back to a pure P. –  Rmano Feb 21 at 23:17
    
It only looks messy because there are a lot of options to customize to your taste. Once you have it the way you like it, it's not messy at all. –  mattdm Mar 5 at 22:20
    
Sure. But I think it's easier to use Av, Tv or M. I'll update my answer because I've learnt about Program Shift. –  BBking Mar 6 at 1:48

I sent the question to pentax support and here is the answer:

S: Cust. wants to know what the difference is between P mode and Tv and Av mode.

T: At P-mode the shutter speed and the aperture will be set automatically. However, the cust. has control over the two values and he can still adjust them. Av mode prioritizes the aperture, so cust. can adjust aperture but shutter speed will be determinted automatically. Tv mode on the othe rhand prioritizes the shutter speed and that is the value the cust can adjust if necassary. The aperture will be set automatically. At the end there is the M-mode where cust. has to set up everything himself.

So it looks like that "P" mode can be regarded as a ''hybrid" of "Av" and "Tv" modes.

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Either way they are designed to give you a picture that is correctly exposed. But you may want to control the aperture or the shutter. As an example, if someone is running and you want there to be no blur in their movement, then using a faster shutter speed will freeze their movement. It will adjust the aperture accordingly, which will allow more light in to balance the shot. The effect of this means the depth of field becomes shallower.

Av is Aperture value, or aperture priority, where you set the required aperture, and the metering in the camera will adjust the shutter speed to correctly expose the image for you.

Tv is Time value, or shutter priority, where you set the required shutter speed, and the metering in the camera will adjust the aperture to correctly expose the image for you.

P mode is Program mode I think, which will set shutter and aperture to a proper value, but should allow you to change either of them to get the same exposure, although I've not particularly used this feature.

Depth of Field, Aperture and Shutter speed are likely to be covered in numerous other questions on here, but for a picture to be correctly exposed, if you make a shutter speed one 'stop' faster, then you counteract that by making the aperture one 'stop' wider (a lower f-number), which results in the same amount of light getting in overall. The difference in the image occurs where the camera can't keep things in focus if they're at different distances away if the the aperture is wider (smaller number). Brief example of this: If the aperture is f22, and you focus on an object 5 meters away, objects that are 10 meters away and objects that are 2 meters away may also be in focus. Conversely, if the aperture is f1.8 and you focus on an object 5 meters away. Objects that are 2 meters away and objects that are 10 meters away are likely to be out of focus (note these are estimates only for the sake of explanation).

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the question is not about difference between Av and Tv modes. I want to know, what they do different from P mode, of P mode gives me the same amount of control. –  tigran Jan 29 at 8:03
    
@tigran your question says what is the point of Av and Tv modes, if they do the same? You could post or find a question asking about P mode if that's what you were trying to ask. I answered the question that you asked. –  laurencemadill Jan 29 at 9:36
    
that is unfortunate. Probably I was not clear enough and after editing by community member the original question got completely lost. –  tigran Jan 29 at 10:01

The manual mentions that the values are restricted in P mode. It may be that it only allows one to be adjusted at a time or it may restrict how far you can adjust the setting (for example, you may not be able to set a value that would result in an over or under exposure.) The manual, unfortunately, does not appear to go in to more details about what the restrictions are.

The TAv mode is probably the closer analog to T and Av as it will adjust the ISO to account for whatever value of shutter and aperture you choose and will not alter the value for one as you adjust the other.

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Jup. That's the point. What exactly this 'the values are restricted in P mode' –  tigran Jan 29 at 8:04
    
It generally means that some input is accepted but the camera may change those values as needed. It may also mean they don't let you go outside of the value needed for standard exposure. –  AJ Henderson Jan 29 at 13:44

Okay, here's an answer from someone who actually owns several Pentax cameras :)

As with all DSLRs, in P mode, by default, it chooses both Aperture and Shutter speed (Note: In the menu, there's an option for "Program Line" that lets you choose whether you prefer a shorter shutter speed for fast moving objects or a small aperture for depth in focus).

However, once you move one of the right dials (provided it's set up to use the dials to preset A or T as shown in another answer), you effectively change it into Av or Tv mode. You know that much already.

Now, the difference between this procedure and setting Av/Tv directly on the mode dial is that the P mode resets to automatically choosing both A and T if the camera shuts off, e.g. due to power saving mode.

That means: If you know you really need Aperture or Shutter priority for a longer time, set that mode explicitly so that it'll remain active even if the camera shuts off. Otherwise, P is usually the more convenient choice because if you have to make a quick shot, it makes a best guess (remember the "Program Line" menu setting!), and if you have the time to plan the shot, you just use one of the right dials to choose an aperture or speed for best effect. And you can then as quickly go back into full P mode by pressing the green button.

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Thanks. Thumb up. Nevertheless @drfrogsplat owns the answer. –  tigran Mar 6 at 21:54
    
Yep, saw your question too late. But happy to see it still helps. –  Thomas Tempelmann Mar 6 at 21:56

To my understanding, P mode is basically a controlled auto, where you may control the ISO, and the rest is decided by the camera.

In terms of control, Auto

With manual mode giving you the maximum control.

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