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07-07-2011, 10:36 AM   #1
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P mode; what's the difference between E-Dial set to P Shift or to Av?

I guess I am being thick and there's an obvious answer to this, but please help me.
What is the functional difference between the following two settings when shooting in Program mode?
E-dial set to P Shift
E-dial set to Av
To me it looks both settings allow the user to bias the camera towards a faster shutter/wider aperture or a slower shutter/narrower aperture. For both settings the Green Button resets the settings to the ones initially computed by the camera.
The only difference I could find is when the E-dial is set to Av the aperture value is underlined (and same goes for E-dial on Tv, I presume).

Are there any subtleties eluding me?

I suspect the question is in some way stupid, but seeing the patience and the kindness of the users of this forum I got the courage to ask it.

Thanks,
Sunday

07-07-2011, 11:08 AM   #2
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Interesting. The K-r manual doesn't have any details at all on Program Shift, that I could find. So you have the ability to shift, in other words change the program that chooses the exposure parameters. But change to what? The upper-tier cameras like the K-5 allow you to select from six or seven programs, each biased for something like high shutter speed or lens sharpness. The K-r must have similar programs. Without a list of programs, the Program Shift is not very useful. The new Program will be biased to... something else.

With "E-dial set to Av", it's more direct. The camera starts off by selecting a Program exposure. If you turn the e-dial, you override those settings by choosing a different aperture value. The Program might say f8, 1/250. Turning the e-dial can set the aperture to f5.6, and the camera will adjust the shutter speed to 1/500 to maintain the same exposure. It's the same as setting the mode dial to Av, but with this technique, you can use the green button to quickly return to P mode.
07-07-2011, 12:17 PM   #3
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Hi Sunday,

I'm assuming that you're referring to a K-5 or K-7.

The differences in modes and e-dial programming make subtle differences in handling.

I'm a birder primarily. I shoot mostly handheld, and opportunistically -- as birds appear, so the lighting can change dramatically from shot to shot. I have found that Av priority, with the rear dial controlling Av, the front dial controlling Ev comp, Program Line set to biased towards faster shutter speeds, and Auto ISO (with the Info screen set with the Auto ISO range selected as default) the most intuitive for me. Others will find different combinations easier to use, I'm sure.

I shoot long teles with TCs most often, so need to shoot them wide open or within a stop so because of the slower than normal max apertures (f4.8 -f7.7). In bright direct sunlight, I can stop down, and do so, but this is not the majority of my shooting. Birds, more often than not, choose difficult lighting -- severely backlit or in shadow or deep shadow in mixed light. This is where direct control of Ev comp works well. Auto ISO allows me to concentrate on the birds more than the settings, and "speed" bias in the Program Line tries to keep shutter speeds higher. I still have to watch these, and if I have the time, I'll change to a fixed ISO or change the working aperture to get deeper DOF or faster shutter speeds.

I could get the same control using different settings and using dedicated buttons and such, but for fast changes of the things that matter most to me, this works well.

Scott
07-07-2011, 03:10 PM   #4
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QuoteOriginally posted by Sunday Quote
I suspect the question is in some way stupid, but seeing the patience and the kindness of the users of this forum I got the courage to ask it.
I used to have a newspaper cartoon hanging up in my office that said:
Don't be afraid to ask dumb questions
They are easier to handle than dumb mistakes !


So, welcome to the forum and ask away !


07-07-2011, 10:29 PM   #5
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Thanks guys.

My mistake: I'm talking about a K-r.
The settings available for the E-dial in P mode are:
P Shift
Tv
Av
OFF
I'll try to give an example so it'll be more clear.
If I set the E-dial to P Shift and press halfway the shutter release I may get the following settings (I will consider a fixed ISO to eliminate one variable):
f5/200
If I move the E-dial one notch to the right I will get f5.6/160
The camera closes the aperture to decrease the exposure with 1/3 EV and slows the shutter down to compensate and regain the third of a stop.
Press the GB - all back to the initial settings.

If I set the E-dial to Av and make the same steps, the same thing will happen.
I will have first f5/200, move the E-dial to the right and get f5.6/160.
GB will reset the values.

In other words, for any setting of the E-dial in P mode, the camera will adjust the aperture/shutter speed pair in order to keep the measured exposure.
And I'm ready to bet the same will happen if I will set it to Tv.

So why 3 settings available?
What other things are changing that I'm not observing when using Av instead of P Shift?
07-08-2011, 02:00 AM   #6
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See if this helps.

Pentax K-r Camera Modes - Full Review
07-08-2011, 04:26 AM   #7
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Yes, that's a comprehensive explanation.
QuoteQuote:
The difference between this [Av or Tv] and Program Shift mode is that the Aperture or Shutter speed are explicitly fixed to your set value, rather than simply biasing the metering system while the camera still selects the actual values of both variables.
My conclusion? There is not any (sensible) difference between the 3 selectable modes. Not for me, anyway.

Thanks again,
Sunday
07-08-2011, 04:32 AM   #8
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QuoteOriginally posted by Sunday Quote
What other things are changing that I'm not observing when using Av instead of P Shift?
The differences between P shift and Av will become apparent as the light changes. P shift will alter both aperture and shutter according to the program line, biased in the direction that you have chosen to shift it. Av will only alter shutter speed. Tv will only alter aperture.
Try to point the camera against different brightness levels in P shift and Av, and watch how the exposure changes.

Sincerely,
--Anders.

07-08-2011, 06:20 AM   #9
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Hi Sunday,

Anders explained it pretty well, but the point of P Shift is that normally, it allows you to shoot in fully automatic mode with the camera choosing shutter speed and aperture according to the Program Line, but gives you the option to immediately override the camera's choices with direct manual control over your choice of shutter speed or aperture.

On the Kr, it's an either or proposition, and you choose to the mode that will override the fully automatic aspect in the "Green Button menu" in the Record Menu section. When you choose to use the Green Button as the Green button in this menu, you then choose whether you'd want the e-dial to activate either Av or Tv mode. When you turn the e-dial the camera switches to the chosen Mode, and stays there until you press the Green Button, which will return you to P Mode.

This allows you to let the camera to do the exposure work for the most part, but allows you to take control if you wish with your chosen Mode with just a roll of th e-dial.

An advantage of the 2 dial models is that you can override P mode with either Tv or Av by simply rotating the front or rear e-dial respectively, then return to P mode with the Green Button.

If you normally shoot in M, Sv, Tv, or Av, then "Hyper Program" as it has been called, is of little consequence.

Scott
07-08-2011, 06:53 AM   #10
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QuoteOriginally posted by snostorm Quote
When you choose to use the Green Button as the Green button in this menu, you then choose whether you'd want the e-dial to activate either Av or Tv mode. When you turn the e-dial the camera switches to the chosen Mode, and stays there until you press the Green Button, which will return you to P Mode.
I'll have to perform the test suggested by Anders over the weekend, there's no substitute for proper experimentation.

However, I find the P mode as very convenient for me, the issue discussed here being only of academic interest (as long as I can tell the camera to do what I want it to do).

Thank you,
Sunday

Last edited by Sunday; 07-08-2011 at 07:01 AM.
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