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11-06-2011, 04:42 PM   #1
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TAV mode question

I love the TAV mode on my K5, but there are situations where it needs a little help. Is there any way to tell the camera that if it hits the limit of the ISO range to change wither the aperture or shutter speed to achieve proper exposure.

I find that if I've set say f/8 and 1/500s that there are times where it will run the ISO down to 80 and then over-expose. There is an "Auto EV Compensation" setting (Uses auto EV compensation when proper exposure is not obtained) that doesn't seem to do anything at all.

Any ideas?

11-06-2011, 06:09 PM   #2
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P282. You can set what changes if you press the green button in that instance.

Not automatic of course.

I'm not certain what the Auto EV Compensation setting does. The documentation is not clear.
11-06-2011, 06:19 PM   #3
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TAv locks two of the three variables, shutter speed and aperture, and only leaves the ISO for the camera to adjust so only so much adjustment is possible. You could try Av or Tv mode in combination with auto-ISO. That allows the camera more of a range to adjust. The downside is of course that you have less control yourself.
11-07-2011, 05:32 AM   #4
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Auto EV compensation should work, but doesn't. In Av mode it does (closing or opening the aperture if correct exposure is otherwise impossible). The argument you would probably soon have seen if I didn't make this post is that it can't work in TAv mode, since it's not clear which of the parameters it should start messing with. Which is a stupid argument, because either is better than just failing. (Same problem (and argument) with AE lock in M not working for ISO.)

So, it's a firmware bug.

11-07-2011, 07:38 AM   #5
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QuoteOriginally posted by areidjr Quote
I love the TAV mode on my K5, but there are situations where it needs a little help. Is there any way to tell the camera that if it hits the limit of the ISO range to change wither the aperture or shutter speed to achieve proper exposure.
The camera warns you that it can't achieve a correct exposure by flashing the ISO setting in the viewfinder and on the top screen. You must then adjust the aperture or shutter speed using the front or rear wheel. That's the way it should be in TAv mode, IMO. If you want the camera to make the adjustments automatically, you'll have to use P mode.

BTW, you can tell the camera to prefer shutter speed or aperture adjustments in P-mode by selecting the relevant Program (Hi-speed, MTF, etc) .

Last edited by audiobomber; 11-07-2011 at 08:16 AM.
11-07-2011, 08:22 AM   #6
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QuoteOriginally posted by drougge Quote
The argument you would probably soon have seen if I didn't make this post is that it can't work in TAv mode, since it's not clear which of the parameters it should start messing with. Which is a stupid argument, because either is better than just failing. (Same problem (and argument) with AE lock in M not working for ISO..
Overexposure is not necessarily a fail, it can be a choice. That's what Ev comp is, you deliberately overrule the camera's auto exposure.

When the camera actvely warns you that it is about to overexpose, the ball is in your court. You can either overexpose because you want to, or make adjustments to achieve correct exposure, or fail because you ignored the exposure warning.

QuoteOriginally posted by drougge Quote
(Same problem (and argument) with AE lock in M not working for ISO.)
I don't know what this means. There is no need for AE lock in M mode, because the settings for aperture, shutter and ISO are set for whatever values you choose. It's a completely manual mode. If that's not what you want, you have to use another mode.

Last edited by audiobomber; 11-07-2011 at 08:56 AM.
11-07-2011, 09:13 AM   #7
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QuoteOriginally posted by audiobomber Quote
Overexposure is not necessarily a fail, it can be a choice.
Of course "correct" exposure is not really up to the camera, but the OP wanted to get what the camera thinks is correct exposure even when the light doesn't match his prefered shutter/aperture combo. Without having to adjust anything. There is an option to do exactly this in the custum functions menu, and the problem is it doesn't work.

Everyone who doesn't want this behaviour is free to not change that custom function.

QuoteOriginally posted by audiobomber Quote
I don't know what this means. There is no need for AE lock in M mode
There is a need. If I change the shutter speed, normally this changes the exposure. If I first activate AE lock, the aperture changes so my exposure remains the same. This is, like almost all functions on modern cameras, not absolutely necessary, but a great convenience. It would be nice if it also worked when changing the ISO, but it doesn't. (Still talking about M mode.)
11-07-2011, 09:25 AM   #8
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QuoteOriginally posted by audiobomber Quote
The camera warns you that it can't achieve a correct exposure by flashing the ISO setting in the viewfinder and on the top screen. You must then adjust the aperture or shutter speed using the front or rear wheel. That's the way it should be in TAv mode, IMO. If you want the camera to make the adjustments automatically, you'll have to use P mode.

BTW, you can tell the camera to prefer shutter speed or aperture adjustments in P-mode by selecting the relevant Program (Hi-speed, MTF, etc) .
Absolutely, TAv is just that... I have control over Shutter and Aperture but I don't care about iso (the k-5 comes in handy). I don't want/need the camera to automatically do something else, which may or may not be my preference. To use TAv mode, I set the shutter speed accordingly to the situation (i.e. indoor or outdoor) to ensure that the iso range is sufficient to cover.

QuoteOriginally posted by audiobomber Quote
Overexposure is not necessarily a fail, it can be a choice. That's what Ev comp is, you deliberately overrule the camera's auto exposure.

When the camera actvely warns you that it is about to overexpose, the ball is in your court. You can either overexpose because you want to, or make adjustments to achieve correct exposure, or fail because you ignored the exposure warning.
I do pay attention to the flashing light in the viewfinder before I press the shutter, if the iso flash, it usually means I am hitting the lower limit of the iso range, in which case I just dial the higher shutter speed until the flashing stops. The Ev comp also comes into play too, but it also has to do the metering method.

11-07-2011, 11:12 AM   #9
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QuoteOriginally posted by drougge Quote
Of course "correct" exposure is not really up to the camera, but the OP wanted to get what the camera thinks is correct exposure even when the light doesn't match his prefered shutter/aperture combo. Without having to adjust anything. There is an option to do exactly this in the custum functions menu, and the problem is it doesn't work.
I just confirmed that Auto Ev works in TAv mode. I took a photo of backlit pillar, with and without Auto Ev. The camera used ISO 100 with Auto Ev disabled, and ISO 140 with Auto Ev enabled. That is exactly what Auto Ev is supposed to do. It's a mode for novices, it makes the camera behave more like a point & shoot and applies compensation so the photographer doesn't have to. It does not work in M or Bulb modes, but it works in the Auto exposure modes (P, Sv, TAv, Tv, Av).

QuoteOriginally posted by drougge Quote
There is a need. If I change the shutter speed, normally this changes the exposure. If I first activate AE lock, the aperture changes so my exposure remains the same. This is, like almost all functions on modern cameras, not absolutely necessary, but a great convenience. It would be nice if it also worked when changing the ISO, but it doesn't. (Still talking about M mode.)
Most people just rotate both wheels simultaneously in opposite directions to maintain exposure. It's very quick and intuitive.

Last edited by audiobomber; 11-07-2011 at 11:19 AM.
11-07-2011, 11:21 AM   #10
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QuoteOriginally posted by derekkite Quote
P282. You can set what changes if you press the green button in that instance.

Not automatic of course.

I'm not certain what the Auto EV Compensation setting does. The documentation is not clear.
That was my problem. The documentation is not clear. I thought it would do something, but it doesn't (at least not in TAV)

QuoteOriginally posted by Ole Quote
TAv locks two of the three variables, shutter speed and aperture, and only leaves the ISO for the camera to adjust so only so much adjustment is possible. You could try Av or Tv mode in combination with auto-ISO. That allows the camera more of a range to adjust. The downside is of course that you have less control yourself.
I thought that it would hit the ISO limit then do something in response. Apparently it doesn't.

QuoteOriginally posted by drougge Quote
Auto EV compensation should work, but doesn't. In Av mode it does (closing or opening the aperture if correct exposure is otherwise impossible). The argument you would probably soon have seen if I didn't make this post is that it can't work in TAv mode, since it's not clear which of the parameters it should start messing with. Which is a stupid argument, because either is better than just failing. (Same problem (and argument) with AE lock in M not working for ISO.)

So, it's a firmware bug.
I'm not sure it's a bug. I thought that there might be some other setting I needed in tandem to get the desired effect.
11-07-2011, 11:24 AM   #11
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QuoteOriginally posted by audiobomber Quote
The camera warns you that it can't achieve a correct exposure by flashing the ISO setting in the viewfinder and on the top screen. You must then adjust the aperture or shutter speed using the front or rear wheel. That's the way it should be in TAv mode, IMO. If you want the camera to make the adjustments automatically, you'll have to use P mode.

BTW, you can tell the camera to prefer shutter speed or aperture adjustments in P-mode by selecting the relevant Program (Hi-speed, MTF, etc) .
I know that the camera warns you. However, being that I wear glasses and the problem mostly happens in bright conditions, it's very difficult for me to see the display. That's why I wanted to use the option. It apparently does not work.
11-07-2011, 11:32 AM   #12
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QuoteOriginally posted by audiobomber Quote
I just confirmed that Auto Ev works in TAv mode. I took a photo of backlit pillar, with and without Auto Ev. The camera used ISO 100 with Auto Ev disabled, and ISO 140 with Auto Ev enabled. That is exactly what Auto Ev is supposed to do. It's a mode for novices, it makes the camera behave more like a point & shoot and applies compensation so the photographer doesn't have to. It does not work in M or Bulb modes, but it works in the Auto exposure modes (P, Sv, TAv, Tv, Av).



Most people just rotate both wheels simultaneously in opposite directions to maintain exposure. It's very quick and intuitive.
I don't think you confirmed anything. Both ISO settings are within the allowable range. The camera just metered a little differently between shots. For it setting to have worked, you would have had to have shot the first one at ISO 80 and then the second would have also been 80 and something else would have had to change (shutter and.or aperture). What you described is normal TAV operation and the setting had no effect.

It's only quick and intuitive if you can see the display or have time to react to the display. I also think you are off base in saying that it's a setting for novices. The green mode surely is and P mode perhaps as well. A novice wouldn't be shooting TAv and digging into the custom menus to solve a particular issue.
11-07-2011, 11:56 AM   #13
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QuoteOriginally posted by areidjr Quote
I know that the camera warns you. However, being that I wear glasses and the problem mostly happens in bright conditions, it's very difficult for me to see the display. That's why I wanted to use the option. It apparently does not work.
Auto Ev does work, but it is not a solution for your particular issue. Its sole function is to tell the camera to implement a compensated exposure, instead of the photographer doing it. In other words, Ev comp allows the camera to expose to something other than 18% gray. You can implement Ev with the Auto Ev menu, which is haphazard and only intended for novices. Or you can implement it manually using the Ev button, or by selecting Manual parameters that are different than the camera's metered exposure.

But what you are asking it to do in TAv mode has nothing to do with Auto Ev. You want the camera to go outside of the shutter, aperture and ISO ranges you've selected and give you a proper exposure, i.e. 18% gray. That is not a compensated exposure, therefore auto Ev doesn't apply.

Last edited by audiobomber; 11-07-2011 at 12:22 PM.
11-07-2011, 12:21 PM   #14
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QuoteOriginally posted by areidjr Quote
I don't think you confirmed anything. Both ISO settings are within the allowable range. The camera just metered a little differently between shots. For it setting to have worked, you would have had to have shot the first one at ISO 80 and then the second would have also been 80 and something else would have had to change (shutter and.or aperture). What you described is normal TAV operation and the setting had no effect.
I confirmed Auto Ev comp in both P and TAv modes. In P mode, it changed the aperture from f/8 to f/6.7. In TAv mode, it couldn't change the aperture or shutter speed, because I selected them. It manipulated the sensitivity within the ISO range that I specified to expose the shot to something brighter than 18% gray. Don't take my word for it, try it yourself on a backlit subject.

QuoteOriginally posted by areidjr Quote
It's only quick and intuitive if you can see the display or have time to react to the display. I also think you are off base in saying that it's a setting for novices. The green mode surely is and P mode perhaps as well. A novice wouldn't be shooting TAv and digging into the custom menus to solve a particular issue.
I would not say that P-mode is for novices. P-mode is extremely useful for anyone, because it allows the user to instantly shift between Av and Tv modes by turning the relevant wheel.

I'm not the only one who thinks it's point & shoot mode. Here's what Pentax support says:

"Thank you for contacting Pentax.

Auto EV would work in any mode other than Bulb or M.

Normally, a camera tries to balance an image to 18% gray.
With auto-EV the camera looks at the scene and applies EV compensation based what it thinks is supposed to be correct.
It may look at a scene of all snow and think, hey, 18% gray is probably not right for this, lets balance it to a brighter level.
This system is of course imperfect, but can help out a newer photographer to get shots correct more often, or help even an experience photographer who might just be in a hurry.

If you are in need of further assistance, please respond to this email or call our technical support center at 800-877-0155."


https://www.pentaxforums.com/forums/344102-post17.html
11-07-2011, 12:48 PM   #15
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QuoteOriginally posted by drougge Quote
Auto EV compensation should work, but doesn't. In Av mode it does (closing or opening the aperture if correct exposure is otherwise impossible).
In Av Mode, Auto Ev would change the shutter speed and/or ISO, never the aperture, which is set by the photographer.

Last edited by audiobomber; 11-07-2011 at 12:57 PM.
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