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11-07-2011, 06:46 PM   #31
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QuoteOriginally posted by audiobomber Quote
I'm using a K20D
That could explain much of the difference we are seeing

11-07-2011, 08:18 PM   #32
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In Tav, when the meter is out-of-range, it doesn't appear to do anything. However, in Av mode (and I assume Tv mode -- haven't tested) it DOES override the settings when you go out-of-range. It specifically will override the setting that is supposed to be locked -- so for instance in Av mode if it has run out of options in terms of adjusting shutter speed and ISO and you are still out-of-range, it will go ahead and change the aperture you've set. You can see it doing this when the iso starts blinking. This is just as another poster described above, so if anyone is seeing this setting do nothing in all modes, that's not right. However, in Tav mode, it doesn't override either the shutter or the aperture and will just allow the over/under exposure.

I guess the next step is priority modes when you can set the min and max for each parameter (like you can with ISO), and also the priority of the order of what is to be overridden with an auto ev mode.
11-08-2011, 03:23 AM   #33
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I have both a K5 and a K20, and I just tested that it does the same thing on the K20.

What audiobomber describes sounds just like the green metering mode to me, which is available on every DSLR ever from every manufacturer.
11-08-2011, 05:28 AM   #34
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QuoteOriginally posted by vonBaloney Quote
In Tav, when the meter is out-of-range, it doesn't appear to do anything. However, in Av mode (and I assume Tv mode -- haven't tested) it DOES override the settings when you go out-of-range. It specifically will override the setting that is supposed to be locked -- so for instance in Av mode if it has run out of options in terms of adjusting shutter speed and ISO and you are still out-of-range, it will go ahead and change the aperture you've set. You can see it doing this when the iso starts blinking. This is just as another poster described above, so if anyone is seeing this setting do nothing in all modes, that's not right. However, in Tav mode, it doesn't override either the shutter or the aperture and will just allow the over/under exposure.
That's what I found as well. In other words, the feature that areidjr wanted, exposure protection in TAv mode, is not available, but it should be available in P,Tv,Sv,Av modes.

11-08-2011, 06:02 AM   #35
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QuoteOriginally posted by drougge Quote
I have both a K5 and a K20, and I just tested that it does the same thing on the K20.

What audiobomber describes sounds just like the green metering mode to me, which is available on every DSLR ever from every manufacturer.
With Auto Ev activated, the camera compensates the exposure when it determines it's needed, which is exactly what Pentax service describes in the email quoted above. That's not surprising to me. This other thing, where it changes settings made by the photographer (e.g. changing aperture in Av mode), that's the surprising part, and why it's more like a Green mode than what I would expect from Auto Ev.
11-08-2011, 09:39 AM   #36
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QuoteOriginally posted by audiobomber Quote
With Auto Ev activated, the camera compensates the exposure when it determines it's needed, which is exactly what Pentax service describes in the email quoted above. That's not surprising to me. This other thing, where it changes settings made by the photographer (e.g. changing aperture in Av mode), that's the surprising part, and why it's more like a Green mode than what I would expect from Auto Ev.
It does say specifically in the option menu itself that it will "override" (it uses that word) user settings when correct exposure cannot be reached -- so it gives fair warning and that feature is off by default I think. I don't think the behavior of that feature in Tav mode is a bug but intentional, or they would have fixed it by now as it acts the same way over a number of different bodies going back years. There is something to the argument that it would be better to just pick one or both (aperture or shutter) to adjust rather than just "fail" and cause a bad exposure, but apparently that is too complicated...
11-08-2011, 10:09 AM   #37
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QuoteOriginally posted by audiobomber Quote
With Auto Ev activated, the camera compensates the exposure when it determines it's needed, which is exactly what Pentax service describes in the email quoted above. That's not surprising to me. This other thing, where it changes settings made by the photographer (e.g. changing aperture in Av mode), that's the surprising part, and why it's more like a Green mode than what I would expect from Auto Ev.
Without Auto Ev compensation activated, in the green ("matrix") meter mode, the camera also adjusts exposure based on some magic decision making algorithm. This is what the email from Pentax service describes. Whoever wrote it was mistaken. It happens.

I stand by my assertion that the settings does absolutely nothing in TAv mode, and only does something in the other automatic modes when the settings you have made make the metered exposure impossible. The name of the setting and it not working in TAv mode are the only surprising things. (Your example differs by half a stop, you need a very controlled test for that to mean anything.)

So, just to verify my assertions, I tried shoting a blank wall with various settings. With or without auto ev comp I get one exposure for center weighted metering, and another for green metering, but only the metering mode makes a difference.

Surprisingly it exposes less for green, when I would have expected more (it's pretty close to the "lot's a snow" example I think), but at least my basic theory held.

QuoteOriginally posted by vonBaloney Quote
I don't think the behavior of that feature in Tav mode is a bug but intentional, or they would have fixed it by now as it acts the same way over a number of different bodies going back years.
If it's intentional I think it's a bug in whoever decided it should be so.
11-08-2011, 12:18 PM   #38
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QuoteOriginally posted by drougge Quote
I stand by my assertion that the settings does absolutely nothing in TAv mode, and only does something in the other automatic modes when the settings you have made make the metered exposure impossible. The name of the setting and it not working in TAv mode are the only surprising things. (Your example differs by half a stop, you need a very controlled test for that to mean anything.)

So, just to verify my assertions, I tried shoting a blank wall with various settings. With or without auto ev comp I get one exposure for center weighted metering, and another for green metering, but only the metering mode makes a difference.
I have to agree. I just tested more carefully with a tripod and was unable to verify my first result. Exposures varied by as much as a stop, but in a non-sensical way, so probably the result of slight lighting shifts (or wonky K20D matrix metering). Sorry for the confusion.

11-08-2011, 12:25 PM   #39
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You can tell when the auto Ev kicks in by the blinking ISO. In Tv & Av, you can also see it changing settings. In Tav, it changes nothing.
11-09-2011, 01:49 PM   #40
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I posed the same question to Pentax and this is the response.

QuoteQuote:
Auto EV Compensation in the K-5 is the feature that allows the camera to automatically apply exposure compensation ONLY in situations when the camera's normal exposure metering is not able to determine the proper exposure settings. The default setting for Auto EV Compensation in the custom settings menu is OFF, meaning the camera does not apply auto EV settings in these situations. Even with Auto EV compensation turned ON, if the camera was able to meter the test exposures you shot for proper exposure you wouldn't see any effect.
This seems to confirm how I understood the function to work, but is still a little too vague to have a complete understanding of exactly where it will take effect, how much it can compensate and in what modes it will operate. I asked Pentax for further clarification.
11-09-2011, 02:00 PM   #41
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It is very easy to see it in action.

Turn the feature on.

Set your camera to Tv mode.

Set the shutter speed to something like 1/1000 or faster and ISO to 100.

Shoot indoors where there is not nearly enough light for that (flash off, obviously).

As you half-press the shutter button, the aperture will read fully open, but if it is dark enough that won't be good enough. The aperture will be blinking in the viewfinder, and your shutter speed will not be set to 1/1000 anymore but it will set it to a value that will actually work, like 1/60 depending on how fast your lens is.

Ta da! Auto EV compensation achieved!

You can cook up similar scenario in Av mode -- this time shutter will be blinking and it will set the aperture to something other than you did.

In Tav mode, however, the ISO will be blinking, but it will neither adjust shutter nor aperture and you'll just get a bad exposure...
11-09-2011, 04:33 PM   #42
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QuoteOriginally posted by vonBaloney Quote
It is very easy to see it in action.

Turn the feature on.

Set your camera to Tv mode.

Set the shutter speed to something like 1/1000 or faster and ISO to 100.

Shoot indoors where there is not nearly enough light for that (flash off, obviously).

As you half-press the shutter button, the aperture will read fully open, but if it is dark enough that won't be good enough. The aperture will be blinking in the viewfinder, and your shutter speed will not be set to 1/1000 anymore but it will set it to a value that will actually work, like 1/60 depending on how fast your lens is.

Ta da! Auto EV compensation achieved!

You can cook up similar scenario in Av mode -- this time shutter will be blinking and it will set the aperture to something other than you did.

In Tav mode, however, the ISO will be blinking, but it will neither adjust shutter nor aperture and you'll just get a bad exposure...
Thank you. That was a very good explanation and it seems to work just like you say it should. Too bad that Pentax couldn't have put an explanation into the manual that made sense along with a list of the modes that the setting effects.

I may need to re-think my use of TAv mode and go back to shooting in Av like I did on my previous DSLRs.
11-09-2011, 05:01 PM   #43
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QuoteOriginally posted by vonBaloney Quote
In Tav mode, however, the ISO will be blinking, but it will neither adjust shutter nor aperture and you'll just get a bad exposure...
AutoEV is a kludge to allow out-of-range operation. In general use it isn't necessary. In TAv mode you need to keep an eye on your ISO range. If you have ISO80-ISO1600 set (a gain adjustment range of 4.3 stops), and the ISO is hanging around either ISO80 (bright lighting) or ISO1600 (dim lighting) a lot, it means that with this light level and your current shutter & aperture settings you are running close to your set ISO range limit. Exceeding this will cause the ISO value to flash in the VF. It is a good idea in such situations to adjust either your aperture or shutter setting first to allow a little exposure leeway so you don't get caught out.

Dan.

Last edited by dosdan; 11-11-2011 at 01:28 PM.
11-11-2011, 04:10 AM   #44
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I think the camera is working as I would expect, the same thing happens in shutter priority when it runs out of apertures. In both cases your asking the camera to take an image with impossible settings and it tells you by flashing the relevant parameter. The number of times I have had a beginner set 1/1000th of a second in low light with an f3.5 aperture lens and then wonder why the images are dark.

It's pretty basic stuff, but there is only one level of light on the sensor that will give a good exposure and the camera tries to give you that, if it can't it tells you, but it allows you to take the image anyway.

Chris
11-11-2011, 11:42 AM   #45
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QuoteOriginally posted by ChrisJ Quote
I think the camera is working as I would expect, the same thing happens in shutter priority when it runs out of apertures. In both cases your asking the camera to take an image with impossible settings and it tells you by flashing the relevant parameter. The number of times I have had a beginner set 1/1000th of a second in low light with an f3.5 aperture lens and then wonder why the images are dark.

It's pretty basic stuff, but there is only one level of light on the sensor that will give a good exposure and the camera tries to give you that, if it can't it tells you, but it allows you to take the image anyway.

Chris
Yes, that is correct normal behavior. BUT if the AutoEV feature is turned on, it is supposed to override your foolishness and set the shutter or aperture to something sensible -- and in Av & Tv mode it does. In Tav mode, it does not.
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