[biz-engineer]

Normally, the auto-exposure program on a Pentax camera will try to set shutter speed proportional to the lens focal length, with aperture and ISO such that to achieve proper 18% grey exposure (based on spot, weigthed or matrix sensing). Av, Tv, Sv, TAv will define what is fixed and what can be changed by the camera to achieve 18% grey exposure. Now, if SR is enabled, nothing changes in how auto-exposure settings are achieved, even if SR would allow a shutter speed slower than the reciprocal of the lens focal length, which means the camera AE doesn't deliver the best possible exposure settings when SR is enabled, as the camera doesn't take advantage of SR performance.

I've tried to find a way to have shutter speed half of the lens focal length (one stop slower than normal), or even 1/4th of the normal shutter speed (two stops slower), but the camera (K1) will set other parameters as if SR was disabled.
If I use TAv, I can force the shutter speed to 1/10th s. for which I know SR will be effective to correct for camera motion, but then if there is more light than necessary at that 1/10th shutter speed, the camera will lower ISO to the minimum (ISO100), the ISO setting will blink in the OVF and the frame will be overexposed, when I would expect that the camera will increase the shutter speed for proper exposure even if I initially set it to 1/10th, but it won't.

So hopping that the camera would automatically correct my exposure setting when proper exposure isn't achieved, I enabled the option in menu C1-4 "Auto EV compensation". Unfortunately, when ISO is stuck blinking at 100, none of the exposure settings is being changed by enabling "Auto-EV compensation".

How can we work around that? Has anyone figured that out already?

[othar]

In my opinion SR is not considered for exposure settings because not everybody is holding the camera equally still. Some need more leeway to get a sharp picture than others and it is more safe to use settings resulting in faster shutter speeds or there would be an outcry that you can't get a sharp picture in auto mode.

TAv leaves the decision for aperture and shutterspeed in your hands by definition, it would be counterproductive if the camera changes those settings on it's own in my opinion. The blinking ISO setting to warn you that a correct exposure is not possible is enough for me.

[biz-engineer]

In my opinion SR is not considered for exposure settings because not everybody is holding the camera equally still. Some need more leeway to get a sharp picture than others and it is more safe to use settings resulting in faster shutter speeds or there would be an outcry that you can't get a sharp picture in auto mode.

For sure, that's one way of seeing why SR shouldn't affect exposure settings.

it would be counterproductive if the camera changes those settings on it's own in my opinion.

I set shutter speed two stops slower than what it should be is SR was disabled, base of Pentax claim 4 stops of SR capability. If ISO100 leads to overexposure with the shutter speed I set too slow, I don't see any issue if the camera increase the shutter to achieve proper exposure at ISO100.

[pschlute]

which means the camera AE doesn't deliver the best possible exposure settings when SR is enabled, as the camera doesn't take advantage of SR performance

In the auto modes the camera is balancing up to all three parameters: shutter speed (shake); aperture (MTF or DOF); ISO (noise). Enabling SR by itself is not a reason for the camera to choose a slower shutter speed, but I agree it could add this into the calculation for some of the auto modes.

but then if there is more light than necessary at that 1/10th shutter speed, the camera will lower ISO to the minimum (ISO100), the ISO setting will blink in the OVF and the frame will be overexposed, when I would expect that the camera will increase the shutter speed for proper exposure even if I initially set it to 1/10th, but it won't.

That is not how TAv works. It is a manual mode with auto ISO. If your scene is too bright for the minimum ISO you need to change the T or A values. If you want the camera to make a compensation for you how do you expect it to do so ? Change the T value or the A value ? Or both. Kind of defeats the object of using TAv mode in the first place.

I remember from film days my old Z-1. Like today's cameras it had Hyper Program mode as well as Tv and Av. In Tv or Av modes the camera would warn of a over/under exposure by blinking the display in the viewfinder and you would get over/under exposure. But in P mode, if you switched to Tv or Av directly with the wheels the camera behaved differently: it would not allow a shutter or aperture value to be set that would give a wrong exposure.

[biz-engineer]

If you want the camera to make a compensation for you how do you expect it to do so ? Change the T value or the A value ? Or both. Kind of defeats the object of using TAv mode in the first place.

In the e-dial menu are defined the program types for Av, Tv, Sv, M, TAv modes. For example, in the e-dial menu , for M mode you set if aperture, or shutter speed or ISO will be the parameter being changed by the exposure program in M mode. My problem is that auto-exposure compensation should work in TAV mode but it doesn't work. Is there anything that should be done such that auto-exposure compensation will work in TAv?

[UncleVanya]

I'm not entirely understanding how you would tell the camera you want it to do this. If you use Av mode and set iso fixed, the camera assumes you know what aperture you want and picks an appropriate shutter speed. Only one value is "right". Unless you pick auto iso the camera is locked into your choice.

In programmed mode or TAv things are more complicated. But you have these other options already that permit you to bias the results.

I guess if you could set the floor shutter speed in P mode it would help with what you want. My personal shooting is typically more about a specific aperture so I almost always shoot in Av or M.

[Penview52]

In the e-dial menu are defined the program types for Av, Tv, Sv, M, TAv modes. For example, in the e-dial menu , for M mode you set if aperture, or shutter speed or ISO will be the parameter being changed by the exposure program in M mode. My problem is that auto-exposure compensation should work in TAV mode but it doesn't work. Is there anything that should be done such that auto-exposure compensation will work in TAv?

Auto EV is an override function. This will give you the chance to change exposure value as in blinking ISO to correct it but not as we thought it would give an automatic exposure.

[biz-engineer]

Only one value is "right". Unless you pick auto iso the camera is locked into your choice.

The idea of lowering the shutter speed to below the reciprocal of the focal length (for static subjects) is to lower the ISO value a few stop to get better image quality by using the capability of shake reduction. The TAv mode works for that as I can slow down the shutter speed when I know what focal length I use, but the camera isn't able to deal with auto ISO when ISO hits limits where normally auto-exposure compensation should take care of overriding user defined setting to achieve proper exposure.

I know, my question requires deep understanding of how Pentax cameras work, I hoped that some people with advanced knowledge of Pentax K1 might be able to help. Basically, Pentax marketing claim is that SR is as good as 4 stops, but no one knows how to use the 4 stops capability to improve the image quality proportionally to SR capability.

[pschlute]

My problem is that auto-exposure compensation should work in TAV mode but it doesn't work

I understand what you mean....eg tell the camera to auto-compensate in TAv mode by adjusting aperture.

Personally, I wouldn't find it useful. When I use TAv mode I can see very readily if my settings are likely to lead to an over/under exposure and I adjust accordingly.

---------- Post added 11-20-19 at 02:24 PM ----------

Basically, Pentax marketing claim is that SR is as good as 4 stops, but no one knows how to use the 4 stops capability to improve the image quality proportionally to SR capability.

You can use Tv or M mode or even TAv mode to set the slower shutter speed yourself. Whether that will improve image quality will depend on other factors. By itself it wont, especially if the ISO is already at 100 and the camera stops down the lens past diffraction point.

I think camera exposure modes have become as complicated as they need to be without adding more esoteric twists. Nothing changes the basics of the exposure triangle.

[fs999]

Have you tried setting AUTO ISO Parameters to Slow, which will lower the lowest shutter speed in Av. Eg 50mm -> 1/25 slow, 1/50 intermediate and 1/100 fast.

[stevebrot]

Normally, the auto-exposure program on a Pentax camera will try to set shutter speed proportional to the lens focal length, with aperture and ISO such that to achieve proper 18% grey exposure (based on spot, weigthed or matrix sensing).

This is news to me. (Will admit to not being clear what is meant by "auto-exposure" in this context...green mode?)

Note: There is long-standing speculation regarding stuff like Auto-ISO sensitivity settings, but the first I had heard it might be related to focal length...BTW, not my experience when researching the behavior in depth several (5+ years) ago.


Steve

[pschlute]

This is news to me. (Will admit to not being clear what is meant by "auto-exposure" in this context...green mode?)

Note: There is long-standing speculation regarding stuff like Auto-ISO sensitivity settings, but the first I had heard it might be related to focal length...BTW, not my experience when researching the behavior in depth several (5+ years) ago.


Steve

Not done any tests myself but I have seen enough reference to this from a number of sources that I believe it to be the case. In Green or P mode (Av ?) it will attempt to keep the shutter speed up as you use a longer FL, and therfore use a faster aperture/higher ISO

[photoptimist]

It's easy to set a slow shutter speed in almost all the modes: TAv, Tv, and M are the obvious ones, but it's also possible in P(w/ Tv hyper), Sv (with Tv shift), and Av (with Tv shift).

That said, it would be nice if Pentax had an AE system setting in which the camera would use slow SR-stabilized T values (of some user-entered number of stops) to preserve optimized A and the lowest possible S in the T-A-S program lines for P, Sv, and Av.

Designing "good" AE logic is kind of hard and falls into two camps. One presumes that the photographer knows best -- the camera never over-rides the user's settings. The other presumes that the camera knows best. Pentax tends to default to "photographer knows best" although the green AUTO mode is a "camera knows best" mode.

[Bob 256]

So you're trying to get the right exposure but want to use a slower shutter speed than the camera picks because shake reduction will allow that?

My K-1 allows that in program mode by getting an exposure normally (hitting the green button if necessary), and then dialing in a lower shutter speed with the front adjustment dial. The lens aperture will be adjusted accordingly with the ISO remaining fixed. The next exposure will retain that shutter speed unless the green button is pressed or a power off/on cycle occurs.

I don't really try to push the shutter speed to it's lowest practical value because there's too much variability in my steadiness and one day I might be able to get an extra three stops with anti-shake while the next it's only half a stop with a cup of java (think this was previously mentioned). Rather, I just go for non-shake control shots mentally and know the shake control is there to help get better results in those cases where it benefits.

[biz-engineer]

Have you tried setting AUTO ISO Parameters to Slow, which will lower the lowest shutter speed in Av. Eg 50mm -> 1/25 slow, 1/50 intermediate and 1/100 fast.

Yew, that's a good point. I use the ISO slow ramp mode, so that improves noise by one stop already. I just wished the ISO ramp setting would allow more than one stop of latitude.

---------- Post added 20-11-19 at 18:00 ----------

This is news to me.

I don't fully understand your comment. I'll try to rephrase: for example, if I use the D-FA 28-105, extended to 105mm, the camera tries to set shutter speed around 1/100th s., if the ISO ramp setting is set to typical, and if aperture and ISO have room for variation (ISO hasn't reached its min or max allowed values, or wanted lens aperture is still within possible aperture range of the lens). If I zoom out the DFA28-105 to 50mm, the camera automatically reduce the shutter speed to 1/50th , except is other parameters don't allow it.

---------- Post added 20-11-19 at 18:18 --------

Designing "good" AE logic is kind of hard and falls into two camps. One presumes that the photographer knows best -- the camera never over-rides the user's settings. The other presumes that the camera knows best. Pentax tends to default to "photographer knows best" although the green AUTO mode is a "camera knows best" mode.

Normally, the C1-4 option (auto-exposure compensation) enabled says that the camera is allow the user setting if the user setting leads to an incorrect exposure. I remembered that this option was the object of questions on the forum some years ago, I retrieved the posts about auto-exposure-compensation, but I was unable to make it work consistently on the K1, I remained puzzled about how auto-exposure-compensation would work on the K1. I hoped that the auto-exposure compensation would override my settings when my settings don't achieve proper exposure, but it didn't...


---------- Post added 20-11-19 at 18:22 ----------

So you're trying to get the right exposure but want to use a slower shutter speed than the camera picks because shake reduction will allow that?

Correct. That's what I want to do, so that when the photographic subject isn't moving, the image quality is much improved when SR is enabled.

---------- Post added 20-11-19 at 18:26 ----------

My K-1 allows that in program mode by getting an exposure normally (hitting the green button if necessary), and then dialing in a lower shutter speed with the front adjustment dial. The lens aperture will be adjusted accordingly with the ISO remaining fixed.

Correct. Except I want to have the aperture defined by me to control the DoF that I want for my image. My wish is that the camera lower the shutter speed and ISO setting if I enabled SR, so that the IQ is significantly better thank to the IBIS of the camera.