[stevebrot]

The lens aperture can't be set as a constrain in P mode.

I guess I don't get it. At issue is whether the camera will take focal length into consideration when determining exposure with auto-ISO enabled. Aperture in P mode is constrained by the program line and is perfectly reproducible for a given LV100. That is how it works.

What I am reading in regards to the original post and comments since is that the proposed hack requires Av mode with auto-ISO or possibly TAv mode with SR set on. You can scratch TAv mode off the list because it does not not follow the auto-ISO settings except for range (ignores the sensitivity parameters and always ramps by 1/2 or 1/3 step ISO intervals). That leaves Av mode with auto-ISO enabled, a variable max aperture zoom mounted, and the default auto-ISO sensitivity setting in play.

Allowing for a bit of sarcasm, perhaps it would be best to ignore the white rabbit next time? As near as I can tell, there is no reason to expect the camera to perform this trick, even if all the assumptions might prove to be correct.

Out of curiosity, what is the use case? What photographic task requires this sort of thing as an automated action?


Steve

[stevebrot]

The lens aperture can't be set as a constrain in P mode. Using the Av mode allows to set the lens aperture as a constrain, setting a aperture value higher than the min of the zoom lens, for instance f5.6 or f8 would remain constant accross the zoom range of your Sigma 17-50 f2.8:4. In Av mode + Auto ISO, the camera would set shutter speed around 1/17th s. at 17mm, 1/30th s. at 30mm and 1/50th s. at 50mm, with ISO value gradually increasing as the shutter speed increases.

I repeated in Av mode and got no difference between SR on and SR off with auto-ISO.


Steve

[othar]

I repeated in Av mode and got no difference between SR on and SR off with auto-ISO.

That's actually one of the things biz-engineer is criticizing about the camera software: not to take SR into account when chosing shutter speeds in an automatic (or half-automatic) mode and the only ordering (while I won't need it) I can understand.

[stevebrot]

That's actually one of the things biz-engineer is criticizing about the camera software: not to take SR into account when chosing shutter speeds in an automatic (or half-automatic) mode and the only ordering (while I won't need it) I can understand.

Ummmm...are we clear what parts of the camera we are talking about? At key is auto-ISO which has nothing to do with shutter speeds. The other is exposure automation, which nothing to do with SR and for which there is no rational for it to return results (Shutter/Aperture) other than that which might be returned using green button or EV meter scale in M mode.

In case it is not clear, supporting such a feature, even as a "hack" is equivalent to inserting uncertainty into a process when the exposure should be strictly deterministic. If such a feature were accidently exposed, most QA engineers would consider it a bug.


Steve

[othar]

Ummmm...are we clear what parts of the camera we are talking about? At key is auto-ISO which has nothing to do with shutter speeds. The other is exposure automation, which nothing to do with SR and for which there is no rational for it to return results (Shutter/Aperture) other than that which might be returned using green button or EV meter scale in M mode.
Steve

While I am in general on your side of the argument and don't think changes like those suggested by biz-engineer are necessary or even usefull for most photographers I am not sure you fully understood his demands (or at lest you understood his demands in a different way than I did )

Auto-ISO was just an unsuccesfull approach to make the camera do what he wanted, but not the key argument here in my opinion.

The main argument in my opinion is: that because SR is claimed to make a difference of up to 4 stops by Pentax this difference should be reflected by automatic exposure programs in that way, that the shutter speed should be higher when SR is deactivated and lower when SR is activated because SR takes care of the resulting increased camera shake (as you pointed out those are two independent systems of the camera at the moment and that is the reason for biz-engineers complaint in my opinion)

I think combining those systems is not desireable in general, because every photographer has slightly different needs for shutter speeds to receive a sharp image and if SR is taken into acount in P mode a lot of beginners will have problems producing sharp images. Also the 1/focal lenght rule of thump for shutter speed is from film days and the high resolution of camera sensors + pixel peeping makes it a lot more difficult to produce sharp images and SR is just a way of counteracting this development and not so usefull in actually reducing shutter speed for handhold photography in general, in my opinion

[biz-engineer]

In case it is not clear, supporting such a feature, even as a "hack" is equivalent to inserting uncertainty into a process when the exposure should be strictly deterministic. If such a feature were accidently exposed, most QA engineers would consider it a bug.

Does that mean all people using M mode are bugging the exposure of the camera? I've use the M mode, and although I bugged the exposure by lowering the shutter speed when SR was enabled, the images came out nicer than without the bug.

---------- Post added 22-11-19 at 13:35 ----------

I'll try a test later today. To me, the logical test would be to use a modern zoom with electronic contacts and an old zoom without electronic contacts where the camera can't know what lens is mounted and see if they behave differently, assuming similar focal ranges and apertures.

The camera obviously reads the focal length and use it for SR and for shutter speed. Fortunately, the camera tries to have a shutter speed at least as fast as 1/FL so that images taken aren't blurred.

When I use my DFA28-105 at 50mm , the camera doesn't automatically set the shutter speed to 1/500th s., it tries to set it close to 1/50th s. and when I use my DFA150450 at 400mm the camera doesn't automatically set the shutter speed to 1/50th s., it tries to set shutter speed around 1/400th s. That's the basic role of the AE program.

[othar]

Does that mean all people using M mode are bugging the exposure of the camera? I've use the M mode, and although I bugged the exposure by lowering the shutter speed when SR was enabled, the images came out nicer than without the bug

No. M mode is designed to give you full controll over your settings. But implementing this in an automatic program mode will probably not be seen as an improvement for most photographers.

[pschlute]

When I first started photography 40 years ago with my trusty MX I was taught that handheld the minimum shutter speed I should generally use should be 1/60 on a 50mm lens (and 1/FL on longer)

This was for two reasons: 1. because 1/60 was a fast enough speed that most folk could hand hold and not shake the camera. and 2. that this was a speed that would freeze most objects not travelling at any speed (so fine for family pictures and street scenes, no good for sports)

The SR technology has meant that 1. is no longer a good rule and that we can use up to 4 stops slower.

2 However is unchanged. It is for this reason that any auto mode that used a slower shutter speed of up to 4 stops when SR is engaged would be disastrous for most photographers.

[Penview52]

posted by biz_engineer

... the camera would set shutter speed around 1/17th s. at 17mm, 1/30th s. at 30mm and 1/50th s. at 50mm, with ISO value gradually increasing as the shutter speed increases. This is true, but you can not lower the ISO by enabling SR because SR is only acting as stabililizer of the frame made by the camera. SR is not a design parameter but a mechanical shock absorber like. SR has its own advantage but it can not influence the ISO to lower it down because it violates the reciprocal rule guide. The higher the speed of shutter the higher the ISO should be to catch the light spur at the moment. SR contribute to counteract the shake, but if you lower the ISO, and enable the AE the camera will shows blinking ISO meaning the camera will not agree with the users preference. SR do not influence the exposure.The advantage of SR can not be incorporated in the design parameters. We do not design camera here but use only and correct the wrong use of it.

[photoptimist]

The focal length speed limit effect is quite reproducible in Av and P mode for me. The K-1's trade-off between shutter speed and ISO is clearly slaved to the focal length. In these modes, the camera refuses to go slower than 1/focal length until the ISO ramps to the user-selected maximum value (I have it set to 204800). If the lens is a zoom that reports FL to the camera, then the camera will automatically raise or lower that speed limit when I zoom. Only if the scene is dimmer than 1/F speed & ISO=max, then the shutter speed slows (with ISO pinned to the max) further until the AE system reaches its lower limit of sensitivity.

Changing the "Auto ISO" line from the default to "slow" or "fast" changes this behavior by shifting the speed limit one stop slower or faster, respectively. Thus, the elements of the fix that biz-engineer wants is already in the firmware with only two changes needed: 1) he'd like TWO independent "Auto ISO" lines: a non-SR ISO line and an SR ISO line; 2) he'd like a greater range of of "slow" options offering 1, 2, 3, or 4 stops on the slow side. Obviously, the factory default for both Auto ISO lines would use 1/F and only users that cared about would change the settings.

The use cases of this feature for me:
1) interiors such as museums and cathedrals
2) dawn, dusk, and dark forest landscape

(And, no, I almost never use tripods anymore because they are heavy and photographically-limiting. I bought Pentax because it has SR so I don't need a tripod under most conditions.)

[pschlute]

rather than delve into the menus why not just use the available option of Hyper P mode (into Tv)....Turn camera on....camera sets an exposure... twist the front wheel down 8 notches (or as many as it takes to get 4 stops) !

[stevebrot]

Does that mean all people using M mode are bugging the exposure of the camera?

No, it means what I wrote, though perhaps I was not clear in my meaning.


Steve

[csa]

All still image that were taken with an ISO setting between 200 and 800 could potentially have been taken at ISO100 is the camera lowered the shutter speed to a value below the reciprocal of focal length when knowing that SR was enabled. If I look at exposure settings in exif files of many photographs in Flickr, a lot of exposure settings are far from being the best possible settings. I've seen things like shutter speed 1/500th and ISO1600, while it could have been 1/25th at ISO100.

And who decides what the "best possible settings" for someone are? As photographers, we decide for ourselves what we wish the camera to do, in order to achieve what WE want in a photo. Perhaps my photos to someone else, could be better, if I had used the "best possible settings"; however, the photos are pleasing to me, so does that not count?

[biz-engineer]

And who decides what the "best possible settings" for someone are?

Well, it seems a lot of people spend more money on cameras having larger sensors for a reason: image quality. Who would not want better image quality whenever it is possible? Why would I shoot at 1/1600 ISO1600 when sharpness would be right there at 1/100th and ISO100?

---------- Post added 23-11-19 at 10:24 ----------

The K-1's trade-off between shutter speed and ISO is clearly slaved to the focal length.

Yes, that's what I could observe consistently.

---------- Post added 23-11-19 at 10:26 ----------

Thus, the elements of the fix that biz-engineer wants is already in the firmware with only two changes needed: 1) he'd like TWO independent "Auto ISO" lines: a non-SR ISO line and an SR ISO line; 2) he'd like a greater range of of "slow" options offering 1, 2, 3, or 4 stops on the slow side. Obviously, the factory default for both Auto ISO lines would use 1/F and only users that cared about would change the settings.

You summarize my wish in two sentences. Perfect.

[pschlute]

Well, it seems a lot of people spend more money on cameras having larger sensors for a reason: image quality. Who would not want better image quality whenever it is possible? Why would I shoot at 1/1600 ISO1600 when sharpness would be right there at 1/100th and ISO100?

I have made this point a few times now and you have not answered. ISO alone does not create better image quality. Your suggested improvement would risk create blurry photographs of everything except a perfectly still scene.

You are also being disingenuous in changing your example to using a shutter speed of 1/100 when previously you were arguing for 1/10. No one needs SR at 1/100 except with a long lens