[Penview52]

When the image quality is not attained by setting the best the photographer wants, post editing is the best way to correct it.
edited:

After knowing that K-1 is a full frame camera i think the reciprocal rule will not apply - only for the cropped sensor and multiply with crop factor and used as a guide but not too obsessed about it.

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Last edited by Penview52; 11-20-2019 at 04:50 PM. Reason: to correct it

[stevebrot]

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.

Does this happen with a fixed maximum aperture zoom or with primes? I know it definitely does not happen with fixed ISO. I am pretty sure it does not happen with fixed ISO.


Steve

[pschlute]

If the aim is to use the lowest ISO possible then use the camera in Tv or Av mode with ISO 100 fixed.

[mikesbike]

If the aim is to use the lowest ISO possible then use the camera in Tv or Av mode with ISO 100 fixed.

Yep. This is my reasoning. In this case, if wanting auto adjustment with a change in lighting, but wanting to control shutter speed, Tv seems the most reasonable option. I think the lens FL factor being determined for shutter speed so conservatively is indeed to guarantee the sharpest possible outcome at the lowest level of competence by the camera holder. Then if wanting to go for a lower shutter speed, Pentax makes it easy to do so, even when using the "P" mode (with fixed ISO).

[UncleVanya]

Yep. This is my reasoning. In this case, if wanting auto adjustment with a change in lighting, but wanting to control shutter speed, Tv seems the most reasonable option. I think the lens FL factor being determined for shutter speed so conservatively is indeed to guarantee the sharpest possible outcome at the lowest level of competence by the camera holder. Then if wanting to go for a lower shutter speed, Pentax makes it easy to do so, even when using the "P" mode (with fixed ISO).

Exactly!

[MarkJerling]

Normally, the auto-exposure program on a Pentax camera will try to set shutter speed proportional to the lens focal length....

I'm not sure that's what's happening at all. I believe the camera is simply adjusting it's settings for the amount of light in the scene.

[MarkJerling]

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.

Exactly!

[stevebrot]

I'm not sure that's what's happening at all. I believe the camera is simply adjusting it's settings for the amount of light in the scene.

I am interested in seeing how this shakes out. I have read the original post several times and don't see the logic trail clearly as to why any of the features mentioned should be exploitable as a feature hack in the manner suggested.


Steve

[stevebrot]

That is not how TAv works. It is a manual mode with auto ISO.

You are correct in your assertion, but TAv is not quite manual with auto ISO because the ISO shift for TAv always shifts in a predictable manner stop-wise (1/2 or 1/3 stops depending on config), while auto ISO may not (e.g. "slow" sensitivity parameter setting or even "standard" under various conditions).


Steve

[biz-engineer]

Normally, the auto-exposure program on a Pentax camera will try to set shutter speed proportional to the lens focal length....I'm not sure that's what's happening at all.

This is happening. The camera does read and use the lens focal length (e.g using a zoom lens) as one of the conditions to set shutter speed. The way to see how the lens focal length changes the value of shutter speed is to use a uniform wall evenly lit, and zoom in and out the lens to see if the shutter speed is changing. I've done that experiement, and I've seen the camera adapt shutter speed to lens focal length to around 1/FL, e.g 50mm => shutter speed = 1/50th s.; 100mm => shutter speed = 1/100th s.
Now if the ISO hit the min possible value or max possible val, the camera won't change the shutter speed even if the lens FL is changed, because the objective of the AE algorithm if to expose correctly in the first place. If A is fixed, ISO is auto and T is auto, the camera will adjust ISO so that to have T = 1/FL.

---------- Post added 21-11-19 at 07:34 ----------

if wanting auto adjustment with a change in lighting, but wanting to control shutter speed, Tv seems the most reasonable option.

Yes. Usually, I want to have control over depth of field, so I use the A mode. IF, on top of having control on the depth of field, I want to also benefit from the SR capability, I have to use the TAv mode, and I have to look at my lens FL and compute in my head the shutter speed that would work with SR. Let say I have set my lens to 105mm for a portrait and the shutter speed to 1/15th s., SR enabled, the camera lower to ISO to 100 blinking because there is still too much light, I have to manually dial a faster shutter speed again. That's 2 manual operations, whereas the camera could have done it automatically by itself. So, yeah you can call me "lazy", but I feel like Pentax camera don't take advantage of SR in the way exposure is achieved. Even if I use the green mode, the camera doesn't lower shutter speed and ISO when I enable SR. The whole Pentax AE operate as if Pentax cameras don't have any sensor stabilisation. Maybe 80% of photographs taken in the last 10 years by Pentax photographers could have had better quality if Pentax camera AE would have consider SR is exposure parameters! Imagine, one million photographs that could have been taken with a lower ISO if Pentax AE would compute differently when SR is enabled.

---------- Post added 21-11-19 at 07:38 ----------

My point is that Pentax messed around pixel shift to improve image quality a tiny bit (on tripod only), while they didn't see that they could massively improve image IQ by simply having AE algorithm gears down when SR is enabled when the cameras are hand held. IMO, AE not using SR status is so big, like the elephant in the room.

---------- Post added 21-11-19 at 07:40 ----------

Anyway, I'm still trying to find a way to have my K1 take advantage of SR within having to use manual mode and compute exposure parameters myself.

[othar]

Yes. Usually, I want to have control over depth of field, so I use the A mode. IF, on top of having control on the depth of field, I want to also benefit from the SR capability, I have to use the TAv mode, and I have to look at my lens FL and compute in my head the shutter speed that would work with SR. Let say I have set my lens to 105mm for a portrait and the shutter speed to 1/15th s., SR enabled, the camera lower to ISO to 100 blinking because there is still too much light, I have to manually dial a faster shutter speed again

While I think I understand what you try to achieve, I don't see the point in doing so. Why would you want to go to the limits of your shutter speed (or respectively to the limits of SR) on purpose if you don't have to (1/15th of a second beeing on the slow side for portraits introdcing motion blur of the model).
You might wanna try Av mode with auto ISO, this maybe gives you the settings you try to achieve.

[Rondec]

I think you need to shoot manual mode. TAv will probably tend to give you a higher iso than you want (camera trying to maintain expected shutter speed) and Tv mode often chooses an aperture that is much wider than you want, say, if you are shooting landscape and want something f8-ish and it chooses f2.8.

I will say that what I do in practice is shoot in Av mode but I choose the iso setting based on the light meter in the camera. So it is dusk and I meter 0.5 seconds at iso 100, I will try iso 400 and see if I can manage to hand hold 1/8 second. Of course this depends on me and is not automatic, but it seems the best way to do it -- particularly because I can chimp my photo after the fact and realize that due to my coffee I really need 1/10 second exposure minimum to hand hold steadily.

[othar]

Maybe 80% of photographs taken in the last 10 years by Pentax photographers could have had better quality if Pentax camera AE would have consider SR is exposure parameters!

While I am not the aimed target for those theoretical deliberations, because I am usually either in M or Av mode, I am highly doubting this declaration.
I am certain a too slow shutter speed is more damaging to image quality as a high ISO value. 99% of the pictures I delete because of bad image quality are related to missed focus or motion blur and not to high ISO noise.

[Rondec]

While I am not the aimed target for those theoretical deliberations, because I am usually either in M or Av mode, I am highly doubting this declaration.
I am certain a too slow shutter speed is more damaging to image quality as a high ISO value. 99% of the pictures I delete because of bad image quality are related to missed focus or motion blur and not to high ISO noise.

I think biz-engineer's point is that if you are using a 50mm lens and are not using a tripod, the camera automatically chooses (if possible) an iso/aperture setting that will keep the shutter speed at 1/50 second. But if you are shooting a pretty static landscape and can actually hand hold 1/10 second with a 50mm lens you could choose a lower iso setting.

TAv mode probably gets pretty close but you need to experiment a bit there to see what you can hand hold and what you can't. But it's probably the best you can do because the camera doesn't really know what your hand holding abilities are.

[othar]

I think biz-engineer's point is that if you are using a 50mm lens and are not using a tripod, the camera automatically chooses (if possible) an iso/aperture setting that will keep the shutter speed at 1/50 second. But if you are shooting a pretty static landscape and can actually hand hold 1/10 second with a 50mm lens you could choose a lower iso setting.

I got that, but I don't think 80% of all the pictures taken are in those specific conditions:

Maybe 80% of photographs taken in the last 10 years by Pentax photographers could have had better quality if Pentax camera AE would have consider SR is exposure parameters!

And if it is already so dark that you reach a ISO value where it would make a difference you would have to check the picture anyway to see if you chose the correct exposure compensation value for those lightconditions, so why don't go manual for those conditions in the first place (and if you purposely go to a slower shutter speed checking for motion blur wouldn't be a bad idea either)