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01-07-2013, 01:48 PM   #1
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Shake Reduction and Av mode

Hi everyone,

I am new to the forum and to the Pentax world.
I just bought the K-30 because of it's low light abilities. I photograph a lot inside houses and in low light conditions.

When i started "playing" with the camera, i noticed something weird (to me).
When in Av mode, the camera chooses shutter speed without taking into consideration the SR mechanism (whether on/off).
The camera usually picks a shutter speed of 1/focal length, and even a third stop faster (!), thus taking the ISO to higher than necessary values (for my usual lighting conditions, and with my lens aperture wide open - somewhere between 1600-3200).
Lowering the shutter speed by 3 stops (as i understand that SR safely allows) would make a huge difference in ISO (from 3200 to 400).
This way - i can not take adventage of the camera SR (as i am not gainig shutter speed from it).
I could ofcourse work in full manual, but it would require my to calculate shutter speeds according to the focal length of my zoom lens, and when fast shooting this is not a good option for me.
What can be done? Why is it like that?
I would appriciate every answer.

Chaim

01-07-2013, 01:59 PM   #2
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The reason it does this is that shake reduction doesn't "give" you 3 or 4 stops for free- it just reduces the chance that camera shake will introduce significant motion blur, and it also depends on how steadily you can hold the camera.

If you think you can hold the camera steadily enough in low light, you could shoot in TAv and dial-in a slower shutter speed. The camera will then consequently use a lower ISO.

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01-07-2013, 02:14 PM   #3
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You can also simply set the ISO to a fixed value, and then it will give you the best shutter speed it can. Similarly, you still use auto-ISO, but set the upper range of the ISO so it will never go beyond a setting you find perfectly acceptable. On the K-5, you can also prioritize the way it chooses the ISO -- slow, normal, and fast. I don't know if the K-30 has a similar option...
01-07-2013, 02:19 PM   #4
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i dont know about the k30 but k-5 has a setting ("iso sensitivity auto setting" first tab, 3rd menu) and from there you can adjust the way it behaves... it has 3 settings, i think you want to adjust it to "slow". I dont really know if it'll make enough difference though...

edit:
i was about to add what vonBaloney said about the upper range of the auto iso... well, i wasnt fast enough

01-07-2013, 02:31 PM   #5
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Thank you both for your quick replies.

From what i read - it is quite "safe" to say that SR would give me 3 stops (although not 4 as Pentax claim). But let's say that it only gives 2 or even 1 stop - if Av mode does'nt take this into consideration - it really makes semi-auto almost useless IMO.

Yes - i could use TAv, but as i wrote before - i would have to "calculate" an appropriate "safe" shutter-speed accodring to my (changing from shot to shot) focal length, and when shooting fast i will probably not get it right (i am not a pro).
As for setting the ISO to a fixed value, or setting the upper auto ISO lower - i could do it, but again - it would not be optimal. If i set it too low - i will get longer shutter speeds than needed. It i set it too high - i will get granier pictures than neccessary.
I can "live" with a picture up to ISO3200, but i don't want to if i don't have to...

I think that when SR is ON, Av shutter speed should have taken it into consiredation (even as 1-2 stops, to be "safe"), or better yet - the meny could include such an option.

Anything else i could do (except for buying a faster lens, whcih will be the subject of my next thread...) ?

vonBaloney - The K-30 does'nt have prioritization as the K-5.
01-07-2013, 02:39 PM   #6
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Hmm, I guess you can make things even easier by just dialing in the shutter speed in hyper program. I generally won't go slower than 1/8s on a stabilized camera and 1/30s on a non-stabilized setup. On Pentax 1/15s is a pretty safe bet, so I would make that your minimum.

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01-07-2013, 02:51 PM   #7
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First of all - isn't dialing the shutter speed in hyper program, the same as Tv ?
Second - 1/15 for 18mm isn't the same as 1/15 for 150mm. Right? So, i still have to figure out a minimum shutter speed for different focal lengths (FL), pay attention to the FL in every frame (which is not easy, as it does'nt show on screen and you have to "feel" where you are on the range), and dial different values for different FL.

Oh well - i guess no easy solution for me (or is there? )
01-07-2013, 03:02 PM   #8
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QuoteOriginally posted by Chaim Quote
First of all - isn't dialing the shutter speed in hyper program, the same as Tv ?
Second - 1/15 for 18mm isn't the same as 1/15 for 150mm. Right? So, i still have to figure out a minimum shutter speed for different focal lengths (FL), pay attention to the FL in every frame (which is not easy, as it does'nt show on screen and you have to "feel" where you are on the range), and dial different values for different FL.

Oh well - i guess no easy solution for me (or is there? )
Yup it's basically the same, just easier.

The shutter speed is the same regardless of focal length. It's just that at longer focal lengths, it's easier to see more subtle movements, as you can consider the image to be more "zoomed in". I shoot a lot with an 85mm lens and nevertheless I was able to use it successfully at slow shutter speeds even below 1/15s, so I don't think you have to worry about calculating it too much every time.

Experience is key in this respect, so I recommend that you just go out and shoot, and eventually you'll see which settings work and which ones don't!


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01-07-2013, 03:19 PM   #9
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QuoteOriginally posted by Adam Quote
The shutter speed is the same regardless of focal length. It's just that at longer focal lengths, it's easier to see more subtle movements, as you can consider the image to be more "zoomed in". I shoot a lot with an 85mm lens and nevertheless I was able to use it successfully at slow shutter speeds even below 1/15s, so I don't think you have to worry about calculating it too much every time.
The reason for what i wrote is just that. In longer FL the subtle movements that always exist tend to blur more the image, so shutter speed should get faster as FL gets longer.
In Av, changing FL from 18mm to 100mm, changes shutter speed by 2 whole stops (and respectively - the ISO), so it does matter quite a lot.

Zoomed at 135mm, do you really think i could go with 1/15 ?
And on the other hand - wouldn't 1/10 or less be enough at 18mm (especially with SR on)?
I find it hard to believe that there is one shutter speed (or even two) that would "cover" me through the whole range or the 18-135, for example.
But as you wrote, i will have to experiment.

Anyway - Av just got a lot less attractive for me...
01-07-2013, 03:23 PM   #10
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While SR can allow up to 4 stops of slower shutter speed, it's reasonable for a manufacturer to set their automatic modes (Av, in this case) to a 1/FL even if we think we can go to less than that. This is because not everyone is capable of keeping steady hands, nor are everyone aware of what SR will do. Therefore, to minimize complaints that the camera sucks and takes blurry pictures, the manufacturer protects themselves in this way.

More advanced users should be either using Tav or M in these situations. Or forcing their maximum ISO to be no higher than their bearable limit (3200 on my k-x).
01-07-2013, 03:44 PM   #11
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While what you wrote makes sense - I think this is not optimal.

Basically, the manufacturer could take the shutter speed even slower, thus "making sure" no blur will be in the pictures even for a "shaky" user, but there is no end to this.

1/FL is enough for a "normal" user. If SR "gives" 3-4 stops, then with SR - 1/FL minus 3-4 stops is enough for the same "normal" user (he doesn't have to know what SR is, for that matter).
Pentax would better serve their users if they would make semi-auto mode suitable for "normal" users.

If Pentax wanted to use SR to "protect themselves" instead of giving the best auto values - they could settle for 1-2 stops, instead of 3-4. This would "protect" them enough while making Av more useful.

Another solution would be to put an option in the Camera Menu, for taking SR into account. It is not hard to implement.
The K-5 has a similar option with its "program line" setting. I have no idea why pentax have not included it with the K-30.

I wish a future Firmware update would change the current situation (maybe some official from Pentax is reading this...).
01-07-2013, 03:49 PM   #12
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You may have a few things confused.

Shake reduction allows up to 4 stops of shutter speed reduction - but not always 4 stops. This is dependent on many factors, and even the 4 stops is somewhat of a standard number that doesn't translate to real world operations. The general accepted shutter speed for non-SR cameras is 1/FL. By aiming for 1/FL, Pentax ensures that their shutter speeds will always be fast enough to prevent shake blur - especially with their SR system assisting.

Again - the SR doesn't guarantee 4 stops, 3 stops, 2 stops, or even a single stop. It just has the capability of assisting for some shots.

Also - the manufacturer doesn't slow the shutter speed to prevent shake blur, they increase it.
01-07-2013, 03:55 PM   #13
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QuoteOriginally posted by Chaim Quote
Another solution would be to put an option in the Camera Menu, for taking SR into account.
That would be the only thing that would make sense to me -- an option that said, "allow slower shutter when SR is enabled" or something like that -- maybe you could even dial in a number of stops. That would be a nice feature, but certainly I wouldn't want them to do that by default.
01-07-2013, 03:58 PM   #14
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QuoteOriginally posted by vonBaloney Quote
That would be the only thing that would make sense to me -- an option that said, "allow slower shutter when SR is enabled" or something like that -- maybe you could even dial in a number of stops. That would be a nice feature, but certainly I wouldn't want them to do that by default.
I thought that the k-5 allows users, as obscura said, to change the ISO settings to fast normal or slow - which I suspect translates to 1/4xFL, 1/2xFL, and 1/FL. They don't go below 1/FL, though.

I may be slightly wrong on the exact definitions of fast, normal, and slow, but I remember reading that somewhere.
01-07-2013, 04:00 PM   #15
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What you wrote is very intersting. I heard some lectures from a distinguished photographer, and he said he relies on SR when setting shutter speed. He said he found out that 3 stops are "safe" on his specific camera, and feels safe to slow down shutter speed accordingly WHENEVER it's needed. I also took a course in photography, and the same was said about SR (or whatever name every manufacturer calls it).

Can you elaborate more on the different factors that influence on whether SR assists or not, and how much it assists ?

About your last line - of course. It was just a momentary mixup.
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