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06-04-2010, 11:36 AM   #46
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i set it to 100-3200 when shooting sports after dusk Av mode or "sport" mode
works great on my kx.

i find autoISO to be poor though when using flash in a very dimly lit scene. the kx will choose a very high ISO. i guess it meters the dim scene and says, heck, it's dim, let's use the highest iso allowable.

06-04-2010, 12:12 PM   #47
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QuoteOriginally posted by alexeyga Quote
Buddy, i'm not here to clue anybody on anything... just gave my opinion and it wasn't the point of my post anyways... what's up? have you felt insulted of something?
I need a sarcasm smiley.
06-04-2010, 03:03 PM   #48
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QuoteOriginally posted by alexeyga Quote
Some of the replies are so funny... people yapping with intelligent faces about iso and stuff without having a slightest clue about how camera's metering system works...
QuoteOriginally posted by Ira Quote
I would say that the above can pretty much be classified as obnoxious.
I agree.
06-04-2010, 03:03 PM   #49
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QuoteOriginally posted by graphicgr8s Quote
I need a sarcasm smiley.
Give me a week to work on one, and we'll see if the Admin includes it.

06-04-2010, 03:06 PM   #50
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QuoteOriginally posted by Bart Quote
I always use Auto-ISO from 100 - 640 on K10D, mostly on Av.
You see the result in the viewfinder.
If you don't like the outcome, simply change either of the appropriate parameters.
One push of the green button brings you back to the automated suggestion.
Easy.
How exactly do you see the different ISO results in the viewfinder?
06-04-2010, 04:42 PM   #51
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How Auto ISO works in Av and Tv

Well, I have a feeling that many don't use Auto ISO because they didn't manage to figure it out how it works. Unknown things scare people, so does Auto ISO

In fact, Auto ISO works pretty straightforward in Av and Tv modes. Auto ISO is implemented in such manner that camera tries to keep ISO as low as possible, it is increased only when necessary.

I will start with Tv mode as it is more simple than Av. In Tv mode camera will open lens aperture to it's maximum value and only after that it will start to increase ISO.
For example I have a lens with maximum aperture of F/2.8:
1/30 f/8 ISO100
1/60 f/5.6 ISO100
1/125 f/4 ISO100
1/250 f/2.8 ISO100
1/500 f/2.8 ISO200
1/1000 f/2.8 ISO400
1/2000 f/2.8 ISO800
When you will decrease shutter speed, changes will happen in opposite direction, first ISO will be lowered to lowest setting and then lens aperture will be closed. Pretty much the same as you would do by controlling ISO manually, isn't it?

In Av mode there's little intelligent trick. ISO is increased when shutter speed drops to approximately 1/<focal lenght> speed. In K-7 you can control this value by setting Auto ISO to slow/normal/fast. Slow means that it's going to allow slower shutter speeds. Let's say, we have f/2.8 lens and Auto ISO limits set to 100-800. Let's say we have 50mm lens, so the threshhold shutter speed is going to be ~1/60 s. then in Av it's going to be like this:

f/2.8 1/250 ISO100
f/4 1/125 ISO100
f/5.6 1/60 ISO100
f/8 1/60 ISO200
f/11 1/60 ISO400
f/16 1/60 ISO800
f/22 1/30 ISO800
f/32 1/15 ISO800

Again - most of us would change ISO in the same manner manually, right?

I don't know how exactly Auto ISO works in P and Green mode - simply I don't use them, so I didn't bother to figure it out. However I am pretty sure that Pentx tries to keep AutoISO as low as possible and increases it only when it is really necessary.

I remember that there were some quirks with auto ISO in it's earliest implementations, however currently Pentax Auto ISO works wery well and I can see no real reason not to use it when you're shooting without tripod in some automated mode.

By the way, don't use Auto ISO with flash - for some reason Pentax has decided to go to the highest Auto ISO limit as soon as you turn your flash on...
06-04-2010, 05:14 PM   #52
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I usually have it set between 100-800, but with the slow algorithm, so that the camera is biased towards lower ISOs. If I am shooting bright or dim light, I will usually go off auto.

Rob
06-04-2010, 10:17 PM   #53
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QuoteOriginally posted by robgo2 Quote
I usually have it set between 100-800, but with the slow algorithm, so that the camera is biased towards lower ISOs.
Camera is always biased towards lower ISO. That parameter controls how slow camera will let shutter speed to become before increasing ISO.

BTW, I've checked Auto ISO in P mode on K-7 and it seems that it had been fixed with some firmware update. Finally I can start using P mode


Last edited by Edvinas; 06-04-2010 at 11:46 PM.
06-05-2010, 04:23 AM   #54
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QuoteOriginally posted by Ira Quote
How exactly do you see the different ISO results in the viewfinder?
eh? I see the ISO chosen by the system in the viewfinder.
06-05-2010, 06:47 AM   #55
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This is off-topic, but everytime I see the title of this thread, I hear Samuel Jackson in Pulp Fiction...."Auto ASA...MF!...Do you use it?"
06-05-2010, 08:27 AM   #56
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QuoteOriginally posted by TaoMaas Quote
This is off-topic, but everytime I see the title of this thread, I hear Samuel Jackson in Pulp Fiction...."Auto ASA...MF!...Do you use it?"
What?
"What ain't no country I ever heard of. They speak Auto-sensitivity mode in what?"

And for the reading (or humor) impaired, click this link...

Use Auto-ISO on my K-x when following my kid around from inside to outside (which is a constant motion and prime photo time). Messing with ISO on the K-x is a PITA and I'm not gonna miss these shots.

I've never touch it on my K20D, but not because of some photo-god hubris about "not letting the camera decide"... just never knew it was there outside of TAv.

Last edited by panoguy; 06-05-2010 at 08:37 AM.
06-05-2010, 11:00 AM   #57
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QuoteOriginally posted by Bart Quote
eh? I see the ISO chosen by the system in the viewfinder.
Understood. I thought you were implying that you see the results
of the various ISOs in the viewfinder.
06-05-2010, 12:33 PM   #58
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It's another tool, useful at times. My K20D is usually in D-Range, ISO=200-1100 or whatever -- but I'm usually fixed at 200 and only go Auto if conditions dictate. So it depends on lens, mood (hurried? desperate? lazy? contemplative?) and light. Sometimes I try to outsmart the camera, and sometimes I let it outsmart me.
06-05-2010, 12:43 PM   #59
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QuoteOriginally posted by opiedog Quote
i find autoISO to be poor though when using flash in a very dimly lit scene. the kx will choose a very high ISO. i guess it meters the dim scene and says, heck, it's dim, let's use the highest iso allowable.
I suspect it's trying to help you avoid the dreaded "nuclear blast" flash look that ruins so many shots - using such a low ISO, fast shutter speed, and/or small aperture that ambient light cannot fill in the shadows. I suspect it's trying to find a combination of settings that will result in the flash acting more as fill - slow sync flash, basically.
09-28-2010, 10:52 PM   #60
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Some of the erratic ISO actions that the OP talked about might be due to the Program Line options in the Custom menu.

On the K20, one is offered in Item 1 these options:
1 Normal
2. Hi speed
3. Depth
4. MTF

I used to use Aperture priority, but then would find during a busy shooting session for theatre plays, that the camera would change settings inappropriately. I then switched to TAV which was really good because i could specify the minimum shutter speed to stop human action, the minimum aperture for the stage depth, and let the camera float on Auto ISO as it is set to do in TAV. Maximum ISO range i would set would be 3200 to 6400 depending on the variable scene lighting.

Teh K20 manual provides absolutely NO guidance on what the "normal" setting does. Its interesting as someone reported that now they have slow medium and fast. I now have it set on Normal and don't have any idea what that means
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