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Subject: "Another Auto ISO Curiosity" Previous topic | Next topic
singlerosa Silver Member Charter MemberSun 13-Apr-14 01:30 PM
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"Another Auto ISO Curiosity"


St. Louis, US
          

I was out shooting my grandson's soccer game yesterday in sunny/cloudy light, so I turned to my friend Auto ISO to assist. On my D7000 (with 70-200 2.8VRII attached) I set the max to 800 and on a batch I shot on aperture priority (f/3.5), a few came out at ISO 640 and ss 1/8000. My question is why wouldn't the camera slow the shutter speed down and lower the ISO? How did it pick this combination? Here's one of the pics (cropped). AF-C, 9-point, center-weighted metering. The picture sucks, but I'm curious about the ISO.



Jim Singler D600/D7K with a bunch of lenses and other assorted stuff

  

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Replies to this topic
Subject Author Message Date ID
Reply message RE: Another Auto ISO Curiosity
briantilley Moderator
13th Apr 2014
1
Reply message RE: Another Auto ISO Curiosity
Howker Silver Member
14th Apr 2014
2
Reply message RE: Another Auto ISO Curiosity
kentak Silver Member
14th Apr 2014
4
     Reply message RE: Another Auto ISO Curiosity
briantilley Moderator
14th Apr 2014
5
          Reply message RE: Another Auto ISO Curiosity
kentak Silver Member
14th Apr 2014
6
               Reply message RE: Another Auto ISO Curiosity
briantilley Moderator
14th Apr 2014
7
                    Reply message RE: Another Auto ISO Curiosity
kentak Silver Member
14th Apr 2014
8
Reply message RE: Another Auto ISO Curiosity
kentak Silver Member
14th Apr 2014
3
Reply message RE: Another Auto ISO Curiosity
Montereyman Silver Member
18th Apr 2014
9
     Reply message RE: Another Auto ISO Curiosity
briantilley Moderator
18th Apr 2014
10
     Reply message RE: Another Auto ISO Curiosity
kentak Silver Member
18th Apr 2014
11
          Reply message RE: Another Auto ISO Curiosity
burchan Silver Member
19th Apr 2014
12

briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Sun 13-Apr-14 02:25 PM
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#1. "RE: Another Auto ISO Curiosity"
In response to Reply # 0


Paignton, GB
          

That sounds normal - depending on what you have your base ISO set to.

In Aperture priority, Auto ISO will only reduce the ISO below your chosen starting point if the required shutter speed exceeds the fastest available.

Brian
Welsh Nikonian

  

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Howker Silver Member Nikonian since 21st Jul 2010Mon 14-Apr-14 03:09 AM
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#2. "RE: Another Auto ISO Curiosity"
In response to Reply # 1


Redmond, US
          

You can make your D7100 only operate within an ISO band you set. e.g. if you set ISO to 200 & in Auto ISO sensitivity Maximum to 1000 it will only shoot within these values.
I find the strangest thing with this is I can see shots set at really odd ISO values like 340.
So now if there is still not a shot the camera can set within these values it starts looking at the Minimum shutter speed you have set. Note that in Aperture priority as you know, you have set the f stop so the camera changes the shutter speed. It will not go below this minimum so it hikes up the ISO to MAximum.
I believe once max ISO is reached it starts with longer shutter speeds until there is a shot but it may well be such a long speed you have a blurred image.
The experts might better tell us if I've got this right!

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kentak Silver Member Nikonian since 03rd Jul 2010Mon 14-Apr-14 05:36 AM
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#4. "RE: Another Auto ISO Curiosity"
In response to Reply # 1


US
          

Brian,

As I understand Jim’s post, his question boils down to “Why did the system raise the ISO when it could have simply selected a slower shutter speed to get an appropriate exposure?”

It seems a valid question.

In Aperture priority mode with auto-ISO, the system, as I understand it, will operate within the following parameters:

Maintain set aperture (no deviation)
Maintain set preferred ISO (if possible, only raising to the set maximum if SS can’t accommodate correct exposure)
Vary SS to obtain correct exposure (avoiding going below set minimum)

Let’s say Jim had set a base ISO of 400 and a minimum shutter speed of 1/1000. Then, the system *should* have given an exposure of ISO 400 @ 1/5000 instead of ISO 640 at 1/8000.

So, the question is why did it not?

Kent

  

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Mon 14-Apr-14 08:22 AM
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#5. "RE: Another Auto ISO Curiosity"
In response to Reply # 4
Mon 14-Apr-14 08:23 AM by briantilley

Paignton, GB
          

>In Aperture priority mode with auto-ISO, the system,
>as I understand it, will operate within the following
>parameters:
>
>Maintain set aperture (no deviation)
>Maintain set preferred ISO (if possible, only raising to
>the set maximum if SS can’t accommodate correct exposure)
>Vary SS to obtain correct exposure (avoiding going below set minimum)

Nearly, but not quite...

In Aperture Priority with Auto ISO:
+ the aperture will always stay at the chosen value;
+ the ISO will start at the selected base value.

...if the scene gets darker:
+ the shutter speed will be lowered down to the pre-set minimum;
+ then, the ISO will be raised until the pre-set maximum is reached;
+ then, the shutter speed will be reduced below the pre-set minimum.

...if the scene gets brighter:
+ the shutter speed will be raised up to the fastest the camera can do;
+ then, the ISO will be reduced below the selected base value.

>So, the question is why did it not?

Presumably because the selected base ISO was 640 (or higher) - hence the caveat at the start of my original response

Brian
Welsh Nikonian

  

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kentak Silver Member Nikonian since 03rd Jul 2010Mon 14-Apr-14 01:04 PM
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#6. "RE: Another Auto ISO Curiosity"
In response to Reply # 5


US
          

Brian,

I agree with your description of how auto-ISO prioritizes in Aperture priority mode. This is why I had asked Jim what he used for the "preferred" (base) ISO--and if he was sure.

My assumption (I know, I know) is that he would have selected a much lower ISO than 640, as it doesn't make much sense to select an ISO only 1/3 stop from your set maximum.

Kent

  

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Mon 14-Apr-14 01:29 PM
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#7. "RE: Another Auto ISO Curiosity"
In response to Reply # 6


Paignton, GB
          


>My assumption (I know, I know) is that he would have selected
>a much lower ISO than 640, as it doesn't make much sense to
>select an ISO only 1/3 stop from your set maximum.

I agree - it's not something I would do. My point was (and is) simply that the original described behaviour might well be normal, depending on the base ISO setting.

Brian
Welsh Nikonian

  

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kentak Silver Member Nikonian since 03rd Jul 2010Mon 14-Apr-14 02:02 PM
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#8. "RE: Another Auto ISO Curiosity"
In response to Reply # 7


US
          

Yes. If Jim can't confirm what his ISO setting was, it would at least be enlightening to know what exposure combinations other images from the same batch had.

So, Jim--if you're listening, help us help you understand this situation.

Kent

  

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kentak Silver Member Nikonian since 03rd Jul 2010Mon 14-Apr-14 04:22 AM
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#3. "RE: Another Auto ISO Curiosity"
In response to Reply # 0
Mon 14-Apr-14 04:28 AM by kentak

US
          

What was your "preferred" ISO setting? And, are you sure? In your auto-ISO setup, what did you enter as slowest shutter speed?

Kent

  

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Montereyman Silver Member Nikonian since 18th Feb 2013Fri 18-Apr-14 05:51 PM
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#9. "RE: Another Auto ISO Curiosity"
In response to Reply # 3


prunedale, US
          

How one thinks Auto ISO works and how it actually works have been very different with every Nikon camera with this feature that I have used. It gets even more complicated when flash is used with its settings for minimum shutter speed and the flash sync also comes into play.

Nikon keeps changing how this setting functions so with each new camera I have to test how it actually works with and without flash. Most of the time I find that Auto ISO is a liability and I will not use it.

In the example of the sporting event with clouds passing overhead the camera set on AP will adjust the shutter speed with no need to adjust the ISO automatically. There would need to be a 4x or greater difference in the light level to need to crank up the ISO amplification. If I am using f5.6 and 1/1600s at ISO 200 in bright light and a cloud passes overhead and I am reduced to shooting at 1/400s that is not going to create problems with my shots.

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Fri 18-Apr-14 07:14 PM
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#10. "RE: Another Auto ISO Curiosity"
In response to Reply # 9


Paignton, GB
          

Apart from the recent introduction of a focal length-dependent option for the minimum shutter speed setting, Auto ISO works the same way on every Nikon DSLR I've used.

Auto ISO in general doesn't play well when using flash, unless you understand what it's doing and why.

Brian
Welsh Nikonian

  

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kentak Silver Member Nikonian since 03rd Jul 2010Fri 18-Apr-14 08:54 PM
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#11. "RE: Another Auto ISO Curiosity"
In response to Reply # 9


US
          

>How one thinks Auto ISO works and how it actually works have
>been very different with every Nikon camera with this feature
>that I have used. It gets even more complicated when flash is
>used with its settings for minimum shutter speed and the flash
>sync also comes into play.

Echoing what Brian said, I can't agree that auto-ISO works inconsistently. It works similarly on the few number of cams I've used over the past few years--D90, D7000, D600, and D7100. I haven't really attempted to use it with flash, and I know others have reported some complications with it, but I suspect it's mostly of matter of getting enough experience to learn how it functions in various modes and settings.

>
>Nikon keeps changing how this setting functions so with each
>new camera I have to test how it actually works with and
>without flash. Most of the time I find that Auto ISO is a
>liability and I will not use it.

On the contrary, I've found it useful in a variety of situations. It's important, however, to understand when and how it will function according to the parameters you set--including the base ISO you choose (I call it "preferred" ISO), the maximum ISO, and the minimum shutter speed, and how it works in each exposure mode.

I've become particularly fond of enabling auto-ISO in Manual mode in shooting situations where I want to lock in a particular aperture and shutter speed and just let the exposure system choose an appropriate ISO for a correct exposure.

>
>In the example of the sporting event with clouds passing
>overhead the camera set on AP will adjust the shutter speed
>with no need to adjust the ISO automatically. There would need
>to be a 4x or greater difference in the light level to need to
>crank up the ISO amplification. If I am using f5.6 and 1/1600s
>at ISO 200 in bright light and a cloud passes overhead and I
>am reduced to shooting at 1/400s that is not going to create
>problems with my shots.

Sure, and that's the way it's supposed to work--it only kicks in when *needed.* In the situation you described, you've allowed enough "room" for your shutter speed to float for the variations in light that you might anticipate. However, if you wanted to stay at 1/400 or above to freeze motion, what harm would there be in enabling auto-ISO and setting a minimum SS of 1/400? That would allow you to keep shooting without worrying about either a too-low SS or having to take your eye off the action to adjust ISO. What's the downside?

Kent

  

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burchan Silver Member Nikonian since 22nd Feb 2012Sat 19-Apr-14 12:02 AM
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#12. "RE: Another Auto ISO Curiosity"
In response to Reply # 11
Sat 19-Apr-14 02:42 AM by burchan

Sydney, AU
          

I find that Auto ISO is great feature is used correctly. The settings of minimum and maximum values should never be used. Minimum should always be minimum and maximum don't matter since choice is grainy picture or no picture at all. By limiting ISO you achieve nothing. I have seen people making mistakes of forcing high ISO in manual or Auto ISO as minimum value and then using the camera in bright daylight.

I have come to conclusion that for best and constant good results
Manual ISO with flash and for long exposures with tripod.

Auto ISO for all hand held photography combined with Shutter priority mode or manual mode. I avoid aperture priority on its own unless I am sure shutter speed wil not suffer.
Using aperture priority hand held risks to slow shutter speed in some situations. Setting minimum shutter speed in Auto ISO don't work because different situations and different lenses require differend settings.
Auto ISO is great but no values should be set restricting its full potential.
In some situation manual ISO is better when used such as controling strong back light of when subject is lit but background is dark.

Visit my Nikonians gallery.

Visit my Nikonians gallery.

  

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