Auto ISO Canon vs Nikon

[Mircula]

Not speaking about anyone else, but I have no idea what you are going on about here

So, with the 40d it is not possible to set a minimal shutter speed or the iso range for the auto iso.

In the manual of my 40d it says (if used in AV mode):

"The iso speed will be set automatically within iso 400-800 so that a shutter speed preventing camera shake will be set ..... "

What is this shutter speed? How does the camera calculate the minimum shake - less shutter-speed and does it consider focal lengths for instance?

Does that make it a bit clearer? Was a bit confusing maybe without reading the manual, sorry english is not my mother tongue.....

[kiwi]

on the nikon you can set a minimum, but it has nothing to directly with camera shake, camera doesnt care how good your technique or what lens you are ysing in this regard, it just says I dont want the camera to go below that iso, but I suppose, indirectly then it will mean that if you start underexposing camera will next start reducing the shutter speed and that fact might start introducing motion blur

[Mircula]

I think there is either a fixed value shutter speed for non shaking set inside the camera or some sort of algorithm considering other factors like focal lengths which have an effect on how low the speed can be without shaking.

I am just wondering if anybody knows this number or algorithm.

I guess the camera first lowers the shutter speed to this number or algorithm and then upps the iso.....but it is kind of vital to know that number to decide if this auto iso feature on a canon is at all useable.....

[fillum]

I find it extremely useful for sport in keeping the shutter speed fast. I've also recently found it to be useful in general shooting situations (after forgetting to turn it off ), particularly in those situations where I'm not concentrating too well on what I'm doing (at a bbq for example).

Does anybody know how the camera decides what shutter speed prevents camera shake?

Are you asking how the camera would know to increase ISO to get a shutter speed to prevent blur due to camera shake? The answer to that is that the camera doesn't know - the photographer sets the minimum shutter speed (when shooting aperture priority) as one of the parameters for auto-ISO. When the meter calculates that the shutter speed will be below your value, it starts boosting the ISO till the shutter speed is back to your minimum parameter setting (if possible). So if you were shooting with a 70-200 for example you might set the minimum s/s to say 1/200, but when using a 17-50 set the minimum s/s to 1/60. You might also use different minimum s/s values if the lens has image stabalisation.



Cheers.

[Mircula]

hello,

that is tv on a canon camera.

In av i set the aperture and my camera decides what the shutter speed will be.

[fillum]

agree, what I want though is to be able to use AutoISO in any semi automatic mode (ie. A/S/P) but when i 'turn the dial' to M mode, I want the camera to turn AutoISO off. I don't have time at a wedding to drive through the menus to turn AutoISO on/off everytime I need to flick to Manual mode.

Campo have looked into using the shooting banks? I haven't used them so don't know what the capabilities are. Downside would be that you probably still need to take your eye away from the viewfinder to change settings.


Cheers.

[kiwi]

camera decides only based on the exposure reading (it wants to create a "good" exposure when it decides what shutter speed to choose for any particular scene), it couldnt care less what other issues it might cause, such as camera shake

Mirculam have you been through the NTP program yet ?

[Tannin]

why dont you think its useful Tony ?

I think my post just above more or less addresses that but in reverse, Darren (I wrote that before I saw your question) - grafting an auto ISO function onto one of the existing major modes (Av for eg) just confuses the issue and winds up giving you less control instead of more.

But using it as you are - as a fully-fledged mode in its own right, to stand alongside Av and Tv - is a different matter.

Then there is the way that I would like to use it: this would need a significantly more complex decision rule system that I can program for my particular needs. Not just a min shutter speed, more like a scripted set of responses to light conditions that mimics what I'd actually do myself. For example, for bird work:

Use ISO 400 to start with, and f/8.

If the shutter speed drops below 1/1000th, go to f/5.6.

If the shutter speed is still below 1/1000th, go to 800 ISO.

If the shutter speed is still below 1/1000th, go to f/4

Go to 1/250th if needed.

If you can't get 1/250th, go to 1600 ISO.

And so on.

Why? Because 1/1000th @ 800 ISO will generally get you a better result than 1/500th @ 400i if you are working with smaller, fast-moving birds. The camera needs to know that. And it needs to know what the next thing to sacrifice is too, and the thing after that.

All of which leads me back to the point that I started with: EITHER we need a much smarter auto ISO (and other things too) system which is fully programmable, OR we just fall back on the old Mark One Human and do it the present way.

Am I making sense?

[pgbphotographytas]

Not speaking about anyone else, but I have no idea what you are going on about here

Basically the OP wants to know how a Canon decides what ISO to use to get a "safe" shutter speed and if this is based on the focal length (as we know with a longer focal length you need a higher shutter speed to avoid camera shake) it is a good question that I think only Canon could answer as I guess it would be buried deep in the firmware.

Paul

[kiwi]

yeah, makes sense

You tried jailbreaking the Canon OS yet ?

I think my post just above more or less addresses that but in reverse, Darren (I wrote that before I saw your question) - grafting an auto ISO function onto one of the existing major modes (Av for eg) just confuses the issue and winds up giving you less control instead of more.

But using it as you are - as a fully-fledged mode in its own right, to stand alongside Av and Tv - is a different matter.

Then there is the way that I would like to use it: this would need a significantly more complex decision rule system that I can program for my particular needs. Not just a min shutter speed, more like a scripted set of responses to light conditions that mimics what I'd actually do myself. For example, for bird work:

Use ISO 400 to start with, and f/8.

If the shutter speed drops below 1/1000th, go to f/5.6.

If the shutter speed is still below 1/1000th, go to 800 ISO.

If the shutter speed is still below 1/1000th, go to f/4

Go to 1/250th if needed.

If you can't get 1/250th, go to 1600 ISO.

And so on.

Why? Because 1/1000th @ 800 ISO will generally get you a better result than 1/500th @ 400i if you are working with smaller, fast-moving birds. The camera needs to know that. And it needs to know what the next thing to sacrifice is too, and the thing after that.

All of which leads me back to the point that I started with: EITHER we need a much smarter auto ISO (and other things too) system which is fully programmable, OR we just fall back on the old Mark One Human and do it the present way.

Am I making sense?

[kiwi]

Basically the OP wants to know how a Canon decides what ISO to use to get a "safe" shutter speed and if this is based on the focal length (as we know with a longer focal length you need a higher shutter speed to avoid camera shake) it is a good question that I think only Canon could answer as I guess it would be buried deep in the firmware.

Paul

what's safe ?

[Mircula]

camera decides only based on the exposure reading (it wants to create a "good" exposure when it decides what shutter speed to choose for any particular scene), it couldnt care less what other issues it might cause, such as camera shake

Mirculam have you been through the NTP program yet ?

Yes been through the ntp. Should i go through it again?

I know that the camera tries to expose correctly, but if auto iso is on it has two options doing so, iso and shutter speed.....

I dont think you get my point....in the manual it basically says that it upps the iso to prevent camera shake. That indicated that the camera must have some sort of index or value or algorithm which tells it how high the shutter speed must be to stop camera shake.

Do we agree on that?

If so, i would be interested in what that minimum camerashakestopping shutterspeed is.

[fillum]

hello,

that is tv on a canon camera.

In av i set the aperture and my camera decides what the shutter speed will be.

I think you missed what I wrote (probably could have been worded better):

the photographer sets the minimum shutter speed (when shooting aperture priority) as one of the parameters for auto-ISO

The photographer sets the desired aperture on the camera then the camera adjusts the ISO till the shutter speed is at least the minimum set parameter value.


Cheers.

[kiwi]

Yes been through the ntp. Should i go through it again?

I know that the camera tries to expose correctly, but if auto iso is on it has two options doing so, iso and shutter speed.....

I dont think you get my point....in the manual it basically says that it upps the iso to prevent camera shake. That indicated that the camera must have some sort of index or value or algorithm which tells it how high the shutter speed must be to stop camera shake.

Do we agree on that?

If so, i would be interested in what that minimum camerashakestopping shutterspeed is.

No, we dont agree.....the camera doesnt determine at what point you get camera shake, you do based on your settings you are primarly determining. There is no index, smarts, or algorithm, you set all the parameters

By the way

http://www.youtube.com/watch?v=YJGYS...eature=related

[Mircula]

what's safe ?

Safe = eliminating camera shake



Paul said want i want to know!

[kiwi]

I'll ask again ? what is safe for you ?

[Mircula]

No, we dont agree.....the camera doesnt determine at what point you get camera shake, you do based on your settings you are primarly determining. There is no index, smarts, or algorithm, you set all the parameters

By the way

http://www.youtube.com/watch?v=YJGYS...eature=related

I dont do.

My camera does in the auto iso situation.

At least it claims to do that in the manual of my 40D!

[Mircula]

I'll ask again ? what is safe for you ?

it is not about what i think is safe, it is about what my camera thinks is safe.

[kiwi]

my point is that even in autoiso you are determining the minimum shutter speed for it to kick in at. So, you control it.

[kiwi]

so, what's a safe shutter speed ?

what's yours Paul ?