Auto ISO Canon vs Nikon

[Mircula]

I use 1/ focal lengths if i want to eliminate camera shake from holding my camera photographing something non-moving as a general starting point.

That is without IS and factoring in the 1.6 crop of my 40D......

[pgbphotographytas]

what's safe ?

1/ focal length was what I have always been told...

[Mircula]

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

I disagree. If I am in av and auto iso is turned on the only thing i decide is the aperture. And maybe a bit of +/- ev.

[fillum]

Sorry Mircula, I missed your posts at 1:56pm and 2:33pm as I was typing a response both times. I understand what you are asking now.

I don't know the answer but perhaps you could find out by running some test shots. Decrease the amount of light till you see the ISO increase. The s/s displayed when the ISO starts to increase will be the minimum s/s value. You could try different lenses to see if that makes a difference to the minimum s/s value.


Cheers.

[pgbphotographytas]

I disagree. If I am in av and auto iso is turned on the only thing i decide is the aperture. And maybe a bit of +/- ev.

Correct.

Case 1:
Camera on AV, F8, ISO 100 you might get a shutter speed of 1/50

Case 2:
Camera on AV, F8, Auto ISO the camera needs to work out what ISO to give it a "safe" shutter speed or else it would pick a random value for the ISO.

What the OP was asking is how it sets that value? With a 30mm lens it might say 1/50th is "Safe" where as on a 300mm lens it might need to set it to 1/300th.

Paul

[Art Vandelay]

This threads a bit confusing.

In Shutter mode, it can't keep a higher speed as it'll stay at whatever you set.
In manual mode it will also keep the shutter you've set.

Out of interest, just had a fiddle with mine (7D) on auto ISO in AV mode while reading this.

It doesn't have an automatic lower limit stop for shutter speed. Tried a few scenarios and focal lengths and it let the shutter go way down beyond hand holdable.

Mircula, I don't understand what the manual is suggesting.

[arthurking83]

I'm an ISO base or lower type of person, but I find Auto ISO to be one of the handiest features of the modern age.

I use it a lot in 'full manual mode', and set it's range from lowest to highest(200-6400) with varying shutter speeds to suit the lens I'm using at that point in time.

Basically.. I'm more like Darren.

My two methods of ISO usage are: lowest(ISO100) or Auto

Campo! if you have a Dxxx or Dx series camera, you're use of Auot ISO in full manual mode is quite easy to control. Use the memory banks for when you want, or not want to, use Auto ISO in manual mode.
I created a [Portrait_Auto ISO] memory bank where the camera is set to use AutoISO as a part of the set of parameters. Other settings in there too, like faster burst rate and 14bit capture, where normally I only use 12bit.

The only really annoying things about Nikon's implementation is that you can't use the ISO ranges below base(Lo-1..etc) and that you can't set AutoISO using the dedicated ISO button and the command wheel. You can only access AutoISO via the menu system, but as Darren said, that's still easy using the Quick Menu(I set it to the top of the menu too! ). I still think, it's not an ideal way to set it.

I suppose the argument Campo made about having the option to turn AutoISO mode off when using full manual mode kind'a makes sense.
But then again that would complicate things a bit too much in simply wanting to switch to manual mode... and that's what the memory banks are there for anyhow! .. as long as you name them appropriately, and they makes sense.
I normally don't use Auto ISO when I use aperture priority mode, and as I don't use shutter priority mode... these two modes coupled with Auto ISO don't really interest me all that much.

For the D300, Nikon only addressed a few silly shortcomings with Auto ISO too. It used to be limited in selecting shutter speeds, and with a new firmware update they basically allow almost all (reasonable) shutter speeds, that the camera is capable of in some cameras.
ie. minimum shutter speeds from 1s to 1/4000s!

1s??? .. I suppose this is handholdable with a UWA lens with VR
1/4000s!! JeeeZ!! .. my brain hurts just thinking of situations for that setting.

[Mircula]

This threads a bit confusing.

In Shutter mode, it can't keep a higher speed as it'll stay at whatever you set.
In manual mode it will also keep the shutter you've set.

Out of interest, just had a fiddle with mine (7D) on auto ISO in AV mode while reading this.

It doesn't have an automatic lower limit stop for shutter speed. Tried a few scenarios and focal lengths and it let the shutter go way down beyond hand holdable.

Mircula, I don't understand what the manual is suggesting.

Hmmm....so if it does not even have that it is completely useless....I will play around a bit with it tonight....

It astonishes me a bit that nobody knows that. Apparently all canon users really dont use auto iso at all....

[etherial]

I'll try and clear this up, I think some Nikon users don't understand the question because they have the flexibility of setting a minimum shutter speed when in Av mode - Canon does not (I wish it did!)

So here I am with my 7D and 70-200 lens, I point it at a blank wall only a metre or so away from me.

Av mode, F2.8, Auto ISO.
at 70mm it gives me a shutter of 1/100 and ISO of 1250
at 200mm it gives me a shutter of 1/250 and ISO of 3200

So clearly the camera is making a determination of a suitable minimum shutter speed and then setting the ISO to suit. It appears that it is looking for the first increment faster than 1/focal length. In my mind it is not fast enough though, and therefore I don't use it.

When shooting dog shows where I want a fast shutter and wide aperture, I flick mine to Manual mode, set the Aperture and shutter and use Auto ISO to automatically deal with the variations in light. So it is useful, but not as flexible as the Nikon method.

[pgbphotographytas]

I'll try and clear this up, I think some Nikon users don't understand the question because they have the flexibility of setting a minimum shutter speed when in Av mode - Canon does not (I wish it did!)

So here I am with my 7D and 70-200 lens, I point it at a blank wall only a metre or so away from me.

Av mode, F2.8, Auto ISO.
at 70mm it gives me a shutter of 1/100 and ISO of 1250
at 200mm it gives me a shutter of 1/250 and ISO of 3200

So clearly the camera is making a determination of a suitable minimum shutter speed and then setting the ISO to suit. It appears that it is looking for the first increment faster than 1/focal length. In my mind it is not fast enough though, and therefore I don't use it.

When shooting dog shows where I want a fast shutter and wide aperture, I flick mine to Manual mode, set the Aperture and shutter and use Auto ISO to automatically deal with the variations in light. So it is useful, but not as flexible as the Nikon method.

Thanks for the info, it makes a lot more sense now

[RaoulIsidro]

Once the Auto ISO on Canon is set/chosen, (5D, 5D2) it seems it isn't programable or changeable. The camera thinks for itself.
The Auto ISO on Nikons have a set up where you choose the highest ceiling the ISO will go, and the slowest shutter speed the camera will select.

[ricktas]

The Nikon Auto ISO system and the Canon one are completely different, you cannot compare what happens on a Canon to that which Nikon allow. The Nikon auto ISO system is much more programmable by the photographer. I think some of the Canon users in this thread haven't realised that.

[I @ M]

The entire subject of auto ISO made me have a think from the Nikon point of view.
We have used auto ISO ( in the limited range of 100 - 800 on D200 bodies ) in conjunction with manual control of the camera in every other aspect as a handy aid when shooting birds in varying and unpredictable light conditions and it has proved worthwhile.

The weekend just past and memory of this thread made me wonder how auto ISO in conjunction with a flash would work ( Nikon ) so I experimented.

To say I am confused is an understatement, there seems to be no predictability with the way the camera chooses to either increase flash output or to increase ISO or a combination of both.

My rather rough and very unscientific testing seems to indicate that the camera chooses to apply an ISO increase and a flash output increase at the same time very very accurately to obtain a correct exposure ---- but --- the manner in which it does the calculations seems to be heavily dependant on distance between subject, flash and camera.

Any thoughts.

[zollo]

canon users are weird

[I @ M]

As a rough example, this shot was taken facing West ( into the sun through the scrub ) and from memory before the flash and auto ISO were brought into play it metered at around 1/30 F/8 ISO 3200 @ 200mm without the flash.

With auto ISO and the flash engaged ( +1/3 flash ev ) and the camera set in manual at 1/640 F/8 @ 200mm the camera chose an ISO of 5400 and pretty dammed good flash exposure to produce the image below.

[Harves]

I use a D300 and use the auto iso for birding. I find it quite useful with the camera set on aperture priority, usually around f/4 or f/5.6, with the minimum shutter speed of 1/1250, along with the auto iso constantly adjusting the third element of producing the correct exposure, can't (shouldn't) go wrong.

Works for me anyway.

[RaoulIsidro]

The Auto ISO on Nikons are more sane and predictable, by my experience with Nikons.
On the Canon, it's just crazy.
Auto ISO on my Canon 40D chose ISO100 for this and proceeded to OVERIDE my f4 setting to f5.6!
(I think I forgot to disable the Safety Shift function)

[fillum]

My rather rough and very unscientific testing seems to indicate that the camera chooses to apply an ISO increase and a flash output increase at the same time very very accurately to obtain a correct exposure ---- but --- the manner in which it does the calculations seems to be heavily dependant on distance between subject, flash and camera.

Any thoughts.

At 1/640 I assume that you are using auto FP high speed sync? With auto FP, max effective flash power is significantly decreased and consequently effective flash distance also decreases. My guess is that the camera will increase ISO when it calculates that flash power is insufficient for the distance. I'd assume that flash output would remain constant in auto FP for any particular shutter speed.


Cheers.

[I @ M]

Phil, yep the reduced "full power burst" of flash is not available with auto fp on at high shutter speeds particularly when at any significant distance.
Even when using high speed synch, you are usually aware of the amount of power being chucked out by the flash from the sound of the discharge/s and the recycle time to "ready" for the next shot and only a couple of times when I was experimenting did I hear and see that a full power drain had occurred in the flash.
Back in the laboratory ( kitchen ) I tried some very simple shots at close distances where power needs wouldn't be compromised even with a high shutter speed and the result was that a correctly exposed shot was taken at 1/800 F5.6 400 ISO. Taking the same shot again but dialling in +1 flash ev saw a brighter shot as one would expect but instead of the camera increasing the ISO by a full stop to 800 it increased it to 720. This and other shots made me think along the lines I have about the camera , flash and the auto ISO combination working in different ways.

Likewise with another shot, straight at the subject about 3 metres away at 1/800 F/5.6 it chose 400 ISO with no sign of high flash discharge. Then simply lifting the flash head to about 45 degrees and bouncing the light from the very non reflective ceiling to light the same subject saw the ISO go straight to 6400 but still a properly exposed image and no sign of the flash working hard.