Auto ISO and TTL Flash?

[Fota]

Hi,

I'm puzzled about the Auto ISO (especially on my D200) and TTL flash (strobe) combination. Hey I'm even puzzled about the auto exposure and TTL flash combo but let's save that for another thread as uw I only shoot in manual mode, and uw is what this forum is all about.

What I mean is that, if the camera decides what ISO to pick based on it's metering system prior to taking the actual picture then it often (always?) will go for a too big ISO. Hey, it would even always pick the largest ISO unless there is enough ambient light (seldom happens on my dives) to shoot without the flash. I presume the sensor has to be set to a specific ISO before recording light, so I guess that is how it works.
But, often the flash (strobe) is powerful enough to brighten the object perfectly, so the lowest ISO could have worked very well with the given aperture and time setting, and of course generated least noise (I hate noise!) Sure, the part of the image not being lit up by the strobe would have become darker, but I could live with that.

Or am I just being totally wrong about all this? :huh:


/Fota

 

[tx51210]

What do you have the limits set to for the minimum and maximum for Auto ISO. If you did not lower the defaults then the max ceiling for ISO would bounce up to 1600iso as you describe. If you lower this to 400 or some other number your higest ISO will never go above this range and AutoISO is then a cool thing.

 

[AUTiger]

I saw the same issue two weekends ago. I had accidentally left the camera set to auto iso with no upper limit. It sometimes bounced up to 1600. You can set a maximum ISO that cannot be exceeded. For land photos, you can also set a maximum shutter time, below which the camera will not increase the ISO. Since I use manual shutter speed when diving, this doesn't help any. I would rather use more flash and keep the ISO down to 100 or 200.

David

 

[Fota]

Yeah, sure I know how to use the auto iso settings and they (as the auto) iso are great when not using flash, but again my thoughts are concerning when using TTL flash/strobe. If the auto iso may even do more harm than good (based on my thoughts above). I mean, if there is enough light from the strobe to use ISO 100, I'd never ever want to use anything above that.

Anyone?


/Fota

 

[tx51210]

Auto ISO is not really needed if you have enough strobe. It is a compromise setting usually used to make the best of less than ideal situations. I ususally have it turned off and set the ISO I want.

 

[RonFrank]

Using a flash (Nikon SB800) with auto ISO ON disables the auto ISO mode. IOW's auto ISO is disabled if the camera detects the use of a flash. The ISO setting selected when using a flash is whatever was set prior to turning Auto ISO ON.

If the camera is not aware of a flash then auto ISO will be in effect when using a flash. Nikon does not believe Auto ISO is an effective setting if using a flash.

Auto ISO is designed for shooting in ambient light with moving subjects. This is why one can set both the max ISO, and minimum shutter speed. This allows someone who is shooting say birds or football to provide a minimum shutter setting, a max ISO value, and the camera will up the ISO as needed as the lighting changes. The camera will select the lowest possible ISO for the given ambient light. Actually very handy for sports shooters.

In Aperture mode if one sets the minimum shutter to 1/125, and then adjusts the aperture it forces the camera into almost a manual mode where the ISO auto adjusts based on the light. Very handy given many shooting situations!

Like so many settings on todays digital wizbang camera's one needs to decide what settings will work best for a given situation. I'd say Auto ISO maybe worth using UW for Wide Angle shots where it's important to have good exposure out of flash range. However there are certainly other ways to go about setting up the camera to get a similar result.

I'm not sure if the D200 detects the use of Ikelite TTL controllers, or Sea&Sea's TTL controller. If it does Auto ISO will be disabled. If not, then one can choose to use Auto ISO with those iTTL flash units.

 

[Fota]

Using a flash (Nikon SB800) with auto ISO ON disables the auto ISO mode. IOW's auto ISO is disabled if the camera detects the use of a flash. The ISO setting selected when using a flash is whatever was set prior to turning Auto ISO ON.

If the camera is not aware of a flash then auto ISO will be in effect when using a flash. Nikon does not believe Auto ISO is an effective setting if using a flash.

Auto ISO is designed for shooting in ambient light with moving subjects. This is why one can set both the max ISO, and minimum shutter speed. This allows someone who is shooting say birds or football to provide a minimum shutter setting, a max ISO value, and the camera will up the ISO as needed as the lighting changes. The camera will select the lowest possible ISO for the given ambient light. Actually very handy for sports shooters.

In Aperture mode if one sets the minimum shutter to 1/125, and then adjusts the aperture it forces the camera into almost a manual mode where the ISO auto adjusts based on the light. Very handy given many shooting situations!

Like so many settings on todays digital wizbang camera's one needs to decide what settings will work best for a given situation. I'd say Auto ISO maybe worth using UW for Wide Angle shots where it's important to have good exposure out of flash range. However there are certainly other ways to go about setting up the camera to get a similar result.

I'm not sure if the D200 detects the use of Ikelite TTL controllers, or Sea&Sea's TTL controller. If it does Auto ISO will be disabled. If not, then one can choose to use Auto ISO with those iTTL flash units.

Hi Ron,

Finally someone who understands my question and thanks for a great and detailed reply.

Hmm so it seems as the D200 doesn't fully understand the presence of the DS-125 as it surely alters the ISO when using it together in auto iso. On the other hand, as you claim that may be OK as I can either use auto iso on wide angles as the background then will decide the exposure and as the flash wont reach that far, altering ISO may be a good choise. Or, I can simply disable auto iso when shooting macro. I will do a few tests with the internal flash in auto iso and see if it works as you say it does. It will be interesting!


Thanks,
Fota

 

[RonFrank]

Hi Ron,

Finally someone who understands my question and thanks for a great and detailed reply.

Hmm so it seems as the D200 doesn't fully understand the presence of the DS-125 as it surely alters the ISO when using it together in auto iso. On the other hand, as you claim that may be OK as I can either use auto iso on wide angles as the background then will decide the exposure and as the flash wont reach that far, altering ISO may be a good choise. Or, I can simply disable auto iso when shooting macro. I will do a few tests with the internal flash in auto iso and see if it works as you say it does. It will be interesting!


Thanks,
Fota

There is not an indicator when auto ISO is disabled with the flash. The words "Auto ISO" may blink, but it will still show the ISO setting as auto ISO. However when you shoot, the ISO will be set based on the last ISO setting.

For macro work or any time when using flash as a primary light source I'd suggest setting auto ISO off. One can achieve similar results by manually adjusting the ISO albeit it will take a few shots to get the background balanced to the flash for example when shooting WA.

Unless the light conditions are changing constantly Auto ISO is not all that useful. Where it comes into play is if you were shooting a football game at dusk, and the ambient light was diminishing. A sports shooter could set his camera to A priority, the Aperture wide open, the minimum shutter to 1/250, and then the ISO would adjust as the light fell while maintaining a shutter that would stop action while keeping the exposure constant. The downside is noise, but sports shooters must often shoot at high ISO's, it's just part of the job.