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A poll about Auto ISO action with hot shoe TTL flash
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<blockquote data-quote="WayneF" data-source="post: 562972" data-attributes="member: 12496"><p>There are several ifs and buts about Auto ISO. Generally flash is best with the lowest usable ISO. Increasing the ambient with ISO to show the incandescent orange is not the best idea mixed with flash.</p><p></p><p>1. First, the Auto ISO being limited with flash to 4x Minimum ISO (or usually to ISO 400) applies only to <strong>relatively late model camera models</strong>. </p><p></p><p>Older iTTL cameras (D70 to D300 era) never increased Auto ISO above Minimum if flash was involved (because we were using flash instead). Seemed right. Point is, there is no one correct answer about how cameras use Auto ISO. Which camera?</p><p></p><p>Intermediate age iTTL (D300S and after, for awhile, not sure of this boundary, but before the D800) ALWAYS increased Auto ISO as much as necessary for the ambient, regardless if flash or not. Was a poor idea for flash.</p><p></p><p>Later models (roughly D800 and after) fixed that, and started the 4X Minimum ISO limit (often ISO 400) for a hot shoe flash. ISO 400 is often about right for bounce flash.</p><p></p><p>2. And 4x Minimum ISO applies only to <strong>hot shoe flash</strong>, the internal flash will still advance Auto ISO for the ambient level, regardless if the flash used or not. Because it is such a tiny flash I suppose.</p><p></p><p>3. And 4x Minimum ISO applies only to <strong>TTL flash mode</strong>. Auto ISO will <strong>never increase</strong> if a manual mode flash is detected. Because Manual flash cannot react to Auto ISO changing.</p><p></p><p>4. And Commander flash use never increases Auto ISO above Minimum.</p><p></p><p>5. But your issue: Any of them, newest models (and even including the older first models that "never advanced Auto ISO if with flash") would increase Auto ISO even more, as high as necessary if the preflash indicated the low ISO was going to be insufficient for the flash power available (for hot shoe flash, NOT with the Commander remotes). So in situations needing a lot of flash power, you can see more than 4x Minimum Auto ISO, simply because it is needed for the available flash power.</p><p></p><p>5b. But this "more than 4x Minimum" part seems untrue of 3rd party flashes like Yongnuo, I suspect because the camera has no knowledge of the available maximum flash power of unknown flash models. TTL measures a weak preflash, and then says "give me X EV more... It does not work with absolute flash power levels. Viewfinder may indicate the higher amount in advance, but Exif says 4x (or 400) then. Similarly, if NOT Auto ISO where ISO cannot increase, in insufficient power situations, the camera metering displays (on the flash LCD) how much more flash power was needed, on Nikon flash models, but not on 3rd party flash. I suppose 3rd party are not designed to display it?</p><p></p><p>As you imply, it is a good thing to watch and be aware, and to control ISO to be our own preference.</p></blockquote><p></p>
[QUOTE="WayneF, post: 562972, member: 12496"] There are several ifs and buts about Auto ISO. Generally flash is best with the lowest usable ISO. Increasing the ambient with ISO to show the incandescent orange is not the best idea mixed with flash. 1. First, the Auto ISO being limited with flash to 4x Minimum ISO (or usually to ISO 400) applies only to [B]relatively late model camera models[/B]. Older iTTL cameras (D70 to D300 era) never increased Auto ISO above Minimum if flash was involved (because we were using flash instead). Seemed right. Point is, there is no one correct answer about how cameras use Auto ISO. Which camera? Intermediate age iTTL (D300S and after, for awhile, not sure of this boundary, but before the D800) ALWAYS increased Auto ISO as much as necessary for the ambient, regardless if flash or not. Was a poor idea for flash. Later models (roughly D800 and after) fixed that, and started the 4X Minimum ISO limit (often ISO 400) for a hot shoe flash. ISO 400 is often about right for bounce flash. 2. And 4x Minimum ISO applies only to [B]hot shoe flash[/B], the internal flash will still advance Auto ISO for the ambient level, regardless if the flash used or not. Because it is such a tiny flash I suppose. 3. And 4x Minimum ISO applies only to [B]TTL flash mode[/B]. Auto ISO will [B]never increase[/B] if a manual mode flash is detected. Because Manual flash cannot react to Auto ISO changing. 4. And Commander flash use never increases Auto ISO above Minimum. 5. But your issue: Any of them, newest models (and even including the older first models that "never advanced Auto ISO if with flash") would increase Auto ISO even more, as high as necessary if the preflash indicated the low ISO was going to be insufficient for the flash power available (for hot shoe flash, NOT with the Commander remotes). So in situations needing a lot of flash power, you can see more than 4x Minimum Auto ISO, simply because it is needed for the available flash power. 5b. But this "more than 4x Minimum" part seems untrue of 3rd party flashes like Yongnuo, I suspect because the camera has no knowledge of the available maximum flash power of unknown flash models. TTL measures a weak preflash, and then says "give me X EV more... It does not work with absolute flash power levels. Viewfinder may indicate the higher amount in advance, but Exif says 4x (or 400) then. Similarly, if NOT Auto ISO where ISO cannot increase, in insufficient power situations, the camera metering displays (on the flash LCD) how much more flash power was needed, on Nikon flash models, but not on 3rd party flash. I suppose 3rd party are not designed to display it? As you imply, it is a good thing to watch and be aware, and to control ISO to be our own preference. [/QUOTE]
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A poll about Auto ISO action with hot shoe TTL flash
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