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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: 563001" data-attributes="member: 12496"><p>There are details, not always obvious.</p><p></p><p>What you are calling Easy ISO is slightly conceptually different. It cannot only affect ISO, that would change exposure. What the wheels actually adjust is shutter speed or aperture, pretty much in the regular way, which then just causes Auto ISO to react with a different number. But the shutter speed or aperture was the change, requiring a different ISO. This is assuming the camera settings still have range to change. If they are at limits and cannot change, then Auto ISO will not change either. So it's also good to pay attention to shutter speed and aperture.</p><p></p><p>In the situation with flash when ISO goes above 4x Minimum (on these more recent camera models), if you can recreate the same situation (camera on a tripod ensures no surprises in how it is pointed after we make changes), then assuming camera Manual mode for fixed shutter speed and aperture, then if you force manual ISO 400 instead of the higher number, then you see that your TTL flash picture will be underexposed by the difference. TTL does always try to do automatic flash, regardless of camera settings, but it only has so much power available. The camera will try to limit Auto ISO to 4x Minimum with a hot shoe flash, but when necessary, ISO otherwise increases above 4x (400) to maintain the flash exposure with the maximum power it has available.</p><p></p><p>Camera mode A is actually similar to manual mode in this case (indoor flash), because we are setting aperture, which is then fixed, same as Manual. And indoors in A mode, the camera Minimum Shutter Speed With Flash is limited at 1/60 second (menu E2), so it is fixed, meaning we are not really concerned about ambient. The only difference in dim places where we need flash is that A mode fixes the shutter speed at 1/60 second, but M mode could use other desired shutter speeds. With Indoor flash, camera mode A normally just implies we are setting shutter speed to 1/60. </p><p></p><p>(Qualification: the Minimum Shutter Speed in the Auto ISO menu can be a factor too. It is allowed to go slower when ISO hits Maximum, but the E2 menu may enforce its own limit with in A or P modes. Generally both limits apply, but I think models may vary slightly).</p><p></p><p>(Qualification: Menu E2 allows this shutter limit to be set slower, and Slow Sync or Rear Curtain Sync will allow it to be the actual slow metered value of the dim indoor ambient. But the only way to get it faster in camera A mode is to go out into brighter light.)</p><p> </p><p>In practice, it doesn't take us long to realize there is no magic in every indoor flash picture always being 1/60 second, and for flash indoors, camera M mode has strong advantages (same aperture setting, but it allows other shutter speeds). </p><p>The flash exposure does not care about shutter speed, but shutter does affect the ambient exposure. So in camera Manual mode indoors, we have additional control over the effect of ambient, to allow ambient in, or to keep it out. Incandescent ambient is typically orange.</p></blockquote><p></p>
[QUOTE="WayneF, post: 563001, member: 12496"] There are details, not always obvious. What you are calling Easy ISO is slightly conceptually different. It cannot only affect ISO, that would change exposure. What the wheels actually adjust is shutter speed or aperture, pretty much in the regular way, which then just causes Auto ISO to react with a different number. But the shutter speed or aperture was the change, requiring a different ISO. This is assuming the camera settings still have range to change. If they are at limits and cannot change, then Auto ISO will not change either. So it's also good to pay attention to shutter speed and aperture. In the situation with flash when ISO goes above 4x Minimum (on these more recent camera models), if you can recreate the same situation (camera on a tripod ensures no surprises in how it is pointed after we make changes), then assuming camera Manual mode for fixed shutter speed and aperture, then if you force manual ISO 400 instead of the higher number, then you see that your TTL flash picture will be underexposed by the difference. TTL does always try to do automatic flash, regardless of camera settings, but it only has so much power available. The camera will try to limit Auto ISO to 4x Minimum with a hot shoe flash, but when necessary, ISO otherwise increases above 4x (400) to maintain the flash exposure with the maximum power it has available. Camera mode A is actually similar to manual mode in this case (indoor flash), because we are setting aperture, which is then fixed, same as Manual. And indoors in A mode, the camera Minimum Shutter Speed With Flash is limited at 1/60 second (menu E2), so it is fixed, meaning we are not really concerned about ambient. The only difference in dim places where we need flash is that A mode fixes the shutter speed at 1/60 second, but M mode could use other desired shutter speeds. With Indoor flash, camera mode A normally just implies we are setting shutter speed to 1/60. (Qualification: the Minimum Shutter Speed in the Auto ISO menu can be a factor too. It is allowed to go slower when ISO hits Maximum, but the E2 menu may enforce its own limit with in A or P modes. Generally both limits apply, but I think models may vary slightly). (Qualification: Menu E2 allows this shutter limit to be set slower, and Slow Sync or Rear Curtain Sync will allow it to be the actual slow metered value of the dim indoor ambient. But the only way to get it faster in camera A mode is to go out into brighter light.) In practice, it doesn't take us long to realize there is no magic in every indoor flash picture always being 1/60 second, and for flash indoors, camera M mode has strong advantages (same aperture setting, but it allows other shutter speeds). The flash exposure does not care about shutter speed, but shutter does affect the ambient exposure. So in camera Manual mode indoors, we have additional control over the effect of ambient, to allow ambient in, or to keep it out. Incandescent ambient is typically orange. [/QUOTE]
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A poll about Auto ISO action with hot shoe TTL flash
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